Author: Jonathan Losos Page 39 of 129

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In recent years, biologists have put out clay model lizards to measure attack rates by birds and other predators. In a recent study published in Herpetology Notes, Vazquez and Hilje put a twist into this approach, by ornamenting some faux lizards with a colorful dewlap-like structure. Sure enough, those models were attacked more. Here’s their abstract:

We investigated how predatory attacks on Norops lizards occur in old-growth and secondary pre-montane wet forests in Costa Rica using clay models. Using models with secondary sexual characteristics also permitted comparison of attack rates between males and females, as well as the specific site of the attack (head, body, or tail). Birds were found to account for the bulk of predation attempts on the lizard models in both forest types, and there was no significant difference in attack frequency between forests. Attempts were more frequently made on males, indicating that colorful, bright dewlaps used to attract females and for territorial displays might also function in attracting predators. Male models received more attacks on the head, suggesting that birds may preferentially target areas of brighter coloration, whereas female models received more attacks on their tail, indicating that birds may not have adopted any avoidance of a potentially less profitable region from which tails can be autotomized.

Closely related to snakes after all?

Two years ago, I wrote an AA post on lizard phylogenetics, summarizing the results of a paper by Gauthier et al. that claimed that analyses based on morphological and molecular data produced very different phylogenies. Moreover, Gauthier et al. argued that the morphological data provided absolutely no support for the phylogeny suggested by the molecular data.

The issue has now been further considered in a recent paper by Reeder et al. in PLoS One. These authors provide some new morphological data and add a tad of previously unutilized molecular data; with these data sets, they recover essentially the same disagreement in phylogenies. However, what is new in this paper is that they perform a combined analysis that analyzes morphological and molecular data together. The results of this analysis are firmly in agreement with the molecular data. To address the possibility that this is simply a result of the much greater quantity of molecular characters, the authors also conducted analyses that essentially weighted the molecular and morphological data equally. Still, the result was the tree produced by the molecular data alone.

Perhaps the most striking point in the Gauthier et al. paper was the claim that the morphological data gave absolutely no support for the molecular tree. This suggested, in turn, that if the molecular tree is correct, then morphological evolution has been extraordinarily homoplasious. However, Reeder et al. dispute this claim, finding that a number of morphological characters support the molecular phylogeny.

Reeder et al. also broke the morphological characters into six subsets: cranial characters; characters related to the jaws, teeth, and hyobranchial apparatus; characters related to the vertebral column; other postcranial osteological characters, mostly related to the limbs and limb girdles; miscellaneous morphological characters, including morphology of the osteoderms, scleral ossicles and tongue; and characters of squamation and external morphology. Their analysis found that only the cranial characters were incongruent with the molecular phylogeny, and they suggested that these were the characters in which homoplasy was rampant, leading to false signal in the morphological analyses.

Overall, the authors make a strong case that the molecular phylogeny is likely to be the correct one and that morphological data, particularly cranial characters, are misleading due to homoplasy. It will be interesting to see whether and Gauthier et al. respond to these analyses.

Here is the take home message from the discussion of Reeder et al.’s paper:

Our combined analyses strongly suggest that the phylogenetic hypothesis for living squamates based on the molecular data is correct. Specifically, our results support the hypothesis that Iguania is placed with snakes and anguimorphs, and not at the squamate root (as suggested by morphological data alone). Our conclusions are based on several lines of evidence, including:

(a) combined analyses of the relevant molecular and morphological data supports the molecular placement of Iguania, even when the molecular dataset is reduced to only 63 characters, less than one tenth the size of the morphological dataset,

(b) mapping morphological characters on the combined-data tree shows that there is actually hidden support for the molecular hypothesis in the morphological data (similar to the number of characters supporting the morphological

hypothesis),

(c) the morphological dataset is dominated by misleading phylogenetic signal associated with convergent evolution of a burrowing lifestyle and associated traits, and a similar problem associated with feeding modes may explain the morphological placement of Iguania, and

(d) the morphological hypothesis is unambiguously supported by only one of six subsets of the morphological data. Conversely, we find no evidence for hidden signal supporting the morphological hypothesis among the 46 genes in the molecular dataset; no genes support this hypothesis. Further, the failure of some genes to fully support the molecular placement of iguanians in Toxicofera seems to be associated with sampling error (i.e. shorter genes).

Anolis sagrei displaying in front of a supertree at the Gardens by the Bay

Two years ago, we posted on a paper in Nature in Singapore documenting the occurrence of the festive anole, Anolis sagrei, in Singapore. The ubiquitous colonizers had turned up in the newly created Gardens by the Bay, an enormous new botanical garden built on reclaimed land at the southern end of the island. AA decided to look into the situation further and sent this correspondent to the “Lion City” to report back on the situation.

