Patterns of avian diversification in Borneo: The case of the endemic Mountain Black-eye ( Chlorocharis emiliae )

Abstract

The Mountain Black-eye (Chlorocharis emiliae) is an endemic white-eye(Zosteropidae) of Borneo with a unique ``sky island{''} distribution. Wecompared mitochondrial ND2, ND3, Cytb, and control region DNA sequences(2,194 nucleotides) to study the phylogeographic relationships of fivepopulations of this species that span its range: Mounts Kinabalu, TrusMadi, Murud, Mulu, and Pueh. These comparisons showed that black-eyesare divided into two main clades that correspond generally tosubspecific morphological groups: one in Sabah, Malaysia (Kinabalu andTrus Madi), and one in Sarawak, Malaysia (Murud, Mulu, and Pueh). Thegenetic and morphologic subdivision of black-eyes disputes the expectedmerging of populations during the Last Glacial Maximum (LGM), whenmontane forest presumably expanded and provided the opportunity forcurrently isolated populations to intermingle. Instead the genetic agingof black-eye populations indicates they diversified long before the LGM,and either did not expand sufficiently in range during the LGM to reachone another, or were reproductively isolated by the time of the LGM andthus prevented from interbreeding. Moreover, the subdivision betweenblack-eyes in Sabah and Sarawak means that this species (and probablyseveral other montane species) has a phylogeographic structureremarkably similar to Borneo's lowland bird populations, which arepresumed to have evolved under different paleo-geographic conditions.The similar phylogeographic pattern found in both montane and lowlandspecies requires that we rethink the causes of bird populationdiversification on the island of Borneo.