Phylogeography of tropical pacific marine algae

Abstract

The tropical Pacific is a unique region to study marine algal phylogeographic patterns. The ancient age of the ocean basin, combined with the presence of numerous islands and archipelagos derived from a variety of geological and biological processes, has yielded several "cosmopolitan" algal species that likely achieved a broad distribution during the times of the Tethys Ocean. These cosmopolitan species consist, in almost all cases, of a series of lineages that can be interpreted as cryptic or pseudo-cryptic species. We review several example studies from the literature that examine phylogeographic patterns of marine algae from the tropical Pacific, and conclude (1) that in all cases the number of species discovered by molecular methods is large, (2) that the increase in diversity is correlated with sampling effort, and (3) that while morphological species are widespread in the tropics, cryptic or pseudo-cryptic species are often more localized, and even appear to have neighboring distribution patterns. These conclusions lead to a call for more large-scale collaborative studies to examine the phylogeographic trends of purportedly cosmopolitan species across the tropical Pacific.