Tag: JMIH2016

JMIH 2016: Variation in Limb Length across Lizard Groups

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Travis Hagey presented some new results from his ongoing research on the evolution of functional traits in lizards. Travis normally works on geckos, but frequently includes Anolis species in his studies. Last year at Evolution, Travis told us about toepad evolution by comparing gecko toepads to those of anoles and skinks. Along the same vein, this year at JMIH Travis talked about patterns of limb-length across different lizard groups.

2016-07-10 10.46.47Travis started with anoles as an example of morphology being correlated with habitat use. As we all know, anole limb length is associated with structural habitat. Lizards like Anolis occultus (a twig anole) use thin perches and have very short legs. Other species that perch on broader substrates tend to have longer legs. Travis is interested in finding out if this pattern holds for other groups of lizards.

He started by comparing anoles to geckos to see if relative limb length differed between the groups. He accumulated an impressive database of hindlimb lengths from many gecko and 2016-07-10 10.50.43anole species and when he looked at the relationship between hindlimb length and body size (SVL), he found that for a given body size anoles tended to have longer limbs than equivalently sized geckos. He then added in data for a number of species from Liolaemus, Tropidurus, and Phrynosomatidae. Interestingly, he found that these other groups all clustered with the anoles. This suggests that there are possibly two relationships between limb-length and body size across lizards.

2016-07-10 10.53.02Travis ended by commenting on how this might relate to habitat use. He analyzed hindlimb length by perch diameter for anoles (red line) and geckos (black line). Geckos, it turns out, have a different relationship between perch use and limb length than anoles: geckos with shorter limbs tend to use broader diameter perches! Travis is still working on this research and is looking for data on limb length for many groups. If you have hindlimb length data from lizards you should email Travis to help out!

JMIH 2016: Phylogeography and Population structure of Anolis cristatellus

Quynh Quach presenting her Master's thesis work at JMIH.

Quynh Quach presenting her Master’s thesis work at JMIH.

Quynh Quach, a master’s student from the Revell Lab at U. Mass. Boston, presented her thesis research on “Phylogeography and Population Structure of Anolis cristatellus on the island of Vieques.” Before Quynh joined the Revell lab, former  post-doc Graham Reynolds and former Losos lab undergraduate Tanner Strickland looked at the phylogeography of Anolis cristatellus across Puerto Rico and the Virgin Islands using mitochondrial DNA (in review). Tanner’s work revealed that there was a mitochondrial break on the island of Vieques, just off the coast of Puerto Rico. The mitochondrial data suggested that there were two genetically different groups of A. cristatellus, one on the East and one on the West of Vieques. The only problem was, as we know, mtDNA patterns are not always supported by nuclear whole-genome DNA patterns. In addition, Tanner’s dataset only consisted of 9 samples from Vieques.

When Quynh joined the lab, she wanted to know more about this pattern. Would this division be supported by nuclear genome analyses? Were these lineages anthropogenically introduced? If not, what was the origin of these groups – historical allopatry followed by secondary contact or isolation by distance? So she set out to answer these questions by collecting 300 tail tips from across the island of Vieques, extracting and sequencing both mtDNA and nuclear DNA.

The mtDNA variation shows a strong geographic pattern.

The mtDNA variation shows a strong geographic pattern.

Quynh first constructed a mitochondrial phylogeny to verify the pattern observed by Tanner and Graham. The mtDNA analysis confirmed that there are 2 mtDNA clades on Vieques with strong geographic patterns. The island-wide pattern of mtDNA variation was not what we would expect if anthropogenic introduction were the cause since this would be unlikely to show such a clear East-West pattern with the small contact zone in the middle. So then how did this pattern arise?

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Analysis with K=2 shows two clear groups associated with the East and West.

To answer that question, Quynh next looked at nuclear DNA using RADseq. She sequenced 48 individuals: 5 from Virgin Islands, 6 from Puerto Rico, and 37 from Vieques, then de novo assembled the genome and called 16,808 SNP’s. She ran STRUCTURE and DAPC analyses on this data and found that the Virgin Island samples form 1 cluster and Puerto Rico and Vieques form a second cluster with 4.1% divergence between the groups. But she wondered, what if we look at just Vieques and specify K=2? When she did this with DAPC and saw a clear geographic pattern similar to what she found with the mtDNA. Finally, she tested whether this represented isolation by distance. She found that there was significantly reduced gene flow between geographically distant individuals, supporting this hypothesis as the most likely cause of the variation.

Lastly, Quynh emphasized that it is important to consider multiple genetic markers and not just rely on mtDNA results. Had the group stopped at their original mitochondrial analysis, they would have reached a very different conclusion.

JMIH 2016: Jonathan Losos, Distinguished Herpetologist

JMIH

The Joint Meeting of Ichthyologists and Herpetologists (JMIH) kicked off here in New Orleans yesterday. In the morning, Jonathan Losos got started with the first of many anole themed talks. Jonathan gave one the plenary addresses as the Herpetologists’ League’s “Distinguished Herpetologist” of 2016. As such, he joins a long list of accomplished herpetologists, including the first recipient of the honor in 1981, the great anole biologist (and Jonathan’s undergraduate advisor) Ernest E. Williams.

In Jonathan’s talk entitled “Known knowns and unknown unknowns: herpetological progress in fits and starts”, Jonathan started by paying homage to Ernest Williams. He managed to find slides from Ernest’s 1981 plenary address in which the perception at the time of anole biology was compared to a well-built building. All there was to know about anoles was known… or so people thought. In reality, the building looked more like this:

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E.E. Williams slide on the state of anole knowledge from 1981

The metaphorical building at the time was in fact only partially built, with bits and pieces of different areas more complete than others. Jonathan’s talk focused on the fact that despite over 3 decades of progress, so much is still unknown about anoles, including basic natural history of many species. And so Jonathan shared with us a few stories highlighting some surprising anole findings and remaining unknowns, featuring the work of his students from the past 20 years:

Genetic diversity:
One surprise finding over the past 30 years is that several anole species have deep 2016-07-07 11.07.29mitochondrial splits. Anolis oculatus, for example, on the tiny island of Dominica has 4 distinct lineages with as great as 10% mtDNA divergence (Malhotra and Thorpe 2000)! And they aren’t the only ones. Rich Glor and Jason Kolbe really broke this story open with their analysis of several anole species showing multiple mitochondrial lineages for each (Kolbe et al. 2007). This brings into question our estimates of diversity. If every species is actually 4+ species, have we underestimated diversity?

New Species:
According to Jonathan, it seems that the “dawn of anole discovery” peaked in the 1970’s – the last very distinctly different anole was discovered nearly 40 years ago. And yet just last month, Luke Mahler et al. published a record of a new species of anole discovered on the island of Hispaniola! Hispaniola has been intensely studied by anole biologists, making this all the more surprising. In honor of the naturalist that found the species in the wild, the authors named the new species Anolis landestoyi. This new species has a striking appearance, similar to a chameleon and to the Cuban “false chameleons” (Chamaeleolis clade of anoles), and brings up the question of whether there might be a seventh ecomorph.

Anolis landestoyi, photo by D. Luke Mahler

Anolis landestoyi, photo by D. Luke Mahler

Territoriality:
Highlighting the work of two other Losos Lab members, Alexis Harrison and Ambika Kamath, Jonathan talked about how little we know abut anole territoriality. Conventional knowledge says that males maintain polygynous territories and don’t move too far. But Ambika has shown in her dissertation work that male Anolis sagrei actually move quite a bit, and Alexis has shown that male Anolis carolinensis mate with females on opposite sides of their site, not just nearby females! In general, Jonathan commented that there is a large amount of work to be done still on social behavior in anoles.

Anolis proboscis (photo by Luke Mahler)

Anolis proboscis (photo by Luke Mahler)

Basic Biology:
Jonathan talked about the Anole Annals darling, Anolis proboscis. This understudied species sports a large nasal projection of unknown purpose. This odd species was thought to be extinct for many years until it was “rediscovered” only a few years ago. While sexual selection seems like an obvious cause of this structure (the females do not possess horns), its not clear what the males use it for. The obvious hypothesis, that it is used for male-male combat, is easily refuted by video demonstrating that this structure bends easily. Moreover, it appears that they can bend the horn, as seen in this video! The mystery of this structure’s function remains unsolved.

Finally, Jonathan talked about an interesting anecdote: that Anolis agassizi from Malpelo island seems to have a strange preference for the color orange, as described by Rand et al. (1975). Jonathan described a recent test of this preference replicating the Chuckles candy experiment (the experiment has been described here on Anole Annals) and confirming that  this species does, in fact, prefer the colors orange and yellow when it comes to Chuckles candy. He also showed a video of A. agassizi swooping in from afar to eat (attack?) an orange. Why are they so attracted to this color? Sounds like a project waiting to happen.

In short, Jonathan emphasized these two main points:
1. Natural history information is key; you need to know basic aspects of biology and natural history to dig into the deeper questions.
2. There are so many questions to be answered about anoles still, and room for all who want to join the party.

 

 

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