SICB 2014: The Ecomorphology of (Some) Australian Geckos

Though SICB 2014 is positively teeming with cool anole talks and posters, there are plenty of other lizards that are getting a lot of attention. Yesterday, I happened upon a fascinating talk by Travis Hagey,  a grad student at the University of Idaho, titled “How geckos stick in nature: ecology and biomechanics of gecko feet.”

Strophurus taenicauda, a grass-bush-like gecko. Photo by Dave Fleming.

Strophurus taenicauda, a grass-bush-like gecko. Photo by Dave Fleming.

Addressing an overflowing room, Hagey used the dramatic diversity of gecko toepads to motivate his central question–can this diversity in toepad morphology be explained by the habitat preferences and perch-use behaviour of these geckos in nature? But going down the path of ecomorphology led to a comparison with anoles: if gecko toepads correlate with their habitat, then what about gecko limb-lengths? Using relationships between limb morphology and perch-type from arboreal anoles as well as rock-dwelling skinks, Hagey left for Queensland, Australia, with three predictions:

1. Geckos with shorter limbs would perch on narrower surfaces

2. Geckos with longer limbs would perch on rocks

3. Geckos with higher clinging ability would perch on steeper perches.

Utilizing a simple measure of lizard clinging ability (the “toe detachment angle,” which is the angle of the clinging surface away from vertical at which a lizard can no longer cling), as well as measuring perch characteristics and limb morphology for 13 species of geckos, Hagey began to look at patterns of ecomorphology. He found that different species occupied dramatically different habitats, with specialization even within the arboreal niche. Here’s what he found for each prediction:

1. Contrary to expectations, lizards perching on narrower surfaces had relatively longer limbs than average.

2. Having longer upper legs, however, correlated with rock use.

3. A higher clinging ability was correlated with having longer toes and shorter limbs. There was a qualitative or clade-specific relationship between the use of vertical perches and higher clinging ability.

Pseudothecadactylus australis, a crown-giant-like gecko. Photo from www.gondwanareptileproductions.com

Pseudothecadactylus australis, a crown-giant-like gecko. Photo from www.gondwanareptileproductions.com

Hagey speculated about the relationship between perch width and limb length in geckos, where he found the opposite pattern from anoles. One distinct possibility is that geckos have, on average, shorter limbs than anoles, meaning that a relatively long-limbed gecko and a relatively short-limbed anole may actually have the same body shape. Hagey is planning a taxonomically broad comparison of body shape and perch use, and hopes to include both geckos and anoles in this dataset–an exciting prospect that could shed light on some remarkable trans-continental convergences in lizard ecomorphology.

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