Adaptive Radiation and Ecological Opportunity in Sulawesi and Philippine Fanged Frog (Limnonectes) Communities

Abstract

Because island communities are derived from mainland communities, they are often less diverse by comparison. However, reduced complexity of island communities can also present ecological opportunities. For example, amphibian diversity on Sulawesi Island is lower than it is in the Philippines, but Sulawesi supports a surprising diversity of Sulawesi fanged frogs (Limnonectes).Here we examine molecular, morphological, and geographical variation of fanged frogs from these two regions. Using genealogical concordance, morphology, and a Bayesian approach to species delimitation, we identified 13 species on Sulawesi, only four of which have been previously described. After evolutionary history is accounted for, a model with multiple body size optima in sympatric species is favored over a "random-walk" model of body size evolution. Additionally, morphological variation is higher among sympatric than nonsympatric species on Sulawesi but not in the Philippines. These findings suggest that adaptive radiation of fanged frogs on Sulawesi was driven by natural selection to infiltrate ecological niches occupied by other frog lineages in the Philippines. This supports a role of ecological opportunity in community assembly: diversification in mature communities, such as the Philippines, is limited by a dearth of unoccupied ecological niches. On Sulawesi, evolutionary novelties originated in a predictable and replicated fashion in response to opportunities presented by a depauperate ancestral community.

A New Species of Stream Frog of the Genus Hylarana from the Mountains of Southern Mindanao Island, Philippines

“…Mindanao is one such island (Hall 1996(Hall , 1997(Hall , 1998(Hall , 2002Yumul et al 2003Yumul et al , 2004Yumul et al , 2008Yumul et al , 2009, indicating that a portion of today's closely related sympatric species might have evolved in isolation on paleoisland precursors in a manner similar to the model assumed for Sulawesi (Evans et al 1999(Evans et al , 2003a(Evans et al ,b, 2008McGuire et al 2007;Sanguila et al 2011;Setiadi et al 2011). Alternatively, it is equally plausible that the new species might have evolved as an isolated high-elevation lineage, in a manner similar to that presumed for some Philippine Platymantis (Alcala and Brown 1999;Brown et al 2015) and Limnonectes (Evans et al 2003a;Setiadi et al 2011).…”

How to fail at species delimitation

“…This pairing of a species discovery method with BPP has been followed by a number of authors (e.g. Barrett & Freudenstein 2011;Setiadi et al 2011). A particularly useful approach may be the pairing of discovery methods that model the species tree to identify putative lineages.…”

“…Some researchers interpret phenotypical variation in the context of delimitations from genetic data (e.g. Setiadi et al 2011;Esselstyn et al 2012;Stech et al 2013) as a way to buttress the results of delimitation analysis. In some systems, morphological differences serve as the basis for taxonomic hypotheses that are validated using genetic data (e.g.…”

Description of a Second Species of the GenusRabdionDuméril, Bibron & Duméril, 1854 (Colubridae: Calamariinae) from Sulawesi, Indonesia

“…Sulawesi is a composite island formed via the geological aggregation of several separate paleo-islands. Partially because of this tectonic history, at least seven areas of endemism have been identified on Sulawesi proper (Evans et al 2003;Setiadi et al 2011;Bacon et al 2013). Correspondingly, many species might be restricted to individual areas of endemism, or exhibit substantial geographic variation across the island.…”