Category: New Research Page 52 of 67

Lizard Conservation in the New York Times

Photo of S. arenicolus by Michael T. Hill from a U. S. Fish and Wildlife handout: http://www.fws.gov/southwest/es/newmexico/documents/Dunes_Sagebrush_Lizards_Handout.pdf

An article in Wednesday’s NY Times reported mixed results from efforts to conserve the rare dunes sagebrush lizard (Sceloporus arenicolus [formerly S. graciosus arenicolus]).  Politics and oil interests are keeping the species off the endangered species list, but the Obama administration has reached a “conservation agreement” that ensures protection for most of the species’s range.  For those interested in delving into the science underlying this story in a bit more detail, some recent peer-reviewed work on this species address the impact of oil and gas development on lizard populations (Smolensky & Fitzgerald 2011), the effectiveness of alternative sampling strategies (Smolensky & Fitzgerald 2010), and genetic diversity within and among populations (Chan et al. 2009).  Smolensky and Fitzgeralds (2011) study of lizard abundances across a variable landscape paints a complicated picture suggesting that several different landscape variables likely impact the lizards, but they surely delighted the oil and gas industry with the following quote: “we did not find clear statistical evidence to support our hypotheses that oil and gas development at our study sites had a direct negative effect on quantity of habitat, quality of habitat, and populations of lizards. ”  Chan et al.’s (2009) study of genetic diversity finds evidence for geographic genetic differentiation of some populations, but does not detect differentiation among individual sand dune blowouts.  In any event, it’s not every day that our favorite type of critter makes it into the newspaper of record!

Sensory Ecology of the Third Eye

A while back in the Annals, I introduced the mysterious (but not mythical) third eye, made even more peculiar by unexpected findings in the Anolis pineal gland (Moore & Menaker 2011). In a later post, I discussed non-visual photoreception—responses to light that do not require image formation—along with some recent evidence that such responses may be tuned to photic habitat in Anolis (Moore et al. 2012). Now I’m connecting the dots: non-visual photoreception in the Anolis pineal gland appears to be adapted to photic habitat (Moore & Menaker 2012).

The pineal gland can’t be seen externally, but it’s just posterior to the parietal eye (tiny circle in the middle) and right underneath the surface of the skull. Photo credit: TheAlphaWolf, License:Creative Commons Attribution-Share Alike 3.0 Unported

Anole – Skink Interaction In Taiwan

The elegant skink, Plestiodon elegans, in Taiwan. Photo by Gerrut Norval

Most community ecology studies involving anoles focus on interactions between anole species. This is not surprising, because in the Caribbean, anoles are extraordinarily abundant and most of their ecological interactions are, indeed, with other anoles. Less studied are interactions with other taxa, the exception being predator-prey interactions, such as those with curly-tailed lizards (discussed many times in these pages, most recently here).

One widespread group of lizards are skinks, the most species rich family of lizards. There are few reports of anole-skink interactions, probably in large part due to the fact that skink diversity in the Caribbean is relatively low, and many species have been extirpated by human agents. However, anoles have been introduced to places around the world where skinks are more abundant, and some reports of interactions have been made. For example, in the Ogasawara Islands of Japan, A. carolinensis has reached high population densities and has been implicated in the decline of the native skink.

Gerrut Norval has been studying the introduced populations of A. sagrei in Taiwan. He now reports an observation of a somewhat odd interaction between a brown anole and a skink in which the anole fell to the ground from a utility pole and then was quickly chased back up the pole by an elegant skink, Plesiodon elegans. Given the relative size of the two lizards, attempted predation was probably not the cause. Gerrut speculates that this is an example of interspecific territoriality, transcending lizard family lines.

In Taiwan, A. sagrei reaches high population densities (as it does just about everywhere it occurs)–possibly cause for alarm for the native herpetofauna. Norval also mentions some intriguing preliminary observations: A. sagrei seems to attain smaller sizes at sites where it co-occurs with other lizard species. Interesting! Hopefully, we’ll hear more from Gerrut soon on this provocative possibility.

Beware Of The Branches: The Impacts Of Habitat Structure On Locomotion And Path Choice

Imagine running quickly among a network of obstacles while attempting to maximize performance. It’s not an easy task, but one that arboreal lizards perform every day. In addition to variable inclines and perch diameters, arboreal lizards often encounter obstacles in the form of branches. The size of these branches, and their spacing, could have a significant impact on locomotor performance, such as sprint speed. Using a clever experimental design, Zachary Jones and Bruce Jayne (University of Cincinnati) recently determined how these important characteristics impact running performance in Anolis sagrei, A. carolinensis, and A. angusticeps (Click here to read paper from the Journal of Experimental Biology).

