Category: New Research Page 19 of 66

Anolis sagrei - male and female

Effect of perch treatment on (A) latency to reproduce and (B) yolk corticosterone.

Competition for perches has been an important factor in the diversification of anoles. Yet, we know little about the influence of perch availability on reproduction. To address this, Dan Warner, Matt Lovern, and I housed male / female pairs of brown anoles (Anolis sagrei) in treatments with either high- or low-availability of perches (Fig. 1).

We found that females reduced how often they used perches when perches were limited. More interestingly, though, when perches were limited, females tended to take longer to begin laying eggs (for the first time in a season; p = 0.063, Fig. 2A) and allocated more corticosterone to egg yolk (p = 0.069, Fig. 2B), although these findings were not statistically significant.

Figure 2. Effect of perch treatment on (A) latency to reproduce and (B) yolk corticosterone.

In many habitats in which brown anoles occur, organic perches are abundant and not likely to be limited. However, in urban areas or on some islands anoles have colonized, perches can be limited. Our study suggests that such habitats may have consequences for reproduction.

Citation for the full paper:

Delaney, DM, MB Lovern, and DA Warner. 2016. Does reduced perch availability affect reproduction in the brown anole? An experimental test in the laboratory. Journal of Herpetology 50:227-232.

JMIH 2016: Variation in Limb Length across Lizard Groups

By Kristin Winchell

On July 11, 2016

In New Research

Travis Hagey presented some new results from his ongoing research on the evolution of functional traits in lizards. Travis normally works on geckos, but frequently includes Anolis species in his studies. Last year at Evolution, Travis told us about toepad evolution by comparing gecko toepads to those of anoles and skinks. Along the same vein, this year at JMIH Travis talked about patterns of limb-length across different lizard groups.

Travis started with anoles as an example of morphology being correlated with habitat use. As we all know, anole limb length is associated with structural habitat. Lizards like Anolis occultus (a twig anole) use thin perches and have very short legs. Other species that perch on broader substrates tend to have longer legs. Travis is interested in finding out if this pattern holds for other groups of lizards.

He started by comparing anoles to geckos to see if relative limb length differed between the groups. He accumulated an impressive database of hindlimb lengths from many gecko and anole species and when he looked at the relationship between hindlimb length and body size (SVL), he found that for a given body size anoles tended to have longer limbs than equivalently sized geckos. He then added in data for a number of species from Liolaemus, Tropidurus, and Phrynosomatidae. Interestingly, he found that these other groups all clustered with the anoles. This suggests that there are possibly two relationships between limb-length and body size across lizards.

Travis ended by commenting on how this might relate to habitat use. He analyzed hindlimb length by perch diameter for anoles (red line) and geckos (black line). Geckos, it turns out, have a different relationship between perch use and limb length than anoles: geckos with shorter limbs tend to use broader diameter perches! Travis is still working on this research and is looking for data on limb length for many groups. If you have hindlimb length data from lizards you should email Travis to help out!

JMIH 2016: Escaping in the City

By Kristin Winchell

On July 10, 2016

In New Research

Kevin Aviles-Rodriguez, from the Revell lab at U. Mass. Boston, gave the second urban anole-themed talk of the meeting. Kevin presented his Master’s thesis work that he conducted with the Kolbe lab at U. Rhode Island in a talk titled, “Structural habitat alterations caused by urbanization influence escape behavior of a common lizard.”

Urban habitats are drastically modified and present novel resources and threats for animals that persist and utilize these spaces. Structurally, urban habitats have different types of surfaces that are smoother, broader in diameter, and often more vertically oriented (90° angle). Urban habitats also present abundant and novel food resources in terms of human food and insects attracted to lights and garbage. But with the abundance of food and novel niche space also comes an abundance of novel predators such as cats and dogs kept as pets.

