Category: New Research Page 49 of 67

Laura Rubio-Rocha, a masters student at UT Knoxville, presented an anole double-header at Saturday evening’s poster session.  In one poster, Laura presented work on thermal physiology of two anole species that occur in the United States: the native green anole (A. carolinensis) and the introduced brown anole (A. sagrei).  By sampling each species from a number of localities across a latitudinal transect extending from southern Florida to southern Georgia, Laura was able to test whether populations or species vary in their ability to tolerate cold temperatures.  To evaluate each species’ ability to tolerate cold temperatures, she used a simple behavioral assay that diagnosed the lower critical thermal minimum (CTmin) as the temperature at which a species no longer responded to physical stimuli.  Although anoles readily recover from this state in captivity, anoles in field aren’t likely to last long when incapacitated.

When CTMin was assessed in the field, Laura found that thermal tolerance largely mirrored the latitude of sampled populations.  Within each species, those that occurred further north were better able to cope with lower temperatures than population sampled further south.  A strong difference between the two species, with green anoles (A. carolinensis) being able to tolerate much colder temperatures than brown anoles (A. sagrei).  The story, however, doesn’t end here.

Recognizing that some degree of variation in a given individual’s cold tolerance might result from acclimation and plasticity, Laura conducted her analyses both in the field immediately after capture and after allowing the animals to acclimate to the conditions of a common garden laboratory environment for several months.  When Laura analyzed her laboratory data, she found that the strong difference in cold tolerance between species persisted, but the differences within populations of each species from localities across a latitudinal gradient were no longer evident.  Her results suggest that some degree of cold tolerance is genetically determined, but that variation within species along a latitudinal gradient is likely a plastic response.

A terrible photograph of Blair Hedges’ presentation (sorry, I was stuck in the back of the room).

Blair Hedges used his talk at WCH7 to present his exciting new results with Caribbean skinks.  You can read more about this work in the paper he published in Zootaxa earlier this year with Caitlin Conn (pdf link from Hedges webpage) and in Jonathan’s previous AA post on this paper. Using analyses of a dataset that includes four genes (three mitochondrial and one nuclear) from 136 individuals representing 14 of 16 genera, Hedges and Conn report discovery of dozens of previously unrecognized species and advocate recognition of 16 genera of skinks across the new world.  Unfortunately, many of the new species identified by Hedges and Conn seem to already be extinct, and Hedges showed some very compelling data to support the hypothesis that the decline of skink populations was a response to the arrival of the mongoose.

Sondra Vega reported the results of a fascinating study of diet in nine Puerto Rican anoles. Using isotope analysis from tail tissue, she concluded that all species are to some degree omnivorous, not terribly surprising in some sense because a number of species have already been reported to eat fruits and berries. What is surprising is that there seem to be two discrete groups, suggesting that some species are more omnivorous than others. In particular, some are more carnivorous (cooki, monensis, pulchellus, and stratulus) and others more omnivorous (cristatellus, cuvieri, evermanni, gundlachi and krugi).

Luke Mahler reported the amazing news (truth in advertising: I’m a co-author) that a large and very distinctive new anole has been discovered in the Dominican Republic. Here’s the abstract:

Discovery of a short-limbed giant Anolis from Hispaniola supports a deterministic model of island evolution and community assembly

We report the discovery of a species of giant anole from Hispaniola that provides new evidence for determinism in the evolution and assembly of Caribbean island Anolis faunas. The new species is most closely related to Hispaniolan ―crown-giant‖ ecomorph anoles (Anolis ricordii clade). However, it is ecomorphologically most similar to Cuban giant twig anoles of the Chamaeleolis clade: both are very large anoles with short limbs and a short tail that tend to utilize relatively narrow perches in cluttered habitats this discovery adds a new dimension to the phenomenon of among-island ecomorph matching that characterizes Greater Antillean anole faunas. In addition, phylogenetic comparative analyses suggest that key aspects of the similarity of Hispaniolan and Cuban giant twig anoles may be the product of evolutionary convergence. Being restricted to a narrow band of threatened mid-elevation forest near the border of the Dominican Republic and Haiti, this new species should be considered critically endangered.

Kat Wollenberg presented a very interesting analysis of geographic variation in Hispaniolan  A. cybotes, distinguishing effects due to environmental differences, microhabitat use, and genetic relatedness. One particularly novel approach was to compare elevational differences that occur independently in a number of different mountain ranges (the different mountain ranges are the red parts in Hispaniola above).

Here’s the abstract:

Diversification within adaptive radiations: the case of Hispaniolan trunk-ground anoles

The evolutionary processes that produce adaptive radiations are still enigmatic to date, as these are by definition recognized after the radiation has occurred, which makes it difficult to study them as an ongoing process. One way to connect pattern to process is to study the processes driving divergence today among populations of species that belong to an adaptive radiation, and compare the results to patterns observed on deeper level. In this paper, we tested whether evolution is a deterministic process with equal outcomes during different stages of the adaptive radiation of Anolis lizards. On the example of a clade of trunk-ground anoles, we inferred the adaptive basis of spatial variation among contemporary populations, and tested whether axes of phenotypic differentiation among them mirror known axes of diversification at deeper levels of the radiation. Although non-parallel change associated with genetic divergence explains the vast majority of geographic variation, we found phenotypic variation to be adaptive as confirmed by spatial convergence across the landscape, as well as genetically independent habitat-associated morphological variation. Morphological diversification of populations occurs recurrently along both tested axes of diversification previously identified in the anole radiation, but different sets of characters are affected.

