Anole Annals

The caption to this photo, which appeared in the Florida Times-Union: the brown anole has overrun Florida. Sometimes called Cuban anoles, they have become the most abundant vertebrate on Florida land.

The Florida Times-Union from Jacksonville published an article today on Florida invasives that arrived from Cuba. Pasted below is what they have to say about our favorite, the brown or festive anole, Anolis sagrei. You’ll have to go to the paper’s website to read about the Cuban brown (or festive?) snail and the Cuban treefrog:

This little lizard has an aggressive streak.

Related: Warming Cuba relations spurs invasive species debate

Swiftly, quietly, the brown anole has overrun Florida. Sometimes called the Cuban anoles, they have become the most abundant vertebrate on Florida land, with recorded populations exceeding 10,000 per hectare.

But really, this is a tale of two lizards. When the brown anole first started to colonize the Florida mainland in the 1940s, it came across another lizard, small and slender just like itself.

The bright green Carolina anole had been the only anole lizard native to Florida, and it had prospered across the Southeast United States. But, suddenly, it found itself in a turf battle with the invading brown anole.

They were both color-changing lizards, between 5 to 8 inches in length, competing for the same territory and the same food. But the brown anole had the upper hand. Back in Cuba, it shared an island with over 60 other anole lizards. It had to bulk up to face its rivals.

“In some sense, it’s better evolved, better adapted to competing with other anoles, so when it gets to Florida, it’s more aggressive and a little bit heavier,” said Yoel Stuart, a post-doctoral researcher in integrative biology at the University of Texas at Austin.

He told the Times-Union that he has heard many native-born Floridians lament the disappearance of the green Carolina anole in recent years, as the brown ones took over.

But all is not lost for the Carolina anole.

Stuart led a study of Carolina and Cuban anoles, and he found that the little green lizards were evolving rapidly to face down the invading force.

For their study, Stuart and his colleagues “battled weather and salt water and malfunctioning motors and leaky boats,” to reach isolated islands on Florida’s Atlantic coast.

They arrived armed with what Stuart describes as “a little extendable fishing pole with a little lasso at the end of it.” And when they spotted a lizard, they tried to slip the lasso around its neck, to collect measurements.

The Cuban anoles had, as expected, settled all but five of the 30 islands they visited. But how quickly the Carolina anoles were reacting surprised the researchers. They had fled to the canopy where, in the course of just 15 years, they had sprouted vastly bigger feet with stickier scales.

“If human height were evolving as fast as these lizards’ toes, the height of an average American man would increase from about 5-foot-9 inches today to about 6-foot-4 inches within 20 generations,” Stuart said in a news release. That would make the average American the same size as a NBA shooting guard.

That rapid evolution will likely allow the Carolina anole to coexist with the brown anole.

“It’s not going to go anywhere,” Stuart said. “It’s just going to be a little less abundant, a little bit higher up in the trees.”

But Stuart sees the brown anole’s rampant success as a warning, especially as other exotic lizards try to make Florida their home. He points out that South Florida is under siege by tegu and monitor lizards.

“People should realize if they buy a pet and can’t keep it, they shouldn’t just release it,” he said. “You never know which one is going to take off and start breeding in the wild.”

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In a recent paper in Life: the Excitement of Biology, Neftalí Ríos-López and colleagues report an observation of a male Anolis gundlachi catching an eating a coqui frog.  Here’s the short story–read the paper for more details: “…we observed a male Anolis gundlachi (Yellow-Chinned Anole: SVL 57.1 mm; tail length 88.1 mm) that sprinted down a trunk (8.7 cm diameter at breast height) of a Sierra Palm (Arecales: Araceae: Prestoea acuminata var. montana [Graham] An. Hend. and Galeano, 1996), dived into the leaf litter, and caught an adult E. wightmanae by his head (SVL 22.4 mm; this individual was not calling).”

By coincidence, shortly before seeing this article, we were alerted that Carmen Reyes had posted this photo on Facebook. Here’s her report: “We just went to visit a friend and I saw this lizard with something too big for him in his mouth. I took a closer look but not too close so I can have a better look… and voilà, it was a coqui…First we thought that he had a cockroach. I took the picture and as I got closer, he moved and started climbing the wall, but the coqui fell from his mouth… so I hope that the coqui is alive.

