Thanks to all who submitted photos for the Anole Annals 2017 calendar contest–we received lots of great submissions! We’ve narrowed it down to the top 24, and now it’s time for you to vote! Choose your 5 favorites in the poll below. You can click on the thumbnail to view full-size images. You have 10 days to vote – poll closes next Friday at midnight (11/17). Spread the word!
Thanks to all of you that have sent in photos for our calendar contest! For those who haven’t sent anything yet, now’s your chance – there is ONE WEEK left before the deadline (next Monday, November 6) so if you plan to submit, be sure to do so soon!
To remind you, the rules are here:
Submit your photos (as many as you’d like) as email attachments to firstname.lastname@example.org. To make sure that your submissions arrive, please send an accompanying email without any attachments to confirm that we’ve received them. Photos must be at least 150 dpi and print to a size of 11 x 17 inches. If you are unsure how to resize your images, the simplest thing to do is to submit the raw image files produced by your digital camera (or if you must, a high quality scan of a printed image). If you elect to alter your own images, don’t forget that it’s always better to resize than to resample. Images with watermarks or other digital alterations that extend beyond color correction, sharpening and other basic editing will not be accepted. We are not going to deal with formal copyright law and ask only your permission to use your image for the calendar and related content on Anole Annals (more specifically, by submitting your photos, you are agreeing to allow us to use them in the calendar). We, in turn, agree that your images will never be used without attribution and that we will not profit financially from their use (the small amount of royalties we receive are used to purchase calendars for the winners). Please only submit photos you’ve taken yourself, not from other photographers–by submitting photos, you are declaring that you are the photographer and have the authority to allow the photograph to be used in the calendar if it is chosen.
Please provide a short description of the photo that includes: (1) the species name, (2) the location where the photo was taken, and (3) any other relevant information. Be sure to include your full name in your email as well.
Thank you and good luck!
Another year, another field season (or seasons) come and gone, and now it’s time to share the great anoles we’ve seen! Get ready for the Anole Annals Photo Contest: 2017 Edition.
As in previous years, the Anole Annals team wants to see your best anole photographs for our 2018 calendar.
Here’s how it works: anyone who wants to participate will submit their favorite photos. The editors of Anole Annals will choose a set of 30-40 finalists from that initial pool. We’ll then put those photos up for a vote on this here blog, and the 12 winning photos will be chose by readers of Anole Annals, as well as a panel of anole photography experts. The grand prize winner and runner-up will have his/her photo featured on the front cover of the 2017 Anole Annals calendar, second place winner will have his/her photo featured on the back cover, and they’ll both win a free calendar!
Before we move on, I’d like to issue a correction from last year’s calendar – due to an unfortunate email miscommunication, we accidentally attributed several photos to the wrong photographer. By the time we realized our mistake, the calendar was already in print. We would like to sincerely apologize to Raimundo López-Silvero Martínez and Rosario Basail, whose photos, Anolis vermiculatus (September) and Anolis garridoi (April) respectively, we mis-credited. But please, take a look and appreciate them here! We will be sure to be more careful this year.
Back to business. The rules: submit your photos (as many as you’d like) as email attachments to email@example.com. To make sure that your submissions arrive, please send an accompanying email without any attachments to confirm that we’ve received them. Photos must be at least 150 dpi and print to a size of 11 x 17 inches. If you are unsure how to resize your images, the simplest thing to do is to submit the raw image files produced by your digital camera (or if you must, a high quality scan of a printed image). If you elect to alter your own images, don’t forget that it’s always better to resize than to resample. Images with watermarks or other digital alterations that extend beyond color correction, sharpening and other basic editing will not be accepted. We are not going to deal with formal copyright law and ask only your permission to use your image for the calendar and related content on Anole Annals (more specifically, by submitting your photos, you are agreeing to allow us to use them in the calendar). We, in turn, agree that your images will never be used without attribution and that we will not profit financially from their use (the small amount of royalties we receive are used to purchase calendars for the winners). Please only submit photos you’ve taken yourself, not from other photographers–by submitting photos, you are declaring that you are the photographer and have the authority to allow the photograph to be used in the calendar if it is chosen.
