Greg Pauly, the world’s authority on the anoles of California [1,2], kindly passed this information along to AA:
Anolis carolinensis (photo by Cowenby, Wikipedia)
Whole genome sequencing approaches are rapidly becoming more accessible and gaining popularity. The development of powerful analytical tools for these data has enabled novel approaches to answering outstanding evolutionary questions. Yann Bourgeois, a post-doc at NYU- Abu Dhabi, is the first to take a whole genome approach to understand the population genomics of Anolis carolinensis in the southeastern United States. Yann presented his work in a poster at Evolution 2018 in Montpellier.
Yann sequenced 27 individuals from across the native range representing the five unique genetic clusters (Gulf Atlantic, Carolinas, North Eastern Florida, North Western Florida, South Florida). He found that the Gulf Atlantic and Carolina populations were nested within the Florida populations, supporting the hypothesis of a northward expansion from southern Florida. He was able to estimate that this colonization of regions north of Florida likely occurred in the past 100,000 years. Interestingly, he also found that this dispersal event was associated with a reduction in X chromosome diversity, suggesting that dispersal was either male biased or that there has been positive selection on the X chromosome.
Whole genome sequencing of 27 individuals from across the native range reveals population genetic structure
Taking this one step further, Yann then investigated patterns of recombination via secondary contact among the genetic clusters. Yann and his colleagues found that there has been gene flow between clusters over periods of secondary contact with interspersed periods of isolation. Limited introgression between Florida and the northern populations suggests local adaptation in the northern populations.
Yann and his colleagues have provided an interesting first look at the evolutionary history of Anolis carolinensis from a genomic perspective. The revealed patterns of expansion, reduced diversity, isolation, and secondary contact raise interesting questions about the origin of new genetic clusters (and perhaps species) and their maintenance with ongoing or periodic gene flow.
For more information on this exciting research, check out the pre-print of the manuscript.
Evolution 2018 may have been a week and a half ago, but the fun doesn’t have to stop just yet. Shane Campbell-Staton reports on the talk by Guin Wogan:
As we all know by now, contemporary climate change is expected to cause problems for species across the globe. Understanding the mechanisms that will allow species to cope with these changes, through acclimation and/or adaptation, is one of the most pressing issues of contemporary biology. Reptiles, and lizards in particular, have been a model for studying the effects of climate on extinction, gene flow, performance, and adaptation. Yet, only recently have we really begun to understand the genetic mechanisms associated with survival and persistence in the face of changing environments. In this year’s Epigenetics and Adaptation session of the Evolution Meeting, Guinevere Wogan – a postdoctoral researcher in Ian Wang’s Lab at UC Berkeley – presented a first look at how variation in the epigenome correlates with climate variation with and between anole species.
Wogan et al. used reduced representation bisulphite sequencing to search for epigenomic associations with environment in two wide ranging species – Anolis cristatellus on Puerto Rico and Anolis cybotes on Hispaniola – both species that occur in a wide variety of habitats from cool, wet forests to dry, arid scrubland. They found some indication of convergent methylation profiles under similar climates within species, suggesting epigenetic signals may be important for acclimation and/or adaptation to local climate. However, this association was not perfect potentially due to habitat use differences between populations. Additionally, they found that variation in climate between populations explains a large degree of variation in methylation profiles between popualtions within each species (75.6% in A. cristatellus and 39.1% in A. cybotes), again suggesting an important role of epigenetic modification in contributing to survival in local environments. However, local climate isn’t the only factor effecting variation in epigenetic modification; they also found strong species level differences in methylation, even when populations occurred in similar environments.
As they continue to work on this study, it will be very exciting to see what further patterns emerge. As we collectively seek to better understand the mechanisms involved in environmental adaptation and acclimation, Wogan et al. are exploring an extremely understudied aspect of Anolis biology that is bound to shed valuable light on the subject. I’ll certainly be on the lookout for this manuscript in the near future.