Photo by Carmen Reyes

Lausanne, Switzerland was host to this year’s European Society for Evolutionary Biology (ESEB) Conference. Despite the great distance between Europe and the native habitat of anoles, they did feature in several presentations: there was one anole talk and three posters, and many references to Anolis research during other presentations.

The single anole talk presented by Katie Duryea, currently at Lund University was about sexually antagonistic selection on body size in Anolis sagrei. The study, conducted on wild lizards across three years, investigated the relationship between fitness (estimated from the number of offspring surviving in the following year) and body size in males and females separately. The study demonstrated a strong positive relationship between body size and fitness in males across all three years. In contrast, selection on female body size varied across the three years. Her study nicely demonstrated sexually antagonistic selection acting on body size in a wild population.

The three posters spanned a wide range of research questions: invasion biology, transcriptome analysis and local adaptation. The first poster in the program was by Wataru Anzai from the University of Tokyo. He studied morphological and behavioural differences between introduced populations of Anolis carolinensis on two Japanese Islands. Sexual dimorphism in body size, head shape and limb musculature differed between the Islands. In behavioural experiments, he demonstrated that these traits were important during male-male competition.

The second poster was from another Japanese researcher, Hiroshi Akashi from Tohoku University. In this work Hiroshi and colleagues sequenced the transcriptomes of three anole species (A. sagrei, A. homolechis and A. allogus) under different thermal environments (5 days 26⁰C and 33⁰C). The study found that the expression of many genes varied with temperature, but that only one of these differentially expressed genes was shared across species.

The final poster was that of Michael Logan from Stellenbosch University. He presented work on thermal adaptation and gene flow in A. sagrei occupying Islands. He found that lizard thermal performance closely matched their local thermal environment, indicative of local adaptation. Interestingly, gene flow was greatest between islands with similar thermal environments, suggesting that effective migration may be higher between these islands.

Overall ESEB15 showcased a tremendous amount of exciting Evolutionary research and if you want to know more here is a link to ESEB15 webpage and abstract booklet, or you can check out some tweets using #eseb15. Some other exciting news from the conference was that in 2018 Montpellier, France will be host to a joint meeting between ESEB and Society for the Study of Evolution (SSE). The joint meeting will be a great opportunity to exchange ideas and establish networks across the pond. The conference structure will be a hybrid between the Evolution and ESEB formats, which differ quite a bit. At ESEB the program is divided into Symposia that are proposed by participants well in advance. Each symposium has 2-3 invited 30-minute talks and ~ 4-6 15-minute selected talks. The size of the meeting is usually capped at about 1500 and this year they had 8 concurrent sessions. If you do the maths (or math as you say in USA), you will notice that most participants do not get accepted for talks (~1/3) and the bulk of presentations are posters. The 2018 meeting will have approximately 2500 people, ~1000 talks and 14 parallel sessions. It would be great to have a strong anole contingent at the joint meeting in 2018, so keep a look out for the call for symposia and the call for abstracts. Hope to see you all there.

Size dimorphism among Anolis habitat specialists from Butler et al. 2003

In recent years the Anolis community has shown greater interest in understanding the developmental bases of anole diversity. As these data accumulate, we can start to synthetically understand the ecological (ultimate) and developmental (proximate) factors that regulated different aspects of anatomical diversification in anoles. Differences between males and females (i.e., sexual dimorphism) is one area that has received a considerable amount of attention among anole biologists interested in obtaining this integrative understanding of anatomical diversity. Over the last decade a number of papers have been published examining the evolutionary patterns of anatomical differences, ecological correlations, and the developmental/physiological processes underlying dimorphism in anoles.

Variation in body proportion (i.e., shape dimorphism) among Anolis habitat specialists from Butler et al 2003.

