All posts by Martha Muñoz

About Martha Muñoz

Martha is a postdoctoral researcher in Sheila Patek's laboratory at Duke University. She received her Ph.D. at Harvard University, where she studyied the evolutionary ecology and thermal physiology of anoles, focusing on the cybotoid anoles from the Dominican Republic. Martha serves as Conference Editor for the Anole Annals. Website: www.marthamunoz.weebly.com

Evolution 2017: Urban Anoles Sprint Faster on Smooth Substrates

Kristin Winchell gives her talk on urban anoles at Evolution 2017.

Kristin Winchell gives her talk on urban anoles at Evolution 2017.

When I think of Puerto Rico, the first thoughts that come to mind are of sunny beaches and lush rainforests. There are, however, also lots of urban habitats in Puerto Rico. San Juan, for example, has two million human residents, and also lots and lots of anoles. Doctoral candidate Kristin Winchell has been studying adaptation in urban anoles for several years. Last year, she published1 her work showing that Anolis cristatellus in urban habitats have longer hindlimbs, bigger toe pads, and more lamellae than lizards in rural habitats.

A connection that was missing, however, was how the morphological shifts she documented related to performance differences in urban versus rural habitats. To get at this question, she conducted sprinting trials with different substrates to see how limb and toe characteristics affect sprinting capacity. Lizards in urban habitats use much smoother perches, such as fences and posts, and so the hypothesis was that the longer limbs and toe pad differences she detected improved sprinting performance on smoother substrates. She used three different substrates for sprinting trials – bark (rough surface), metal (smooth surface), and painted concrete (very smooth surface). She found that, overall, lizards sprinted more slowly on more slippery substrates. On average, lizards sprinted at 60% of their maximum capacity, indicating a strong performance hit when using slippery substrates.

Kristin confirmed that the urban anoles were better at sprinting on all substrates – including the slippery ones – than rural anoles. When she explored the results in greater detail, she found that only lamella number explained variation in sprint performance, with no appreciable effects of limb length or toe pad area. Kristin’s elegant study demonstrate how we can document evolution on recent timescales, and shows how urban environments provide strong selective pressures for the animals that live in them.

1. KM Winchell, RG Reynolds, SR Prado‐Irwin, AR Puente‐Rolón, LJ Revell. 2016. Phenotypic shifts in urban areas in the tropical lizard Anolis cristatellus. Evolution 70:1009-1022

SICB 2017: New Insights into Pre- and Postcopulatory Selection in Anoles

Doctoral candidate Ariel Kahrl presents her research on sperm evolution at SICB 2017.

Doctoral candidate Ariel Kahrl presents her research on sperm evolution at SICB 2017.

Every year since 2013, the Division of Ecology and Evolution (DEE) hosts the Huey Award Symposium at the annual SICB meeting. The Huey award is given for the best student presentation in DEE, in honor of Ray Huey, professor emeritus at the University of Washington. Ray’s career featured a lot of key research on anoles, and so there is often good representation by anole biologists at the Huey award. At this year’s symposium, Ariel Kahrl, a graduate student in Bob Cox’s lab at the University of Virginia, presented her research on pre- and postcopulatory selection in Anolis lizards.

We know that male competition for mates occurs both before copulation (mating success) and after copulation (sperm competition). Her research focuses on investigating the evolutionary connection between these two phases of competition. She found that larger males have smaller relative testis size, indicating a tradeoff between pre- and postcopulatory success, as larger males will have better success gaining access to females, but less sperm available for mating.

When she looked at testis and sperm morphology in greater detail, a few interesting patterns emerged. First, she found that testis size evolves faster than body size, consistent with other studies showing that reproductive organs evolve faster than other body traits. She also found that the midpiece section evolved faster than the head and the tail of the sperm. Importantly, the midpiece section of the sperm was strongly associated with male condition and sperm swimming speed, whereas the head and tail of the sperm were not associated with male  condition or sperm swimming performance. She further hypothesized that sperm count may be a more important target of selection than sperm morphology.

SICB 2017: Urban Anoles Like It Hot

Postdoctoral scientist, Dr. Shane Campbell-Staton, presents his work on CTmax shifts in Anolis cristatellus at SICB 2017.

Postdoctoral scientist, Dr. Shane Campbell-Staton, presents his work on CTmax shifts in Anolis cristatellus at SICB 2017.

Greetings from New Orleans, where SICB 2017 is well underway! Kicking off the conference was Dr. Shane Campbell-Staton, currently a postdoctoral researcher at the University of Illinois, Urbana-Champaign. Shane presented some work he has been doing with Kristin Winchell, a graduate student in Liam Revell’s lab at the University of Massachusetts, Boston. Kristin’s work focuses on how the crested anole, Anolis cristatellus, adjusts its biology to life in urban areas. In previous work, Kristin documented adaptive shifts in limb and toepad morphology in these anoles in urban areas, a shift she correlated with the broader perches urban anoles use.

In this neat follow-up study, Shane and Kristin have documented how perch temperatures in urban Puerto Rican habitats are higher than in natural environments on the island. In response, urban Anolis cristatellus have a higher heat tolerance. Results from a common garden experiment indicate that the urban shifts in heat tolerance are primarily due to plasticity. At the moment, Shane is performing genomic analyses to search for signatures of selection on heat tolerance.