(A) Dorsal view silhouettes of the three Anolis study species compared against the diameter of the running surfaces. The lizards and cross-sectional areas of the running surfaces are all shown to the same scale. All running surfaces were cylindrical, but only one-half of the largest diameter is shown. (B) Schematic diagram of the peg treatments (not to same scale as the lizards). Pegs along the top center were placed at 10 cm (TC10) or 20 cm (TC20), horizontal pairs of pegs (HP) were placed every 10 cm, and alternating pairs of pegs (AP) oriented vertically or horizontally were placed every 10 cm along the length of the primary running surface (gray). The cylinder with no pegs (NP) is not shown.

Similar to previous studies, increases in perch diameter resulted in increased sprinting speed. With pegs added to the perch, things changed. When pegs were placed at 10cm intervals, and sticking directly up from the top of a 3cm-diameter perch, running performance of A. sagrei was sliced in half compared to running on a peg-free perch or a perch with pegs sticking out from the sides. Especially for the smaller perch diameter treatments, the number of pauses increased with increased branching, and this was greatest when the pegs came out from the top of the perch. This increase in pausing results in a decrease in overall speed (increased transit time) as they move through their habitat.  This is also a result found by Higham et al. (2001), where turning angles in the locomotor path resulted in increased pausing in Anolis lizards.  The take home message is that branching can have a negative impact on locomotion, forcing lizards to take longer getting from point A to point B.  This could make them vulnerable to predation or reduce their ability to effectively capture prey.
Luckily, the array of pathways in an arboreal habitat provides an opportunity for Anolis lizards to select what works best for them.

Anole Endocrinology Papers from Meetings Last Summer

Another week brings another nice batch of anole publications from a few previously held meetings. This batch comes from a combined special issue of General and Comparative Endocrinology that features articles from The Inaugural Meeting of the North American Society for Comparative Endocrinology (NASCE) and the 7th International Symposium on Amphibian and Reptilian Endocrinology and Neurobiology (ISAREN) held last July.  The papers from this meeting are now available at the journal’s page at Elsevier ScienceDirect.

Wade (2012) provides a nice review of structure and function of three sexually dimorphic anole features in green anoles (Anolis carolinensis): the forebrain, the dewlap neuromuscular system, and the copulatory neuromuscular system.  She also reviews comparative studies across anole species of the dewlap system and provides a detailed discussion of endocrine regulation in green anoles.  Cohen & Wade (2012) investigated “Aromatase and 5 alpha-reductase type 2 mRNA in the green anole forebrain: An investigation of the effects of sex, season and testosterone manipulation.”  Finally, in a non-anole paper about other iguanid lizards Hews et al. (2012) investigate “neuroendocrine correlates of aggression differences in adults of two Sceloporus lizard species.”

 

Rediscovery Of The Enigmatic Ecuadorian Horned Anole

Male Anolis proboscis. Photo by Jonathan Losos

Of all the anoles great and small, near and far, green and brown, one stands out for its combination of elegance, charm, and mystique. I refer, of course, to the Ecuadorian horned anole, Anolis proboscis, denizen of Andean forests, possessor of an enchanted sword, and all-around lizard of mystery. Now, however, the veil has been lifted, as the first reports on the biology of the previously unknown lizard have just been published in Breviora, a journal of the Museum of Comparative Zoology at Harvard.

Rediscovered by birdwatchers. How embarrassing. Photo by Wanda Parrott.

The mystery comes in three acts. The first concerned the continued existence of the horned anole. The species was discovered in 1953 and over the next 13 years, another five were found, all male like the first, all from the vicinity of the Ecuadorian town of Mindo. Then, for four decades…nothing. Many feared the species extinct, perhaps a victim of the deforestation that has ravaged so much of the Western side of the Andes. All this changed in 2005 when a group of birdwatchers spied one crossing a road near Mindo (mind you, this is an arboreal lizard—insert your own joke). Anolis proboscis lives!

