Application of Lianeage-Based Species Concepts to Oceanic Island Frog Populations: The Effects of Differing Taxonomic Philosophies on the Estimation of Philippine Biodiversity

Abstract

Appreciation of the magnitude of Philippine amphibian diversity has fluctuated A over the past 150 years, with current estimates of diversity awing to progress during five distinct phases in Philippine herpetology, These include: (1) the early taxonomists' period, before the turn of the last century; (2) the career of E. Taylor in the 1920s; (3) the work by R. Inger in the 1950s; (4) the collaboration of A. Alcala and W Brown between the 1960s and the 1990s; and (5), the current efforts to synthesize and compre-hensively review Philippine amphibian diversity in the context of a lineage-based species framework for species recognition. Until recently, taxonomic studies in the islands have all been conducted in the absence of an explicit species concept or within the context of the Polytypic Species Concept (a variant of the Biological Species Concept). In fhb - paper, we argue that the latter should no longer be applied to Philippine vertebrates because it is a philosophical framework that is not necessarily consistent with evolutionary history. Rather, we suggest the adoption of lineage-based species concepts such at the Evolutionary Species Concept (Simpson. 1961; Wiley, 1978) or The General Lineage Concept (de Queiroz, 1998, 1999) because both of these approaches result in the recognition of taxa in a manner that s logically consistent with known evolutidnary history. The geological history of the islands of the Philippines and the known common history of the vertebrates that occupy those landmasses are particu-larly amenable to interpretation within a lineage-based definition of the species. Due to the unique geological history of the Philippines and the insular isola-tion postulated for many of its endemic amphibians, we argue that lineage-based species concepts. are the most appropriate approaches for use in taxonomic studies of Philippine amphibians because populations on these islands' possess known evolutionary histories and predictable evolutionary fates as deep-water island endemics. Thus, the identification of lineages is straightforward and can be applied to species groups in a rigorous and repeatable fashion. Application of lineage-based species concepts also barters more realistic- estimates of Philippine biodiversity and should further promote conservation efforts fueled by estimation of species numbers and percent endemicity.

In this paper we review several recent studies that have resulted in significant increases in estimated species numbers within Philippine Amphibia and discuss the historical significance of recent work. Finally, we note several as-of-yet unchallenged polytypic species complexes in the Philippines and suggest various taxonomic groups in need of comprehensive review within the context of lineage-based species concepts.