Revisiting Gillespie 2004

In a paper published in Science in 2004, Rosemary Gillespie demonstrated that both dispersal and in situ speciation contribute to accumulation of species numbers of Tetragnathid spiders on Hawaiian islands. Moreover, accumulation, whether through dispersal or speciation, happens in a way that no island contains more than one species of a particular ecomorph, i.e. in a non-random fashion. Gillespie’s findings provided support for the idea that community assembly is governed by universal principles, whether at ecological or evolutionary scales. Twelve years after the paper was published, I spoke to Rosemary Gillespie about how she got interested in this topic, her memories of field work and what we have learnt since about the adaptive radiation of spiders on the Hawaiian islands.

Citation: Gillespie, R. (2004). Community assembly through adaptive radiation in Hawaiian spiders. Science, 303(5656), 356-359.

Date of interview: 30th September 2016 (via Skype)

 

Hari Sridhar: I wanted to start by asking you about you how your interest in this topic came about. By looking at your profile on Google scholar I realized that you started by doing a lot of work on the behavior of spiders, and sometime in the early 90s you also started working on systematics and  adaptive radiation. So can you tell us a little about the history of this interest?

Rosemary Gillespie: Yes. I did my undergraduate degree at Edinburgh University. I went to university to do ecology and then became more interested in behavioral ecology and really being more interested in birds. But the thing is, as you might know, in many of the European university systems you do an Honors year, and in the Honors year you focus on a specific research project and with one person. I wanted to work on feeding behavior in birds actually, and I was really interested in the work of one of my professors, Philip Ashmole, who is a bird behavioral ecologist. I signed up to work with Philip Ashmole, but then he offered a project of spiders and that’s how I started working on spiders.

During my Honors year at Edinburgh I became really interested in the work ofSusan Riechert, a professor at the University of Tennessee in Knoxville who works on the behavioral ecology of spiders. And so for my PhD I applied to work with Susan and left Scotland to come over to Tennessee. I was a behavioral ecologist throughout my PhD, studying the feeding ecology and behavior of long-jawed spiders, Tetragnatha elongata, in North Carolina. These spiders are found all over the world, though almost always over water, so I was trying to figure out why they select web sites over water, and how they do it. After my PhD, I accepted a post-doc fellowship at the University of Hawaii, to look at the feeding behavior of Hawaiian happy-face spider, which I applied for because that was exactly what I had done for my PhD. I came over to Hawaii and, really, I mean, it was quite intoxicating, to be honest. First of all, the Hawaiian happy-face spider is an interesting little theridiid – a cob web spider that includes Black Widows and house spiders – and it’s got lots of different colors that are genetically inherited. There are many interesting things about happy-face spiders, but the most interesting thing was that there were many other spiders in the forest and they were clearly long-jawed spiders, Tetragnatha – the same group that I’d done my PhD on in North Carolina. But the big difference in Hawaii was that they are not just over water, and indeed are found throughout the forest. So I started looking more at them and, you know, the diversity was just amazing. And then I found that actually very few of them had been described. So for awhile I worked with a professor in Japan –Chiyoko Okuma. Okuma was planning to do the taxonomic work, initially, that’s what we’d arranged, but tragically she died right at the very beginning, before she could do anything. And so, you know, here was this incredibly exciting radiation of spiders almost entirely undescribed. The question then was why you get such diversity – ecological and behavioral as well as morphological. The only way to understand it is from an evolutionary perspective. So I first had to kind of turn myself into a taxonomist and then more of an evolutionary biologist just so that I could really understand the behavioral ecology of the group. It was just as a means to understand, to make sense of, what I was seeing, I suppose.

 

HS: Were you still a post-doc when you started doing this work?

RG: Well that’s where there was a big advantage. I was a post-doc.  Initially, I was on a small grant from the Whitehall Foundation for work on the happy-face spider. This was my first post-doc, and when I found that there was all of this other stuff going on with the adaptive radiation of Tetragnatha, it made me just want to keep looking and keep figuring out what was going on. So I applied to many different small pots of local funding in Hawaii. The Nature Conservancy of Hawaii gave me some funding, as did the Hawaii Department of Land and Natural Resources, and let’s see, the Bishop Museum… all sorts of little pots of money, none of it very much, but it allowed me to stay in the islands and to have complete freedom to basically just live in the forest and get a really good feel for what’s going on with these animals.

 

HS: Who were you working with on your post-doc on the happy-face spider?

RG: My initial post-doc was with Bruce Tabashnik, a professor at the University of Hawaii at Manoa. There is an interesting kind of little snippet here. The Hawaiian happy-face spider is a really colorful and very pretty spider with all sorts of color forms. Sam Gon, a biologist who is from Hawaii, had just finished his PhD at the University of California at Davis – he was just one small step ahead of me – and had gone back to Hawaii, written a grant to study the happy-face spider and had received funding from the Whitehall Foundation. He wrote that grant with Bruce, whose research was in the area of biological control – really quite different the behavior of a forest-dwelling spider. Therefore, when Sam was took the position of Ecologist for the Natural Heritage Program of the Nature Conservancy of Hawaii, Bruce needed a post-doc. And so when I arrived in Hawaii, it was Sam, who still works with The Nature Conservancy of Hawaii on cultural awareness and biodiversity, who really kind of got me into the native system there. However, Bruce was just a great person to work with. He was very helpful with working on conceptual ideas, statistical approaches and things like that, even though his work was quite different to what I was doing. So it was really kind of a close relationship with Sam Gon and The Nature Conservancy at that time. After I was done with the initial post-doc, when I was writing grant proposals just to allow me to keep doing the work, I partnered with several professors at the University of Hawaii so that I could actually receive funding. Initially it was Bruce Tabashnik who hosted me, and then Steve Palumbi, a professor in Zoology at the University of Hawaii at the time, and who is actually a marine ecologist and evolutionary biologist, agreed to be the PI of many of the later proposals. This started because I was working with Henrietta Croom, a molecular biologist and professor at the University of the South in Sewanee, Tennessee. Henrietta did some of the pioneering molecular work on the Hawaiian spiders, in the late 80s, working with Steve and me. Steve was also a great person to work with, though his research was on a very different system.

 

HS: I’d like to ask you a little bit about the development of this piece of work. In ‘94 you published a paper in PNAS, which – correct me if I’m wrong – was your first paper on this area of research…

RG: So actually the first paper, and that was a monumental amount of work, was one that I published in…I think it was 91 and then 92. Those were these species descriptions, where I just was defining what the entities were. Up until then the whole lineage had been pretty much completely unknown, and so those were the early papers that started to get things off the ground; those taxonomic papers. But yes, the paper in ‘94, the PNAS paper, that was with Steve Palumbi and Henrietta Croom. I got a position at the University of Hawaii in ’92; I suppose it was, as a researcher. I was split between a research unit there and the zoology department, but I continued to work closely with Steve Palumbi on a lot of this work.