Kevin wanted to know how Anolis cristatellus from San Juan, Puerto Rico and South Miami behaved in urban habitats compared to forest habitats when perceiving a predation threat. Although there are obvious costs of not escaping a predator successfully, there are also costs of fleeing when not necessary in terms of lost feeding opportunities and disrupted social interactions (mating, territory defense). Kevin wanted to know if the urban environment influenced escape behavior decisions. Specifically, he had two objectives: (1) To quantify escape behavior (squirreling, jumping, or sprinting) and how this relates to different types of perches found in urban areas. (2) To measure flight-initiation distance (FID), or how close one can approach an animal before it flees, to see if there are differences between forest lizards and urban lizards.

Kevin found that as perch diameter increases, the probability that a lizard will squirrel around a perch or sprint up the perch increased and the probability of jumping decreased. Interestingly, when he also looked at perch use, he found that the majority of lizards were using perches of thinner diameter where the probability of jumping was highest. Urban lizards also tended to use more isolated perches, which he defined as the number of nearby potential perches within 1 meter. When nearby perch density was lower, lizards tended to jump less – perhaps not all that surprising since they have fewer places to jump to. Kevin also found that escape strategy differed based on the type of perch used. In urban habitats, on trees and on metal posts lizards squirreled more frequently than they did in forest habitats. Interestingly, on cement walls (e.g. buildings) lizards did not jump at all and mainly sprinted to escape. Kevin offered a few possible explanations for this trend. For one, building perches tend to be more isolated than trees and so it may simply be that lizards on these substrates have nowhere to jump to. A second possibility is that the lizards have trouble jumping from these perches since they are more vertical than the optimal angle for jumping (39-42°, Toro et al. 2003).

In his final analysis, Kevin found that flight initiation distance (how close you can get to the animal before it flees) was very short for animals perched on urban trees and metal posts. In fact, he commented that on some occasions he was able to get close enough to touch the lizard before it fled! This difference was significantly shorter than for animals perched on trees in the forest and for animals perched on painted concrete walls in the city.

JMIH 2016: Anolis conspersus Color variation and Habitat Use

By Kristin Winchell

On July 10, 2016

In New Research

Bright and early this morning, Christopher Peterson kicked off the anole talks of the day on the topic “Intraspecific color and habitat use variation in Anolis conspersus.” Christopher noted that on Grand Cayman there appear to be three color morphs for A. conspersus: brown, blue, and green and asked if color morph was correlated with habitat use. Christopher captured 309 lizards across the island, photographed them for color analysis, and took a large number of habitat measurements plus basic morphology of the lizards (mass, SVL). When analyzing the color data, however, he noticed that the picture was not so clear: many of the lizards had both blue and green coloration. Since these were not discrete groups, instead he analyzed body pattern, which appeared to be more discrete and showed the same geographical variation. In general, lizards on the East of the island were brown and spotted while the lizards on the West of the island were green/blue with vermiculated pattern.

Using a complex logistic regression, Christopher analyzed the discretized character state with his habitat and morphological measurements. Disappointingly, he found no associations between morphology or habitat use with body patterns. He concluded that the variation in pattern and coloration is probably best explained by geographic location alone and that future genetic analyses may help clear up if this is a geographical cline with isolation by distance.

JMIH 2016: Phylogeography and Population structure of Anolis cristatellus

By Kristin Winchell

On July 9, 2016

In New Research

Quynh Quach presenting her Master’s thesis work at JMIH.

Quynh Quach, a master’s student from the Revell Lab at U. Mass. Boston, presented her thesis research on “Phylogeography and Population Structure of Anolis cristatellus on the island of Vieques.” Before Quynh joined the Revell lab, former post-doc Graham Reynolds and former Losos lab undergraduate Tanner Strickland looked at the phylogeography of Anolis cristatellus across Puerto Rico and the Virgin Islands using mitochondrial DNA (in review). Tanner’s work revealed that there was a mitochondrial break on the island of Vieques, just off the coast of Puerto Rico. The mitochondrial data suggested that there were two genetically different groups of A. cristatellus, one on the East and one on the West of Vieques. The only problem was, as we know, mtDNA patterns are not always supported by nuclear whole-genome DNA patterns. In addition, Tanner’s dataset only consisted of 9 samples from Vieques.

