Anole Annals

Anolis onca basking. Photo by Gabriel Ugueto.

The ecological niche is one of the most controversial concepts in ecology with a long history of debate about its definition and scope. Some authors have suggested that this concept should be abandoned (see for example McInerny & Etienne, 2012a,b,c), while others, including me, consider that this controversial history, and a plethora of definitions, should not preclude its use. However, it needs to be explicitly defined to known exactly we are talking about.

The ecological niche is understood as the set of environmental factors that allow a local population to persist without immigration from others sources (Hutchinson 1959). Some evolutionary ecologists have envisioned the ecological niche as a phenotypic extension of a species and therefore subject to natural selection and other evolutionary process. Based on this, in my doctoral dissertation, I evaluated whether the ecological niche (or more precisely, the climatic niche), as a population-level trait, can promote species diversification in Anolis lizards. Although there are several studies linking organismal and species’ level traits with speciation, there are few exploring this association in Anolis lizards.

Our study exploring this was recently published in the Journal of Biogeography (Velasco et al. 2016). Explicitly, we adopt  Hutchinson’s niche definition using only coarse-grain variables (or the Grinnellian niche dimension; see Soberón 2007). To do this, we compiled an extensive occurrence database for 328 species with help of several colleagues. Using climatic layers from WorldClim database, we calculated a set of niche metrics for species and clades, including mean niche position (based on PCA analyses), niche breadth (based on Mahalanobis distances) and occupied niche space (as a proxy of climatic niche diversity).

We compared how climatic niche breadth and occupied niche space differ among regions (insular vs. mainland) and clades (Fig. 1 & 2). Mainland species and clades tend to exhibit larger niches than Caribbean clades and species (Fig. 1).

These differences were maintained after controlling for range size differences. We suggest that these differences are directly related to the available climatic space in each region. For instance,  Caribbean islands exhibit a limited climatic space in comparison with  mainland regions and therefore insular clades occupy all available climatic conditions in each island (Fig. 2). By contrast, mainland clades are more restricted to climatic conditions and therefore occupy only a portion of all available climatic conditions (Fig. 2).

We correlated these niche metrics with species diversification using a calibrated time tree. We found that anole clades occupying warmer and drier areas diversified more than clades occupying very humid and colder areas. In addition, anole clades with narrow niches tend to speciate more than clades with widespread niches (Fig. 3). Our findings suggest that climatic specialization has played a strong role in anole diversification with differences among insular and mainland settings.

It would be interesting to evaluate whether other traits (e.g., body size, geographical range size, or other Eltonian niche dimensions) also play a similar role on cladogenesis in Anolis lizards and evaluate their relative importance in diversification dynamics.

References

Hutchinson, G.E. (1957) Concluding remarks. Cold Spring Harbor Symposia on Quantitative Biology, 22, 415-427.

McInerny, G.J. & Etienne, R.S. (2012a) Ditch the niche ? is the niche a useful concept in ecology or species distribution modelling? J. Biogeogr., 39, 2096-2102.

McInerny, G.J. & Etienne, R.S. (2012b) Stitch the niche ? a practical philosophy and visual schematic for the niche concept. J. Biogeogr., 39, 2103-2111.

McInerny, G.J. & Etienne, R.S. (2012c) Pitch the niche ? taking responsibility for the concepts we use in ecology and species distribution modelling. J. Biogeogr, 39, 2112-2118.

Soberón, J. (2007) Grinnellian and Eltonian niches and geographic distributions of species. Ecology Letters, 10, 1115-1123.

Velasco, J. A., Martínez-Meyer, E., Flores-Villela, O., García A., Algar, A. C., Köhler, G. and Daza, J. M. (2016), Climatic niche attributes and diversification in Anolis lizards. J. Biogeogr., 43: 134-144. doi:10.1111/jbi.12627

As 2015 comes to an end, now is a good time to reflect on the year in Anole Annals. Fortunately, our good friends at WordPress have provided us with a nice summary.

For all the details on how things went down on Anole Annals in 2015, check out WordPress’s full report.

Recently, Jackson Weaver, Danielle Losos, and I spent two weeks researching both Anolis lineatus and Anolis bonairensis in the Netherland Antilles, specifically on the islands of Curacao and Bonaire. Working alongside Dr. Losos, Dr. Herrel, and Dr. Fabre, we observed the various activities of the lizards, filming them for periods of up to thirty minutes to analyze the behavioral characteristics of both species. Furthermore, we investigated the mystery of the asymmetrical dewlap of Anolis lineatus–why does one side of its dewlap exhibit a lighter shade than the other? This short video documents our research process and explores our intriguing results. We are currently in the process of writing papers on these subjects, and are releasing this video to give background knowledge on the topics of our studies.

We hope you enjoy this short film about our excursion!

That’s right, the sale you’ve putting waiting for on zazzle.com: 50% off calendars through Monday. That’s $11 per calendar. You can’t afford not to buy one…or two. Use the code SAVEAFTRXMAS.

While you’re shopping on zazzle, check out the Anole Annals store there. Everything’s on sale for at least 20% off, including the ecomorph line of watches, ties, playing cards and more.

At last we’ve found a place in the Caribbean that Anolis sagrei hasn’t invaded: Cuba! Because, of course, A. sagrei is native there, as well as 63 other species of anoles. In fact, there are no introduced anoles on Cuba, which is quite unusual. There are, however, a number of other herps that have invaded there, as a recent paper in Herpetological Conservation and Biology by Borroto-Páez discusses. Here’s the abstract:

The number of introductions and resulting established populations of amphibians and reptiles in Caribbean islands is alarming. Through an extensive review of information on Cuban herpetofauna, including protected area management plans, we present the first comprehensive inventory of introduced amphibians and reptiles in the Cuban archipelago. We classify species as Invasive, Established Non-invasive, Not Established, and Transported. We document the arrival of 26 species, five amphibians and 21 reptiles, in more than 35 different introduction events. Of the 26 species, we identify 11 species (42.3%), one amphibian and 10 reptiles, as established, with nine of them being invasive: Lithobates catesbeianus, Caiman crocodilus, Hemidactylus mabouia, H. angulatus, H. frenatus, Gonatodes albogularis, Sphaerodactylus argus, Gymnophthalmus underwoodi, and Indotyphlops braminus. We present the introduced range of each of the 26 species in the Cuban archipelago as well as the other Caribbean islands and document historical records, the population sources, dispersal pathways, introduction events, current status of distribution, and impacts. We compare the situation of introduced herpetofauna in Cuba with that in other Caribbean islands. We also document impacts, areas of missing information, and possible directions for future research. The paper contributes a systematic review as well as new knowledge for national and international agencies and databases. This information is critical for use in conservation, management, and eradication. Additionally, it alerts management authorities as to specific pathways of introduction for proactive action, which may be used to avoid potential introductions.

A typical PCA table that I trawled from the internet.

This post isn’t really very anole-specific, but because lots of studies of anoles use principal component analyses, I think it’s at least tangentially relevant.

PCA is a way of to reduce the variation in a data set to a few dimensions by constructing new variables that combine variables that are highly correlated with each other into a smaller number of variables called PC axes. I won’t go into the details of the method here, because Ambika Kamath explains all in a post she wrote on her blog a while back.

What I want to mention here is how we interpret these new statistical axes. Back in my day, computer programs spit out a matrix of numbers like the one above, which we called “loadings.” These values represented how strongly an individual’s value for each variable was correlated with the individual’s score on the new axes. So, for example, in the table above, values on PCA axis one correlate most strongly with an individual’s values for the top four variables (sodium, calcium, magnesium and chloride concentrations) and most weakly with melt percentage and some other variables.

Now, everyone uses the computer program R to conduct PCAs, and R, too, spits out “loadings.” But those are not your father’s loadings (or my loadings). Rather, those values are the coefficients of the new equation that defines the PCA axis (a PCA axis is a linear regression of all the variables). Thus, in the example above, individuals that scored high on PCA 1 would have the largest largest concentrations of the top four variables; an individuals melt percentage would have little impact on an individual’s score on PC I. Back in the day, we could also access those values, but we called them “coefficients.”

Does this really matter? Only to the extent that what much of the literature used to call “coefficients” is now called “loadings” and what used to be called “loadings” apparently isn’t routinely spit out by R. And, more importantly, most R users are completely unaware of the switcheroo.

Ambika did a very preliminary analysis to see whether the values of coefficients (new “loadings”) and correlations (old “loadings”) are very different. Her tentative conclusion is that they aren’t, so maybe this doesn’t matter much, but it might be worth looking into more.

Elsewhere on Anole Annals, Silas Ginn responsed to a question about what shape anole eggs have. I believe his response deserves a wider audience and so am putting it up here as its own post:

Indeed, anole eggs are long and skinny when they’re laid. But due to their leathery flexible skin, they can expand like a balloon and will grow with age and moisture. I’ve only got experience with Knight anoles, green anoles and probably four or five types of different brown anoles, but they’re all about the same – except that the Knight anoles HATCH at the same size as a green or brown anole.

As for hatchlings of green or browns, they’re so tiny it’s just remarkable! My old workplace was “infested” with a few species of geckoes (in Calgary Alberta, Canada – of all places!) and the baby geckoes popped up all over the place, especially in the filing cabinets where they obviously preferred to lay their eggs between pieces of paper, due to their being hidden & protected so well.

But yeah, at one point I brought in some house-plants – this was a huge ware-house complex where we ran an aquarium fish and reptile importer supplying Western Canada’s pet-shops, plus an outlet to the public, and a custom tank building shop in the back, quite a lot of space and amounting to more than 700 aquariums all told – and the whole place with 35-40ft ceilings and kept at upwards of 30-degrees Celcius all of the time, naturally humidity was such that it actually RAINED inside of the place on a regular basis – a problem in that it brought down the decades-old asbestos spray-on fire retardant insulation material from the ceilings – but we had some very nice sky-lights as well, if it had been kept up better it would’ve made a fantastic space well I mean really fantastic ’cause I loved it even WITH the dust and cockroaches ha-ha.

ANYWAY yeah I brought in some house-plants to liven the place up – should’ve left ’em when I moved on, ’cause they’ve all died since. There was a huge Munstera deliciosa “swiss-cheese plant” which I potted up on top of overhead wooden beams that had been there for decades, as some type of over-head system for a belt-driven power supply back when it was a SWEAT SHOP and then a SLAUGHTER HOUSE for chickens, yuck – we kept the beams for our water supply and oxygen for bagging fish, plus running heated/de-gassed tank-change water, and a master air-line gang-way for running hundreds of little valves off of for all of the little bubblers etc.

But yeah what I did with it MYSELF, was to support some house plants. And this one Munstera got HUGE – it sent out aerial roots, if you know Munstera you know the type I mean – but THESE ones got long enough that not only did they hang down the nine-ten feet to drink from a puddle on the ground beneath it (how did it know there was a puddle there?) which pooled on the polished concrete floor, from leaking tanks, over-spills from the automated tank over-flow water-change system (tanks were individual, and what looked like the typical system where everything’s on a loop, was simply a fill line from huge tanks in the back, run with big pumps only during water changes, and the over-flow went directly to the drains. Which were typically blocked up and one such drain which had been permanently blocked by our swimming-pool canister type “Sand-Filter” from our Koi pond system (several ponds ganged together on one filter) had a huge cray-fish living at the bottom of it, as though the building itself were a concrete island with a lake or ocean below it, and drain pipes more like tunnels carved by urchins or other such burrowing creatures … such was the ecosystem of the place!)

Anyway yeah, that Munstera plant threw out aerial roots that first reached the puddle on the floor, but then I began to wrap ’em around the wooden beams to keep ’em out of the way, and they kept growing down and down – once they’d got a taste of the mineral-rich water down at the bottom there was no stopping ’em! And I kept looping ’em over and over, they kept growing until this became a semi-daily task, where the roots would grow more than ten inches in one night! INSANE house-plants.

But the best of ’em all, was a 30ft Ficus tree. I had been keeping my Knight anoles in ficus trees from the very beginning, and they’d laid their eggs in the pot at the bottom, whereupon they hatched out better than any other time when I tried to incubate ’em artificially.

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Thanks once again to everyone who participated in our photo contest. We received over 200 photos! The results are in, and the winning photos have been assembled into the Anoles 2016 Calendar! The grand prize winner is the photo above, Anolis bahorucoensis, taken by Carlos De Soto. In second place is the photo below, Anolis cristatellus, taken by JP Zegarra.

You can view the rest of the winning photos in the 2016 calendar here! Congratulations to all the winners!

In addition, because we had so many incredible photos, we have created an extra calendar: Obscure Anoles 2016! This calendar features some of the best photos of less common or rarely seen species and behaviors. We hope you enjoy!

Happy holidays, and we wish you all the best in the coming anole-filled year of 2016!

I’ve just returned from a trip to Martinique collecting data for a project I’m working on. In the process of collecting data and animals to bring back for work in the lab, I was able to travel all over to see Anolis roquet across the island, and photograph the different ecotypes/subspecies and their habitats. I was extremely impressed with how variable the island and the Anolis were, and I thought I’d share some of those images with everyone here.

As a bit of background, Martinique is formed from five separate geological regions that each were represented historically as their own precursor islands that joined together to form the current island (Thorpe et al. 2008). As a result of this process, A. roquet on the island is represented by four modal haplotype lineages, with their distribution strongly correlating with the boundaries of those geological regions, except for one modal haplotype lineage being shared between two (Thorpe et al. 2003). Anolis roquet lives across the island in a wide range of habitat types. Their occurrence in disparate habitat types has yielded a number of ecotypes with highly variable coloration and patterning (Thorpe et al. 2012). This variation was significant enough that six subspecies of A. roquet were described by Lazell (1972), all of which are pictured below.

While in Martinique, we were staying in an area called Gros-Morne, which is in the north-central part of the island. This area is part of the central geologic region and the Anolis in this area are from the mesic/transitional ecotype, which is the most widespread form and is what has been considered to be the nominate subspecies, Anolis roquet roquet. This particular portion of the central geological region, however is toward the montane area, so here the animals are more toward that end of the spectrum than the xeric form. Here are a couple photos of animals from this area, as well as a couple shots of the garden and area they were collected:

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