Category: New Research Page 60 of 66

More On New Dactyloa Phylogeny

On August 11, 2011

Barely even kissing cousins: A. aequatorialis on the left and A. fitchi (photo thanks to Chris Funk) on the right.

The new Castañeda and de Queiroz phylogeny of Dactyloa is an important advance in our understanding of anole phylogenetics. Prior to this paper, relationships among clades within Dactyloa had been little studied; indeed, the monophyly of Dactyloa was in question, with a viable alternative being that Dactyloa is a paraphyletic group from which the rest of Anolis sprang. Not only have Castañeda and de Queiroz convincingly laid this possibility to rest, but they have identified five strongly supported clades. As the previous AA post on this paper noted, these clades are geographically coherent, revealing five geographically distinct theaters of Dactyloa diversification.

The paper has important implications in several other respects:

1. Size evolution: Dactyloa is known for its giant anoles (officially defined by Lazell as an anole exceeding 100 mm in snout-vent length). Almost all giant Dactyloa belong to the latifrons clade, all members of which, save one, are giants.

2. Convergence: In a number of cases, species that were thought to be closely-related were found to occur in different clades. The most amazing of these are A. aequatorialis and A. fitchi (pictured above), so similar in appearance and ecology that they were thought to be sister taxa that replaced each other on opposite sides of the Andes. However, it turns out that they are not at all closely related and belong in different clades.

3. Evolutionary divergence: an underexplored aspect is the extent of evolutionary diversification within clades of Dactyloa. Though much remains to be learned, it is clear that diversification has been quite extensive, as a number of the clades contain an ecomorphological array of species. The Western clade, for example, contains species such as festae, peraccae, chloris, aequatorialis, and gemmosus, which are very distinct from each other morphologically and utilize different parts of the structural habitat. Collecting the necessary morphological, ecological and behavioral data to trace the pattern of Dactyloa radiation will be an exciting challenge in the coming years!

In sum, this paper importantly advances our understanding of anole evolution. If now we could only crack that Norops nut!

New Phylogeny for the Dactyloa Clade of Anolis

By Rich Glor

On August 7, 2011

In New Research

Phylogenetic tree from Castañeda & de Queiroz's concatenated dataset (left), instability of relationships among five major clades resulting from analyses of mtDNA (top center) and nDNA (bottom center), Anolis (Phenacosaurus) heterderma from Juan Salvador Mendoza's Flickr (http://www.flickr.com/photos/ecoterror/page6/) (top right), and geographic distributions for major clades identified by Castañeda and de Queiroz (bottom right).

A few days ago, I discussed a paper that proposes assignment of anoles to a new family called Dactyloidae. Today, I want to call attention to another new paper about anole systematics and taxonomy that involves a clade beginning with ‘dactyl’: the Dactyloa clade of Anolis. The Dactyloa clade includes around 80 species of anoles found across southern Central America, northern South America, and the southern Lesser Antilles. Although most anole biologist believe that its best to continue recognizing the species in this clade as members of a unified Anolis, the Dactyloa clade does seem to represent one of the few genera proposed by Guyer and Savage that is largely monophyletic (albeit with the addition of species previously assigned to Phenacosaurus).

