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.
- A Hierarchy of Niches in Puerto Rican Anoles - July 27, 2022
- Puerto Rican Anole Diet Samples Available to a Good Home - October 19, 2018
- Anoles Are Habitat Specialists at the Individual Level Too - January 16, 2017
Gianna Coppola
Hi! this is really interesting. I am not a scientist, but I think that perch curvature makes sense, and it seems like it would be a bit more accurate. I’m glad that no anoles need to be killed for diet samples, but it must be a bit tricky flushing the stomach of such a tiny lizard!
The graph you included is also interesting, and the data makes sense– ecomorph greatly determines a lizard’s perch choice. It looks like sex can determine an anole’s choice for perch height, which is also interesting. I’m surprised that body temp is influenced by species more than it is by the site.
This is an interesting study, and it is neat to see how different factors can determine an anole’s choice of perch, diet, etc.
Jerry Husak
Cool paper, Travis! I remember seeing you working on those enclosures that year – too bad that didn’t work out!
-Jerry