 

HS: Did you have any experience doing taxonomic work before this or was that something you just picked up when you started this work?

RG: I had zero experience in taxonomic work prior to this and so I was really fairly intimidated to start with. I’d hoped that Chiyoko Okuma might have been able to do it because it was not something that I saw myself doing. It just seemed like it was a world unto itself. So I talked to a lot to the late Herbert Levi, who was a professor at Harvard University and who just died in 2014, whether he might be willing to carry out the formal descriptions. But he said, “Well, you know the spiders more than anyone and so you should be the one that does it.” And you know it was really him saying that that gave me sufficient confidence, I suppose, to be able to go ahead and actually do the descriptions myself. I think if he’d said, “Oh, you need someone else to help you”, then I don’t think I would have had the confidence to go ahead and just do it myself.

 

HS: At what point did you realize that this was an “adaptive radiation”?

RG: Fairly early on. Like I said, in North Carolina these spiders lived over water. You find similar spiders here in Berkeley, you find them in Scotland, you find them in China, you find them all over the world, and they almost invariably live over water. They are long, kind of brown, skinny things and they build these flimsy orb webs over water. They’re designed really to catch small weak and light insects that come up from the water, and they do quite well at capturing those. I was so surprised when I got to Hawaii, and pretty much the first thing I saw was these spiders that looked just like the Tetragnatha I had studied in North Carolina, but here they were in the forest; they weren’t in the “right” habitat. When I first started working in Hawaii, I based myself on the island of Maui, working in The Nature Conservancy of Hawaii’s Waikamoi Preserve. I had only been there for a few months when I had a visit from a colleague, Vince Roth, and his wife Barbara. We went in to the forest together, and I was showing him the Tetragnatha that were in the “wrong” place and we started looking at the other spiders that were there. They were doing all sorts of different things. I just remember Vince saying, “You know, I think all of these are Tetragnatha!” So, we brought them back to my house in Pukalani and found that indeed they were all Tetragnatha, just a whole diverse assemblage of different kinds of morphologies. As I studied them over the subsequent months and years, I, initially, focused on ones that were more the shape that I was accustomed to, but then I even found ones that looked round and colorful, and they were all Tetragnatha. This single lineage really dominates the aerial environment there. They do pretty much everything. There are some that build webs and then a whole lineage that doesn’t build webs. For a long time, I was ignoring the very little ones because I thought they were just immature ones.  I didn’t want to collect a whole bunch of immature spiders because you can’t identify them properly. So I was leaving them behind. And then just by accident I’d collected one, and it turned out that it was actually a mature male. So I had to start collecting the little ones, and that led to another taxonomic paper later on, that focused on the small representatives of this radiation, because they got missed out from the first set of descriptions.

 

HS: Do you remember when Vince Roth visited you?

RG: That would be when I first got to Hawaii, which was in 1987, just after I finished my PhD. There were quite a few years there when I was basically just living in the field. I worked closely with the people from Haleakala National Park, trying to get to every habitat possible and on every island just so that I could you have a solid understanding of what was going on in terms of the adaptive radiation of the lineage.

 

HS: What was the specific motivation for this paper- the Science paper in 2004?Was this something that was planned in advance, or was this something that you decided to write-up because of a particular interesting finding at that point in time?

RG: So, here’s the thing.  Having published these early taxonomic papers, I went to a meeting, the International Congress for Arachnology, the main spider conference, which was in Brisbane in Australia that year. I talked about the adaptive radiation of Hawaiian Tetragnatha. At that point I had no molecular information and so I was trying to figure out relationships based on morphology, which can be very problematic in the situation of adaptive radiations, because the force of natural selection is very strong, and there are numerous cases of convergence (where species look similar when they are not related). Anyway, I was measuring characters and looking at all the features that I could find. So, all the early publications, in the late 80s and very early 90s, were based on morphology. We were starting to get molecular data (the work with Henrietta Croom and Steve Palumbi), in particular mitochondrial data, and we were getting allozyme data, but the initial work was based entirely on morphology. The first set of descriptions that I did was for the different species within the spiny-legged lineage, the ones that don’t build webs, and have spiny legs and they run around the vegetation. But then I wanted to see what the evolutionary history within that group is, just to figure out how they diversified. What I found interesting was that I could go to any wet forest habitat on any island, and I would almost always find four species of the spiny-legged spiders: one that’s green and lives under leaves, one that’s large brown and lives on tree trunks, one little brown that lives of twigs and one maroon that lives on mosses. It was just so striking that you almost always get the same set of forms, or “ecomorphs” on each island. The green ecomorphs on one island look just like the green ones on every other island, and likewise the large brown, little brown, and maroon. So, at the meeting in Australia, I talked about the close affinities of the green ones across islands … surely the green ecomorphs must either be the same species or be very closely related (and likewise the large brown, little brown, and maroon). But then, you know, we got a hold of the molecular data and it told us a totally different story, that the different green ecomorphs are not their own group (and likewise maroon ones and the brown ones). Rather, they have independently or semi-independently evolved the same set of ecomorphs on each of the different islands. So it was really this kind of incredible realization that these things that looked as if they were so similar and then to find that actually they were not that closely related. That was fairly mind-blowing to me. And that that was why this paper came about.

 

HS: Which year did this meeting happen?

RG: The meeting in Australia was in 92.

 

HS: Sorry if I missed this, but how exactly did the meeting help?

RG: So, at the meeting I presented the morphological work, and then they asked for papers coming out of that, you know, papers associated with the conference. This is when I wrote up the early paper that was published in The Memoirs of the Queensland Museum, which basically shows that the ecomorphs that look the same fall together, which of course we now know is not the case at all; it’s just convergence.

 

HS: Over how many years was the work that is presented in this paper done?

RG: Ha, well, so this is hard to say. That was the first really major paper that showed something, about the radiation. So it was really, it was really, building on the work that I’d been doing since 1986. That sounds kind of sad doesn’t it? But yeah, there were a lot of information that went into that, and a lot of, you know, just understanding of the group that I’d just built up over the years. I mean, I’d done little papers about it, and I had a chapter with Henrietta Croom that was published in a book that Warren Wagner and the late Vicki Funk, both botanists at the Smithsonian, put together, Hawaiian Biogeography: Evolution on a Hotspot Archipelago, published in 95; this was a tremendously important resource, bringing together all the work that was just starting to emerge. There were several other papers that came out as well, in fairly small journals because the work hadn’t matured yet. I suppose the 2004 paper really represented where the work was, at least some elements, as it was starting to reach maturity.