Please provide a short description of the photo that includes: (1) the species name, (2) the location where the photo was taken, and (3) any other relevant information. Be sure to include your full name in your email as well. Deadline for submission is November 6, 2017.
Good luck, and we look forward to seeing your photos!
Cities and urban areas are expanding rapidly around the world, altering the environment and creating very different ecological and selective pressures for organisms that live in urban habitats. A few of the most striking differences between urban and natural habitats are higher temperatures and a huge increase in artificial substrates like the walls of buildings. These artificial substrates (e.g., metal, concrete) are not only significantly smoother than natural (i.e., trees) substrates, but also absorb, retain, and radiate heat differently. Consequently, organisms may alter their behavior to better deal with these and other challenges of city life. Since anoles cannot internally regulate their temperature, behavioral shifts may be driven by perch substrate properties, temperature, or some interaction of the two.
Kevin Aviles-Rodriguez (U. Mass. Boston) addressed this question in urban Anolis cristatellus in San Juan, Puerto Rico. He created experimental enclosures in which each wall was a different substrate: wood, plastic, painted cement, and metal. He placed individual lizards into the enclosures and observed which wall they were perched on throughout the day. He also recorded the temperature of each wall, to determine how perch temperature of each substrate type influenced perch choice. Aviles-Rodriguez conducted this experiment in both urban and forest populations, and predicted that urban lizards would use artificial substrates more readily than forest lizards.
Interestingly, he did not find that to be the case – lizards from both urban and forest habitats used bark much more than any other surface. However, when lizards did use artificial substrates, they tended to use metal and cement when these perches were cooler, suggesting that perch temperature is a factor in perch choice. Aviles-Rodriguez plans to test these hypotheses more thoroughly by conducting additional experiments across more urban replicates to see if the same pattern emerges. He also plans to experimentally control the temperatures of different perch substrates in his enclosures to see whether lizard choices are primarily driven by perch substrate or temperature.
Anolis distichus is well-known in the anole world for the high degree of ecomorphological variation within the species, especially in dewlap color. In fact, there are 18 described subspecies! While there is some gene flow between various subspecies and populations, the phenotypic differences are maintained, which suggests strong selection. But the fine-scale genetic structure underlying these traits is not well understood. Anthony Geneva and colleagues decided to explore the genomic basis of adaptive divergence in a well-described hybrid zone between two A. distichus subspecies. The first, A. d. ignigularus, has a white dewlap, and occupies a dry forest habitat while the second, A. d. ravitergum, has a red dewlap and inhabits a wetter habitat. The two subspecies occur along a transect from dry to wet, and they hybridize in a narrow contact zone in the middle. These two subspecies provide a great system to explore the link between adaptive and genetic divergence.
Geneva sequenced individuals using RNASeq across an environmental transect from wet to dry, including allopatric and sympatric populations of both species. He examined levels of divergence and introgression to explore which genomic loci might be the basis for the ecological adaptive divergence between these two species. He found a suite of candidate genes that differ between the two subspecies, as well as several that show signs of introgression between the two. Interestingly, several of the divergent genes are involved in two traits that likely are impacted the environment – insulin signaling, which may relate to metabolic differences between hot and cool climates, and vision, which may relate to differences in light availability and signal efficiency. Most of the introgressed genes, on the other hand, relate to conserved pathways, suggesting that these genes play similar roles in both subspecies.
Adpative divergence in anoles has been a topic of interest for a long time, and Geneva’s study provides and a valuable insight to the genetic basis of this interesting phenomenon.
Sexually antagonistic selection occurs when traits are beneficial for one sex, but detrimental to the other. This commonly occurs in species with sexual dimorphism, such that one trait is positively correlated with fitness in one sex, and negatively correlated with fitness in another. But in many organisms, the sexes do not become dimorphic until maturity – that is to say, juveniles all look pretty much alike, even when adults show clear differences between males and females. Which leads to the question: how does sexually antagonistic selection change over an organisms’ lifespan? Research from studies of Drosophila flies suggests that this is the case, but the question hasn’t been well-studied in vertebrates.