 

Blogging for SICB 2017: Anole Annals Wants YOU!

Society for Integrative and Comparative Biology logo.

Society for Integrative and Comparative Biology.

It’s late November, which means a few things: Winter is coming, Westworld is wrapping up, people are going to lose their minds on Black Friday, and, most importantly, the annual meeting for the Society for Integrative and Comparative Biology (SICB) is upon us. SICB is one the biggest annual meetings for biologists in the United States, and it is a venue where Anolis research is prominently featured. This year’s meeting, which will be held in New Orleans during the first week of January, is no exception. By my count there are 35 talks and posters featuring anoles. I’ve been attending this meeting regularly for nearly a decade and I’m fairly certain this is a new record. I think that this particularly high turnout really speaks to the increasing prominence of anoles as model organisms for ecological and evolutionary studies.

With great prominence, however, comes great responsibility. We like to cover every presentation, whenever possible and also focus on giving spotlights to undergraduates and graduate students as much as possible. Every year we rely on many conference participants to blog about posters and talks. If you’re an undergraduate or graduate student, blogging is a great way to practice writing to a broader audience. Moreover, if you blog for AA and are presenting at SICB, we guarantee that we will cover your presentation. Bloggers at all levels of experience are welcome to blog – undergrads, graduate students, postdocs, and faculty! Please email me at mmm109@duke.edu or leave a comment for this post if you’re interested in blogging for AA at SICB and we’ll get you started. I will provide detailed information on how to blog and will also be at the conference (and blogging for AA) and can provide assistance. See this post from SICB 2016 for an example. Thanks very much!

SICB 2016: Can Geckos Run Fast When It’s Wet Outside?

Austin Garner, an undergraduate at the University of Akron.

Austin Garner, an undergraduate at the University of Akron.

Anoles, geckos, and some species of skinks have adhesive toepads that allow them to cling to substrates. This adhesive ability is remarkable – anoles, for example, can hang from a glass pane using just one toe. Gecko adhesion is particularly well studied, but most research has focused on how these animals cling to dry surfaces. In their natural habitats, however, geckos often have to contend with wet surfaces.

Austin Garner, an undergraduate at the University of Akron working with Peter Niewiarowski, wanted to know whether geckos could move effectively on wet substrates. He measured sprinting performance in two species of gecko, Gekko gecko and Chondrodactylus bibronii, across a 2-meter vertical racetrack that was misted with water. Average sprint velocity on wet substrates did not differ significantly from the average sprint velocity on dry substrates, indicating that geckos can sprint equally fast on slippery surfaces. The substrate material, however, influenced how often geckos slipped. Geckos slipped more on glass substrates compared to acrylic substrates. Austin hypothesized that this is likely due to the surface chemistry of glass. Glass is a hydrophilic substrate, meaning that water is attracted to its surface more so than the surface of acrylic. Interestingly, the frequency of slipping differed among species. Chondrodactylus bibronii, a species of gecko from an arid habitat, slipped more often than G. gecko, a gecko found in the tropics. Although C. bibronii slipped more on wet substrates, this species did not suffer a decrease in average sprint velocity on wet substrates. This suggests that C. bibronii is somehow compensating for the slipping observed on wet substrates, but Austin is unsure of the mechanism behind this compensation. Overall, his study suggests that geckos can travel on wet substrates up to 2-meter without a reduction in their adhesive ability, and that at least one species of gecko can compensate for any loss of traction caused by the presence of water.

SICB 2016: Trade-offs Among Performance, Growth, and Immune Function in Juvenile Lizards

Husak and Poster

Dr. Jerry Husak presents his poster at SICB 2016

*This post was written by David Delaney, a Ph.D. student in Fred Janzen’s lab at Iowa State University.*

Organisms must balance tradeoffs between performance, growth, immune function, and reproduction in order to maximize fitness. Adults and juveniles experience different life history pressures because juveniles are not reproductively mature, whereas adults should invest in reproduction. Thus, adults and juveniles may balance these life-history traits differently.

Dr. Jerry Husak of the University of St. Thomas presented on a study that he and undergraduate co-author Jordan Roy conducted to examine if adult and juvenile green anoles vary in resource allocation. To do this, 22 lizards were trained on a treadmill whereas 23 lizards were not. Training consisted of running lizards on a small pet treadmill 2 times per week. The incline was increased every two weeks for a period of 9 weeks to increase training intensity.

They found that training reduced the body mass of juveniles, which did not occur for adults. Training increased endurance capacity which also occurred in adults, however adults had a sex effect that juveniles did not. Training did not affect body length in juveniles, whereas it increased adult body length. Training eliminated the sex differences in juvenile immune function which did not occur for adults. Training increased hematocrit and heart ventricle mass which was also found for adults. In addition, juveniles exhibited very high variation in their response to training. Overall this study shows that juvenile green anoles balance these tradeoffs differently than adults, which likely reflects differences in the importance of certain life history traits throughout ontogeny.