 

HS: In the same year, around the same time, you also published a paper in PNAS, which was on the web-building spiders in this group…

RG: Exactly. This was the work of Todd Blackledge, a professor at the University of Akron, Ohio, and then a post-doc with me. That paper was equally interesting because we showed that there was convergence in web forms for the web-building spiders, even though the spiders that inhabit those webs really look quite different. They’re pretty much all over the place, the inhabitants of the webs. But it is the webs that show this convergence in much the same way that the morphology converges and in the spiny-legged spiders. In other words, a given habitat on any island will, for example, have spiders that spin small tight webs, others that spin large loose webs and others that spin large tight webs. Each of these web types has evolved independently on each island.

 

HS: In the Introduction of the paper you talk about adaptive radiations on remote islands and say that two patterns have emerged: 1. a predictable number of species can exist for a given area driven by higher rates of speciation, and 2. the end product of an adaptive radiation is often a non- random set of species. For both these points, you cite papers by Jonathan Losos. Was Losos’s work something you followed closely and drew inspiration from?

RG: Yeah absolutely. Jonathan Losos’s work has been very influential in what I have been doing. He was really the person that pioneered similar work in the Caribbean with Anolis lizards and showed that you get repeated evolution of the same form in these lizards. The patterns you get, in both the spiders in Hawaii and the lizards in the Caribbean, are remarkably similar. What’s interesting is exactly why we see similarities in the evolutionary history these two groups, with repeated evolution of similar ecomorphs on different islands, and yet other groups don’t show this kind of parallel evolution of the same form. But the bottom line is, yes, absolutely, the work of Jonathan Losos, and also that of Dolph Schluter, are probably the two that played the biggest role in the development of ideas that I was formulating at the time.

 

HS: I notice that a number of your papers are single-authored? Was this work that you were doing more-or-less on your own, in the field and the lab work?

RG: Of course there were many people that were instrumental to the development of this work. I had already published key papers with Henrietta Croom and Steve Palumbi. I also started working with George Roderick, also a professor, and who became my husband. Through these growing collaborations, I extended the molecular and allozyme work to gain deeper insights into the evolutionary history of the radiation. However, the work was all firmly anchored in the ecology and behavior of the different species – which ones lived where and why. The foundation in natural history allowed me to explore different ideas. So yes, many of these papers were on my own.

 

HS: Can you give us a sense of the field work for this study –  how often would you visit these islands and long would you stay there?

RG: For the first few years, when I first started doing the work, let’s say ‘87, ‘88, ‘89 –  those early years  – I spent most of my time in the field. I was based on Maui for the first year or two but I went to all of the islands. I tried to go to every habitat that I could. As I mentioned, I worked very closely with people at Haleakala National Park on Maui, and there were a couple of people there that were really important in the early development of the work. In particular, Art Medeiros, a biologist with an extraordinary depth of knowledge of the islands, and who is currently working on a remarkable restoration project on Maui, and the late Lloyd Loope [who died in 2017]. Both Art and Lloyd were hugely important in identifying places to go and just figuring out the biology of the organisms. I’d go with Art to a lot of new places, and we would always find new spiders. We spent endless hours discussing the characteristics of the new species we found, and what other habitats might have spiders with similar attributes. And so, yes, I spent an immense amount of time in the field.

 

HS: I was curious about the names for the ecomorphs – green, maroon, large brown and small brown. From the beginning, did you know that these were the names you were going to use? Did you consider other names?

RG: I had my made-up names for all of the different species and species groups. So when I described the species, I simply latinized or otherwise formalized, the made-up names. For example, I called one of the big brown species, “humpback” because it was a large brown species with a humped body. So when I described it formally, I called it Tetragnatha ‘quasimodo’ after the hunchback of Notre Dame. In terms of the ecomorphs themselves, I simply use the most obvious feature, their color, to describe them. However, there is a suite of attributes that goes along with an individual ecomorph. For example, the maroon one, I’d initially called that red-and-green; but it is characterized by a set of specific behaviors associated with its tendency to live in mosses and similar kinds of microhabitats.

 

HS: What about the other two – the green and small brown?

RG: The small brown, those are just the little brown ones and you know when I ended up describing those ones… I mean they’re kind of obscure little brown things…and there are various names that I’d given them. I’d decided those ones I was going to give Hawaiian names. So their names are various combinations of spiny (kuku in Hawaiian), small (iki), and banded (kikokiko), so we have Tetragnatha kukuiki, T. kikokiko, and T. kukuhaa. I never did that again because it was just too difficult to keep on top of the latin names that I’d given them.

 

HS: The green?

RG: There were so many different species that were green and so I made up different names for green – emerald, olive, lime … and I had various other names for green. But the green ecomorph was just fairly obvious. However, there are many other attributes that go along with being green. Most notably, species in the green ecomorph live under leaves, and have a specific diet associated with this microhabitat. They tend to have very long leg spines, and are more agile than the other ecomorphs.

 

HS: Was this is the first time you used these terms for the ecomorphs in a paper?

RG: Yes, exactly.

 

HS: Do you continue to use the same terms today?

RG: Yes.

 

HS: Do you remember how long the writing of this paper took and when and where you did most of the writing?

RG: So that was in Berkeley. Yeah, the writing took a while actually because initially I was trying to figure out what was the most interesting aspect of the paper – whether it was the actual repeated evolution of the same form or whether it was just that on a single island you get this very large number of different species. I ended up focusing more on the point that, on east Maui you get a surprising number of species, and multiples of a single ecomorph. And so I focused on that aspect in the end, when I wrote the 2004 Science paper. Actually, it took well over a year to write, in particular figuring out the appropriate angle. I would write part of the paper, and then think about it a bit, and then think about other things I wanted to include, or other angles I wanted to take ..so, it went in kind of bursts of writing, and so I’d have it almost written and then want to change the focus a bit. So, yes, it took well over a year.

 

HS: Do you have a writing routine – a particular time of the day in a particular place when you do your writing?

RG: Well, that’s a tough one. For writing papers, I feel you just need to kind of get in a zone, you just need to get rid of all distractions. You can’t have people coming to the door. So yes, I either write in coffee shops or…writing at home is fine, writing on the aeroplane is great.. you know just when you cannot move or do anything else. That’s the way to get papers written, or at least that’s what I find.

 

HS: In addition to the fascinating story you present, one of the things that I really like about the paper are the figures. Did you do all the figures yourself?

RG: Yes. To be honest, I’m not the most artistic. For the taxonomic papers, I had to figure out how to draw the spiders. At one point, I had an artist help – at the University of Hawaii, we had an artist who would provide scientific illustrations for members of the department – but it’s really up to the author to point out the key attributes that must be highlighted. So I just felt like I didn’t have enough control, and accordingly I just started doing my own illustrations.

But, the cover for the journal… so, you know we got the cover there? There were two photos and those where taken by David Liittschwager and Susan Middleton, noted photographers of rare species. I had gone into the field with them quite a bit when I was in Hawaii, and they took some really beautiful pictures of the spiders. And I do remember when I got the 2004 Science paper accepted, a colleague in the department, Wayne Getz, came into my office and I said, “Oh, I’ve just got this paper accepted in Science”, and he said “Oh, are you going to get the cover?”, and I said “Well no, I just don’t have good enough pictures for the cover”, and he said “You have to get the cover. Just go over and get a good picture.” So that’s when I contacted David Liittschwager to see whether he had pictures, and, yes, he had great pictures. They take some fantastic pictures of arthropods from different Pacific Islands. That’s the story of the cover.

 

HS: One of the photos you use in the paper was taken by a W. Haines..

RG: Oh, Will Haines. Yes. Will is an extraordinary entomologist with a deep understanding of the natural history of Hawaii. He works mostly on a radiation of moths in Hawaii. Many others have taken pictures in the past of the spiders. And most recently, a few of my students have taken some really incredible pictures, which they still haven’t got published, but they should do so soon. Two recently graduated students, Darko Cotoras and Andy Rominger, very diligently took pictures of every specimen that they collected, and so we’ve got many more pictures now. And the equipment is  just much better now.

 

HS: I wanted to ask you about the Acknowledgements: could we go over the list of people and ask you how you knew them and how they helped?

RG: Yes.

 

HS: You thank “J. Losos, G. Oxford, S. Pimm and G. Roderick for comments and suggestions on the paper”.

RG: Geoff Oxford is my very close collaborator in England. With me, he works mostly on the Hawaiian happy-face spider, so you’ll see lots and lots of Oxford and Gillespie papers. But those are really just on the Hawaiian happy-face spider work. In England, he works mostly on a spider that has diverse color pattern very similar to Hawaiian happy-face, in the genus Enoplognatha, specifically E. ovata. The Hawaiian happy-face spider system is parallel to the one he’s been working with for a long time, though the color diversity in the Hawaiian happy-face spider is much greater than that of E. ovata. Geoff spent a couple of sabbaticals with me and he’s just a very close collaborator.

George Roderick is my husband. We work a lot together and we met in the field in Hawaii. He’s done a lot of fieldwork with me.

 

HS: Did you send drafts of the paper to Jonathan Losos and Stuart Pimm for comments?

RG: Yes. I asked Stuart Pimm for suggestions on how to pitch the paper. He was super helpful. I’ve known Stuart for quite awhile because he was at the University of Tennessee when I was there, and then he worked in Hawaii. I saw him a lot in Hawaii, and he’d come and visit us. I’ve just known him for a very long time and he’s a very close friend.

Jonathan, I just know about his work, and also I see Jonathan at a lot of meetings and things. So, yes, I know Jonathan well and admire his work tremendously.

 

HS: You also thank the NCEAS. Did you spend time there when you were writing up this paper?

RG: Yes. They have these group meetings, and Jonathan Losos organized one on adaptive radiation. That was just a fantastic group that he brought together for a series of meetings. So Peter Grant was there, Ole Seehausen, Tom Givnish, Dolph Schluter, Michael Donoghue, Bob Ricklefs, Scott Hodges, and others. There were just some really great people and so there was a lot of really good discussion there.

 

HS: Then you thank a few of people for logistic support- AC Madeiros

RG: That’s Art Medeiros, who was hugely important in the field work and gaining insights into the natural history of the Hawaiian Islands. We did a lot of stuff together early on, you know, just getting into the many different sites, and often finding new species of spiders.

 

HS: B. Gagne

RG: Betsy Gagne, who sadly died earlier this year [2020], was in charge of permits in Hawaii. She worked at the Department of Land and Natural Resources there. She’s one of these people who is very much an entomologist, and makes things happen. She was married to Wayne Gagne, who was really one of the major players in entomology, when entomology had a kind of resurgence in Hawaii. He, together with Frank Howarth and Steve Montgomery, really brought Hawaiian entomology into kind of the limelight in the eighties. It was in the early eighties when they did a huge amount of work. And then Wayne died suddenly and tragically, actually just after I got to Hawaii. Betsy continued to work on just making sure that entomology was always strong in Hawaii. That’s what she was really passionate about. While with the Department of Land and Natural Resources, she was involved primarily in facilitating permits for people, and making sure they did the right thing and  getting reports and all that kind of stuff.

 

HS: And then you thank J. Giffin

RG: Jon Giffin. He was on the Big Island at the time and we went into the field together to collect some of the little spiny-leg species. So yes, that was for access to one of the key field sites, the dry forest on the west side of the Big Island. A very knowledgeable entomologist, he has worked on multiple conservation projects.

 

HS: And R. Bartlett

RG: Randy Bartlett. That was for his help in gaining access to the West Maui watershed. Randy Bartlett used to work for Maui Land & Pine, which is now the Puu Kukui Watershed Preserve. It’s this area in West Maui which was really hard to get to at the time when I started working in Hawaii. And Randy was the one that that gave us access. There are many places in Hawaii are really really difficult to get to and so we rely heavily on the help of others to facilitate access. Randy would drive us up to where we could start hiking into the forest because the trail starts above the pineapple fields. Randy was tremendously helpful there.

 

HS: You also acknowledge support from the Schlinger foundation and the NSF

RG: Yeah, so the position that I currently have is the Schlinger chair in entomology, which was funded by Evert Schlinger. Evert Schlinger, who died in 2014, was actually an incredible entomologist in his own right. He worked on flies and, in particular, flies that parasitize spiders, and so he was very familiar with both spiders and flies. He funded a number of research programs based both on spiders and flies He funded positions at the Cal. Academy as well and various others across the country – one at UC Davis, which has recently been filled by Jason Bond who works on mygalomorph spiders. So he’s actually made a huge difference for many people that are studying these different groups. Through his philanthropy, the whole field has benefitted hugely.

 

HS: What about the Bishop Museum? Was this where the collections were housed?

RG: Yes.  That’s where the collections are deposited. There were very few collections actually before I started my work there. Most of the collections were actually in Paris or in London, with a few in the Bishop Museum The main thing working with the people at the Bishop Museum was that I could have access to the materials that I needed for doing taxonomic work – all the vials, the alcohol. When I started working in Hawaii, I was very unfamiliar with the protocols for labeling and all the inks and everything that are needed and the whole deal about accessioning and everything. I worked very closely with people at the Bishop Museum, in particular David Preston, an outstanding entomologist who has since retired from the museum, and they were super helpful in every imaginable way. I also received funding from the Bishop Museum back in 1990, to study the adaptive radiation of the Hawaiian Tetragnatha.

