Author: JessicaStapley

Postdoctoral Researcher working on the evolution of a dewlap colour-pattern polymorphism in a Panamanian anole

From Across the Pond: Anole Presentations at ESEB 2015

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

 

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

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

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

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

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

 

 

Panamanian Anole Population in Decline

 

Left: A. apletophallus. Right: Decline in abundance of A. apletophallus on BCI

Left: A. apletophallus. Right: Decline in abundance of A. apletophallus on BCI

Monitoring populations over long time scales is one of the most important endeavours in ecology, but maintaining funding over decades is a huge challenge when the tenure of most research grants is only 3 years. The Smithsonian Tropical Research Institute (STRI) has made a concerted effort to address this problem and established long-term monitoring of animals (including an anole), plants and environmental variables on Barro Colorado Island (BCI) and the nearby forests surrounding the Panama Canal. These data provide a rare glimpse into the long-term changes in populations and climate in the tropics.

Recently, we used these data to investigate how population abundance of the anolis lizard Anolis apletophallus has changed over time and whether climate was related to abundance and population growth rate. The study recently published in PLOS ONE identified a decline in lizard abundance over the 40-yr study period. We also observed boom and bust fluctuations in population abundance and found that cycles in population growth rate were related to global weather cycles known as el nino and la nina. Specifically, population growth rate was lower one year after el nino (warmer-drier) events. This decline in abundance and the negative relationship of population growth rate with el nino events is alarming, as el nino events are expected to increase in frequency and severity in the future. Changes in the abundance of this lizard may also have knock-on effects to many other animals in the forest because these lizards are eaten by a range of animals including birds, snakes, other lizards, spiders, ants, bats, monkeys and opossums.

The long-term decline in abundance that we identified is consistent with findings of another long-term study of amphibians and reptiles in Cost Rica by Whitfield et al in 2007. In their study they identified a decline in the leaf litter amphibians and reptiles and suggest this is due to a climate driven reduction in leaf litter. In a more recent follow-up study they provide further evidence of this. Although, we did not measure leaf litter, there is no evidence of a reduction in leaf litter on BCI. The parallel declines that were observed in Panama and Cost Rica are worrying and emphasize the importance of long-term data to help us understand how anole populations are coping with climate change.

Most of the hundreds of researchers that visit STRI’s research station on BCI scarcely notice the anoles. Some are drawn to the monkeys or bats, but most are there to study tropical forest ecology making use of the famous 50ha plot: a forest plot where every free standing tree has been measured every five years since 1980. I can understand how some might overlook the anoles in the forest, they can be extremely well camouflaged, but as readers of AA know, anoles are also highly conspicuous.

Cryptic_ConspicuousAA

Left: Spot the A. apletophallus on the forest floor. Right: Male A. apletophallus displaying

Thankfully, BCI’s anoles have not always been overlooked. The most abundant anole on BCI is Anolis apletophallus (previously limifrons), so abundant that Stan Rand, STRI’s world-renowned herpetologist, described it as the ‘most abundant vertebrate in the forest.’ Thanks in part to Stan’s interest in this little brown anole, the species was the focus of much research on BCI in 70-80s most notably by Robin Andrews. Robin’s research on the ecology, physiology and life history of A. apletophallus remains some of the most detailed knowledge of a mainland anole today. Her work also had a lasting legacy at STRI, and the population monitoring that she began still continues today, some 44 years on.

The annual census, which has been continually funded by STRI, has been able to persist largely because of the efforts of STRI scientists.

Twin embryos

Twin embryos of A. apletophallus dissected from a single egg that failed to hatch.

During my research project on A. apletophallus I dissected many eggs that failed to hatch  but I was very surprised to discover two embryos in this egg.  The female had mated in the wild and laid many normal single embryo eggs before and after this one. Twin embryos have been observed in other lizards (e.g Agama agama (Herptelogica 1967,23:57), leopard geckos and bearded dragons) but I did not find any previous report in anoles. Thought it my interest the AA readers. Anyone else seen this?

 

Female eating her infertile egg

httpv://www.youtube.com/watch?v=3ni3QbKgesI

Last year Martha Muńoz posted on AA about odd behaviors of captive anoles.

Following recent posts about the production of “slugs” or infertile eggs, I thought the readers of AA might be interested in this short (low quality) video of  an A. apletophallus female eating her infertile egg. I think this was a very rare event (only observed once – out of many females) and probably an artifact of being in captivity. Possibly the egg rolled off a leaf or branch and the female grabbed it thinking it was an insect. In the wild the infertile eggs would be consumed very quickly by any number of things – like ants or fungus.

Like others breeding anoles, I have thought a lot about the production of infertile eggs. Female A. apletophallus are egg factories; in the absence of sperm they will produce infertile eggs continuously. I have always thought this was strange – it seems like a waste of resources – why don’t they reabsorb or eat their infertile eggs. The female “knows” the egg is infertile – it is deposited with little or no shell and she does not bury it like a fertile egg.  I presume hormones play an important role in governing this bury or do not bury behaviour. In the case of apleotphallus, all mature females have sperm and when they are relocated into captivity will produce fertile eggs. So I think it is fair to say that in nature they are never lacking sperm, so they will not produce infertile eggs often. Hence under normal circumstances there is no cost to producing these “slugs.”

Considered breeding anoles in situ?

If you are lucky enough to live in the tropics then you can do away with incubators, endless tinkering with temperature, humidity and light regimes and let nature do it for you. I have been breeding A. apletophallus in Panama for almost two years and thought I should share with you my take on breeding anoles “in situ.”

Left: Mesh cages hanging in the shade house. Right: Newly emerged hatchling.

I use a very basic shade house that is situated on the edge of the forest. The temperature and humidity are similar to the forest where the lizards live. In the shade house, the lizards are housed individually in mesh cages that I constructed from pop-up laundry hampers and mesh bags. Each cage is outfitted with three branches and a plastic leaf. Females have a shallow soil plate to lay eggs in, which they happily do. I feed adult lizards every three days and at the same time check for eggs. All eggs are removed and placed in a plastic cup with water and cotton wool, which is then placed inside a ziplock bag. Eggs are “incubated” at ambient temperature (~45 days). When the eggs hatch the hatchlings are transferred to plastic boxes with a mesh lid. These “baby boxes” also contain three small branches and a plastic leaf. Hatchlings and subadults are feed every other day. All lizards are sprayed daily with water. Although there is probably room for improvement, this has been a successful and economical strategy to breeding anoles in the tropics. For anyone who wants more details I have posted this on my webpage under “animal husbandry.”

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