When Quynh joined the lab, she wanted to know more about this pattern. Would this division be supported by nuclear genome analyses? Were these lineages anthropogenically introduced? If not, what was the origin of these groups – historical allopatry followed by secondary contact or isolation by distance? So she set out to answer these questions by collecting 300 tail tips from across the island of Vieques, extracting and sequencing both mtDNA and nuclear DNA.

The mtDNA variation shows a strong geographic pattern.

Quynh first constructed a mitochondrial phylogeny to verify the pattern observed by Tanner and Graham. The mtDNA analysis confirmed that there are 2 mtDNA clades on Vieques with strong geographic patterns. The island-wide pattern of mtDNA variation was not what we would expect if anthropogenic introduction were the cause since this would be unlikely to show such a clear East-West pattern with the small contact zone in the middle. So then how did this pattern arise?

Analysis with K=2 shows two clear groups associated with the East and West.

To answer that question, Quynh next looked at nuclear DNA using RADseq. She sequenced 48 individuals: 5 from Virgin Islands, 6 from Puerto Rico, and 37 from Vieques, then de novo assembled the genome and called 16,808 SNP’s. She ran STRUCTURE and DAPC analyses on this data and found that the Virgin Island samples form 1 cluster and Puerto Rico and Vieques form a second cluster with 4.1% divergence between the groups. But she wondered, what if we look at just Vieques and specify K=2? When she did this with DAPC and saw a clear geographic pattern similar to what she found with the mtDNA. Finally, she tested whether this represented isolation by distance. She found that there was significantly reduced gene flow between geographically distant individuals, supporting this hypothesis as the most likely cause of the variation.

Lastly, Quynh emphasized that it is important to consider multiple genetic markers and not just rely on mtDNA results. Had the group stopped at their original mitochondrial analysis, they would have reached a very different conclusion.

Australian Cryptoblepharus: Convergence across a Continent

By Mozes Blom

On July 3, 2016

In New Research

When it comes to adaptive radiations, the diversification of Anolis is one of the most striking examples. While Anolis is therefore a well-known rock stars in the league of adaptive radiations, in this blog post I would like to introduce you to one of the mere mortal examples; skinks from the genus Cryptoblepharus.

Cryptoblepharus skinks (“Cryptos”) are small diurnal lizards that have rapidly diversified and are known for their widespread distribution with species present in the Malagasy region, on the Australian continent and on many island archipelagoes in the Indo- and wider Pacific. Furthermore, species that occur on similar substrates are notoriously difficult to identify based on morphological characteristics and a more accurate estimate of species diversity has only recently been accomplished using a widespread genetic screen with allozyme markers (Horner & Adams, 2007).

Distribution of Australian Cryptoblepharus and the three habitat specialists. (a) Topographic map of Australia with the mean point of each species’
distribution plotted and coloured according to habitat type (for complete distribution maps, see Horner & Adams (2007)). In situ photographs of (b) arboreal, (c) littoral, and
(d) rock specialists (green, blue, and red dots on the topographic map, respectively).

Whereas species within the same habitat are highly cryptic, species that occur on different substrates (‘rock’, ‘trees’ or ‘beaches’) are relatively easy to distinguish. Rock Cryptos for example, traverse the red sandstone escarpments that are iconic for the Australian outback (think ‘Uluru like’ in terms of color and rock type) and they look very different from Cryptos that occur in a more mesic or coastal habitat. In a recent paper (Blom et al., 2016) we focused on the Australian radiation and explored whether habitat specialization explains current patterns of phenotypic variation in ecologically relevant traits. Using a comparative approach, we quantified the presence of distinct adaptive peaks, the frequency of shifts between such peaks and ultimately discuss the role of ecology in promoting continental radiation.

