15.1 Friday, Jan. 4 Singing out from sky islands: sunbird song evolution across the Eastern Afromontane MCENTEE, JP*; PENALBA, J; BOWIE, RCK; University of California, Berkeley firstname.lastname@example.org
Song evolution is thought to be important to the diversification of extant birds, because songs are functionally critical in social interactions such as mate choice and are thought to diverge rapidly among isolated populations. The sky island distribution of the Eastern Double-collared Sunbird (EDCS) species group (Nectarinia spp.) allows examination of song divergence among spatially isolated populations at varying degrees of evolutionary relatedness. In this study, we examine the trajectory of song evolution among these populations; phenotypic differences were assessed at levels ranging from within-species to among-species divergences. Previous authors have reasoned that song in song-learning species should be especially subject to rapid divergence in allopatry, regardless of ecological differences or divergence in other traits. Multi-locus molecular phylogenies indicate that six to eight distinct EDCS lineages have evolved, and moreover that several individual EDCS populations have existed in isolation long enough for reciprocal monophyly in mtDNA to develop. Our study indicates that, while major shifts in song phenotype have occurred coincident with molecular divergence, spatial isolation alone does not appear sufficient for substantial song divergence to accrue. Conservatism in learned song phenotypes despite the opportunity for divergence in isolation suggests the possibility that social selection can promote not only directional change but also stasis.