Author: Jonathan Losos Page 28 of 130

Professor of Biology and Director of the Living Earth Collaborative at Washington University in Saint Louis. I've spent my entire professional career studying anoles and have discovered that the more I learn about anoles, the more I realize I don't know.

Bob Trivers Publishes His Memoirs, Lizards and All

All evolutionary biologists are familiar with Robert Trivers, but many do not know that some of his most important work was conducted on Anolis lizards. This work–as well as the rest of Trivers’ life–is featured in his just-published memoirs, Wild Life: Adventures of an Evolutionary Biologist. I had the good fortune to review the book for Current Biology. You can read my review, but the short story is: a fascinating book about one of the great figures–and characters–of modern evolutionary biology. And in case you’re wondering, it was the publishers who put a collared lizard, instead of an anole, on the cover. Available on Amazon for $12.99!

Nectarivory by and Predation upon Anolis occultus: Natural History Data at Last!

nectarivory

Remarkably little is known about the natural history of the Puerto Rican twig anole, Anolis occultus, except where it sleeps. The reason is simple: thepredation animal is small, moves slowly, is highly cryptic and probably spends a lot of its time amidst the twigs high in the canopy. As a result, there have been reports of only a handful of animals located while they are active.

In a just published paper, Ríos-López and colleagues report two new observations of these charming little lizards, one of nectarivory (above) and the other, sadly, of predation by a kingbird (right). In addition, the paper presents a comprehensive review of what we know about this species and its conservation prospects.

 

What Is a Dewlap and How Many Times Have Dewlaps Evolved?

Not a dewlap? Photo by Morley Read.

In a recent paper, Hagman and Ord discussed how dewlaps have evolved multiple times, often with different underlying anatomy. This is an excellent paper, but I was intrigued that Polychrus, sometimes considered the sister taxon to anoles, in part because of its apparently anole-like dewlap (see above), was not considered to have a dewlap.

I wrote Terry Ord, asking “I didn’t understand one thing. You seem to say there is no evidence for extendible dewlaps in several species of Polychrus, but a quick Google reveals plenty of images of these species with dewlaps extended. I take your point in the previous sentence that actual observations of the dewlap being used are rare, but did you really mean to say that they don’t exist at all?”

Terry responded: “What I found when attempting the first paper of this series (Ord et al. 2015, Journal of Evolutionary Biology) is that relying on photos alone is really problematic for identifying a moveable dewlap (a.k.a., a dewlap like anoles or Draco or Sitana).

For example, if you google Sceloporus — who definitely don’t have dewlaps — you’ll find photos where species do appear to have something like a small dewlap. In fact, I found an image of what was clearly a Sceloporus that looked to have an engorged throat that was remarkably similar to your Polychrus photo… All the google images I’ve found so far that are obviously Polychrus (and not anoles) could quite easily be engorged throats akin to Sceloporus and other non-dewlaped iguanids/agamids.

But the clincher for me is that all the hyoids we’ve looked at so far for both Sceloporus and multiple species of Polychrus (and other non-dewlaped iguanids/agamids) all look very similar (e.g., see Fig 5a in the JEB paper and supplementary info). The point being, the mechanics of the hyoid simply isn’t functional in the capacity of extending a dewlap like in anoles and others.

Of course, while the mechanics of the hyoid in extending the dewlap in anoles is well described, how Draco do it and some other genera is unclear. I’m hoping someone will look into detail on the biomechanics of the dewlap extension in non-anole groups because it can clearly be very different to anoles — e.g., the attachment points for key muscles for the anole dewlap are absent in Draco, so they’re sticking that dewlap out using a very different mechanism. Regardless, there are still key signs in the hyoid that point to a moveable dewlap in Draco (and other genera) that are not present in Polychrus.

Proof of a Polychrus dewlap would have to be a video of a Polychrus extending the dewlap because videos of Sceloporus quickly reveal that its an engorging (“puffing”) of the throat, so direct observation is a solid alternative to looking at the hyoid.

The taxonomy of “Polychrus” is potentially sketchy and not all species really are of that genus. Which means I also wouldn’t be surprised to see a species that has been classified Polychrus, but really isn’t related to all the Polychrus species we’ve examined the hyoids of, actually having a convincing moveable dewlap.

But at the moment, Polychrus = a moveable dewlap, all the evidence says otherwise. I also wonder whether the historical association of Polychrus as basal to anoles resulted in reaffirming wishful thinking field observations into the current myth.”

Terry’s next email made the distinction clear (as well as his unwarranted agama-philia): “If your notion of a dewlap is a prominent ornament that is dynamic in some sense (becomes extended through puffing out the hyoid in general or pushing out the CII in particular), then there are many many examples in agamids, and a handful in iguanids. I would definitely include Sceloporus, too.

