Phylogeography of Sula: the role of physical barriers to gene flowin the diversification of tropical seabirds

We examined mitochondrial cytochrome b sequence variation in masked Sula dactylatra,red-footed S. sula, and brown S. leucogaster boobies sampled from islands inthe central and eastern Pacific Ocean and in the Caribbean Sea. Each species showeda different phylogeographic pattern. Whereas haplotypes in masked and red-footedboobies were shared across the central and eastern Pacific (i.e., across the EasternPacific Basin), brown booby haplotypes were not shared across the Eastern PacificBasin. Although most masked booby haplotypes from the Pacific were distinct fromthose in the Caribbean, one haplotype was shared across the Isthmus of Panama.Red-footed and brown boobies, however, did not share haplotypes across theIsthmus of Panama. We estimate that divergence of these regional populationsoccurred within the last 560,000 years. Thus, the Isthmus of Panama and the EasternPacific Basin (albeit to a lesser degree) appear to have played a role in thediversification of these species.

Tammy E. Steeves et al., JOURNAL OF AVIAN BIOLOGY 34: 217-223, 2003