 

HS: Could you also say a little about the help you received from “Haleakala National Park, Nature Conservancy of Hawaii, State Department of Land and Natural Resources, and Hawaii Natural Areas Reserve System”?

RG: The scientists at Haleakala National Park on Maui were crucial getting the work started. When I first arrived in Maui, I was there on my own. However, I met Lloyd Loope and Art Medeiros, both working at the National Park at the time, and learned so much from them. So I would frequently meet Lloyd in Pukalani (he lived in Makawao), and we would drive together to the Park Headquarters which was up at about 7000ft elevation on Haleakala. I would spend many days working there with Lloyd and Art, discussing ideas and learning about the natural history of Hawaii. I would also go into the field with Art, to some of the most magical forests on Maui – the bogs on the NE rift of Haleakala, Kipahulu Valley, and the dry forest of Auwahi, among many others. Importantly, from Art I learned a deep appreciation for the Hawaiian culture, and the “mana” or spiritual energy of the land.

None of the work would have happened without the Nature Conservancy of Hawaii (TNCH). The initial post-doc to work on happy-face spiders came about because Sam Gon took a position with the Nature Conservancy. However, it was Sam that knew the system, and where the spiders were. So when I arrived in the islands in 1987, he took me to the Nature Conservancy’s new Waikamoi Preserve (established in 1983), together with the Preserve manager, Rob Rydell. I selected a focal site for my work in the Preserve, and worked closely with Rob, and also Alan Holt, the Director of TNCH’s science program. over the course of my time on Maui. On Molokai, Ed Misaki, the Preserve Manager for the Kamakou Preserve, was at the time working out of his garden shed. He would let me take their vehicle to get up to the Preserve, and stay in their cabin. The Nature Conservancy also provided funds for my work in 1989, to study the natural history and systematics of the Hawaiian Tetragnatha.

With regards the State Department of Land and Natural Resources, I received funds in 1991 and 1992 from the DLNR’s Hawaii Natural Area Reserves System. Robert Lee was the person in charge at the time, and I worked closely with him in securing the funds that allowed me to survey the spiders in some of the Natural Area Reserves on the islands, notably Hono O Na Pali and Kuia on Kauai, Pahole and Mt Kaala on Oahu, and Puu O Umi, Puu Makaala, Laupahoehoe, Kipahoehoe, Kahaualea, and Manuka on the Big Island.

 

HS: Did this paper have a relatively easy ride through peer review? I’m asking because it was submitted in September and accepted fairly quickly, in November.

RG: Yes. I think in Science and Nature the turnaround is pretty quick. It’s either in or out. So yes, it was pretty quick, once it got in there.

 

HS: And was Science was the first place you submitted this to?

RG: Yes, it was. It wasn’t the second! No, it was the first place. Part of the motivation, I suppose, in actually submitting it there in the first place was, to me, that the whole system is tremendously exciting. It’s not just the spiders, it’s not just the repeated evolution. It’s the fact that you can use the Hawaiian Islands as a system to understand the dynamics of the evolutionary process. First, the isolation of the islands means that (before humans) there were very few colonists from outside the islands. As a result, those that reached the islands were often able to diversify into multiple species through adaptive radiation. Moreover, because the archipelago is a “hotspot”, the islands are arranged chronologically, with the oldest island of Kauai in the north west, the youngest island of Hawaii (the “Big Island”) in the south east. So each island effectively serves as a “slice in time”, with the Big Island representing the earliest stages in the evolutionary process, and the island of Kauai the oldest stage. Thus, it is possible to look across progressively older islands and see how evolution plays out over time. It’s an incredible system. And the spiders, they’re just one example of a radiation that had received almost zero attention up until that point,  and I just very badly wanted to get it recognized –  to get the Hawaiian Islands recognized as a system for looking at the evolutionary process, and get spiders recognized as an incredible group for illustrating how evolution plays out over that island chronology.

 

HS: Do you think that that has happened? After this paper, do you think people have recognized the value of the Hawaiian Islands system to examine how evolution plays out?

RG: Much more so, for sure. The funny thing is that so many people, up until that point, had said, “Oh, you work on happy-face spiders”. For whatever reason the Hawaiian happy-face spider appeals to people – deservedly so. But the name is appealing and people can kind of get why it’s called the happy-face spider, because of their colorful form that some of them have. I just thought that while the Hawaiian happy-face spider is cool for so many things, the system of the long-jawed spider – the Tetragnatha system – is amazingly cool. There’s so much more diversity and so much more going on really. And so I very much wanted to get people to recognize that there’s much more going on in Tetragnatha. And all of a sudden here you’ve got this paper that shows something that’s super interesting, that’s not the happy-face spider. I think the very first comment I got on the 2004 Science paper was when someone came in to my office and said, “I loved the picture of the happy-face spider on the cover of Science.”  It’s not a happy-face spider! The interesting thing there –  if you look – I don’t know if you’ve got that cover picture, I can send you that  – it’s a green spiny Tetragnatha, but it does have a color polymorphism that’s in some ways similar to the happy-face spider. And that color polymorphism means it probably evolved the same purpose as it did in the happy-face spider  – to kind of confuse predators. That’s what we’ve argued for happy-face spiders –  they have all these color morphs to confuse their  predators. Anyway, the point is simply that people tend to associate spiders in Hawaii with the happy-face spiders. This is fine, but I think that slowly, gradually, over the years, people have begun to recognize that there is a lot more going on in the islands. It just takes awhile for everyone to understand just how much the whole system has to offer and how much more still needs to be done. For example, Henrik Krehenwinkel, who worked as a post-doc with me for several years and is now [2020] an Assistant Professor at Trier University in Germany, has developed genomic tools to understand how whole communities of arthropods have evolved over this island sequence. The reason he was attracted to this system is because he understands what it has to offer, and he’s really taking it to a whole new level. He’s been looking at how diversity changes with the age of the community, as you go from the very youngest community to the older ones on the older islands. Many of my students are studying different components of the system. Natalie Graham, who has almost finished her PhD [2020], is asking how food web structure changes over evolutionary time; Jun Ying Lim, who is now [2020] at Nanyang Technological University in Singapore, is working with Henrik on arthropod community turnover across the island elevation gradient. And Andy Rominger, now [2020] an Assistant Professor at the University of Maine, is developing theory to explore how the ecological communities might be expected to evolve. We are also expanding the understanding of the how the communities evolve by looking at other island systems across the Pacific, work that is being led by former graduate student Susan Kennedy, who is working closely with Henrik [2020].

