Author: Travis Ingram

I mostly study freshwater fish ecology and evolution in New Zealand, but I spent two years as a postdoc in the Losos lab looking at the niches of Puerto Rican anoles and working on comparative methods for studying convergence.

A Hierarchy of Niches in Puerto Rican Anoles

By Travis Ingram

On July 27, 2022

In All Posts

Anolis cristatellus

I can’t call myself a herpetologist, let alone an anologist, these days – now I mostly work on freshwater fish in Aotearoa/New Zealand, though I have dabbled in collaborations on native NZ geckos and skinks. Nonetheless, I was pleased to recently publish a paper on Puerto Rican anoles that was a decade in the making.

My one proper field season with anoles was back in 2012 when I was a postdoc with Jonathan Losos. I tried some experimental enclosures that didn’t ultimately work out, and took some pictures that contributed to a macroevolutionary study of dewlap size. In between these projects, I decided to pull together a dataset of several niche dimensions in the anole community around the El Verde Field Station. My undergraduate assistant Tanner and I collected data from 200 anoles of six species (Anolis pulchellus, A. krugi, A. cristatellus, A. gundlachi, A. stratulus, A. evermanni) in three ecomorph classes, with the idea to measure how niches were partitioned among ecomorphs, species, and sexes. We measured the usual perch characteristics and body temperature, and also collected diet samples non-lethally using gastric lavage (stomach flushing).

Nothing much happened for some time, as I had moved on to a second postdoc and then my current job at the University of Otago. A few years ago when Jonathan was clearing out his former lab, I put out a call for interest in the stomach samples that were still sitting in a drawer, and was lucky enough to spark Sean Giery’s interest in a collaboration. Sean, now at Penn State, has plenty of experience counting terrestrial invertebrate samples, and he made quick work of processing the stomach contents.

Now that the data set was complete, I just had to find some time to revisit it. Last summer I had study leave on Rēkohu/Chatham Island, and made use of the down time between fieldwork days to get the analysis done and written up. We used hierarchical analyses to estimate how much of the variation in perch characteristics*, body temperature, prey size, and prey composition was partitioned among ecomorphs, species, and sexes.

*I used perch curvature rather than diameter as the second measure, along with perch height. Curvature is just the reciprocal of the radius, assuming a cylinder, but it allows missing data (anoles perched on walls or the ground, for which a measure of diameter is meaningless) to be included assuming that these have effectively zero curvature. It made sense to me, but I’d be interested to hear if other practitioners find this intuitive or not.

Percentage of variation explained by ecomorph, species, sex, site, individual (far right columns only) and residual variation in each niche dimension

The results aren’t going to blow your mind, and they confirm a lot of what is already understood about Greater Antillean anole communities. As expected based on decades of previous work, variation among ecomorphs explained the largest share of perch height and curvature, and variation among species nested within ecomorphs explained by far the most variation in body temperature. Perhaps the more surprising results were that ecological sex dimorphism explained little of the variation in any niche dimension, and that a large fraction of most dimensions was unexplained.

My feeling is that this approach to measuring multidimensional niche diversity in communities is more interesting than any particular result of this study. An idea I quite like is using this hierarchical approach for a comparative study of different communities. For example, one could ask how the partitioning of variation at each level changes over time as communities assemble, or how it changes across some natural or anthropogenic gradient. There is also room to do analyses that properly incorporate variation among individuals – we did include individual diet variation in a version of the analyses (using multiple items in one stomach as replicates), but the same individuals should be sampled repeatedly over time to see how consistent their foraging patterns really are.

All in all it has been fun thinking about anoles again after a long break. Our paper is available to read for free in the Journal of Zoology.

Puerto Rican Anole Diet Samples Available to a Good Home

By Travis Ingram

On October 19, 2018

In All Posts

Anolis evermanni on the boulders in the stream at the El Verde Field Station. Photo by Jonathan Losos

My former postdoc advisor and AA co-founder Jonathan Losos recently reminded me that I left some unused samples in a drawer in the lab that he has now moved out of.

In 2012, I spent some time in Puerto Rico, collecting niche data for six anole species (A. cristatellus, A. evermanni, A. gundlachi, A. krugi, A. pulchellus and A. stratulus) among other things. I collected some samples for stomach content and stable isotope analysis that I never got around to processing before I moved on to the next postdoc. As I’m now based in New Zealand and back to working on fish, it’s not worth the complications of importing samples that I don’t have immediate plans to use.

Anolis gundlachi. Photo by Travis Ingram.

At Jonathan’s suggestion, I am making the samples available to any anologists who can give them a good home. The data are unlikely to lead to anything groundbreaking, but could make for a nice integrated study of niche partitioning and could be a good student project for someone.

