Tall Tales of a Tropical Squirrel

Abstract

The Tufted Ground Squirrel, Rheithrosciurus macrotis is an endemic of the South East Asian island of Borneo. This species is remarkable in several aspects. Phylogenetic research indicates that its nearest living relatives are a group of South American squirrel species (Mercer & Roth, 2003). It is unclear how the evolutionary lineage leading to Rheithrosciurus ended up on Borneo without leaving behind any known relatives on either the Asian or North American land masses. The lineage of ancestors of Rheithrosciurus occupying Eurasia is either extinct without known fossil remains or the genus supposedly colonized Borneo in an independent long-distance colonization event (Mercer & Roth, 2003). More recent studies indicate that the Rheithrosciurus lineage diverged from a group of Palaearctic species of the genus Sciurus as early as 36 million years ago, and colonized Borneo overland from South East Asia (Pečnerová & Martínková 2012