 

HS: The reason I asked if Science was the first place you submitted this to is because people usually seem to submit to Nature first. I’ve done a few interviews based on Science papers and in most instances, the paper was submitted to Science after it was rejected by Nature.

RG: Oh, interesting. No, I did not send it to Nature. Science was the first for whatever reason. I can’t remember why, but it might have been because I had a note in Nature a while before, back in ’92, on another Hawaiian spider, Doryonychus raptor, that has a very long claw and impales its prey directly from the air. Maybe I thought, “Well, I’ve already done Nature; I’ll do Science now!” I don’t know, I really can’t remember.

 

HS: Do remember how many rounds of review it went through?

RG: I can’t remember to be honest. No, I think it went through two… I’m pretty sure it went through two, because the first time reviews were very much sitting on the fence And then I wrote back to the editor – I suppose it was Andrew Sugden – and pointed out the merits of the study and he went along with it. So yes, it went out again.

 

HS: Did you have to make substantial changes?

RG: I don’t think so.  I think the changes were really more details. I think the story itself was solid. The data were solid. Although the sequence data was just mitochondrial, I also had allozyme data which told a similar story in terms of evolutionary relationships. And allozyme data provide fairly good nuclear markers that at least give you more confidence than mitochondrial DNA alone. I mean, given what was available at the time, the data were really not bad at all.  I mean if I did it now, of course, they’d say, “Oh, we want far more markers”, and allozymes went out with the dinosaurs! But it’s kind of silly that people abandoned allozymes, to be honest, because they were great markers and there was minimal fuss and bother. It was easy enough to just get them, and as long as you had enough of them they provided a pretty good indication of relationships.

 

HS: Do you remember how Science decided what to put on the cover then?

RG: You know when  my colleague came in and said that I had to get the cover, to be honest, I hadn’t even thought of the cover. That’s when I talked to David Liittschwager and then I asked Science whether they’d be interested in having a cover and they said yes. It was very straightforward. I mean, it’s a very good photograph. David is a professional photographer, and it just so happened that we’d spent a lot of time together. So yes, I think it was a fairly straightforward process. It was just me communicating with them and then sending the picture.

 

HS: Did the paper attract a lot of attention when it was published?

RG: It did, yes. I remember I did quite a few interviews at the time and I … yeah, I’m trying to remember, it’s quite a long time ago now…but yes I did quite a few interviews. Yeah one of them I think was actually picked up by some creation group..oh, that might have been the PNAS paper. Anyway, by and large there was quite a lot of attention on that for awhile, which was fun to see. And still, you know, the interesting thing is that the story has certainly borne out, and now we can start to look at things in much more detail as to exactly how this convergence happens. What we’re doing now is looking at the convergence from a genomic perspective. I have a student, Ellie Armstrong, currently [2020] a PhD student at Stanford, who has actually sequenced the genome for one of the Hawaiian spiders. So what we are trying to find out is exactly how you get the evolution of the different ecomorphs. On Maui, for example, we have the green the maroon and the little brown living together and they are each other’s closest relatives, but they show very different ecomorphs. And so with the genomic data, what we would like to do is be able to get a feel for exactly how evolution has happened – what switches have gone on and off to get the repeated evolution of the same ecomorphs, and how they diverge, one from the other. Now, we can hopefully get at that with this genomic data.

 

HS: What about within academia? Were these results spoken about a lot at that time and were they considered controversial?

RG: Yeah, so the big thing there was the finding of higher diversity on Maui, the second youngest island. The idea is that, as species accumulate, the diversity increases quickly (over evolutionary time), so as to give more species than expected for an island of that area at around 500k years. This idea still remains controversial. What’s quite cool is that as more people have looked at this, the more we are finding that actually it’s something that’s real, and that that other groups show the same kind of patterns. Not all of them; other groups of organisms show different patterns, but this phenomenon of very high diversity, this overshoot or whatever, can be modeled, as Losos and Gavrilets did in a paper in 2009. And as people look at it more, it seems like it’s fairly intuitive that you might get this kind of overshoot. There’s no reason to expect that organisms just reach some kind of magical number and then level off. For many groups, in particular those that that radiate prolifically, it seems that many of them show this pattern, where you get very high diversity early on and then it drops off. I did a book chapter actually with Bruce Baldwin, a botanist colleague here at Berkeley and who works in Hawaii as well -just to show how many different groups show this pattern of very high species diversity per unit area on islands that are relatively young, dropping off on older islands. That paper came out of symposium I attended that Jonathan Losos, again, organized with Bob Ricklefs at Harvard; I think it was in 2007. It was called The Theory of Island Biogeography Revisited, celebrating 40 years since the publication of MacArthur and Wilson’s seminal The Theory of Island Biogeography. Bruce and I wrote a paper that basically built on this idea of the high diversity fairly early on and then dropping down later, and just looking at that as a general pattern.

 

HS: And at the time the paper was published did you anticipate at all that it would have such a big impact on the field?

RG: Well, I suppose I hoped it would. I mean the biggest thing I hoped was that people would recognize that spiders in Hawaii went beyond happy-face spiders! But, in terms of the impact with regard to patterns of species diversity, and how they change over evolutionary time, I suppose, no, I hadn’t really… I focused on that in the 2004 Science paper and, as I say, that kind of pattern has been borne out, but in my own mind I just kind of wanted to draw attention to the radiation itself. And so yeah, to be frank, I suppose it was kind of a surprise that the idea of the diversity “overshoot” drew the attention that it did, which I think is really good because it highlights kind of the dynamic nature of species accumulation, which is really very important.

 

HS: Do you know what the paper mostly gets cited for ?

RG: I don’t know the answer to that; I’ll have to look. Now I’m starting to get intrigued so I can check that out.

 

HS: I was just wondering if you had a sense already; I will look it up myself.

RG: I’d be really intrigued to find this out myself.

 

HS: I’m looking at Figure 4 and I want to ask you: You talk about forest areas  – I wanted to ask you about whether these islands have changed a lot from the time you worked on them for this paper ?