Until now. In his Evolution talk, Aaron Reedy (University of Virginia) described his work testing whether sexually antagonistic selection changes over ontogeny using our favorite workhorse of evolutionary ecology, the brown anole (A. sagrei). Anolis sagrei are sexually dimorphic, with adult male body sizes up to 30% larger than females, but juveniles are monomorphic. Reedy and colleagues sampled A. sagrei on several small islands in a Florida watershed four times a year, capturing thousands of adults and juveniles. They measured the body size of all lizards captured, and combined this morphological data with survivorship data to determine how selection was acting on body size in adults and juveniles.
They predicted that juvenile males and females would experience concordant selection, while adult males and females would experience antagonistic selection. And this is exactly what they found: for juveniles, body size was correlated with survival in the same way between sexes. But in adults, this was not the case. In the first year of sampling, there was no selection on body size for adult females, but positive selection for males, such that bigger males survived better. Interestingly, during the second year of sampling, the relationship flipped – females experienced positive selection on body size, and males experienced negative selection. The reasons for this shift are uncertain, but the main point is clear – sexually antagonistic selection does indeed change over ontogeny. Reedy et al. are planning to follow up this great new research by expanding their study to look at more islands and more traits to get at the finer points of these selective differences, so stay tuned!
As a lineage splits and diversifies, species’ traits diverge in different ways. For example, as anoles diversified in the Caribbean, trunk-ground anoles’ bodies become muscular and stocky, trunk-crown anoles’ heads become long and thin, and grass anoles’ tails become long and slender. This process of adaptation to different environments seems simple and intuitive, but the evolution of traits is not so simple.
Most traits don’t evolve independently – changes in one trait are often correlated with changes in another trait, which can constrain a species’ response to selection. This correlation between traits is represented by the genetic variance-covariance matrix (G matrix). The size, shape, and orientation of the G matrix determine the speed and direction of morphological change, and defines the “line of least genetic resistance” along which a species can evolve. But of course, as species diverge and their traits shift, the correlations between these traits themselves may not stay constant – that is to say, the G-matrix itself can evolve. Which means that G represents both a constraint on evolutionary change, as well as a product of evolution itself. So does the G matrix evolve along with species divergence, or does it limit morphological evolution?
In his talk at Evolution 2017, Joel McGlothlin (Virginia Tech) described his efforts to address these question in anoles. As a poster child of adaptive radiation, Anolis provides an excellent opportunity to explore the dynamics of G matrix evolution and evolutionary constraint. To that end, McGlothlin and colleagues estimated G matrices for seven anole species (no easy task), including representatives from three ecomorph categories. He laid out the following question: has the G matrix evolved as Anolis diversified? Or do we see a signature of constraint conserved across anoles?
First, McGlothlin and colleagues found that the G matrix has indeed evolved in the course of Anolis diversification: the shape, orientation, and size of the G matrix was different for each species studied. More closely related species had more similar G matrices, and there was a weak link between ecomorph and G matrix structure, but overall, G was clearly different across the seven anole species. This suggests that trait correlations (and therefore species’ potential responses to selection) are not necessarily constant across the anole radation.
However, despite this overall divergence, one important aspect of the G matrix – its orientation – was similar across all anole species sampled. This suggests that the line of least genetic resistance has remained constant throughout the diversification of anole ecomorphs, and is deeply conserved. So even though individual species’ trait correlations have changed as anoles have diverged, the signature of morphological constraint has persisted. The study provides a fascinating illustration of the complexity of morphological evolution, and provides a fresh new link between micro- and macro- evolutionary processes in Anolis lizards.
I’ve been looking through a lot of anole museum specimens lately, and I’ve noticed that many of them have pretty pronounced endolymphatic glands, which made me curious about their prevalence and function in anoles generally.
