New Research – Page 59

: Anolis aeneus. Photo from http://www.kingsnake.com/westindian/anolisaeneus5.JPG.

Surprisingly few studies have examined how anole population density varies geographically, much less trying to explain why. In a recent study, McTaggart and colleagues surveyed herpetological abundance across Union Island (8.4 km²) in the Grenadines (near Grenada). Anolis aeneus was by far the most abundant herp on the island and was found almost everywhere. However, its abundance did vary from 0 to 62 individuals seen in visual encounters performed during the course of a morning and an afternoon. The sites lacking A. aeneus were a mangrove and a transect from a scrubby coastal hillock to a beach; overall, anole abundance was strongly correlated with vegetational complexity (categorized based on the number and variety of trees, height and connectedness of the canopy, and extent of human disturbance), perhaps not surprising for an arboreal lizard often found high in trees.

Notes from a Common Garden Experiment

By Yoel Stuart

On September 8, 2011

In New Research, Research Methods

The cages in which females are individually housed during the common garden experiment. Each cage has a bamboo perch and a plant in potting soil where the lizard can lay her eggs.

We are in the midst of a common garden experiment in which we’ve taken gravid Anolis carolinensis females from morphologically differentiated populations in the wild and returned with them to the lab where we are collecting eggs to incubate and hatch. Obviously I needed some gardening tools to pull this off, so I headed to bestofmachinery.com to get some since our local hardware burned down and still under construction. We’d eventually like to know whether the offspring of these females maintain the differentiation observed in the wild under common growth conditions. If yes, this is good evidence that the differences we’ve observed are a result of genetic changes among populations, rather than phenotypic plasticity during development and growth. A few notes from this ongoing experiment follow.

headed

bestofmachinery.com

What Do You Get When You Combine Three Lizards and a Chicken?

By Rich Glor

On September 7, 2011

In Anole Genome Research, New Research

Anolis carolinensis (http://www.birderslounge.com/2008/07/green-anole-amore/), A. marmoratus (from willy.ramaekers flickr: http://www.flickr.com/photos/27048739@N02/), Polychrus marmoratus (from Pierson Hills flickr: http://www.flickr.com/photos/nclarkii/), chickens (from http://ww.animalpicturesarchive.com/)

New primers for sequencing nuclear loci from Anolis!

Availability of genomic loci for sequencing has long been a major stumbling block to evolutionary inference in non-model taxa. In anoles, for example, several decades of work relied almost exclusively on mitochondrial DNA. As part of the Anole genome sequencing initiative, my lab group collaborated with the Broad Institute to identify conserved primers that can be used to amplify nuclear loci from across Anolis. We ultimately tested 200+ primer pairs, most of which were identified by comparing the genome of Anolis carolinensis to genomic data from two related lizards (Anolis marmoratus and Polychrus marmoratus) and the chicken (others came from recent work in the Jackman lab).

Anolis Video from Day’s Edge

By Yoel Stuart

On September 5, 2011

In Anole Art, Literature, and Humor, Introduced Anoles, New Research, Notes from the Field, Research Methods

Another video about Anolis research from Day’s Edge Productions. Cool research! Great footage!

Anole Genome Paper Published Today!

By Rich Glor

On August 31, 2011

In Anole Genome Research, New Research

Image copyright Andrew M. Shedlock.

The anole genome paper is out in Nature today (although links on Nature’s own page only take you to a list of authors at the present time, I’m assuming this glitch will be fixed shortly). Nature also published a brief commentary highlighting some of the most interesting discoveries from this work. For more coverage of work related to the genome, check out this post and stay tuned to Anole Annals – we’ll have a bunch more genome posts over the next few days.

Does Global Climate Change Threaten Tropical Lizards?

By Jonathan Losos

On August 26, 2011

In New Research

Anolis allisoni (photo from http://www.kingsnake.com/westindian/anolisallisoni2.JPG)

Everyone’s worried about global warming. For a long time, frogs hogged the herpetological spotlight, with concern that the global amphibian crisis might be driven by climate change. However, in recent years, there has been a growing realization that lizards may be in trouble, too, and again the finger has been pointed at climate change.

One hypothesis put forward by Ray Huey and colleagues is that as temperatures warm, open-adapted species will be able to invade forests, which previously had been too cool for them, and the cool-adapted forest lizards, living in a now warmer home and faced with competition from the invaders, would have nowhere to go and would be in big trouble. Preliminary data from Puerto Rico support this model, and Huey and colleagues have returned to the enchanted island to further test the hypothesis.

Michael Logan, a graduate student at Dartmouth, has set out to test this idea elsewhere, working in the Bay Islands off the coast of Honduras. These islands are particularly interesting because they are one of the few places where Caribbean and mainland anole faunas meet, with members of the sagrei and carolinensis species groups of Cuba coexisting with several mainland species. This juxtaposition is interesting in its own right, but it turns out that the Caribbean species are warm-adapted, open-living species, whereas the mainland species are cool-adapted, forest types. Logan’s goal is to test the hypothesis that as warming occurs, the warm-adapted species will be able to enter the forest, with potentially adverse effects on the species therein. In a recent issue of Biodiversity Science, a newsletter put out by Operation Wallacea, Logan reports preliminary results from last year’s field season, and they’re not what you might expect.

Not Your Typical Genome: Homogeneous Anole Genome Lacks Isochores Common in Other Amniotes

By Rich Glor

On August 23, 2011

In Anole Genome Research, New Research

Figures from Fujita et al. illustrating relative homogeneity of GC content across the anole genome (left) and shifts in GC3 along branches in the vertebrate tree, with black branches indicating descreases of GC3 and gray branches indicating increases of GC3 (right).

Genomes are rarely homogeneous aggregations of Gs, As, Ts, and Cs. Indeed, variation in basepair frequency can have important implications for how genomes, and the organisms they generate, evolve. Regions with relatively homogenous GC content that extend for more than 300 kb known as isochores are prominent features of previously sequenced amniote genomes. Isochores are associated with a range of important variables, including gene density, intron length, DNA replication timing, and gene expression. GC-rich isochores also tend to experience high rates of recombination, resulting in elevated effective population sizes and increased efficiency of purifying selection relative to drift.

A Little Worm “Told” Us …

By Gerrut Norval

On August 22, 2011

In Introduced Anoles, New Research

Studying the brown anole (Anolis sagrei) in Taiwan has presented me with numerous new opportunities, one of which is an introduction into parasitology.

A Kiricephalus pattoni nymph under the skin of a female brown anole (Anolis sagrei), collected in southwestern Taiwan.

The first parasites I found in A. sagrei in Taiwan were relatively large worm-like parasites that are often visible as a lump under the skin of the lizard. Unfortunately, my first samples were lost by the person I had sent them to for identification. But luckily, I found some more, and with the assistance of C.R. Bursey and S.R. Goldberg, the parasites were identified as the nymphs of the pentastome, Kiricephalus pattoni. Together we reported A. sagrei as a new host of this parasite in Taiwan (Norval et al., 2009).

Growing Limbs – But Not the Kind With Leaves.

By Thomas Sanger

On August 18, 2011

In New Research

Stages of limb development for A. sagrei

As lineages rapidly diversify, such as in the history of anoles, does their developmental-genetic architecture constrain the rate or direction of evolutionary change? In other words, could the processes controlling the production of variation, the variation that natural selection acts on, affect patterns of phenotypic evolution by generating some phenotypes more readily than others? While theoretical discussions like these have been prevalent for over a century, developmentally-based constraints were not formalized in the context of modern biology until the 1980’s, fueled by an influential paper by Maynard-Smith and colleagues and the re-synthesis of evolutionary and developmental biology. Since then evo-devologists have been testing the plausibility of developmental constraints by examining the developmental bases of traits that have independently evolved multiple times; phenotypes that have repeatedly evolved using the same mechanisms may be indicative of constraint (because the precise interpretation of these patterns and appropriate level of analysis are contentious I will leave further theoretical discussion of constraint to future conversations).

In a recent paper, for which I am the lead author, we set out to examine whether developmental constraints could have affected diversification of anole limb morphology.

How Many Times Have Lizard Dewlaps Evolved?

By Jonathan Losos

On August 15, 2011

In New Research

Polychrus gutturosus flashing its stuff. Photo from http://www.bijagual.org/images_reptiles/reptiles_image_links/pages/polychrus_guttorosus_3_JPG.htm

One interesting implication of the recent finding that Anolis and Polychrus are not closely related concerns the evolution of the dewlap. The two genera were long thought to be close relatives in part because they both possess what appear to be similar dewlaps. The new phylogeny indicates that these structures are not indicative of common ancestry, but rather that the two clades have convergently evolved very similar structures.

Dewlap-like structures have, in fact, evolved repeatedly in iguanian lizards (the clade that contains iguanids [in the old, broad sense], agamids, and chameleons). Some of these dewlaps are different from that of anoles—such as the flap of iguanas and the triangular dewlap of Draco—but the dewlaps of the agamid genera Sitana and Otocryptis are dead ringers for those of anoles. In fact, one might argue that Sitana out-anoles anoles with its regal fan pictured below.