Ray Huey and Luisa Otero in front of their poster

Anole Annals has previously had a number of posts on the exciting ongoing project in Puerto Rico examining climate change and thermal biology of anoles. Last night, Luisa Otero presented the results of one aspect of the project, examining the reproductive biology of Anolis cristatellus in a forest and an adjacent (i.e., across the street) open habitat. Previous work by Ray Huey (specifically, his dissertation research in the 1970s) showed that in the open in lowland Puerto Rico, crested anoles are able to thermoregulate and maintain a high and constant body temperature, but in the forest, where good sunspots are scarce, anoles don’t thermoregulate and have lower temperatures.

Luisa’s work confirmed that this pattern has not changed even as Puerto Rico has warmed in recent years–open habitats are still thermally preferable for crested anoles. The exciting new twist is that Luisa examined the reproductive rate of the lizards. Every month of the year, more female anoles are gravid in the open habitat, but this result is particularly striking in the winter, when reproduction slows down in the open, but seems to cease entirely in the forest. Hence, differences in thermal biology do appear to have strong effects on individual fitness and presumably population dynamics, and, at least for now, global warming has not changed the relative suitability of different habitats.

Two posters presented at last night’s session examined how anoles respond to predators. In one, Lisa Cantwell of the University of Tennessee conducted a laboratory study on A. sagrei in which she played different bird calls to see if they would respond differently to predators versus non-predators. And, indeed they do, as the graph on the left shows–compare in particular panels c and d, showing that the behavior exhibited depended on which bird call they heard. The next step in the research, now underway as Lisa’s doctoral research (this started as an undergrad project!), is to take this work into the field to study free-ranging anoles.

Anoles beware–this guy’s as bad as he looks.

The second project was also the result of undergraduate research, this time Chris Peterson, who presented research conducted at the La Selva Biological Research Station in Costa Rica as part of an OTS course. Chris and a colleague presented the ground dwelling Anolis humilis with either one spider, a prey species, or two spiders, both the prey and another spider that actually–horrors–eats anoles. They wanted to see whether they were less likely to attack the prey spider in the presence of the predatory one and whether the size of the prey influenced the decision to attack in the presence of the predator. Results seemed to confirm these predictions: the anoles were more likely to attack in the absence of the predator, and when they did attack, it was usually in the presence of a larger prey spider (when alone, size of the prey did not influence likelihood to go for it).

One final tangent–note that the title of this poster uses the generic name Norops. Rumors are swirling here in Vancouver that a new paper is about to appear and reignite the battle over anole nomenclature with a new proposal to split Anolis into multiple genera. Stay tuned!

It’s all there if you magnify the image!

In recent years, the Central American species A. cupreus has been split into six species. Jenny Gubler, working in Kirsten Nicholson’s lab at Central Michigan, presented a poster on the results of a genetic analysis of variation in this group. Examining mitochondrial DNA, she found support for the monophyly of the entire group and for existence of A. dariense, but that A. villai belongs within that species. Biogeographically, a clear separation is seen between those on the Pacific and Atlantic sides of the continental mountain range chains, and the clade is arrayed from north (basal) to south (highly nested), in support of previous work.

We’re now at the halfway point in the World Congress, and so far its been fabulous. As noted previously, most of the anole action is backloaded into the last two days, especially Monday, which explains in part the radio silence on AA thus far. The other reasons for the lack of reportage are that, first, the meeting has been non-stop, leaving little time for posting and, second, that many of AA’s contributors spent all yesterday afternoon in the inaugural meeting of the Anoline Lizard Specialist Group, discussing anole conservation issues, and thus missed a number of anole talks. We’ll hear more about ALGS later, and hopefully other WCH attendees will jump into the void and tell us what we missed yesterday.

Your intrepid correspondent did sneak out of the ALGS meeting to catch one talk yesterday. Joe-Felix Bienentreu of the Senckenberg Research Institute in Frankfurt reported on his studies of the A. pachypus species complex in Central America. In recent years, the group has been split into five species; Bienentreu focused on variation in pachypus itself, which occurs in Costa Rica and western Panama. Within this range, the species shows considerable variation in dewlap color, with some red, some yellow, and some containing both; in all, five groups were initially identified based on dewlap color. An examination of 40 scale and morphological characters for more than 200 specimens across this range led to grouping the first initial groups into two main groups. Genetic analysis with mitochondrial DNA is partially congruent with these groups, but shows some discrepancies.

The ribbon cutting for WCH7 in Vancouver is hours away, and it promises to be a grand occasion. The best and the brightest of herpetology will be there–a month ago, registration already topped 1600. Needless to say, the highlight of the meeting will be the talks and posters on anoles, 24 in all. In June, Emma Sherratt provided the list, but it’s worth re-posting, with the addition of one newly discovered talk (which didn’t use the words “anole” or “Anolis” in the title, and thus was missed). And, to whet your appetite, we provide links to previous AA posts on some of these talks. Don’t miss all the action, either live in Vancouver, or virtually here in AA‘s pages:

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