Draco Shares the Anole Limb Length–Perch Size Relationship

A recent study in Oecologica by Terry Ord and myself found striking parallels in habitat use and morphology between the phylogenetically distinct Anolis and Draco genera.  Draco (family: Agamidae), for those who don’t know, is a genus of gliding lizards found throughout southeast Asia that are similar to anoles in that they communicate with conspecifics using bright and diversely coloured dewlaps (see picture).

IMG_2234  anole

(L: Draco sumatranus; R: anole)

A defining characteristics of anole ecology is their ecomorphology – a description of the species microhabitat and its morphological adaptions for thriving there. Anole species living sympatrically avoid interspecific competition by partitioning their habitats and resources, and consequently develop morphological adaptations that are suited to their slice of the habitat. As Draco species are also often found in sympatry, we tested whether competition pressures had resulted in similar habitat partitioning and corresponding morphological characters (or ecomorphs). Whilst it’s perhaps a bit early to suggest that Draco have  evolved the full complement of anole ecomorph classes, the Draco taxa studied largely clustered into two groups that shared characteristics with the Greater Antillean anoles. The figure below (panel b) shows a combined Draco/anole phenogram, based on morphology and ecobehaviour (the anoles are labelled only by ecomorph). The Draco species fall out largely in line with groups of ‘trunk-ground’ anoles towards the top of the phenogram, and ‘trunk-crown’ anole towards the bottom. Phenogram ecomorph

One of the better diagnostic features of the Greater Antillean anole ecomorphs are the differences in perch use and subsequent differences in limb length. The plot below shows total hindlimb length (size-free residuals) of adult males of Draco species and Greater Antillean anoles, as a function of perch circumference.  The relationship between limb length and perch size is nearly identical between the groups, with a very similar slope, and only a difference in y-intercept owing to differences in body length (Draco bodies are elongated to accommodate gliding membranes).  The same unit increase in perch size results in the same unit increase in limb length for both genera.

These results are surprising considering that this relationship has not been found in species that are more closely related to the Greater Antillean Anolis (see study for references) and because Draco and Anolis have very different ‘key innovations’ for locomotion in their respective habitats (toe pads for Anolis and gliding membranes for Draco). This implies that Draco species have experienced interspecific competition over resources in similar ways to the anoles, resulting in homologous character displacement. 

About Danielle Klomp

I’m a PhD student researching behavioural ecology at UNSW in Sydney. I am working on a highly speciated genus of agamids, called Draco, which are unique in their ability to glide long distances using extensible membranes supported by elongated rib-bones. Draco also have extensible dewlaps, similar to the anoles, which are diverse amongst species, often brightly coloured and are used in territorial and mating displays. My research examines the mechanisms maintaining the diversity in dewlap colour and display, the interplay between this diversity and environmental variables and how this leads to new phenotypes and speciation.

5 thoughts on “Draco Shares the Anole Limb Length–Perch Size Relationship

  1. What a cool study! Are there any non-Draco agamids sympatric with the species you’re looking at, and do you think it might be possible that they fit in to other ecomorph roles?

    1. Thanks Ambika! That’s totally right – there are a bunch of other agamids living in the same forest patches as Draco. Some with similar morphology to Draco, but some that are very different. A comparison looking at different genera including species found both in sympatry and allopatry would be pretty interesting, considering they’d have different possible phylogenetic restrictions.

  2. Thanks Danielle! I spent a big chunk of my career studying the Draco-Anolis parallels but your stuff is even niftier than my (obvious) morph and color items.
    Skip

    1. Thanks Skip – it’s a really interesting system, especially as an Anolis analog. Your Philippines / Lesser Antilles comparison was formative for this work. Hope to chat more in the future!

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