In a paper published in Molecular Phylogenetic and Evolution, Castañeda and de Queiroz generate new phylogenetic trees for this group based on DNA sequence data from three loci (two mitochondrial and one nuclear) sampled across 40 of 82 previously recognized species, two new species, and 12 outgroup taxa. Castañeda and de Queiroz’s analyses of concatenated and individual gene datasets using GARLI and MrBayes recover support for five well-supported and geographically cohesive clades within Dactyloa. Three of these clades closely match groups defined based on previously morphological and biogeographic analyses: Phenacosaurus, the roquet series, and the latifrons series. Two of the clades identified by Castañeda and de Queiroz were not diagnosed by previous morphological analyses, but do make sense biogeographically: one of these clades occurs across the eastern cordillera of the Colombian Andes and the Venezuelan Andes (the “eastern” clade of Dactyloa) and the second can be found across the western and central cordilleras of the Colombian Andes, the western slope of the Equadorian Andies and the Pacific lowlands of Panama, Colombia, and Ecuador (the “western” clade of Dactyloa). The monophyly of two clades previously identified by morphological analyses – the aequatorialis and punctatus series – is strongly rejected by the new molecular data, reaffirming problems that have long plagued taxonomic studies of mainland anoles based on morphological data. Relationships among the five well-supported and geographically-cohesive clades identified by Castañeda and de Queiroz are poorly supported and unstable among analyses, seemingly due to short basal branches. Although their results clearly indicate the need for taxonomic revision of Dactyloa, Castañeda and de Queiroz reasonably suggest that any such revisions should await more comprehensive species-level sampling is available.

New Multilocus Phylogeny Confirms that Polychrus is Not Sister to Anolis

By Rich Glor

On August 3, 2011

In New Research

A time calibrated tree from Townsend et al. and photographs of Polychrus (from http://reptile-database.reptarium.cz/species.php?genus=Polychrus&species=gutturosus), Anolis, and Basiliscus (from http://scienceblogs.com/tetrapodzoology/2009/01/something_new_about_basilisks.php)..

For decades, anole have been assigned to Polychrotidae, a family or subfamily of Iguania whose core members have always included Anolis and Polychrus. In spite of the morphological similarities shared by these genera, molecular studies conducted over the past decade have consistently recovered a non-monophyletic Polychrotidae and have never recovered strong support for a sister relationship between Polychrus and Anolis. In recent Bayesian and maximum likelihood analyses of 29 loci sampled from 47 iguanians and 29 outgroup taxa, Townsend et al. (2011) drive the final nail in the coffin of the notion that Anolis and Polychrus are closely related and form a clade that should continue to be recognized as Polychrotidae. The sister-group relationship between Anolis and Polychrus is completely absent from the posterior distribution of trees generated from Townsend et al.’s 29-locus concatenated dataset and this relationship appears in only one or two of their 29 single-gene trees. As a result, Townsend et al. limit Polycrhotidae to Polychrus and resurrect the family name Dactyloidae for Anolis. Although they acknowledge that Dactyloidae is a less intuitive name for this clade than Anolidae, the latter is junior synonym of the former, having been coined by Cope (1864) some 20 years after Fitzinger (1843) recognized Dactyloidae. Students of squamate phylogenetic systematics should definitely check this paper out, Townsend et al.’s results concerning Polychrotidae are only one of their many interesting insights.

Hedges Team Rediscovers Anolis darlingtoni

By Rich Glor

On August 2, 2011

In Anoles and Anolologists in the News, Natural History Observations, New Research, Notes from the Field

Image of Anolis darlingtoni from http://www.philly.com/philly/blogs/evolution/A-Long-Lost-Lizard-is-Found-in-Haiti.html

Last week, Blair Hedges led a team of scientists, journalists and naturalists on a helicopter tour of some of the most remote forested habitats remaining on Haiti’s Tiburon Peninsula. For anole enthusiasts, this expedition’s most remarkable find was the rediscovery of Anolis darlingtoni, an enigmatic species that hasn’t been seen since 1984. As reported by Faye Flam at Philly.com, expedition member Miguel Landestoy spotted a single animal sleeping around 2m up in a tree fern. This seems to have been the only darlingtoni recovered by the expedition, but full trip details are still filtering in.

Even with this rediscovery, Anolis darlingtoni remains the rarest anole on Hispaniola, and the one that is the most immediate danger of extinction. Luke Mahler and I went to a great deal of trouble to search for A. darlingtoni in remnant forests at the western end of the Tiburon Peninsula a few years ago and came up empty, so I know that finding this species is no easy feat. My congratulations to Blair, Miguel, and the rest of the team!