Typical Habitat of Anolis onca, close to the ocean.
Anolis onca
I kept Anolis onca, as a hobbyist, in the late 90s; they were available via European breeders who had obtained them on Isla Margarita, Venezuela. I had some breeding success with them at that time, and have always found them fascinating. I assumed their range was specific to Margarita Island, but only later via Anole Annals saw a photo from Manaure and realized that they were also found in Colombia. I travel frequently to Colombia and know that area of the northeast where the photos were taken, so when I was in the area, I would look for them.
Typical Habitat with Milkweed
I first saw them about 4 years ago, during a day trip near Rioacha, the Departmental Capital of La Guajira. The first ones I saw were very small juveniles which were sunning themselves in very thick piles of discarded branches, and so were difficult to catch, handle and photograph. In a subsequent trip in 2017, I enlisted the help of some of the local Wayuu (the indigenous group that is predominant in that area of the country). They called them the “lizard that doesn’t move,” which is a very apt description of their habits.
The habitat in the region is characterized as being dry Chaparral (though with very few trees), and is very windy. While looking for Anolis onca, we would find nests of the local dove species, which choose to nest on the ground versus in the low lying trees probably due to the wind. The main shrub is a species of Milkweed, and animals were found within yards of the Ocean.
I am no newbie to looking for Anolis, but A. onca really is very different in its behavior compared to many of the anoles I had previously observed in the wild. While you often find them on the ground in the midst of thickets of vegetation on the beach, they are very slow and deliberate in their movements and as you approach them. They only seldom move when approached, even when you are very close to them. They are almost twig anole-like in their behavior and obviously rely on camouflage as their first line of defense.
Despite the sparse nature of vegetation in their habitat, ground dwelling habitats and relatively large size for an anole (about 4-5 inches SVL and 6-7 inches in TL), they are a challenge to find. I would estimate that we saw only one animal every 1.5 hours of searching (there were three of us actively looking). We probably saw nine over about 12 hours of searching.
I would be very curious to hear from others who have observed them in the wild, and if Anolis annectens, which is closely related, is similar in its habits.
A. onca male flaring Dewlap on Capture
I found these two specimens in my farm located in the municipality of Santa Sofia, department of Boyacá, Colombia. The living specimen was found near a stream in a wet area, while the dead specimen was found in the house of the farm. The farm is located in an Andean forest at about 2300 meters above sea level where plants such as oaks and eucalyptus trees predominate, among others.
The nursery trade is a known vector for many invasive species including anoles. Anoles have quite the affinity for laying eggs in the moist soil of potted plants, which may then be transported to various locations. Indeed, the nursery trade is the suspected vector for introductions to Hawaii and California of A. carolinensis and A. sagrei and likely accelerated their spread within those states. In fact, citizen scientists on iNaturalist document a reasonable number of brown anoles well outside their normal range. These observations have a distribution that suspiciously coincides with locations of Home Depots and Lowes. However, while the nursery trade is a suspected vector for other species of anoles, verified instances of long-distance transport via the trade are fewer and farther between.
An (as yet) unidentified anole hatchling transported from Puerto Rico to Virginia. From user kimjy3 on iNaturalist.org
One recent observation on iNaturalist documented a hatchling anole that popped out of a potted plant shipped from Puerto Rico as the user unwrapped it…in Alexandria, Virginia. Can anyone on Anole Annals having experience with Puerto Rican anoles and their hatchlings help ID this little one? The user reports that the anole does not have blue eyes; instead they are brown or black.
Feel free to add IDs/comments on the iNaturalist observation as well!
Claire Dufour, Postdoctoral Fellow at Harvard University, presents her research at the 2018 Joint Congress on Evolutionary Biology in Montpellier, France.