RG: Yes. There are certain invasive species that have really done a number in many different habitats. Ginger is a plant that can pretty much takeover wet forest habitats in Hawaii and has invaded a lot of these places. It just kind of creates huge stands. The invasion of ginger has become much more severe since I started there. And other invasions have also taken off as well, with one big one being the Coqui frog which is from Puerto Rico. It’s a pretty little frog and it makes a characteristic call ‘Co-Qui’ –which is pleasant until you get it at the densities that you find on the Big Island. It loves the wet forest in Hawaii and reaches huge densities and seems to eat pretty much any of the native arthropods; and associated with that, the numbers of native arthropods are plummeting. So, to answer the question, –  yes, there are some very noticeable and very frightening impacts that you see currently. And you sometimes just feel totally desperate. And it’s not clear whether the work that we are doing is totally esoteric and whether we should just give up. At the same time, one of the people that I mentioned earlier  – Art Medeiros –  has been working on the dry forests  of Maui, in an area called Auwahi. He started work there not too long after I got to Hawaii. The dry forest is on the south slope of east Maui and it was in pretty good shape until kind of1930s-1940s when it declined precipitously as a result of cattle grazing, fire, and invasive species. So the Nature Conservancy, just before I got to Hawaii, fenced off an area just to try and protect some of the habitat, protect it from cattle grazing. And what happened was that the grass all grew up, and the ranch manager – the owner of the land  – said that he just couldn’t have this big patch of grass in the middle of his ranch. And so The Nature Conservancy just had to pull out because, at that point at least, they didn’t have funds to do management. They had funds to buy land, but they didn’t have funds for management. Art’s feeling was that the trees were still there; they were not actually dead yet, although they were pretty much dead. He said, “You know, we’ve got to do something”, and so he got the whole community galvanized and they fenced off an area so that the cattle couldn’t get in, and they then killed the grass. Then, in greenhouses that the ranch manager gave them, they planted some of the fast growing native shrubs and trees and then physically planted in these native shrubs and trees. And the forest is coming back now. I mean, it’s intense and endless work, but, if enough people do it, it can be done. You can now see these big swathes of forest, if you look on Google Earth, on the south slope of east Maui. You see kind of regular patches of forest, but these are patches that are fenced in. They are regenerated forest, but they’re native forest; you now start to get the native trees that haven’t been planted there; they are now growing up in that understory. So it’s incredibly exciting to see that. Interestingly, Paul Simon found out about this project, and gave the proceeds of one of his concerts to the Auwahi restoration project. I think that this project shows what is possible if we put our minds to it. The onslaught of invasives such as the Coqui frogs and the ginger and ants, etc, etc, make us think that conservation in Hawaii is simply not possible. But then you see what Art has achieved and you think, “Well, it’s not impossible”.

 

HS: Are the spider numbers going down as a result of the frog invasion?

RG: It’s really hard to know. Almost certainly, but the frogs, at the moment, are actually edging their way up. They’re still round about at 1800 to 2000 feet. I have a colleague Kerry Shaw, a professor at Cornell. Kerry emailed just a few days ago to say that she was just up in this area  -there’s a reserve there  – she said that the crickets that she works with are completely gone from that area, and it’s just over run with frogs. She was just desperately upset about the whole thing. Most of the spiders are just a little bit higher; it’s a different group that you tend to get lower down.  I haven’t been to where Kerry was myself, over the last few years, so I don’t where things stand.  I want to go there and look as well.

 

HS: When was the last time you were in the island?

RG: Oh, let’s see when was I there?  I suppose it’s been just over a year now, but I’m going back in November.  I have students going the whole time. So one, Ashley Adams, has just come back and we were talking this morning about all the work she’s doing. She’s trying to figure out how the spiders may use chemicals in recognizing each other, with changes in chemistry associated with species formation. The thing is, in this radiation you get, whatever, eight or more species that are all each other’s closest relatives and they are all living together in the same place, and so what she’s trying to figure out, given that they are nocturnal and their webs are pretty flimsy, how do they recognize each other? She’s looking at the cues they use to actually recognize their own species – pheromones carried on the silk, in particular, – that’s what she’s been focusing on . But she was out there with a bunch of undergraduate students from the department.

I have another student, Susan Kennedy, who is currently a post-doc at the Okinawa Institute of Science and Technology, who was doing isotope work. She’s looking at the niches of the spiders  -quantifying the niches  – and looking to see how their diet changes according to their species, and also for the communities of spiders, how the diets change with the age of the community. Another student, Darko Cotoras, has been using genomic tools to understand how populations became subdivided. And Henrik, of course, has been out there multiple times now. In particular, he’s been studying different elevation gradients, and looking at turnover across the gradients, as well as looking at changes over this temporal  sequence. So yes, it’s a lot of different projects going on there, and I go out there just whenever I can.

 

HS: This sort of leads into what I wanted to ask next, which is: what kind of an impact do you think this paper had on your career and also on the subsequent trajectory of your research?

RG: Well, at that point I was already at Berkeley, and that hasn’t really changed much. It hasn’t changed anything I’ve done; it’s just added some credibility to what I knew was going on there, and that it was actually very exciting. So I suppose that’s the biggest thing, for better or for worse, because there are a lot of problems with just getting a Science paper. you know. Is that any better than an Evolution paper? But somehow getting it into Science did give it that credibility that was fairly important at that time,  for people to say, “Oh yeah, this is actually a really cool system for understanding these kinds of processes”, and Hawaii isn’t just kind of this oddball place where these weird radiations pop-up. It can be used basically as a natural lab for understanding processes of diversification, looking at how diversification happens across time, using the different ages of the islands.

 

HS: At the time this paper was published, did you already know that this was going to be the major area of research in your career?

RG: Yes. I mean I’ve just really kind of kept doing what I see is important. I mean I love this. When I first saw the spiders in the forest of Maui, and recognized them as a radiation, I wanted to understand why they were so diverse and what their different ecological roles were. When I first found them I really knew that this is what I would want to do for a long time, but that was way back, you know, in 1987 or whenever, when I first found them.  So yes, I have known for a long time I suppose that this is what I wanted to do. The biggest shift was really changing from behavioral ecology to more evolutionary approaches, when I went to Hawaii. But I think having this background in behavioral ecology has been tremendously important because one of the most compelling aspects of the Hawaiian system is that it allows detailed understanding of ecology and behavior across the evolutionary time frame provided by the chronological arrangement of the islands. Basically, the system provides an avenue for integration across these fields. So I think it’s been really beneficial to have a background in behavioral ecology coming into the whole study.

 

HS: Today, 12 years after this paper was published, would you say that the main conclusions of this paper still hold true, more-or-less?

RG: Oh, absolutely. Absolutely.

 

HS: If you were to redo this study today, would you would you change anything? Would you do anything differently, given advances in technology, in theory and analytical techniques?

RG: No. Well, I’m basically redoing it with another group that does a very similar thing –Ariamnes spiders, which are stick spiders; really cool little animals. Of course, we would always like more data. What’s interesting for the Hawaiian spiders is that, as we accumulate more data, the story really hasn’t changed. So, yes, it would be great if I could have had more data, but actually, as far as we know, based on the massive amounts of data that we now have, that the story wouldn’t have changed whatever.

 

HS: What about the phylogeny? Has that changed in any way using new markers and new methods?