Endolymphatic glands serve as calcium reserves, and are present in many animals, including a number of reptile and amphibian clades. According to Etheridge (1959), these glands are present in anoles and a few of their close relatives (e.g. Polychrus), but not in any other Iguanians. But it looks like most of the research on their function (in reptiles) has focused on geckos. In geckos, the size of the glands has been shown to fluctuate in response to both stress and reproductive activity, supporting the idea that the stored calcium is used in egg production, both for the yolk and the shell (Brown et al. 1996, Lamb et al. 2017). However, in anoles and geckos, these glands are present in both males and females, so their function isn’t limited to providing calcium for eggs (Etheridge 1959, Bauer 1989, Lamb et al. 2017).
But I haven’t found much information on these glands in anoles. I personally haven’t noticed them in the wild, but so far I’ve found very pronounced glands in 13/66 museum specimens, and some of them are really striking (see photos)! So I’m curious to hear, how often do you other anole-ologists see these enlarged glands? Is there any other literature about their prevalence, seasonality, or function in anoles that I’ve overlooked? Seems like we might be lagging behind the gecko crowd on this topic!
Bauer A (1989) Extracranial Endolymphatic Sacs in Eurydactylodes ( Reptilia : Gekkonidae), with Comments on Endolymphatic Function in Lizards. J Herpetol 23:172–175.
Brown SG, Jensen K, DeVerse HA (1996) The Relationship Between Calcium Gland Size, Fecunduty and Social Behavior in the Unisexual Gecks Lepidactyluse Lugubris and Hemidactylus Garnotii. Int J Comp Psychol. doi: 10.5811/westjem.2011.5.6700
Etheridge R (1959) The relationships of the anoles (Reptilia: Sauria: Iguanidae) an interpretation based on skeletal morphology.
Lamb AD, Watkins-colwell GJ, Moore JA, et al (2017) Endolymphatic Sac Use and Reproductive Activity in the Lesser Antilles Endemic Gecko Gonatodes antillensis (Gekkota: Sphaerodactylidae). Bull Peabody Museum Nat Hist 58:17–29.
Thank you to all who sent in photos for our contest; we received a total of 101 submissions! We’ve tallied the results and consulted our panel of experts, and are ready to announce the winners for Anoles 2017. The grand prize winner is the photo above, Anolis equestris potior, taken by Jesús Reina Carvajal. The second place winner is below, Anolis aquaticus, taken by Lindsey Swierk. Congratulations!
The rest of the winners can be seen in the 2017 calendar here! Click the link to order your calendar, just in time for the holidays. Congratulations to all the winners, and thank you again to everyone who participated!
Happy holidays! Can’t wait to see the submissions next year!
Thank you to everyone who submitted photos for the Anole Annals 2016 calendar contest, we received so many great submissions! We’ve narrowed it down to the top 30, and now it’s time to vote! Choose your 5 favorites in the poll below. You can click on the thumbnail to view full-size images. You have 5 days to vote – poll closes on Monday at midnight (11/21).
Thank you to everyone who has sent in photos for our calendar contest, we’ve been getting some excellent submissions! There are FIVE DAYS left before the deadline (this Friday, November 4) so if you plan to submit, be sure to do so soon!
As a reminder, here are the contest rules:
Submit your photos (as many as you’d like) as email attachments to firstname.lastname@example.org (note the change in email address from last year). To make sure that your submissions arrive, please send an accompanying email without any attachments to confirm that we’ve received them. Photos must be at least 150 dpi and print to a size of 11 x 17 inches. If you are unsure how to resize your images, the simplest thing to do is to submit the raw image files produced by your digital camera (or if you must, a high quality scan of a printed image). If you elect to alter your own images, don’t forget that it’s always better to resize than to resample. Images with watermarks or other digital alterations that extend beyond color correction, sharpening and other basic editing will not be accepted. We are not going to deal with formal copyright law and ask only your permission to use your image for the calendar and related content on Anole Annals (more specifically, by submitting your photos, you are agreeing to allow us to use them in the calendar). We, in turn, agree that your images will never be used without attribution and that we will not profit financially from their use (nobody is going to make any money from the sale of these calendars because they’ll be available directly from the vendor).
Please provide a short description of the photo that includes: (1) the species name, (2) the location where the photo was taken, and (3) any other relevant information. Be sure to include your full name in your email as well. Deadline for submission is November 4, 2016.