In another excellent study exploring the effects of anthropogenic activity on evolution in anoles, Postdoctoral Fellow Claire Dufour is investigating how the recent introduction of Anolis cristatellus from Puerto Rico to the island of Dominica may be driving changes in the display behavior of Anolis oculatus, a Dominica native. Specifically, Dufour is asking whether interactions between the A. cristatellus and A. oculatus are consistent with patterns of Agonistic Character Displacement, in which interference competition between the newly sympatric species results in shifts in traits affecting the rate, intensity, and outcome of interspecific aggression.
To begin, Dufour and colleagues constructed a pair of robots that mimicked the typical look and display behavior of a male A. oculatus and A. cristatellus. She then traveled across Dominica and presented over 130 wild male A. oculatus with one of the two robots, and recorded the display behavior exhibited in response. Beyond measuring the duration of the response display, Dufour also tracked the proportion of time spent by the A. oculatus engaging in any of nine specific display behaviors, such as dewlap extensions, push ups, nuchal crest presentations, and others. By repeating this experiment among populations of A. oculatus existing sympatrically with A. cristatellus, as well as populations not yet invaded by A. cristatellus, Dufour was then able to ask whether variation in display time or composition among the native anoles could be attributed to the presence of A. cristatellus. Indeed, this turned out to be the case.
Anolis oculatus living in allopatry from the introduced A. cristatellus were found to engage in longer display bouts when presented with the conspecific robot, and shorter display bouts when presented with the unfamiliar A. cristatellus robot. Alternatively, A. oculatus occupying habitats already intruded by the A. cristatellus increased the duration of time spent displaying, regardless of which robot was presented. In addition, A. oculatus were also found to alter the behavioral composition of their displays when occupying habitats shared by the introduced A. cristatellus.
Dufour and colleagues capitalized on a rare opportunity to document the very early stages of a species invasion, and in turn improve our understanding of how human-mediated species introductions can promote evolutionary change. As changes in behavior are often the first response to novel competition, these results are consistent with the criteria of Agonistic Character Displacement, and support the claim that the introduction of crested anoles in Dominica has indeed driven a shift in the behavior of native anole communities. While the consequences of these shifts on the outcome of interspecific competition are still unclear, it will be interesting to see how differences in display behavior develop over time, and further, whether these initial changes in display behavior could lead to additional shifts in behavior or morphology among these newly interacting species.
Dr. Kristin Winchell at the 2018 Joint Congress on Evolutionary Biology
Human activity is well recognized as having evolutionary consequences, and studies on the prolific Anolis genus continue to show us just how adaptable these lizards can be. Dr. Kristin Winchell, a Postdoctoral Research Associate at Washington University in St. Louis, MO, is investigating the relationship between human activity and evolution in Puerto Rican crested anoles, with a current focus on how selection across urban habitats might be driving changes in morphology and behavior among the lizards.
In an elegantly designed study, Winchell and colleagues collected over 120 male crested anoles (Anolis cristatellus) from forests and urban areas across the island. The team then assessed the ability of these anoles to perform a series of tasks representing normal daily activities, such as sprinting and clinging. By comparing anole performance on natural substrates like wood to their performance on more urban substrates such as concrete and metal, the team determined that the lizards consistently performed better on natural substrates, yet decreased their velocity when perches were inclined. Specifically, the crested anoles sprinted at less then half of their maximum speed on painted concrete, up to 32% slower on metal compared to wood bark tracks, and as much as 34% slower when surfaces were steeply inclined.
Winchell and colleagues measured differences in limb length and toe pad morphology among urban-caught and forest-caught anoles.
In addition to performance assessments, detailed scans of toe pad and skeletal morphology were collected and analyzed, allowing Winchell to identify differences in morphological traits underlying any variation in performance. Upon comparison, the pattern was clear: lizards living in cities had significantly longer limbs, more lamellae on their front toe pads, and larger overall rear toe pads. Longer hindlimbs in particular were found to positively influence velocity across substrate types, surely a selective advantage for anoles tasked with sprinting between the amply spaced urban perches. However, the urban phenotype is not without cost, as longer forelimbs were found to negatively influence velocity on more steeply inclined surfaces, as well as increasing the lizard’s likelihood of slipping. As all urban populations measured shared these phenotypic traits, however, the advantage of increased speed seems to be worth the costs.