Compared to other anoles, crown-giant anoles have relatively low levels of size dimorphism, but vary greatly in body proportion. Males and females tend to vary in relative limb length, head proportions, and in the dimensions of their adhesive toe pads. In a recently published paper Vanhooydonck et al. examine the timing of divergence between male and female A. baracoae. They raised 23 individuals (9 males, 14 females) for 3.5 years, repeatedly measuring three anatomical traits and bite force 11 times over this time period. The authors found that bite force and dewlap size exhibit significant differences in growth between the sexes. Their analysis further suggests that these traits diverge at different times during ontogeny – bite force diverges during juvenile growth while dewlap size does not diverge until sexual maturity – illustrating the independent regulation of dimorphic traits during development. Head length and hindlimb length did not appear to have sexual differences, although it would be interesting to also perform a formal analysis of adult size and shape dimorphism on A. baracoae to see if this species has similar dimorphic trends compared to other crown-giant anoles.

The developmental bases of size dimorphism in A. sagrei from Cox et al. 2009

These results are consistent with other studies that show a mosaic pattern of male and female phenotypic divergence. Using a longitudinal study of male and female A. sagrei, Cox et al. 2009 showed us that body size dimorphism in this species begins early in juvenile life, only three weeks after hatching. Sanger et al. showed that dimorphism in facial length can emerge through two distinct developmental strategies, one early in ontogeny and one at the time of sexual maturity that appears to be clade-specific. Additional research on that compares across traits and among species will further elucidate the number of ways that dimorphism can arise in anoles. Further work that overlays an ecological perspective onto these patterns will also allow a more thorough understanding of whether natural or sexual selection is the primary driver of these differences in timing. As this future work progresses new insights into the evolutionary processes of anatomical diversification are sure to follow.

A male Red-eyed Coquí (Eleutherodactylus antillensis) courting a female coqui in St. Thomas, U.S. Virgin Islands. Photo by Brittany Barker.

A Mountain Coqui (Eleutherodactylus portoricensis) at El Yunque National Forest, Puerto Rico. Photo by Alejandro Ríos-Franceschi.

Contemporary climatic change is affecting species distributions, with important consequences for the long-term persistence and evolutionary potential of biodiversity. Endemic species on small, isolated islands are often particularly vulnerable to environmental change due to their restricted distributions and modest population sizes. Exploring how island biotas have responded to past climatic conditions may yield insights into their potential responses to changing conditions.

In our study recently published in Ecography, we sought to extend current knowledge on the role of late Quaternary climate in shaping distributions, diversification, and speciation dynamics in tropical islands. We conducted the study on two ecologically distinctive Eleutherodactylus frogs in Puerto Rico, the smallest and most easterly of the Greater Antilles. Whereas the mountain coquí (Eleutherodactylus portoricensis) is restricted to cool and moist understory montane forest habitat in Puerto Rico, the red-eyed coquí (E. antillensis) is a habitat generalist with a broad elevational distribution on most of the larger islands of the archipelago. We used ecological niche models under past and current climate to derive hypotheses regarding how stable climatic conditions shaped genetic diversity in E. portoricensis and E. antillensis. To test our hypotheses, we conducted phylogeographic and population genetic analyses based on mitochondrial and nuclear loci of each species across their range in Puerto Rico.

As predicted, regions with a large area of long-term suitable climate were associated with higher genetic diversity in E. portoricensis and E. antillensis, suggesting larger and more stable populations. Long-term unsuitable climatic conditions in the Río Grande de Loíza Basin, a warm and arid landscape that physiographically separates the Central and Luquillo Mountains of Puerto Rico, is a barrier to gene flow between populations of both species. These results are consistent with a previous study that suggested that temporally stable climatic conditions promote the accumulation of genetic diversity in the Puerto Rican lizard Anolis krugi.

Our findings illustrate the role of persistent suitable climatic conditions in promoting the persistence and diversification of tropical island organisms. The rate of climate change we’re experiencing now is faster than at any time in the last millennium, which highlights the urgency of understanding how small, isolated island endemic species respond to environmental change.

Brittany S. Barker

University of Arizona, Department of Ecology and Evolutionary Biology

The gray-dewlapped green anole. Photo by Harry W. Greene

Everyone knows that Florida green anoles have pink dewlaps. However, one population in western Florida has a grayish-green dewlap (see above). Several years ago, AA had two posts on these lizards (1,2). The significance of the gray dewlap remains to be determined. Is this population on the way to becoming a new species?