Anole Genome Research: New Primers for All!

By Rich Glor

On July 28, 2011

In Anole Genome Research, New Research

Table from Portik et al.'s Conservation Genetics paper reporting new primer pairs for amplification of nuclear loci (left side) and a phylogeny generated using some of these loci from Stanley et al.s' 2011 MPE paper on cordylids (right panel).

A new study by Portik et al. used the anole genome to develop more than 100 new primer pairs for the amplification of nuclear-encoded DNA from squamates, some of which have already proven useful for inferring relationships within and among species. Portik et al.’s carefully thought out strategy for marker development – which focused on rapidly evolving protein-coding loci – ensures that their loci will be particularly useful for phylogenetic analyses. First, Portik et al. focused on intronless protein-coding genes, with the goal of limiting length variation and simplifying alignment. Second, recognizing low variability relative to non-coding regions as a potential limitation of protein-coding loci, Portik et al. focused exclusively on developing markers from loci that are more variable than the first third of RAG-1 (one of the most useful and widely-used of the nuclear genes used previous phylogenetic studies of squamates). This strategy yielded 104 genes and led to development of primers for 170 gene fragments ranging from 407-2,492 bp. Portik et al. conducted limited PCR testing on 70 of these loci and found varying degrees of success across five squamate families, including Scincidae, Varanidae, Agamidae, Cordylidae, and Gekkonidae. More importantly, some of the loci have already proven useful for phylogenetic studies of skinks (Portik et al. 2010 , Portik et al. 2011), cordylids (Stanley et al. 2011) and iguanids (anole genome paper, which is currently in press at Nature).

While high throughput sequencing technology will eventually render PCR primers and Sanger sequencing nothing more than curiosities from a previous generation, this time is at least a few years away. In the meantime, Portik et al. have given the herpetological community some very useful new tools to play with.

Competition, Predation, and Selection: The Usefulness of Scientific Debate

By Adam Algar

On July 26, 2011

In New Research

Kidd Cay, one of the islands included in the Calsbeek and Cox (2010) study (photo from Losos and Pringle, 2011).

Chances are that if you read this blog, then you also tend to note when Nature publishes something anoley. Thus, you’re probably already aware that last week Losos and Pringle published a reply to a paper by Calsbeek and Cox that appeared in Nature last year. In that paper, C&C concluded that competition is a more important agent of selection than predation for island anoles. In their reply, L&P point out limitations in the original study’s major assumptions, experimental design, and statistical analyses. Rather than go into all the gory details, I suggest you look at their reply directly. Just don’t let your non-anolologist colleagues or family members get a look at their Fig. 1a or you’ll lose any credibility you might have once garnered by speaking about the rigours of field work. As is usual, C&C have also published a reply to the reply where they respond to the criticisms, re-performing some analyses. Again, I don’t want to focus on the details; I’d rather let each reader decide for themselves.

Personally, I enjoy reading replies and replies to replies and if it gets to a reply to a reply to a reply, well even better! It’s the way science should work – someone publishes something, there is debate, and the scientific community self-corrects if necessary. However, recently an article in Ecosphere entitled “Do rebuttals affect future science?” by Banobi et al. challenged this view.

A Hearty Meal Impairs A Lizard’s Jumping Ability

By Jonathan Losos

On July 18, 2011

In New Research

Jumping green anole. Photo from http://www.people.umass.edu/chiyun/Site/Research.html

Ever try playing softball after a barbecue? Doesn’t work so well, does it? Now imagine trying the long jump–just the thought makes me a little queasy. But animals in the wild have to do this all the time. Does it affect their performance? Lizards and other animals are known to have their running abilities diminished by carrying a large load, such as a meal or eggs, but no one previously has looked at the effect of increased weight on jumping.

Until now. In a recent paper, Kuo et al. increased the weight of green anoles 30% by wrapping a weighted cloth around their midsection and then induced them to jump (pdf of the paper here). As a control, they wrapped light paper around the lizard in the same manner. As you might expect, the encumbered anoles were less proficient leapers; jump distance declined 18% and takeoff speed 10%. However, their accuracy, as judged by ability to land on a target, was not affected.

Anole Research Cleans Up on Awards at JMIH

By Rich Glor

On July 13, 2011

In New Research

A figure illustrating dewlap color variation in the distichus species group from Anthony Geneva's award winning poster.

Two posters on anole evolution presented at JMIH last weekend were honored with SSAR poster awards. Anthony Geneva, a PhD student at the University of Rochester took home the prize in the Evolution, Genetics, & Systematics category for his poster on “A Multi-locus Molecular Phylogeny of Distichoid Anoles.” Mingna Zhuang, an undergraduate researcher at UC Berkeley, won in the Ecology, Natural History, Distribution, & Behavior category for her poster on “Comparative Gliding Performance of Anolis carolinensis and Anolis sagrei.” Although not on anoles, it also bears noting that Daniel Scantlebury’s study of adaptive radiation in Sphaerodactylus – which has been inspired partly by work on Anolis – won the SSAR’s Henri Seibert Award for best student talk on Evolution/Systematics. Congrats to Anthony, Mingna, and Dan!

Is An Anole Smarter Than a Fifth Grader?

By Jonathan Losos

On July 13, 2011

In New Research

Manuel Leal and Brian Powell have just published a paper in Biology Letters demonstrating that lizards are smart. Before getting to the details, though—here’s the important point: check out the videos! They’re pretty amazing (here, scroll down and click on the videos).

Here’s the story: working with the Puerto Rican trunk-crown anole, A. evermanni, Leal and Powell presented lizards with an experimental apparatus in their home cages with two wells, in one of which was a dead phoenix worm (whatever that is). Next to the well with the worm was a little round disc similar to a poker chip. The lizards learned to go to the well and find and eat the worms. Then the experimenters placed the chip halfway over the well. Again, no problem.

Now comes the cool part. The experimenters completely covered the well containing the worm with a blue chip. Remember, these are Anolis lizards that usually find their prey by looking for movement—they don’t go digging around in the underbrush. Still, four out of the six lizards figured out how to get the mealworm: two of them bit the chip and removed it from covering the well, while two others figured out how to use their snouts as a lever to flip the chip off the well. This is pure problem-solving, and it uses novel behaviors, rather than simply transferring a natural behavior to a new context! And the two lizards that failed to get the worm came up with their own solution, hitting the center of the chip with their snout—but this was ineffective in dislodging the chip.

Once the lizards had learned to find the worm under the chip, the experimenters then conducted a discrimination trial, giving the choice of a blue chip and a yellow chip. Without error, the lizards always went to the blue chip; subsequently, they were presented a blue chip versus a blue-and-yellow chip, and they still had no problem.

Pretty amazing for a lizard, if you ask me, but it gets even better.

JMIH 2011: More Anole Posters

By Rich Glor

On July 12, 2011

In New Research

The Sunday night poster session at JMIH 2011 had a few more anole offerings. Melissa Moody from Iowa State reported on a laboratory experiment on the developmental and fitness consequences of varying Anolis sagrei egg incubation temperature and humidity. Anolis sagrei eggs seem relatively robust to the variation experienced during this experiment. Paul Cupp of Eastern Kentucky University asked whether ground skinks (Scincella lateralis) and green anoles (Anolis carolinensis) could detect chemical deposits from the Eastern Milk Snakes (Lampropeltis triangulum); he found evidence that the skinks could detect these deposits while the anoles could not. Finally, Mingna Zhuang discussed comparative gliding performance of Anolis carolinensis and Anolis sagrei. She found that A. carolinensis is a considerably better glider, perhaps due to the fact that it has a flatter gliding posture than A. sagrei.