The samples contain:

• Stomach contents from at least 30 anoles of each of the six species, obtained via gastric lavage and stored in ethanol in eppendorf tubes.
• Tail tips taken for stable isotope analysis, dried and stored in eppendorf tubes.
• Dried tissue samples from herbivorous (katydids x 10) and detritivorous (land snails x 10) invertebrates to use as isotopic baselines.
• Additional pieces of the same tail tips, stored in ethanol in Eppendorf tubes, which could be used for genetics if needed.

The samples should still be in good shape, though they’ve spent the last six years boxed up in a drawer. All the anoles were released live, so I don’t have specimens. However, for each individual I have recorded:

• collection date, GPS location and elevation
• environmental temperature
• body (cloacal) temperature
• perch height and diameter
• body orientation and position in sun vs shade
• sex and SVL

The idea behind collecting these data was to quantify how much of the variation in different niche dimensions was attributable to differences between ecomorphs (trunk-crown, trunk-ground and grass-bush), between species (two species per ecomorph), and between sexes. I would be happy to donate the samples to someone who can make good use of them, or to collaborate with someone who would like to follow up on this small project idea.

If you are interested in taking over the samples, please get in touch with me in the next couple of weeks (after that they will likely be disposed of).

Travis (email)

Anoles Are Habitat Specialists at the Individual Level Too

By Travis Ingram

On January 16, 2017

In New Research

Anoles are probably best known for the ecomorph story: the presence of specialized species adapted to the same sets of structural microhabitats on different islands. Anoles in the Greater Antilles have contributed hugely to our understanding of both the evolutionary history and the contemporary ecology of communities of specialists.

While they are better known for specialization of species in communities, anoles have also contributed to our understanding of within-species ecological diversity. Around the same time that Ernest Williams was developing the ecomorph concept, Roughgarden (1972) used data from Lesser Antillean anoles to introduce a new framework for investigating the extent to which a population’s niche width (i.e. the diversity of habitats it uses or prey it eats) is determined by variation among individuals versus variation within individuals. For example, individuals in a population of Anolis roquet differ in the size of prey they consume, mainly because larger individuals can catch and ingest larger prey items. While Roughgarden’s early work set the stage for an explosion of studies of individual specialization over the past decade or two (reviewed in Araújo et al. 2011), surprisingly little work has been done to revisit individual specialization within species of anoles. In particular, we don’t know enough about how much individuals specialize in important aspects of microhabitat that differentiate ecomorphs, especially perch height and perch diameter.

“Gar” lived alone on my desk, so I don’t know if he was an individual specialist or not

Anole Annals contributors Ambika Kamath and Jonathan Losos have helped to fill this gap with a study just published online in Evolution. Ambika and her team spent a summer observing microhabitat use of a population of brown anoles (Anolis sagrei) in a forested park in Gainesville FL. They marked lizards with colored beads, and repeatedly recorded individual lizards’ perch height and diameter, compiling a total of over 1000 observations of 80 anoles. They grouped perch heights and perch diameters into classes, then compared the distribution used by each individual to the distribution used by the whole population (or to the distribution available to that individual) using a proportional similarity index. The mean value of this index gives a measure of the overall degree of individual specialization in a population, as lower overlap values tell us that individuals are specializing on a subset of the available perches.

Another Call For Anole Dewlap Photos

By Travis Ingram

On August 23, 2013

In All Posts

Dear readers of Anole Annals,

Last year, I posted here requesting photos of extended dewlaps of adult male anoles of any species, for use in a study of the relationship between dewlap size and speciation rate. I thank all the readers who sent in one or a few photos, as well as the prolific photographers who have contributed many more. I even chipped in a few of my own photos last summer in Puerto Rico:

Thanks to everyone’s contributions, I’m up to around 185 species, even better than I’d hoped for. Before I start the analyses, I wanted to put out another call for photos, to see if anyone who missed the first post can help to fill in some of the species that are still missing from the collection.

Did the Adaptive Radiation of Anoles Happen in Stages?

By Travis Ingram

On March 7, 2013

In New Research

Do events unfold in a predictable sequence when organisms undergo adaptive radiation? Anoles have diversified in many ecologically important characteristics as they have radiated both in the Caribbean and on the mainland. As one of our best-understood cases of extraordinary evolutionary diversification, they make a great system in which to ask how ecological diversity builds up during adaptive radiation.

The idea that anoles radiated in stages dates to at least 1972, when Ernest Williams derived some hypotheses from his observations of Puerto Rican Anolis in particular, drawing upon earlier work by Stanley Rand and Rodolfo Ruibal. Williams noticed that the most closely related species on Puerto Rico tend to belong to the same ecomorph class and occupy similar structural habitats (e.g. branches, trunks or twigs), but occur in different thermal habitats (e.g. closed forests or hot open areas). He proposed that anoles on Puerto Rico diversified first in structural habitat, and later in thermal habitat, a pattern that might scale up to the entire adaptive radiation of Anolis. While this idea has been discussed many times, and helped to inspire more general hypotheses about stages of radiation (e.g. Streelman and Danly 2003), until now it had not been tested using modern analytic techniques that incorporate phylogenetic information for many species.