As in previous contests, the Anole Annals team is calling for submissions of your best anole photographs for our 2017 calendar.
The editors of Anole Annals will choose a set of 30-40 finalists. Twelve winning photos will then be selected by readers of Anole Annals and a panel of anole photography experts. The grand prize winning and runner-up will have his/her photo featured on the front cover of the 2016 Anole Annals calendar, second place winner will have his/her photo featured on the back cover, and they’ll both win a free calendar! (Last year we had so many submissions we had to make two calendars; check them out here and here).
The rules: submit your photos (as many as you’d like) as email attachments to email@example.com (note the change in email address from last year). To make sure that your submissions arrive, please send an accompanying email without any attachments to confirm that we’ve received them. Photos must be at least 150 dpi and print to a size of 11 x 17 inches. If you are unsure how to resize your images, the simplest thing to do is to submit the raw image files produced by your digital camera (or if you must, a high quality scan of a printed image). If you elect to alter your own images, don’t forget that it’s always better to resize than to resample. Images with watermarks or other digital alterations that extend beyond color correction, sharpening and other basic editing will not be accepted. We are not going to deal with formal copyright law and ask only your permission to use your image for the calendar and related content on Anole Annals (more specifically, by submitting your photos, you are agreeing to allow us to use them in the calendar). We, in turn, agree that your images will never be used without attribution and that we will not profit financially from their use (nobody is going to make any money from the sale of these calendars because they’ll be available directly from the vendor).
Please provide a short description of the photo that includes: (1) the species name, (2) the location where the photo was taken, and (3) any other relevant information. Be sure to include your full name in your email as well. Deadline for submission is November 4, 2016.
Good luck, and we look forward to seeing your submissions!
In recent years, the study of microbiomes – the communities of microorganisms living in certain environments or in association with hosts – has boomed. It’s long been understood that microorganisms (especially bacteria) can play a big role in host health, but recent work has also shown that microbes can have a huge impact on many other important facets of a host’s life, from growth and development to behavior. Despite the importance of these microbiomes, the ecological and evolutionary processes that shape them are still not very well understood.
In a recent study, Ren et al. (2016) decided to use our favorite model system to better understand the relationship between host and microbiome. As a classic example of an adaptive radiation, Anolis lizards provide an opportunity to test both ecological and evolutionary factors that might be influencing their microbiomes. In this study, the authors asked whether the evolutionary and ecological diversification of a host lineage (anoles) has structured the biodiversity of the gut microbiome community.
The authors used several approaches to address this question. First, they sampled gut microbiomes (using fecal samples) from six Puerto Rican anole species representing three ecomorphs: two trunk-crown sister species (A. evermanii and A. stratulus), two grass-bush sister species (A. pulchellus and A. krugi), and two trunk-ground species (A. cristatellus and A. gundlachi). They predicted that microbiomes of species of the same ecomorph would be more similar to one another than to species of different ecomorphs, reflecting an influence of either ecological similarity or phylogenetic relatedness on gut microbiome composition. Second, they sampled invasive populations of two trunk-ground species in Florida (A. cristatellus and A. sagrei) in sympatry and in allopatry to explore a) whether species that are phylogenetically distinct but ecologically similar have similar gut microbiomes and b) whether gut microbiome is influenced by the local environment. Lastly, they documented individual variation in gut microbiome composition over time by recapturing and resampling marked individuals.
The most striking result of the study was the huge amount of variability in gut microbiome composition between individuals (Fig 2, Ren et al. 2016). For example, on average, any two gut microbiomes only shared 7% of their bacterial OTUs (“Operational Taxonomic Units,” you can think of them as bacterial species). Such high variability from one individual to another is notable, compared to studies of other organisms.
In their analysis of the Puerto Rican anoles, the researchers found that gut microbiomes were more similar between conspecifics than between individuals of different species, but only weakly so. Perhaps more surprisingly, there was no difference in gut microbiome composition based on ecomorph. The authors suggest that this lack of distinction between ecomorphs may stem from the fact that most anoles are dietary generalists; although different ecomorphs do partition habitats, they still overlap in the types of arthropods that they consume, which could impact their gut microbiomes. The authors find further support for this conclusion in their separate analysis of temporal variation in A. sagrei. The composition of an individual’s gut microbial community fluctuated greatly over time, suggesting that transient factors (such as variability in diet) have a significant impact on the gut microbiome.