The photo above made its way onto the internet and to the attention of Steve Poe, an expert on locating hard-to-find anoles, who led a team of American and Ecuadorian scientists back to Mindo in the summer of 2009. Poe’s approach to finding day-active anoles is seemingly perverse: he stays up all night looking for them. The reason is simple: many anole species sleep on narrow twigs or leaves, presumably because approaching predators will produce vibrations on the flimsy perches, alerting the lizards to impending danger. Although this strategy may be effective in avoiding predators that creep, crawl or slither along branches, it’s not so well-suited to avoid detection by flashlight-toting herpetologists, who are attuned to locating the tiny reptiles—which conveniently blanch to a pale color at night—even when they’re roosting 20-30 feet high in the canopy. Poe’s team quickly located a large number of lizards, establishing that the species not only exists, but seems to have a healthy population.

Unbeknownst to Poe, another team of researchers independently had discovered a new horned anole locality. This team, from the Ecuadorian Museum of Science in Quito, located five specimens of the horned anole at two sites 11-13 km northeast of the original collecting locality, slightly extending the known range of the species. Both groups published detailed descriptions of the anatomy of the species—the Ecuadorian group last year and Poe’s team as the first of the Breviora set published today—describing previously unknown variation in horn size and shape, as well as differences in color and patterning both among males and between the sexes.

And, speaking of differences between the sexes, that leads to the resolution of mystery number two. Ever since the species was first described and the initial half dozen specimens collected, lizard enthusiasts have wondered—what about the females? Do they have horns, too? Of course, in the absence of any information on the natural history of the species, it was hard to have an informed opinion. Is the horn used in self defense, in which case the lady lizards could probably use one as well as the guys? Or is it used by males to fight amongst themselves, or even as an ornament used to woo or titillate? Nobody knew, and so it was anybody’s guess whether the females were nasally adorned or not. But now we know the answer. Before I reveal it, take a moment and take a guess: yes or no? When you’re ready, scroll past the lovely photo of another male and see for yourself.

 

Male Anolis proboscis. Photo by Luke Mahler

Female Dewlaps

Fig. 1 from Harrison and Poe illustrating dewlap differences between males (top) and females (bottom).

The function and evolution of anole dewlaps have been the focus of studies for decades. As flashy, showy displays of color, it’s no wonder that dewlaps even captured the attention of Darwin. However, most studies to date have focused solely on male dewlaps leaving female dewlaps much neglected (but see Johnson & Wade, 2010 and Vanhooydonck et al., 2009). While the possession of dewlaps is less common in females than males, and female dewlaps are often rather diminutive compared to the male’s, the mere presence of female dewlaps in a good number of species, combined with striking variation in color, pattern and size across the genus, begs the question of what is driving the evolution and maintenance of such female ornamentation?

Get Your Anole Fix: 17 Anole Abstracts from SICB

As reported previously at Anole Annals, The 2012 meeting of the Society of Integrative and Comparative Biologists (SICB) was packed with anoles (1, 2, 3, 4, 5, 6).  At least 17 talks or posters mention Anolis in title (complete list below the fold)!  The abstracts from this meeting are now available via PDF from the Society’s journal Integrative and Comparative Biology.  I was excited to see all of the new anole content as it appeared on Web of Science and other indexes, but disappointed that these titles were only associated with abstracts.  To all of you who presented: please get this stuff published, many of your titles are very compelling and the anole community can’t wait to learn more!

Enclosing Anoles In Puerto Rico

I’ve recently arrived at El Verde Field Station in Puerto Rico for my first real field season working with anoles. My main goal is to carry out enclosure experiments looking at the different components (resource competition and predation) of the interactions between anole species. I’ll post more about the research later, but for now I want to give a rundown of the enclosures I’ll be using.

Coffee Drinking Anoles

Have you heard about the extremely expensive (and delicious) coffee from Indonesia made  from beans that have passed through the digestive system of civets (hence called “cat poo” coffee because civets are sometimes called civet cats? Did you know that a similar coffee is produced in Central America, made from beans pooped out by Norops anoles? Well, that’s not what this post is about.

Rather, it’s about several recent studies on anoles in coffee plantations.  One recent study, discussed at further length by Rich Glor, compares the biodiversity of sun and shade coffee plantations in Puerto Rico. The authors note at the outset that biodiversity tends to be higher in shade coffee areas, and wanted to see whether that was true in Puerto Rico. In a truly herculean effort, they censused the lizards, birds, insects and vegetation in six plantations, three shade, three sunny. This was a lot of work. Just for the lizards, they individually marked (via paint spray gun) nearly 5000 anoles.

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