A new species of Sun Skink (Reptilia: Scincidae: Eutropis) from the Zamboanga Peninsula, southwestern Mindanao Island, Philippines

Abstract

We describe a new species of lizard in the genus Eutropis Fitzinger 1843 from the southwestern tip of the Zamboanga Peninsula on the western part of Mindanao Island, Philippines. The new species is related to Eutropis rugifera, which is a secretive, forest-adapted skink that ranges widely outside the Philippines from the western extent of its distribution on Nicobar Island (the type locality) through southern Peninsular Malaysia, Sumatra and the Mentawai islands, Borneo, Java, and as far east as Bali Island. The discovery of a new, morphologically distinct, and genetically highly divergent Sun Skink lineage in the low elevation forests of Zamboanga Peninsula creates a puzzling disjunct geographic distribution (E. rugifera has not been reported from the Sulu Archipelago). The new species is estimated to have diverged ∼10–16 mya from E. rugifera, from which it appears to have an extralimital and isolated distribution. Considering the dynamic geological history and ancient continental origin of the Zamboanga Peninsula, colonization by the new species may have been facilitated by pre-Pleistocene overseas long-distance dispersal, saltatory range expansion and subsequent contraction/extinction in the Sulu Archipelago, and/or possibly paleotransport on the ancient crustal fragment of Zamboanga. The new species is known only from Zamboanga City’s primary surface water supply catchment at the lowest elevations inside the boundaries of Pasonanca Natural Park, despite the fact that there have been historical surveys of herpetological diversity at multiple sites to the northeast (Zamboanga, western Mindanao) and to the southwest (Sulu Archipelago). The new species, thus, may be limited to just the tip of the Zamboanga Peninsula, possibly rendering Pasonanca’s low elevation forests its most critical habitat resource for long term persistence and survival of the species.