Evolution 2016: Polar Vortex Revisited

By Kristin Winchell

On June 23, 2016

In All Posts, New Research

Shane Campbell-Staton giving his talk at Evolution 2016

We’ve heard about the effects of polar vortexes here on Anole Annals before. The infamous 2013/2014 event brought record-breaking snow and low temperatures to the Southern U.S., leaving people and animals both a little chilled. This created the perfect opportunity for Shane Campbell-Staton to investigate the effects of such extreme events on thermal tolerance of the native Carolina Anole, Anolis carolinensis. Shane also spoke about this at SICB earlier this year, and AA contributor Martha Muñoz covered the talk pretty thoroughly here on Anole Annals. Nevertheless, I’ll summarize some key points here in case you missed it.

An unlucky lizard during the polar vortex snow storms in the South.

Shane got lucky in the sense that he had measured thermal tolerance in August 2013 for populations affected by the polar vortex, 5 months before the event. Typically, the cold arctic air is tightly constrained around the North pole, but periodically the boundaries weaken and the cool air expands southward. These events are not regular, so Shane had no idea one was coming that winter or that it would extend so far south. It was serendipitous that his study populations, 3 in Texas and 1 in Oklahoma, were impacted by the extreme weather event. This species, particularly in the Southern portion of its range, is not used to low temperatures and reports came in of anoles dying off during the storm.

Air temperatures for January 5-7, 2014, compared to the 1981-2010 average. Map by NOAA Climate.gov

So Shane returned in August of 2014 and sampled again, curious as to how this cold impacted thermal tolerance. He found that tolerance to low temperatures, measured as critical thermal minimum (CTmin), was lower in some populations after the event! Even more, the difference was greatest in the Southernmost population (Brownsville, Texas). Shane returned again in the fall of 2014 to see if this effect persisted or if it was simply a plastic response to the event. He found that the populations sampled in 2014, and presumably their offspring, still had lower critical thermal minimums. This result suggests that the extreme cold weather had caused an evolutionary shift in cold tolerance via natural selection: only the animals that could tolerate the cold temperatures survived and passed on their cold-tolerance genes. Shane went on to conduct a common garden study to verify that the trait was not simply a plastic response. He found that the lower CTmin persisted in lab-reared animals: strong evidence that these shifts had a genetic basis.

Lastly, Shane looked at the functional genomics of cold tolerance. Using liver tissues to obtain transcriptomes (representing expressed genes), he found several gene modules associated with thermal tolerance including some associated with respiratory electron transport chain, lipid metabolism, carbohydrate metabolism, and angiogenesis/blood coagulation. He also found that the gene expression patterns in the Southern populations affected by the storm resembled the Northern populations that more regularly experience cool temperatures, indicating a common genetically based adaptive response across populations.

Evolution 2016: Rapid Morphological Evolution in Urban Environments

By Alex Gunderson

On June 21, 2016

In All Posts, New Research

We as a species are rapidly changing the global environment. The changes that get the most press are those related to climate, but we are also changing the structure of environments through land development. This leads to many important questions, one of which is whether or not the novel environments that we construct can drive evolutionary change. Kristin Winchell, a graduate student in Liam Revell’s lab at UMass Boston, has been addressing this question in the Puerto Rican lizard Anolis cristatellus, which is common in urban settings. Kristin hypothesized that urban environments should select for longer legs and greater surface area of lamellae (the morphological structures on anole toes that let them grip flat surfaces). Her reasoning was that long legs should allow animals to run faster, which should be beneficial in cities where perches and refuges are further apart than in dense natural forests. Greater surface area of lamellae should be beneficial for better grip of smooth man-made surfaces. Kristin compared morphological traits of multiple pairs of urban/natural environment populations and her hypotheses were supported. Not only that, but differences between populations were maintained in individuals developed under common garden conditions, consistent with a genetic basis of the differences. You can see these results in Kristin’s excellent recent paper in Evolution. Kristin also presented some new preliminary results that directly link the morphological changes she has observed to performance on man-made surfaces. Overall, Kristin’s work indicates that urban environments can be a potent force of rapid microevolutionary change and highlights that we are not only changing the abiotic landscape of the globe, but the evolutionary landscape as well.