SICB 2016: Adaptive Shifts in Anolis carolinensis Following the Polar Vortex

Shane Campbell-Staton gives his talk at SICB 2016.

Shane Campbell-Staton gives his talk at SICB 2016.

Climate change isn’t just leading to greater average environmental temperatures – it’s also leading to an increase in the frequency and severity of extreme weather events, such as heat waves and hurricanes. Of interest to Shane Campbell-Staton, a post-doctoral researcher in the Cheviron Lab and a recent graduate from the Losos Lab at Harvard, is understanding how the recent polar vortex in North America impacted the native green anole, Anolis carolinensis. The polar vortex of winter 2013/2014 set several records in snow fall and in all-time low temperatures in the south, and also led to severe weather in the midwest and east.

Shane found that, immediately following the polar vortex event, cold tolerance (CTmin) was significantly lower in lizards from southern Texas, as low as in lizards from much higher latitudes. He suggested that this result stems from differential survivorship during the event – lizards in south Texas that were more cold tolerant (i.e., had a lower CTmin) were more likely to survive the winter vortex  than less cold tolerant individuals. He then returned to south Texas a few months later and sampled both the survivors and their offspring and found that the decrease in CTmin persisted, indicating a potential evolutionary shift in cold tolerance. He put the final nail in the coffin by running a common garden experiment, where he demonstrated that, even when reared under common laboratory conditions, offspring exhibited cold tolerance similar to their parents, indicating high heritability in this trait and that the shift observed in nature was evolved rather than due to plasticity.

Shane then examined the response to the weather event at the genetic level by sequencing liver transcriptomes. Transcriptomes quantify patterns of gene expression levels for all genes regulated in a tissue; hence, by examining what genes are differentially expressed following cold stress, we can figure out the molecular underpinnings to cold adaptation and acclimation. He found that gene expression in survivors from the south closely resembled expression patterns in northern lizards, indicating a shared molecular pathway to cold tolerance adaptation in lizards from both habitats. The gene expression modules (or groups of genes) that exhibited a strong statistical association with CTmin variation were overrepresented for genes associated with oxidative phosphorylation. Oxygen consumption, which feeds oxidative phosphorylation, is directly related to CTmin: Animals that are more cold tolerant consume less oxygen during cooling. Hence, the expression differences in oxidative phosphorylation may pinpoint a proximate mechanism for cold tolerance adaptation.

You can learn more about Shane’s work on adaptation following the polar vortex in his recent Harvard Horizons talk.

SICB 2016: An Investigation Of Brain Lipid Composition Between Ecomorphs

Jake Stercula presents his poster at SICB 2016.

Jake Stercula presents his poster at SICB 2016.

*The following post was written by Chris Robinson, a Master’s student in Matt Gifford’s lab at the University of Central Arkansas.*

Both between and within ecomorphs, anoles can experience a wide range of temperature conditions. As ectotherms, anoles rely on external conditions to thermoregulate, and therefore species found in different environments may have evolved unique biochemical mechanisms to adapt to their respective environments.

Using both field and laboratory studies, Jake Stercula, an undergraduate working with Michele Johnson at Trinity, is investigating how membrane fluidity, which aids in cell function, of the brain is regulated by temperature and lipid composition. The saturated:unsaturated lipid composition ratio controls cell membrane fluidity, where a higher ratio provides less fluidity. Stercula and colleagues hypothesize that species within a thermal environment (warmer or cooler) will have more similar lipid ratios and fluidity than between thermal environments regardless of ecomorph, and that anoles in warmer thermal environments will have a higher saturated:unsaturated lipid ratio.

To test this, they are conducting three studies. First, they quantified body temperature of anoles from warmer and cooler areas within the grass-bush, trunk-crown, and trunk-ground ecomorphs in Puerto Rico (Figure 1). Second, to test for lipid composition plasticity, A. carolinensis male and female pairs were housed in either a 26°C or 35°C room (6 pairs in each). After six weeks, the lizards were sacrificed and their brains were collected to quantify the lipid composition ratio using mass spectroscopy at the University of Texas Health Science Center in San Antonio. Finally, to quantify membrane fluidity, they are growing astrocytes from A. carolinensis at 28°C and 35°C and predict that astrocytes from the warmer condition will be less fluid than those from the cooler condition.

This study could provide novel insight into how anole species have adapted to their thermal conditions. We look forward to seeing the rest of the results!

Figure 1. Body (dark columns) and perch (light columns) temperature comparisons between species that perch in the sun (sun) versus in the shade (shade).

Figure 1. Body (dark columns) and perch (light columns) temperature comparisons between species that perch in the sun (sun) versus in the shade (shade).

SICB 2016: Lizards Rapidly Generate More Force During Locomotion than Biting

*The following post was written by Chris Robinson, a Master’s student in Matt Gifford’s lab at the University of Central Arkansas.*

Like at every SICB conference, anoles are well represented among the talks and posters here in Portland and we here at the Anole Annals couldn’t be more thrilled to see the love for one of our favorite genera.