Interestingly, the two invasive trunk-ground species in Florida showed a much stronger pattern: despite being of the same ecomorph, the gut microbiomes of the two species were significantly different from one another. The authors suggest that the strong signal in these not-so-closely-related invasive anoles along with the weak signal in the closely-related Puerto Rican anoles might indicate that Anolis evolution could have impacted the diversification of the gut microbiome over long evolutionary timescales, but the Puerto Rican radiation just is too young for such microbiome divergence to have occurred. But it’s also possible that the difference in the microbiomes of the two invasive anoles is just a holdover from the source environments (Puerto Rico and Cuba) that has been maintained in their invasive ranges. To throw another wrench into the works, the authors also found that allopatric populations of one of the invasive species (A. cristatellus) were different from one another, while those of the other invasive species (A. sagrei) were not.
So does host ecology impact gut microbiome? Does host phylogeny? Or host environment? Ren et al.’s study suggests possibly yes to all, but with limited (and somewhat conflicting) evidence, it’s hard to draw any certain conclusions. Perhaps more poop from more branches of the Anolis tree will hold the answers.
Find the full paper here:
Ren, T. et al., 2016. Does adaptive radiation of a host lineage promote ecological diversity of its bacterial communities? A test using gut microbiota of Anolis lizards. Molecular Ecology.
I was recently doing some anole field work in the Gulfo Dulce area of Costa Rica, and I came across a lizard that has me stumped. Perhaps some more experienced AA readers have some insight – any idea what species this little guy is? To me, it looks a bit like A. limifrons and a bit like A. carpenteri, but not completely like either (and carpenteri isn’t supposed to occur in the Gulfo Dulce area). It was in an area of pretty thick primary forest, perched about 6 ft or so up a tree trunk, and it ran quite high when I pursued it. I’d appreciate any tips!
Adaptive radiation is one of the most intriguing processes in evolutionary biology, and anoles are one of the well-studied examples of this process. Anoles have diversified into over 400 species across the Caribbean and Central America, and contain a multitude of highly divergent morphological and behavioral types. Thanks to an impressive history of research on this clade, we now know quite a lot about the phenotypic aspects of this adaptive radiation; however, we still don’t have a good understanding of the genetic mechanisms underlying this diversity of form, physiology, and behavior. The recent advent of next-generation sequencing, and thus the ability to quickly sequence entire genomes of non-model organisms, offers a tantalizing possibility for investigating the genetic basis of adaptive radiation in Anolis.
Tollis et al., in a lightning talk at Evolution, take advantage of these new genome-sequencing techniques to approach the genetics of adaptive radiation in Anolis. To understand the genetic mechanisms underlying the adaptive radiation of anoles, they preformed de novo genome sequencing on three Anolis species (Anolis frenatus, Anolis apletophallus, and Anolis auratus), chosen to capture different sub-groups of the Anolis phylogeny. With these data, and the published genome sequence of Anolis carolinensis, they looked for patterns in the rate of evolution compared to other vertebrate groups. They also looked within the Anolis genome to detect specific genetic regions associated with selection across the anole radiation.
Tollis et al. found that, in general, anoles appear to have a high rate of molecular evolution for a vertebrate species, which may parallel the high rate of phenotypic evolution seen in this clade. In addition, Tollis et al. looked for signatures of selection across the four Anolis genomes and identified regions associated with reproduction, olfactory reception, and limb development. This last category is of special interest, given that anoles are notorious for changes in limb morphology between species and that limb morphology is one of the key components of ectomorphs in the Greater Antilles. Tollis et al. have provided a great example of using new genetic tools to approach fundamental questions about the mechanisms underlying adaptive radiation.
