Biogeographic and phylogenetic investigations of the pantropical genus sargassum (Fucales, Phaeophyceae) with respect to gulf of Mexico species

Abstract

The genus Sargassum, despite considerable research efforts, is still one of the most systematically complex and problematic genera of the brown algae. In order to evaluate the adequacy of sectional to series level designations in the tropical subgenus, an ambitious effort was began that will eventually include all of the east Isthmian species in a global phylogenetic analysis for the genus. This research effort is based on extensive seasonal field survey work and molecular-based parsimony analysis (chloroplast encoded ribulose-1, 5-bisphosphate carboxylase spacer region) of collected voucher specimens. The present analysis indicates that the Gulf/Caribbean species do not cluster as they are traditionally classified but form a strongly supported clade representing a single biogeographic unit in the Malococarpicae section of the subgenus Sargassum. Four of these species share an insertion/deletion event with some of the Pacific species, suggesting a shared evolutionary history between the two ocean basins.