Christopher Anderson, a post-doctoral associate in Thomas Roberts’ lab at Brown University, gave a talk examining how muscle physiology influences whole organism performance in five species of anoles. His group examined two muscles, the M. ambiens pars ventralis (a swing phase muscle of the leg important for locomotion) and the M. abductor mandibulae externus superficialis anterior (a muscle in the jaw used in biting), to see if they differed from each other in how they perform in order to meet their functional demands. The muscle of the leg, which is used in sprinting, is cyclically activated and deactivated as an organism moves, whereas the muscle of the jaw is used more episodically.

Anderson and his colleagues found that the leg muscle builds passive tension at shorter lengths and has a twitch time that is 1.3-2.0 times faster than that of the jaw (to see how twitch time relates to sprint speed, see the post about Noel Parks’ poster). From this, Anderson concluded that these muscles are tuned to meet their physiological demands. Locomotion muscles, which are used frequently, generate a lot of force rapidly and the quickly developing passive tension in these muscles may serve as a form of protection for the muscle during active lengthening.

SICB 2016: Genetic Drift and Morphological Adaptation in Anolis sagrei from the Bahamas

Hanna Wegener giving her talk on Anolis sagrei from the Bahamas at SICB 2016

Hanna Wegener giving her talk on Anolis sagrei from the Bahamas at SICB 2016

Small islands are great systems in which to study evolution, in part because their isolation and simplified landscapes makes them amenable to experimental studies. For example, previous experimental work on Anolis sagrei in the Bahamas by Losos et al. (1997) and Kolbe et al. (2012) found evolutionary changes in hindlimb length driven by adaptation to structural habitat over only a few years.

Hanna Wegener, a Ph.D. student studying with Jason Kolbe at the University of Rhode Island, wanted to know if morphological differences associated with habitat use also manifest in natural (rather than experimentally introduced) populations of Anolis sagrei from the Bahamas. She examined genetic (microsatellite) and morphological variation from male and female A. sagrei on seventeen islands in the Bahamas. Despite the islands being separated by very small geographic distances (no more than three kilometers and typically only a few hundred meters), populations on the islands were genetically differentiated. Her genetic analysis further found high levels of inbreeding on each island.

Unlike the findings on the experimental islands, Hanna did not find any correlation between perch diameter and hindlimb length. She did find that female density was high on the islands, and that density correlated strongly with head length and injury frequency, suggesting that competition influences morphological differentiation on these islands. Overall, Hanna found that morphological patterns varied considerably among islands and among males and females. She suggests that this variation is due to stochastic effects on small islands, namely genetic drift, due to the extinction and colonization dynamics in response to hurricanes.

SICB 2016: Hot Lizards in the City

Andrew Battles presents his work on Anolis cristatellus and A. sagrei at SICB 2016.

Andrew Battles presents his work on Anolis cristatellus and A. sagrei at SICB 2016.

Greetings from SICB! Sessions are off to a roaring start here in Portland. At Monday’s poster session, Andrew Battles presented his work on the thermal ecology of urban anoles. Andrew, a Ph.D. student working with Jason Kolbe at the University of Rhode Island, presented his work in the poster session for the prestigious Huey award.

Around the world, many natural habitats are being replaced with artificial, heat-absorbing structures, such as concrete and metal. This is a really big deal for the animals that perch on these substrates, particularly ectotherms, which derive their heat from external sources. Andrew examined environmental temperatures and canopy openness at a variety of urban and natural sites in (and around) Miami, Florida. What he found was that urban perches (posts, building walls, etc) were considerably warmer and more exposed than natural perches.

He then examined body temperatures for the lizards Anolis cristatellus and A. sagrei that are commonly found in those habitats. On average, A. sagrei had higher body temperatures than A. cristatellus. Both species benefitted from warmer urban structures early in the morning, as they were able to reach temperatures in their preferred range sooner than in the cooler natural sites. In light of these results, Andrew’s next work will examine patterns of physiological divergence in urban and natural habitats. Congratulations to Andrew for being a finalist (and the sole Anolis ambassador) in this year’s Huey Award Symposium.

SICB 2016: What Do You Want to Read About?

Screen Shot 2015-12-04 at 12.27.29 PMIt’s that time of year again: The weather is getting colder, lights and trees are going up, and mulled wine and eggnog are on the menu. I’m obviously referring to the annual meeting of the Society for Integrative and Comparative BIology (SICB). If you’re new to our blog, you’ll learn that SICB is a big deal here at Anole Annals. We like to keep our readers abreast of new and emerging trends in Anolis research. The upcoming SICB, which will be held from January 3rd to 7th in Portland, Oregon, will be no different from previous years. In between trying craft beers and local coffees, we’ll be busy blogging away about new studies in anole ecology, physiology, biomechanics, and evolution.

As you probably also know, anole research is on the rise. The program for the 2016 SICB meeting suggests that this trend is continuing. By my count, there will be 26 anole-related talks and posters at the upcoming meeting, so anoles will certainly have a strong presence. You can see a table with the talks and posters listed here. One of the downfalls of so many talks, however, is that it’s logistically challenging to cover everything on this blog. So, if you’re interested in reading posts from the upcoming meeting, do fill out the poll below. I recognize that there is overlap between topics, but I just want to get an idea of what priorities I should set at at the meeting. On another note, if you will be attending the meeting and you are interesting in blogging, please email me at martha.munoz@gmail.com. We are always looking for bloggers and I can help get you set up to make things easy.