The invasive brown anole A. sagrei is a territorially polygynous species, and male aggressive behavior is an important trait that affects male fitness. Aggressive behavior is quite variable across individuals and populations, and can differ based on intra- and inter-specific community context. As AA regulars know, A. sagrei is also a very successful invasive species; it has been established in southern Florida for decades, and has been steadily spreading north along the gulf coast, colonizing new regions of the US. Populations at the leading edge of the range expansion experience different biotic and abiotic environments than established populations, which can lead to different selective pressures and divergence in relevant traits. Invasive populations of A. sagrei thus provide a good opportunity to explore variation in aggressive display behavior across different ecological contexts.
Julie Wiemerslage decided to take that opportunity and explore the variation in aggressive behavior across different populations of A. sagrei. In her poster “Population Differences in Territorial Aggression in the Invasive Brown Anoles, Anolis sagrei” she proposes the following two hypotheses: 1) Lizards at the leading edge of the range expansion will be more aggressive, allowing them to outcompete other species in their new range 2) Lizards at the leading edge will be less aggressive, because population densities will be lower than areas with established populations.
To test these hypotheses, Wiemerslage collected male lizards from a) native populations, b) well-established invasive populations, and c) recent invasive populations and brought them to the lab for behavioral trials. For each population, she placed pairs of males together in a cage and quantified aggressive behavioral traits including pushups, head bobs, lunges, and dewlap flashes (don’t worry, the lizards were tethered so they couldn’t actually harm one another). She found that aggression was lowest in the leading edge populations, supporting hypothesis 2. Interestingly, the most aggressive populations were the well-established invasive populations, while individuals from the native range showed an intermediate level of aggression. The cause of this pattern is unclear, though Wiemerslage suggests that more information about these source populations (such as density, community composition) will improve our understanding of the factors affecting aggressive behavior.
Researchers that are interested in ecological and evolutionary dynamics through time often make inferences about past patterns and processes using modern data, such as DNA sequences and geographic distributions of extant taxa. But this is not the only possible approach. Studies of extinct taxa and populations using fossils can provide direct measures of species distributions and abundances in the past, which are often impossible to accurately infer with modern data alone.
In her talk titled “Extinction biases and their ramifications on Caribbean lizard communities,” Melissa Kemp described her research using fossil data to characterize the former herpetofaunal community of several islands in the Caribbean. She explored the following questions linking extinction to community ecology: 1) how has extinction proceeded in the Caribbean lizard community? 2) what is the impact of species extinction on the whole community? 3) can we predict future patterns of extinction using fossil data?
To characterize past extinction patterns, Kemp measured species abundance and morphological traits of fossil remains through time in lizard communities in the Caribbean. She sought to determine whether certain taxa underwent more local extinctions, and whether extinctions were correlated with certain morphological traits. She also quantified community evenness to see how extinction events affect the whole lizard community. She found that one family, the Leiocephalidae, has gone extinct more often than others. Interestingly, in a four-species community in which Leiocephalidae went extinct, anoles went from relatively average abundance to becoming the dominant taxa, a pattern which continues to this day. Modern Leiocephalids have been shown to predate on anoles, so this community shift may have been a result of predator release. In addition, anole body sizes increased after Leiocephalid extinction, lending further support to the predator release conclusion.
After looking at historical patterns of extinction and diversity, Kemp explored whether fossil data might give us insight into current and future patterns of extinction. For example, are species that have gone extinct in some areas vulnerable to extinction in other parts of their range? And if so, what traits are causing this vulnerability? To address these questions, Kemp compared traits of extinct taxa to traits of modern successful introduced species, which are likely to have a very low risk of extinction. She found that extinct species tend to have different reproductive modes and habitats from introduced species, suggesting that these traits may have played a role in their extinctions. In addition, modern species with similar suites of traits as the extinct taxa may be more vulnerable to extinction in the future.
Kemp’s research shows that it’s not always best to leave the past behind. Fossil data enhances our understanding not only of extinct species, but of modern ecological and evolutionary processes as well.
Species divergence is driven by a wide variety of forces, but two of the strongest predictors of speciation are the amount of time a lineage has persisted in a landscape, and the ability of lineages to move through a landscape. Lineages are more likely to diverge when they have occupied a landscape for a long time, and/or if their ability to move is restricted, thus limiting gene flow.
In his talk titled “Geographical factors promoting diversification of the northern Andes and Brazilian Cerrado regions: the case of frogs and Anole lizard species,” Carlos Guarnizo described his efforts to test whether these patterns hold true in both different landscapes and different taxa. He surveyed two herpetofaunal communities in two diversity hotspots in South America: frogs in the northern Andes mountain range and Anolis lizards in the Brazilian Cerrado. The montane Andean landscape is structurally complex and covers a range of altitudes, while the Cerrado region is a more uniform savannah-like environment, with intermediate structural complexity. Guarnizo used species distributions and genetic data to look at patterns of diversification across these landscapes to explore which landscape characteristics lead to higher levels of divergence and speciation.
He found that in both areas, topography was a strong predictor of divergence; specifically, more structurally complex landscapes led to higher levels of genetic divergence between sister lineages. These genetic breaks are also often deeper than previously realized, likely representing cryptic species. Despite these strong genetic splits, the niches occupied by sister taxa are generally well-conserved, lending support to the conclusion that landscape structure – rather than adaptive divergence – is responsible for the genetic divergence observed. Interestingly, in Andean frogs, Guarnizo found that the strongest genetic breaks did not occur across mountain peaks as previously thought. Instead, valleys appear to be the strongest geographic barrier to dispersal.
These cases show that landscape topography is a strong factor determining genetic divergence across different landscapes and taxa (including anoles), and may lead to high levels of cryptic speciation.
It’s true, they’re not anoles, but lizards of the genus Liolaemus form another extremely diverse clade, occupying one of the broadest climatic and elevational niche ranges of any vertebrate. Whether the ecological and phenotypic diversity of this genus are correlated, as is the case in adaptive radiation, remains an open question. Studies of the whole genus have shown that body size diversification is consistent with expansion into different ecophysiological niches, but other morphological traits don’t show the same pattern. Yet much of the ecology of the genus is unknown, so it is difficult to draw any definite conclusions.
In her talk “Evolution of niche and ecomorphological traits in a phylogenetic context in lizards of the Liolaemus bibroni complex,” Dan Edwards sought to address this gap in understanding of Liolaemus by focusing on one species complex within the genus, L. bibroni. The L. bibroni species group is composed of 26 species that occupy a broad range of habitats representative of those occupied by the genus as a whole. To explore their history of genetic and morphological diversification, Edwards constructed a phylogeny of the group, characterized rates of diversification, and measured a suite of relevant morphological traits. She found that there has been an increase in trait diversification over time, consistent with the colonization of new habitat types. In addition, she found that ecology and body size are significantly correlated, supporting previous results from studies of the genus as a whole. Other morphological traits were not as clearly associated with habitat type, but there do appear to be possible patterns of ecomorphological divergence in response to divergence in habitat. Edwards plans to further characterize the evolutionary relationships and explore more ecomorphological traits of Liolaemus species to resolve this question.
Many exaggerated phenotypic traits, such as the large and colorful dewlaps of male anoles, increase fitness of individuals who possess them. But these traits are often energetically costly. Too high an investment in showy or extreme traits can come at the cost of an individual’s health and performance. Such traits are therefore said to be condition-dependent; that is, individuals will not develop them unless they are already in a healthy condition.
John David Curlis and colleagues explored several potential condition-dependent traits in two closely related Central American Anolis species, A. limifrons and A. humilis. He quantified a number of sexually and naturally selected traits and tested whether they varied by body condition to see whether any of them were condition dependent, and whether the degree of condition dependence varied between two closely related species. None of the traits he tested were condition dependent in A. limifrons, but two traits – jaw width and dewlap size – were condition dependent in A. humilis. He therefore concluded that the degree of condition dependence of these traits is evolutionarily labile. In addition, A. humilis dewlaps are generally larger than A. limifrons, which suggests that condition dependence may be a more important force affecting traits that are subjected to stronger sexual selection. Taken together, these results suggest that condition-dependence of sexually-selected traits may be playing a role in dewlap diversity (and perhaps other phenotypic traits) throughout Anolis lizards.