In a recent paper in Herpetologica, Macedonia and colleagues analyzed the display behavior of the gray-dewlapped population. They found that the gray-dewlappers’ display does differ, though not greatly, from a nearby pink-dewlapped population. However, when they compared their data to yet another pink-dewlapped population, they found that there was greater variation in the displays of the two pink populations than between the gray and pink populations. Thus, it doesn’t seem that the gray-dewlapped population’s behavior is particularly distinctive. What’s up with the gray dewlaps remains to be determined.

Here’s the paper’s abstract:

Green Anoles (Anolis carolinensis) are comprised of red-dewlapped (RD) forms that are found throughout the southeastern USA and a gray-dewlapped (GD) form that is restricted to southwest Florida. Prior research has shown that RD A. carolinensis produce headbob displays of three distinct types that differ primarily in their temporal patterns. Based on known morphological, physiological, and genetic differences between GD and RDpopulations, we hypothesized that these populations also would differ in headbob display structure. To test this hypothesis we quantified 440 displays from 39 males (24 GD and 15 RD) and assigned displays to type using numerical decision criteria. Although comparison of the same display types between GD and RD males revealed differences in the durations of several homologous display units (i.e., bobs or interbob pauses), only one unit differed following statistical correction for multiple comparisons. By taking into account all display variation in both populations simultaneously, however, discriminant function analysis correctly assigned display units with high accuracy to population and display type. Nevertheless, differences in unit durations often were greater between two RD populations occurring within Florida than they were between our GD and RD study populations. Thus, despite our demonstration of differences in the display temporal structure between GD and RD forms of A. carolinensis, these differences appear to be no greater in magnitude than those observed between RD populations.

Photo by Karen Cusick

Karen Cusick recounts this scary encounter on Daffodil’s Photo Blog.  The green turned around, to face its impending doom head on.

Photo by Karen Cusick

And then….

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In a recent paper in Life: the Excitement of Biology, Ríos-López et al. report observations of predation on a variety of Puerto Rican lizards. Iguanas and Ameiva suffer much of the brunt of predation (including a beagle with a juvenile iguana in its mouth), but reports include A. cristatellus eating both A. pulchellus and A. stratulus (which was subsequently regurgitated–perhaps because it was too large?–and immediately devoured by an Ameiva that ran up to the fallen carcass). In addition, a tody (above) brought an anole back to its nest.

Leo Fleishman and colleagues have just published a cool paper in Functional Ecology, “Why do Anolis dewlaps glow? An analysis of a translucent visual signal.” Co-author Manuel Leal provides the back-story on how the paper–which he refers to as “experimental natural history”–came to be in his lab’s blog, Chipojo lab.

And the New Scientist provides a nice summary of the article in its post: ”

Luminous lizard lotharios ahoy! In the dark undergrowth of the forest, it’s not easy to be seen. Male Anolis lizards use colourful throat fans, called dewlaps, to woo females as well as ward off rivals and predators. But one species has a neat trick to make itself stand out even more – it uses an optical illusion to make its dewlap appear to glow.

The dewlaps are translucent, which means they can transmit as well as reflect light. However, because most objects in the lizards’ environment – such as rocks and tree trunks – simply reflect light, our eyes “expect” them all to appear relatively dull. By transmitting light from the background, the dewlap tricks our eyes – and the eyes of other lizards – into thinking it is actually a light source, says Leo J. Fleishman of Union College in Schenectady, New York, who has studied the lizards for years.

Fleishman’s team was curious to find out why the trick evolved – was the glowing dewlap a way to increase contrast with darker backgrounds or a way to make its colour clearer?

To explore the issue, Fleishman’s team examined the photoreceptors in the lizard’s eyes to work out how they would view the dewlaps. They found that the glow did not create more contrast with the background, which naturally contains other bright spots – where a patch of sunlight passes through the vegetation, for instance. But the glow did significantly reduce the visual overlap, as the lizard’s eyes would experience it, between the throat fans and the colours of natural backgrounds.

The glowing dewlap may be more common than we think. Only a few of some 400 species of Anolis lizards are known to carry the trait, but Fleishman has seen photos suggesting other species’ dewlaps might glow too.

“My guess is that the phenomenon will turn out to be widespread once people start looking, but very few people have looked,” he says.

Here’s the paper’s summary:

Summary