RG: The phylogenetic approaches have changed a lot. Traditional approaches were based on Sanger sequencing. This approach provides long, high-quality sequences but suffers from a number of limitations including the ability to sequence only a single locus per reaction. In contrast to Sanger sequencing, Next Generation Sequencing technologies provide vastly larger quantities of data much faster and for far less money. As a result, next-gen sequencing approaches have rapidly taken over. So, yes, the availability of data is really shifting things tremendously. But to tell that particular story, we didn’t need any more data than we showed in the 2004 Science paper.

 

HS: The phylogeny remains more-or-less the same?

RG: Yes.

 

HS: Have you discovered any new species since then?

RG: Well, yes, there have been many new species. Still most of the Tetragnatha are not described. We’ve only described probably less than half of them. Once journals started accepting papers without species names, I pretty much stopped doing descriptions, once I got these papers out. To be honest, I think that’s a bad idea, because then people like me just won’t ever describe the new species. And I think they really need names, they need formal descriptors. For from many of the Hawaiian spiders, I know what the entities are, and so I just need to describe them. But it takes time, and scientists get rather little credit for taxonomic papers, and so they go to the bottom of the pile, which is unfortunate I think.

 

HS: In the supplementary material you say you didn’t sample Tetragnatha mohihi because it hasn’t been found since the original collection in 1988. Have you found it since then?

RG: Yes. It seems to be doing fine, but it’s very localized. It’s just in one little place, and I know exactly where to go to get more of them. So it’s there and it’s doing fine at high-ish elevation. It seems to like areas that are somewhat dryer. There are just little pockets of habitat that are dry enough for that particular species

 

HS: Did you find it in Kauai, the island where it was originally collected?

RG: Kauai. Exactly.

 

HS: I wanted to ask you about specific sentences in the paper where you suggest what might be useful to do in the future and also what was unknown then. One of the things you say is about the youngest Hawaiian island. You say that on that island, “This distribution might suggest that, over time, these Hawaii Island populations would diverge in allopatry from conspecifics on Maui, with each ecomorph on Hawaii unchanged from its closest relative on Maui.”

Is there any evidence that this is happening, that there’s a divergence between the Hawaii island populations and the Maui population?

RG:  So what we find in all groups that we’ve looked at, where you get populations both on Maui and the Big Island, there are huge population genetic differences, certainly in these Tetragnatha but also in happy-face spiders and in Ariamnes – the stick spiders I was talking about. In the insects I’ve been looking at, there also seem to be huge genetic differences between populations. And it seems, by and large, that, even when you get the same species on the on two different islands, they are monophyletic – quite distinct –on each of the two islands. Some would argue that then they have got to be different species, but then you get into the semantics of what is a species.

 

HS: You hint at the importance of competition itself in structuring these communities. Is that something you’ve studied subsequently?

RG: Competition is super hard to get at, but what we can do is start to look at selection. We can start to look at selection when you have similar ecomorphs in sympatry versus allopatry. That’s what Darko Cotoras, while a student in my lab, looked at for his PhD. He was interested in the co-occurrence of ecologically equivalent species on East Maui, and showed that recent divergence of the same species (and same ecomorph) occurred in allopatry. He found that divergent populations of the same species can then interact when they subsequently come back together, which may provide the conditions necessary for ecological divergence and independent evolution of ecomorphs. So it does seem that competition is playing a role, or at least has been involved in leading to these differences. The next step now is to use genomic tools,and look at signatures of selection across the genome, and in particular see what regions of the genome are under selection.

 

HS: After this paper was published have you ever read it again?

RG: Ah! Yes, bits of it. Not the whole thing. And certainly know it inside out. Nothing much has changed about it, but I should read it again just to make sure.

 

HS: If you compare this  paper to those you write today, do you find any striking differences?

RG: Well, you know, I should go through and see that. I’m sure yes. Because for most things when I go through and start doing grant proposals and start working with text that I’ve written ages ago, I always see parts that should be changed! I read a section and think “That sounded horrible!” So yes, I think it’s inevitable that your style of writing changes at least a bit.

 

HS: Would you count this is a favorite among all the people you’ve written?

RG: Yes. Absolutely.  It was a lot of fun to write, it was a lot of fun to talk to people about, and it was just a lot of fun to do.

 

HS: What would you say to a student who is about to read this paper today? What should he or she take away from this paper written 12 years ago?

RG: The main message is still there: that you get repeated evolution of the same form. It’s not complete, but it’s very much a pattern. And actually we’re finding that in different groups as well. And which groups show repeated evolution of the same sets of ecomorphs and which don’t is really quite interesting in itself. So that’s one of the things. And then the other thing is that species accumulation is just a very dynamic process. It’s not just a steady accumulation of species over evolutionary time and then leveling off. Instead, there’s a lot more going on in the early stages of differentiation. At the moment we have a project where we’re looking at the super early stages of diversification on the Big Island, to try and see exactly how populations start to separate. This is the earliest stage in the process of adaptive radiation; the next stage is how species start to accumulate, as they do in particular on the intermediate aged island of Maui. The focus of the 2004 Science paper was that next stage, and the biggest thing was the finding of so many species of the same ecomorph on the island of Maui, with very few species on the Big Island (because the process is just starting) and on the older islands (where the number drops down to an equilibrium of one species per ecomorph). So I think the important message there is just that the process is a dynamic one. There’s a lot going on. In other lineages, you do get a steady accumulation, right up to the oldest island. This is what we showed in that paper that I was mentioning with Bruce Baldwin, that some lineages reach their highest diversity on the oldest island, though most of the groups that show the steady accumulation are small lineages and ones that don’t undergo very rapid radiation into taxa that come back together in a single place.

 

HS: In the last line of the paper you also talk about how “ecological and evolutionary processes of species buildup lead to fundamentally similar outcomes”, and therefore that “universal principles may underlie the process of community assembly”. Given all that we have learnt subsequent to your study, what would you have to say about this statement today?

RG: I think that is absolutely true. That, over ecological time scales it’s just what Dan Simberloff found in a paper that that he did with E.O. Wilson, when he was testing the idea of island biogeography using little mangrove islands. He showed that you get steady accumulation of species through immigration, and then some go extinct, and you end up with a community of species that actually fits together better than just a totally random assembly. And so what it seems like in the Hawaiian system, is that there is an analogous effect, though processes are operating much more slowly, because there is a much greater role for evolution and adaptation (as opposed to species arriving by immigration and just “slotting in”). But in terms of the assembly of the community, there’s nothing radically different between species accumulation over evolutionary or over ecological time. The same kinds of things are going on, in terms of the species coming together and the kinds of things that are dictating species diversity patterns at a site. It’s still the same factors that are governing changes in abundance and diversity. It’s just that the process takes place over a much longer time scale, because you’ve got much less immigration.