Reporting for duty at the Gardens at approximately 930 am on the morning of 16 April, we quickly determined that the lizards are common in the lushly planted gardens pretty much wherever we went. The only exception was an open meadow housing a statue, where we did see an introduced agamid lizard (below). This area was only searched for three minutes, however, and it would not be surprising to find the anoles in the shrubbery surrounding the statue (below). The other place the lizards were not seen were in the two spectacular indoor cool houses, the Flower Dome and the Cloud Forest. Both are kept at temperatures possibly too low for the lizards, and also likely are fumigated.

Introduced Calotes versicolor at Gardens by the Bay

Otherwise, however, the anoles seem to be everywhere and it seems unlikely, given the luxuriance of the vegetation, that they can be eradicated (and we know how well such elimination efforts have fared in Taiwan—not).

The question is whether the anole will spread to the rest of Singapore, and from thence to Malaysia. Given the heavy motor traffic bringing visitors to the gardens, it seems inevitable that the anoles will hitch-hike their way across the bridge and colonize the main island of Singapore, which is for the most part one big Anolis sagrei habitat, with plenty of tropical vegetation everywhere. Moreover, the gift shop at the Gardens was selling orchids. I don’t know where they came from, but if on site, that is a great way to distribute brown anoles far and wide.

It’s not clear whether the anole is already present on the Singaporean main island. One commenter on our previous post said that it had been seen elsewhere, and I was told that there were unsubstantiated reports that it had been observed in the Singapore Botanical Garden. I spent several hours there myself and saw the anole mimic pictured on the right, but no anoles.

My prediction is that in ten years, Anolis sagrei will be very common in Singapore. But let’s see what the varanids, the Calotes and the birds have to say about that.

Meshaka and Layne have just published a masterful review of the native herps of southern Florida in Herpetological Conservation and Biology (freely downloadable). Of most interest to readers of these pages is the treatment of Anolis carolinensis, and it is indicative of the quality of this work: the six pages devoted to the natural history of the green anole is the most authoritative and comprehensive of which I’m aware, covering the literature for this species not only in southern Florida, but throughout its range. This monograph is the starting point for anyone interested in green anole biology. In addition, this section shows how surprisingly little we know about the biology of this species. For example, most of the information on green anole diet comes from Wayne King’s work from 1966.

This volume will be useful to anyone interested in the herpetology of southern Florida.

Photo by Janson Jones

Look at this poor fellow. Over on Phostracks, Janson Jones describes him and his demeanor thusly:

“Still, the most compelling characteristic of this anole was its passiveness. It wasn’t dead. Far from it, actually. The anole actively watched me, tracking me with its eyes. Still, when I rolled the lizard on its back, it just laid there like a puppy wanting a belly rub. Except for two or three miserable feeble attempts at escape, this anole was entirely passive (and clearly in need of a good dinner). It was just worn the hell out and in dire need of a vacation.

I placed the anole on the side of an unpopulated tree trunk to see if it could or would hang on (see image bottom left; image is rotated 90 degrees). No problem. It did just fine. It even moved around a bit. Then, when I started creeping back close again, nothing. It just sat there. Passive.

So, to quote Diondre Cole, “What’s up with that?” Any ideas? Any opinions? Any speculations?”

For more photos and entertaining description, check out the full post.

We’ve had posts on this spectacular anole before. Jesus Reina Carvajal reports: “During the last three years, I have been lucky to see them every single time I have visited the area but they are really hard to find. I find them in the wild on Cayo Santa María. They live exclusively on that island. Nowhere else in the world.

They eat insects, other lizards and small birds. They have a powerful bite. This last individual I could follow during hours since I saw it early in the morning and I could make many pictures and films until it left the place. That day I felt very happy!”

More of Jesus’s photos can be seen in the Flickr album he created.

Photo by Jesus Reina Carvajal

Photo by Jesus Reina Carvajal

Stroud and Beckles published this photo of a crested anole with a half-grey dewlap in the December 2014 issue of Herpetological Review. Cresteds dewlaps are usually orange or yellow–this is very unusual.

This is reminiscent of the famous gray-dewlapped A. carolinensis as well as this odd crested anole found by Neil Losin.

What’s up with these wacky anoles?

Congratulations to our friends at Tropical Herping for their photo in this month’s National Geographic.

Anolis sagrei with a regrown tail. Photo by Philip Fortman

Kristin Winchell has the answer. Check it out on her blog, Adaptability. Here’s a shot of the poster she discusses: