The Glor Lab

I was fortunate to assist Prof. Jimmy McGuire (UC Berkeley) with a field trip to Sulawesi, Indonesia during the fall of 2005.  During the trip I saw a number of remarkable animals (aquatic skinks, Draco, tarsiers, frogs that give birth to tadpoles, etc.), but one of my fondest memories is catching frogs high up on Mt. Lompobatang, near the tip of Sulawesi’s south west peninsula.  In the course of one night we bagged a number of species including the small, colorful, and polymorphic Rhacophorus edentulus; the massive, semi-arboreal Rana chalconata; and the bumbling toad Bufo celebensis.

The evening was memorable for a number of reasons.  First of all, one person in the group inadvertently grabbed a handful of poo while lunging for a Rhacophorus (herping and indigenous poo is a hilarious combination we Glor-labites have come to expect).  Hilarity aside, I recall marveling at how distinctive the Indonesian Rana are from their North American counterparts.  R. chalconota looks like a long, slender bullfrog with expanded toepads.  They can be seen calling several feet off the ground, and are ecologically and morphologically distinctive from the typical stream/pond frogs we have in the United States.  Granted, it’s now widely recognized Rana was a trashcan genus, and North American Rana and R. chalconota are not closely related (I think chalconota has been transferred to Hydrophylax).

A short while later, my foot was sexually assaulted by a gregarious male Bufo celebensis (fortunately I had on boots).  This specimen mistook my foot splashing in the margins of a temporary pool for a female, hopped over, and latched on…  I immediately recalled the countless times a similar occurrence has happened in the United States with our native bufonids.  In addition to their shared sexual indiscretion, B. celebensis is similar to say, a Bufo woodhousei in other ways: both have dry, warty skin, enlarged paratoid glands, similar locomotion, and similar breeding requirements.  I left that night with an appreciation for the distinctiveness of the ranid frogs, and the overwhelming similarities of the bufonids.

In the 5 Feburary 2010 issue of Science, Ines Van Bocxlaer et al. present the case that cosmopolitan distribution of bufonids is in part due to this similar phenotype.  They identify several traits that correlate with large range size in extant toads, and show range expansions in the history of the family correlate with the emergence of these traits.  Curiously, this “optimal range-expansion phenotype” emerged prior to the diversification of toads, and underwent little change during their diversification.  Thus, speciation appears detached from adaptation and range expansion seems to be the driver of toad diversity.
Gradual Adaptation Toward a Range-Expansion Phenotype Initiated the Global Radiation of Toads

For lab meeting next week we’re going to read a provokative new paper on adaptive radiation.  After suggesting that adaptive radiation is an ambiguously defined and unavoidably problematic concept, Olson and Arroyo-Santos argue that we abandon the use of the term entirely.  If you’re not already familiar with the modern definitions of adaptive radiation that are being criticized by Olson and Arroyo-Santos you might want to consider tackling a bit of background reading.  Recommendations include chapters 15, 16, and 17 in Lizards in an Evolutionary Tree, the first and second chapters of Schluter’s book The Ecology of Adaptive Radiation (parts of which are available via Google Books), and Givnish’s chapter on issues and approaches to adaptive radiation in his edited volume on Molecular Evolution and Adaptive Radiation (partly on Google Books).