Figure 11 from Williams (1972), modified to show only the 8 species in the main Puerto Rico radiation.

Parasites Regained

By Travis Ingram

On July 16, 2012

In Natural History Observations

A few weeks ago, we collected the common grass-bush anole Anolis pulchellus around the El Verde Field Station for an enclosure experiment looking at interspecific interactions. We stored the lizards in baggies in the lab for a day or two, moved them to their enclosures for just under three weeks, and we’ve recently finished recapturing them from the enclosures. After measuring their growth and sampling their diets, we put them back where we found them so they could continue on their way with a great story to tell their friends.

One unlucky anole, however, never made it to its enclosure. When I retrieved its bag to take to the experiment site I found the following tragic scene:

Enclosing Anoles In Puerto Rico

By Travis Ingram

On May 28, 2012

In New Research, Notes from the Field

I’ve recently arrived at El Verde Field Station in Puerto Rico for my first real field season working with anoles. My main goal is to carry out enclosure experiments looking at the different components (resource competition and predation) of the interactions between anole species. I’ll post more about the research later, but for now I want to give a rundown of the enclosures I’ll be using.

Crowdsourcing Anole Dewlap Photos

By Travis Ingram

On March 11, 2012

In All Posts, New Research

I come to you, anologists of the world, with a request for your photos of anole dewlaps. I’m planning a study of dewlap size evolution across the Anolis phylogeny, but there’s not much data available for many of the less common species. I know many anole-hunters take pictures of their quarry with dewlaps extended after catching them, so I thought I’d try to extract data (e.g. dewlap length and area) from a collection of photos. If you have photos you might be able to share, please read on, and feel free to contact me if you have questions.

Requirements:

-The photo should show a live, adult male caught in the wild. Its dewlap should be fully extended – ideally either of its own volition or with tweezers, but fingers are ok as long as at least 90% of the dewlap area is visible.

-The anole’s entire head should be in the photo (so I can scale dewlap size relative to head size). If there’s a ruler or object of known length in the photo that’s even better.

-The photo should be close to a side-view profile (give or take no more than about 10 degrees angle in any direction).

-At a minimum, identify the species and the approximate location (country or island). Please do include any extra information you can share (e.g. date, latitude/longitude/altitude, snout-vent length of anole, weather…), but I know this may not be available for all the photos.

Clearly I’m new to this – any photo better than this one should be useable.
Check out the comments section of this post for some better examples.

If you have one or more suitable photos you can contribute, please send them to me as an attachment to an e-mail. If you have large files or many photos (more than ~5MB) that may not make it through e-mail servers, drop me a line and I’ll send you a link to a Dropbox folder instead. If you are willing to give permission to use the photo (with full credit, of course) in potential blog posts, web pages (e.g. Encyclopedia of Life entries), or publications, please say so in the e-mail; otherwise I will only use the photos to extract basic measurements.

Thinking about Speciation in Hungary

By Travis Ingram

On September 3, 2011

In Research Methods

I just finished attending a workshop in Kesthely, Hungary on Niche evolution and speciation – two of my favorite topics. Sadly there was no Anolis news to report from any of the excellent talks, but the work I presented is related to one of the anole projects I’m planning for my postdoc.

Speciational evolution is, as the name implies, evolutionary change that occurs rapidly when one species is being split into two; this means the amount of evolution in a lineage should depend on the number of times speciation has happened in its history. This contrasts with the standard Brownian motion model of gradual evolution where the amount of evolution depends on the length of time that has passed.

Speciational evolution might occur for a number of reasons (for example, due to genetic drift in small geographically isolated populations), but when one trait shows speciational evolution and another does not, we may be able to infer something about the process of speciation. For example, speciation may involve divergence in habitat (the ‘beta-niche’), or in traits that affect local resource use within a habitat (the ‘alpha-niche’).

First Post by an Aspiring Anologist

By Travis Ingram

On June 1, 2011

In Notes from the Field

I’m writing this en route back to Vancouver, after getting my first taste of anole fieldwork in the Bahamas the last few weeks. This summer I’ll be finishing my PhD thesis at UBC on the evolution of food web structure in marine and freshwater fish (see here for my previous research). For my post-doc, I’ll be working with Jonathan Losos at Harvard, asking some related questions using anoles as a study organism.

To get to know the system, I’ve been working with Jonathan, Rob Pringle, and others, helping to set up a terrific experiment around Staniel Cay in the Exumas (see Jonathan’s post for details). It’s been my first foray into anole ecology, and really to terrestrial ecology in any habitat. It was slow going at first, but I learned a few food web sampling techniques, and rapidly improved my ability to spot anoles in the vegetation on small islands. I spent most days helping to spray paint Anolis sagrei to estimate population sizes on the islands.