REVIEW OF BULLIMUS (MURIDAE: MURINAE) AND DESCRIPTION OF A NEW SPECIES FROM CAMIGUIN ISLAND, PHILIPPINES

Abstract

Bullimus is 1 of 15 genera of murid rodents endemic to the oceanic portion of the Philippines (i.e., excluding Palawan and other islands on the Sunda Shelf). Two species have been recognized previously: B. bagobus, widespread on Mindanao and on islands that were connected to it during Pleistocene periods of lower sea level and B. luzonicus, occurring only on Luzon. Recent surveys have revealed a 3rd species endemic to the small island of Camiguin, located just north of Mindanao and isolated from that large island by deep water. Multivariate analyses support the recognition of these 3 species. The new species of Bullimus from Camiguin is distinguishable from congeners by its smaller size, soft and uniformly dark pelage, inflated braincase, shorter palate and incisive foramina, more divergent molar toothrows, and other cranial and dental features. The patterns of variation and island distribution in Bullimus are consistent with our understanding of regional geography; the 3 species occur on separate islands or island groups that remained isolated during periods of lower sea level. The discovery of a species endemic to Camiguin reflects the fact that this small island is close enough to Mindanao to have received some nonvolant mammals by overwater dispersal, but its isolation has been sufficient to promote speciation.