As rates of urbanization continue to increase, further studies examining the response of taxa adapting to urban environments will be imperative. With Winchell’s plan to explore performance and morphological differences in other anole species living across the urban-forest continuum, it will be exciting to learn how these traits are affected within species originating from other territorial and arboreal microhabitats.
Cities were hot at this year’s Evolution meeting because they provide valuable petri dishes for asking myriad evolutionary questions. For example, cityscapes tend to create and retain heat–the so-called urban heat island effect–resulting in significantly elevated temperatures in urban areas relative to nearby undeveloped landscapes. Hot cities thus provide scientists an opportunity for asking questions about how plants and animals adapt to tolerate high temperatures. These questions are especially relevant as the built landscape continues to creep into less-developed surroundings and the globe as a whole experiences year after year of record temperatures.
Dr. Shane Campbell-Staton and colleagues used steep thermal differences between cities and nearby forests in four municipalities in Puerto Rico to determine whether, and to what extent, lizards may have adapted to warmer temperatures in the city. First, they found that operative temperature does change: lizards in cities use warmer perches and they operate at higher body temperatures than their forest counterparts. When brought back to the lab, however, those city lizards did not continue to function better at higher temperatures than their forest counterparts.
So what might be underlying this thermal plasticity?
Campbell-Staton and his collaborators then brought lizards back to the U.S., bred them, and raised the offspring in common conditions. Surprisingly, they found that the differences they observed in the wild populations disappeared in the next generation, an indication that this thermal ability is a plastic response to the thermal environment.
This thermal plasticity observation generated another question: Is thermal plasticity the target of natural selection in urban heat islands? To investigate this, Campbell-Staton isolated and analyzed transcriptomes of skeletal muscles in lizards from the hot city and cool(er) forests. Indeed, after the lizards were subjected to controlled heat treatments in the lab, they found a suite of candidate genes that were expressed at different levels between the populations. More genomic wizardry is planned for the very near future.
The work is ongoing and a very exciting paper is coming together. Keep your eyes peeled because it will certainly make a splash. Additionally, if you’re interested in this kind of work, Campbell-Staton has just started a lab at UCLA and is actively recruiting new lab members. Shoot him an email here.
The anole dewlap is a powerful visual signal to attract sexual partners and repel rivals and predators. The diversity of dewlap color has fascinated researchers for decades, environmental lighting and species competition being among the potential drivers of its evolution. At the Evolution meeting in Montpellier, Winter Beckles, PhD student at the University of Miami, presented his great study on the bark anole. Anolis distichus invaded Miami through multiple introductions events. Intriguingly, these little lizards occupy a range of habitats and present polymorphisms in their dewlap color within populations.
For his PhD, Winter and his colleagues measured the reflectance spectrum of the habitat and of the dewlap of 20 to 25 males per population. They found a strong positive correlation between the relative abundance of habitat UV light and the UV light reflected by the dewlaps. But that was before Hurricane Irma hit Miami in September 2017. And what a destruction it was: the trees, the canopy, the plants and by consequence the habitat lighting, were affected by this catastrophic event.
Despite the obvious negative consequences of the hurricane, this event gave a great opportunity to test the effect of extreme habitat change in the variability of dewlap color in the bark anole. Thus, after Irma, Winter and his colleagues immediately returned to each field site to collect reflectance data of the habitats and dewlaps: Irma altered the light profiles across sites and the correlation between dewlap and ambient light disappeared. In order to track how the relationship between dewlap color and habitat lighting develops over time, Winter plans to collect data in 2018: maybe the correlation will be back. Looking forward to seeing the paper.
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