If your notion of a dewlap is more specific to something that is part of a complex behaviojral display and involves rapid extension of a structure that is complex in temporal and amplitude characteristics, then it’s basically anoles, Sitana/Otocryptis, Draco and possibly one or two other agamids.

Agamids still clinch the diversity stacks in all regards – ha!”

Also not a dewlap

Puerto Anole Action Shots from Facebook: Predation by Ameiva and Maybe a Frog and Pooping

ameiva eating anole

lizard pooping

pr

New Research on How Tail Regeneration Works

Tail successfully regenerated.

Recent years have seen renewed interest in the mechanisms underlying tail regeneration in reptiles, and anoles have been a major study organism. The latest word comes from Thomas Lozito and Rocky Tuan who have just published a paper, “Lizard tail skeletal regeneration combines aspects of fracture healing and blastema-based regeneration” in Development.

Abstract

Lizards are amniotes with the remarkable ability to regenerate amputated tails. The early regenerated lizard tail forms a blastema, and the regenerated skeleton consists of a cartilage tube (CT) surrounding the regenerated spinal cord. The proximal CT undergoes hypertrophy and ossifies, while the distal CT resists ossification for the lifetime of the lizard. We hypothesize that differences in cell sources and signaling account for divergent cartilage development between proximal and distal CT regions. Exogenous spinal cord implants induced ectopic CT formation in lizard (Anolis carolinensis) blastemas. Regenerated spinal cords expressed Shh, and cyclopamine inhibited CT induction. Blastemas containing vertebrae with intact spinal cords formed CTs with proximal hypertrophic regions and distal non-hypertrophic regions, while removal of spinal cords resulted in formation of proximal CT areas only. In fate mapping studies, FITC-labelled vertebra periosteal cells were detected in proximal, but not distal, CT areas. Conversely, FITC-labelled blastema cells were restricted to distal CT regions. Proximal cartilage formation was inhibited by removal of periosteum and could be recapitulated in vitro by periosteal cells treated with Ihh and BMP-2. These findings suggest that proximal CTs are directly derived from vertebra periosteal cells in response to BMP and Ihh signaling, while distal CTs form from blastema cells in response to Shh signals from regenerated spinal cords. Thus, lizard tail proximal CTs develop independently from tail blastemas, resembling cartilage calluses formed during fracture repair, while distal CTs are derived from the blastemas similar to regenerated salamander tails.

Anole Research Mentioned in New York Times: Nice Op-Ed on Urban Evolution

Kristin Winchell’s research on Puerto Rican A. cristatellus evolution in cities is referred to in a nice piece in the New York Times by Menno Schilthuizen.

Great New Article on Horned Anole: They’ve Become a Tourist Attraction!

 

And an Ecuadorian student has studied the use of their horns in intraspecific interactions. Read all about it on BBC Earth.

Risque Anole Bachelorette Party Cake

cakeWe’ve seen anole wedding cakes and thesis defense cakes, but here’s a new one. Anole research veteran Natalie Jacewicz reports:

For my bachelorette party, my bridesmaids went to an erotic bakery (quite the business niche) in Boston and brought the shop pictures of Anolis lizards. The bakery evidently usually deals in, er, human encounters, so only had skin-toned frosting, and the store clerks weren’t sure if they could do anything lizard themed. But the shop owner evidently got really into the project, did a lot of independent anole research, and produced the cake below. Yes, that is a bridal veil on the yellow one.

Giant Anole Hunting in South Florida

Anolis garmani. Photo by Janson Jones.

Over on phostracks.com: Florida Wildlife, Ecology and More, Janson Jones reports on a very successful trip to Miami that yielded many anoles, most notably the Jamaican crown-giant, Anolis garmani and the Cuban knight anole, Anolis equestris.

Photo by Janson Jones.

 

Musings on the Lizards, Snakes and Other Herps of Florida

Photo by Janson Jones

Janson Jones is at it again. Actually, he’s been at it for a year, but somehow that slipped below our radar. The former purveyor of Dust Tracks on the Web has a new venue, phosTracks.com: florida wildlife, ecology and more.

Like it’s predecessor, phosTracks is full of keen natural history, engagingly presented and complemented by gorgeous photography. And better yet, anoles are one of Jones’ two favorite animals, neck-and-neck (hard as it may be to believe) with watersnakes.

Check out some of Jones’ recent musings on:

curly-tailed lizards:

Photo by Janson Jones

red-headed agamas:

Photo by Janson Jones

Anolis cristatellus:

Photo by Janson Jones

and more! Stay on these pages for some of his giant anole goodness coming up soon!

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