Climate Niche Evolution in Anoles – New Research by Adam Algar and Luke Mahler

Anolis shrevei, a species inhabiting extreme cold environments on Hispaniola.

Anolis shrevei, a species inhabiting extreme cold environments on Hispaniola.

Caribbean anoles are widely recognized as a key example of “adaptive radiation,” or the diversification of a group of organisms into different ecological niches*. Anoles in the Greater Antilles (Cuba, Hispaniola, Jamaica, and Puerto Rico) diversified into multiple types of habitat specialists, or “ecomorphs,” so-named for the portion of the structural habitat that they most often occupy. For example, “twig” anoles are found on the distal ends of branches. They have relatively short limbs (and, often, prehensile tails) for navigating their spindly habitat. The ecomorphs have evolved a myriad of morphological features suited to their microhabitat use. But diversification into different structural niches comprises only one dimension of their radiation across the Caribbean. Anoles have also diverged into distinct climatic habitats in the Greater Antilles, such as Anolis shrevei (pictured above), a montane species found at high elevation in the Cordillera Central mountain chain of the Dominican Republic. Some anoles are restricted to desert scrub habitats, others to cloud forests, and others to warm lowland environments. The list goes on!

But how does climatic evolution fit into the bigger picture of the Anolis adaptive radiation across the Caribbean? In a previous study, Mahler et al. (2010) suggested that “ecological opportunity” (roughly, the lack of competitors for ecological niche space) influences rates of morphological diversification into different portions of the structural habitat. In a study just published in Global Ecology and Biogeography, Adam Algar (University of Nottingham) and Luke Mahler (University of Toronto) sought to test the idea that ecological opportunity also influences rates of climatic niche evolution in Caribbean anoles. Although they are tropical, several of the Caribbean islands possess considerable elevational variation , which has created substantial thermal variation and the potential for climatic niche evolution in anoles (See Figure 1 below).

Portion of Figure 1 from Algar and Mahler (in press) showing temperature variation in the Greater Antilles (a) and the Lesser Antilles (b)

Portion of Figure 1 from Algar and Mahler (in press) showing temperature variation in the Greater Antilles (a) and the Lesser Antilles (b).

Algar and Mahler first quantified two temperature axes (mean temperature and temperature seasonality of species’ localities) of the climate niche for 130 Anolis species on each of the islands in the Greater Antilles, as well as from the northern and southern Lesser Antilles (i.e., the series of small, volcanic islands that dot the eastern Caribbean Sea). The first temperature axis (PC 1) correlated with thermal  minima and maxima and the second temperature axis (PC 2) correlated with temperature seasonality.

Figure 2 from Algar and Mahler showing how rates of thermal PC 1 relates to climate heterogeneity (a), and geographic area (b). (c) shows how rates of thermal PC 1 evolution correlate with climatic heterogeneity after correcting for geographic area. Relationships depicted in (b) and (c) are statistically significant.

Figure 2 from Algar and Mahler showing how rates of thermal PC 1 relates to climate heterogeneity (a), and geographic area (b). (c) shows how rates of thermal PC 1 evolution correlate with climatic heterogeneity after correcting for geographic area. Relationships depicted in (b) and (c) are statistically significant.

They showed that rates of niche evolution for thermal PC 1 was significantly higher in geographically larger regions (Fig. 2b). Thermal PC 1 was, however, unrelated to climatic heterogeneity (Fig. 2a). But, when the residuals of the relationship between thermal PC 1 and geographic area were regressed against climatic heterogeneity, they did recover a significant positive relationship (Fig. 2c), indicating that, over a given area, thermal niche evolution is faster in regions with greater climatic heterogeneity. They conducted the same analyses for thermal PC 2 (temperature seasonality) and, as with PC 1, found no relationship between evolutionary rate and climate heterogeneity and a positive relationship with area. However, in contrast to their results with PC 1, even after controlling for geographic area, they did not recover a significant relationship between evolutionary rate and climatic heterogeneity.

To determine whether the relationships between evolutionary rate and island area could be due to the higher species numbers found on larger islands, they regressed the evolutionary rate against species number. They did find a strong relationship between species number and evolutionary rate. However, given that island area and species number are highly correlated, this result was not unexpected. Thus, they were unable to fully disentangle how island area and species might interact to influence rates of the climatic niche evolution.

In short, Algar and Mahler found that island area greatly influenced the rate of climatic niche evolution. It has long been recognized that island area is a major determinant of species richness and species diversification on islands – on islands above a certain threshold size, in situ speciation can occur. In this study, Algar and Mahler add climate niche radiation to the list – on islands above a certain size, climatic niches can diverge considerably. But how, specifically, does island area contribute to rates of climatic niche evolution? The authors suggest that larger islands allow more speciation along elevational gradients, such as mountains, which can result in climatic specialization (either during the process of speciation or post-speciation). On small islands, they argue, high gene flow may swamp out the effects of climatic divergence even where climatic thermal heterogeneity exists and, when such specialization does occur, those species may be susceptible to higher extinction rates (due to their smaller geographic ranges). In short, climatic niche evolution presents an equally important (though relatively understudied) aspect of the Anolis adaptive radiation in the Caribeean.

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*Scientists differ in their definition of adaptive radiation, though most can agree with the idea that it involves adaptive diversification. Here I follow the definition of Losos and Mahler (2010).

Works Cited

Algar, A. C., and D. L. Mahler. In press. Area, climate heterogeneity, and the response of climate niches to ecological opportunity in island radiations of Anolis lizards. Global Ecology and Biogeography.

Losos, J. B., and D. L. Mahler. 2010. Adaptive radiation: the interaction of ecological opportunity, adaptation, and speciation. Pp. 381-420 in M. A. Bell, D. J. Futuyma, W. F. Eanes, and J. S. Levinton, Eds. Evolution Since Darwin: The First 150 Years. Sinauer Associates, Sunderland, MA.

Mahler, D. L., L. J. Revell, R. E. Glor, and J. B. Losos. 2010. Ecological opportunity and the rate of morphological evolution in the diversification of Greater Antillean anoles. Evolution 64:2731-2745.

Evolution 2015: Let the Anole Talks Begin!

Logo for the Evolution 2015 conference.

Logo for the Evolution 2015 conference.

This year’s Evolution meeting just kicked off at the Casa Grande Hotel in the lovely coastal town of Guarujá, Brazil. There are some great anole talks lined up for this year’s conference. Kristin Winchell, a Ph.D. candidate in Liam Revell’s lab at the University of Massachusetts, Boston, will be giving a talk titled, “Urban Evolution: Natural selection and genetic basis of phenotypic shifts in urban Anolis cristatellus.”

The talks on Puerto Rican anoles don’t end there. Matthew McElroy, a Ph.D. candidate in Adam Leache’s lab at the University of Washington, will present a talk titled “Comparative phylogeography of co‐distributed Anolis lizards from Puerto Rico.”

Finally, Fernanda de Pinho Werneck, who is based out of the Instituto Nacional de Pesquisas da Amazonia in Manaus, Brazil will present a talk titled, “Cryptic lineages and diversification of an endemic anole lizard (Squamata, Dactyloidae) of the Cerrado hotspot.”

Stay tuned to Anole Annals for upcoming posts on all the anole talks! You can also follow the happenings at Evolution 2015 on Twitter using #Evol2015.

Updates on Anolis lividus from Montserrat’s Volcanic Exclusion Zone

Image of the 1995 eruption of the Soufrière Hills volcano on Montserrat.

Image of the 1995 eruption of the Soufrière Hills volcano on Montserrat. Photo from Wikipedia.

On July 18, 1995 something big happened on a tiny little island in the Lesser Antilles. The Soufrière Hills volcano erupted on Montserrat, an island only about 40 square miles in size that is nestled between Nevis, Antigua, and Guadeloupe. The eruption buried the (then) capital city of Plymouth under several meters of ash and pyroclastic flow. More than a dozen nearby towns were also destroyed. Residents in the south of the island had to evacuate, leaving their homes and land behind. Since then, Montserrat has experienced considerable volcanic activity. In fact, when I was on the island in 2010, I witnessed a major dome collapse, an event that was magnificent to see on the ground, and was even observable from space. I’ve spent some time trying to find Anolis lividus, Montserrat’s endemic anole, across the island, with particular focus on finding it in the south, where volcanic impact has been greatest. Montserrat is basically divided in half by the Belham River Valley, a barren bed of ash that effectively separates the habitable north of the island from the more inhospitable south. I’ve spent many hours in the south of the island searching for A. lividus over a few years. In my experience, the lizards were not abundant (if to be found at all) south of the Belham. Granted, access to this region was very restricted, so I didn’t get to spend a whole lot of time there, but I only ever saw two lizards (a mating pair) on a tree in Richmond Hill, a part of the southern half that’s in Zone C. Towns in Zone C are close to the Belham River Valley and are occasionally opened up for visitors when the volcano has been quiet for a while. Currently, Zone C has ‘unrestricted access’, meaning people can visit day and night without an escort. There is also a relatively unexplored portion of Montserrat southeast of the volcano (the South Soufrière Hills) that has plenty of good habitat and is isolated by the rest of the island by the volcano. There have been a few focused expeditions to that part of the island (for example, to collect individuals of Leptodactylus fallax, the ‘mountain chicken’ frog, for a breeding program), but I haven’t been able to get there.

My interest in A. lividus lay mostly in understanding how recolonization works. Can the lizards cross the Belham River Valley, or is it too hot and inhospitable? As access to inner zones increases, will humans mediate transport into the south of the island? If they get there, will they persist? Although I haven’t been to the island in a few years, I remain very interested in the system. I recently received news on Anolis lividus from Nicolas Tirard, a new resident on the island. He had visited Zone C (which is currently open to daytime visitors) and found an individual of A. lividus. Nicolas informed me that he spotted the lizard (a male) on the terrace of an abandoned home in Richmond Hill, which is the same neighborhood where I found lizards almost six years earlier. Nicolas spent about 30 minutes canvassing this area and only found one lizard. For anyone with experience finding anoles in the Caribbean, particularly in the Lesser Antilles, we know that they are generally much more abundant than that. So I would reckon that lizards in Zone C are probably still pretty scant. I wonder if the lizard Nicolas did find descended from previous inhabitants in that area (for example, from the mating pair I observed earlier), or whether there have been more recent dispersal events. He went back on another occasion to St. George’s Hill, which he says is more densely forested than Richmond Hill, and saw three lizards there. When I visited St. George’s Hill a few years ago it was pretty barren, so clearly the habitat is recovering there.

Anolis lividus from Richmond Hill, Montserrat.

Anolis lividus from Richmond Hill, Montserrat. Photo by Nicolas Tirard.

I asked Nicolas if he thought that humans were transporting the lizards (accidentally or otherwise) to Zone C through increased transit. Nicolas reckons the lizards can get there on their own right now. He says, “I don’t think it is a human-mediated recolonization, even if there is traffic going back and forth, because the vegetation has grown again in the Belham river, and it is probable that anole can now cross it by themselves.” The finding that the Belham is vegetated is interesting – during my visits there it was a hot, barren bed of ash. The only herps I saw there were enterprising iguanas, boldly basking on piles of hot ash. I also saw an iguana on the roof of a house once in Richmond Hill. As the exclusion zone becomes more accessible, I hope that people will try to find A. lividus (and other organisms) there and, hopefully, share their observations with the Anole Annals.

Nicholas shares his observations on his blog. He has also seen a blind snake (Typhlops) and several iguanas in the exclusion zone. Check out his blog for more.

Another image of the male Anolis lividus spotted in Richmond Hill.

Another image of the male Anolis lividus spotted in Richmond Hill. Photo by Nicolas Tirard.

Neat Ditty About a Thermoregulating Lizard

Screen Shot 2015-02-22 at 10.26.03 PMHarry Bird and the Rubber Wellies is described as a nomadic folk band, and they’re based out of Dublin, Ireland and Bilbao, in the Basque Country of Spain. Maybe it’s the cold rainy climes of both those places that inspired these musicians to create a wistful song about a tropical lizard basking on a palm tree. It’s a catchy tune, so check it out.

Here are some of the lyrics from the song:

“When Sun come out / Out come the lizard / Lazing around / And a’flicking her tail/ When Sun go home / Home go the lizard / Till the Sun come out again.”

“See the way she slide / My, what a lizard! / She got so many beautiful scales / She the way she shine.”

“Oh she’s catching flies / That greedy lizard / Her long sticky tongue / Doesn’t make any sound / She gets pomegranate / Out of the cupboard / That’s the way to wash them down.”

 

ASH 2015: Size and Coloration of Draco Dewlaps

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A slide from Danielle Klomp’s talk showing how color is used in communication by some species of lizards. Check out the quick guest appearance by an anole.

The diversity of anole dewlap shapes, colors, and patterns is one of their most distinctive features. But anoles are not the only squamates with flashy dewlaps. When it comes to such accoutrements, anoles have some stiff competition from their Agamid cousins in the Indo-Pacific region, the ‘flying’ dragons (Draco). Draco lizards don’t really fly, of course. Rather, they can laterally expand their ribs and the connecting membrane to create a ‘wing’, which they use to glide between trees in their habitats. If you haven’t seen how they do this, it’s more than worth a watch. Lest you think anoles get left behind in this respect, we do know that some anoles glide, as well, even if they don’t exhibit the impressive wing-like structures that Draco lizards have.

 

Slide from Danielle's talk showing Draco lizards and their geographic distribution.

Slide from Danielle’s talk showing Draco lizards and their geographic distribution.

As I learned at Danielle Klomp’s talk at ASH 2015 last week, their dewlaps are almost as impressive as their gliding ability. Danielle is a PhD student working with Devi Stuart-Fox and Terry Ord and her dissertation has focused on studying the evolutionary ecology of Draco lizards. This past week she presented her work on these lizards’ dewlaps and what role they may play in sexual selection. Danielle examined dewlap size and coloration in 13 species of flying dragons. Overall, she found a strong negative correlation between color contrast (meaning they stand out relative to background coloration) and dewlap area in male lizards. Thus, she found that male dragons either had big dewlaps or conspicuously colored dewlaps, but not both. These results suggest that sexual selection for male conspicuity is occurring, but why can’t lizards exhibited large, conspicuously-colored dewlaps? Danielle suggested that having dewlaps that were both conspicuous in color and size were either too risky (meaning that they would be considerably more vulnerable to predation) or too costly to produce or maintain, though the precise mechanism underlying this pattern remains uncertain.

Continue reading ASH 2015: Size and Coloration of Draco Dewlaps

ASH 2015: Fossil Anoles Provide Clues into Ecological Diversification

 

Emma Sherratt gives her talk on fossil anoles

Emma Sherratt gives her talk on fossil anoles

The annual meeting for the  Australian Society of Herpetology (ASH) is wrapping up here today in the lovely town of Eildon, Australia. Just because we’re a continent away from the native distribution of anoles doesn’t mean that anoles were not represented at the meeting. Yesterday afternoon Emma Sherratt, new faculty at the University of New England in Armidale, Australia, presented some of her post-doctoral work on fossil anoles preserved in amber. Emma began by saying that Caribbean anoles represent one of the oldest examples of extant adaptive radiations. Despite the age of this radiation, most of the work on the Caribbean anoles (and other adaptive radiations, for that matter), has focused primarily on living species, with historical inferences drawn from DNA analyses. She pointed out that historical insights based on analyses of extant species only should be treated with caution, unless there is corroborating information from the fossil record.

We know, she said, that islands are typically inhabited by a single lineage of ecomorphs (with subsequent diversification within ecomorphs). The fact that most ecomorph groups are represented by a single lineage on an island suggests that once an ecomorph niche is filled, it cannot be replaced, an idea known as ‘niche incumbency’. She argued that we can use fossils to assess that hypothesis – if fossil anoles pertain to same lineages of ecomorphs (e.g., the cristatellus clade of trunk-ground anoles, or the carolinensis group of trunk-crown anoles), then that would support the idea that ecomorph niches were only filled once. If extinct anoles fell into different lineages of ecomorphs, distinct from those that are extant today, then that would support the idea that ecomorphs could be replaced on islands, which would suggest that niche incumbency need not be occurring. Of course, it could also be possible for niche incumbency to have occurred if there were two lineages of the same ecomorph present on the same island, as long as the incumbent lineage drove the more recent one to extinction. But the hypotheses proposed by Emma were certainly a reasonable first pass to understand the origin of ecomorphs on the Caribbean islands.

Anoles have been fossilized in Hispaniolan amber, which we know to be about 15-20 million years old. All you folks who are anxiously awaiting the next installment of Jurassic Park be advised – this means that the famous amber used to get dinosaur DNA is far too young, as the dinosaurs (save for birds, of course) went extinct about 62 million years ago. For her study, Emma accessed an impressive 38 anole fossils preserved in amber. By far this is the largest data set of fossilized amber anoles ever examined. And, beyond their utility for understanding the process of diversification, anoles caught in amber are stunning fossils and the high resolution reconstructions that Emma makes using x-ray CT scans are equally impressive.

Emma found strong evidence that Hispaniolan fossil anoles fall into known ecomorph categories. To determine this she compared morphological details from extant species to the fossil anoles. Overall she found substantial morphological variation in the fossils, particularly in 20 of the best preserved and most complete fossils. Amazingly, Emma found that some of the fossils fell very clearly into the trunk-crown, trunk, trunk-ground, and twig ecomorph classes! She was further able to determine that the trunk-crown fossils fell into the chlorocyanus group of extant Hispaniolan lizards, and, with less confidence, evidence that the trunk-ground lizards fell into the cybotes group of extant Hispaniolan lizards. Thus, the results are suggestive that, once an ecomorph niche is filled, it prevents other lineages from evolving into it, which is consistent with niche incumbency. Obviously it is not possible to fully rule out the alternative – that species of other ecomorph lineages existed in the past – but certainly the results are a tantalizing glimpse into the processes that forged the current Caribbean fauna. In short, she found that most ecomorphs recognized today are not only present in the Miocene fauna, but also are represented by members of the same clades. Together, her results were consistent with the idea that niche incumbency occurred in the Caribbean radiation of anoles, which would indicate that interspecific interactions have regulated morphological diversity for millions of years.

Australian Society of Herpetology 2015 Meeting: Follow #ASH15 on Twitter

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Greetings from Eildon, Australia, where the 2015 meeting for the Australian Society of Herpetology (ASH) is currently underway. Today is the first full day of talks and posters and I’m excited to learn what’s new and exciting in herpetology. Although the focus is predominantly on Australian amphibians and reptiles, there are several presentations on non-Australian herpetofauna, as well. Anoles are also represented as I will be giving a talk on my work on Hispaniolan anoles and Emma Sherratt will be speaking about her work on fossil anoles. If you would like to see what’s going at ASH, feel free to follow the conference on Twitter using #ASH15.

Observations of Anolis allisoni on the Island of Roatan, Honduras

Marine biologist (and occasional anolologist) James Hewlett, a Professor at Finger Lakes Community College, shared a few photos with me from his recent trip to Roatan island. Jim was in Roatan to do reef surveys, but in the few moments he wasn’t under the water, he was out looking for anoles. He found numerous Anolis allisoni, even at midday, when it was stifling hot. Anolis allisoni are known to be quite abundant on this island, and do exhibit quite a bit of variation in coloration.

Anolis allisoni is not the only anole found on Roatan. It probably comes as no surprise, but the brown anole (A. sagrei) has made its way to the island. Jim did not observe any brown anoles on his recent trip, but I reckon they’re still there and doing just fine. Despite his best efforts, Jim was unable to find the other native Roatan anole, Anolis roatanensis. A few years ago, Jonathan Losos was also unable to spot this creature on his first day of herping, but eventually did find it (see photo in comments below) by visiting more forested areas on the island. If you visit Roatan and manage to spot this species, please do share. We’d love to see more photographs of it.

In the meanwhile, here are some of Jim’s images:

Continue reading Observations of Anolis allisoni on the Island of Roatan, Honduras