Evolution 2016: Using Field Experiments to Understand Life-History Trade-Offs

By Alex Gunderson

On June 21, 2016

In New Research

Anolis sagrei. Photo by Alex Gunderson

The concept of trade-offs, that if you want to increase your performance in one function you have to decrease performance in another, is fundamental to ecology and evolution. However, detecting trade-offs and the underlying mechanisms that give rise to them is extremely difficult. In his talk, Bob Cox summarized years of research that he and his collaborators have done to understand life-history trade-offs in realistic ecological contexts using the brown anole (Anolis sagrei). Bob’s general approach is to experimentally manipulate the reproductive effort of individuals by removing ovaries and testes before releasing them onto cays in the Bahamas. He then estimates important ecological and physiological parameters such as survival, fat reserves, and immune function to see if he can detect trade-offs between reproductive effort and these other traits. In general, he has found that reproductive investment significantly decreases survival and physiological performance and that effects are often contingent upon factors such as the presence or absence of predators. Check out Bob’s website for a more information about his integration of experimental, ecological, and evolutionary studies to understand how trade-offs shape animal life-histories.

Evolution 2016: Using Anoles to Understand Shifts in Forests

By Kristin Winchell

On June 20, 2016

In New Research

Ivan Prates presents his poster at Evolution 2016.

Here at Evolution 2016 there have been a lot of anole talks and posters. In fact, there have even been several that pretend to not actually be about anoles. Ivan Prates presented a poster which he insisted, despite multiple pictures of anoles and the use of anole DNA, was not actually about anoles… Instead, this poster was actually about the historical extent of Brazilian forest cover (or so he says).

In short, Ivan used genomic data to understand historical patterns of dispersion and distribution of South American anoles in order to infer patterns of rainforest expansion and contraction. He suspected that the geological data gave a false interpretation of rainforest patterns in Amazonia and the Atlantic Forest in Brazil, and that anoles could help tell the true story of how the forests have changed over time. By looking at species with strong genetic signals associated with forest shifts he hypothesized that true forest patterns could be elucidated based on the historical demography of these species.

Ivan and coauthors looked at three species of lizards: Anolis punctatus, Anolis ortonii, and Polychrus marmoratus. They used the next-generation sequencing technique Genome by Sequencing (GBS) to answer three main questions: (1) Did all 3 species experience range expansions simultaneously? (2) Did populations expand and contract at similar points in time? (3) How did population sizes vary over time? While all three of these questions are about anoles, don’t forget that this poster was actually about the forest.

Ivan found that the Atlantic Forest individuals composed a monophyletic group nested within the Amazonian lineage. This suggests that the anoles of the Atlantic Forest on the coast actually arose from a single colonization event from Amazonia. The land between Amazonia and the Atlantic forest is presently quite arid compared to the rainforest – more like grassland. This presumably forms a barrier to contemporary dispersal, which implies that historical dispersal must have involved greater habitat connectivity. So Ivan’s results support the hypothesis that the forests experienced a drastic historical expansion creating a contiguous habitat that enabled dispersal around 1 million years ago. Interestingly, the timing for the dispersal of all 3 species was approximately the same. A million years ago seems to have been the ideal time to move to the coast for Brazilian anoles.

Ivan and his colleagues also looked at how populations size changed over time. He found that whereas Anolis punctatus experienced a trend of population expansion, Anolis ortonii and Polychrus marmoratus experienced population contractions. It was surprising to the authors that these species did not respond the same – why did only one of the species experience population expansions? They suspected that the expansion of one species might be related to the population contractions of the others, perhaps because of competition. However, their analysis on synchrony of population trends proved otherwise. They found that although trends within species were synchronized across populations, between species the shifts in demography were asynchronous. In other words, when one species expanded or contracted in population size, the others were stable. Ivan concluded that this was support for the idea that these populations were not influencing each other and that instead there was some other factor independently controlling population size fluctuations – perhaps precipitation patterns.

In conclusion, Ivan told me a lot about the demography of anoles during the Quaternary, and a little about the forest. I look forward to hearing more about his “forest” research on these understudied mainland anoles!

Click for a larger version of Ivan’s poster!