Phylogeography of Asparagopsis taxiformis (Bonnemaisoniales, Rhodophyta) in the Hawaiian Islands: two mtDNA markers support three separate introductions

Abstract

A.R. Sherwood. 2008. Phylogeography of Asparagopsis taxiformis (Bonnemaisoniales, Rhodophyta) in the Hawaiian Islands: two mtDNA markers support three separate introductions. Phycologia 47:79–88. DOI: 10.2216/07-39.1Fifty-six samples of the gametophyte stage of Asparagopsis taxiformis, principally from the Main and Northwestern Hawaiian Islands, were obtained from field collections and archived herbarium material. Of these, 36 were successfully sequenced for the cox2-3 spacer region, and 42 for the COI gene. Parsimony analyses of both regions for the Hawaiian collections revealed relationships that were consistent with those previously published for global A. taxiformis samples, which also included a number from the Hawaiian Islands. The Main Hawaiian Islands are dominated by lineage 1, which is known from the Pacific coast of Central America and Hawai‘i. The Northwestern Hawaiian Islands, with one exception, contain a single widespread lineage (2) that is known from the Indo-Pacific, central Mediterranean and southern Portugal. A third lineage (4) is present in Hawai‘i only along a localized region of the south shore of O'ahu, but is widespread in tropical and subtropical waters outside of the Hawaiian Islands. Based on collection dates from archived herbarium material and the distributional trends of the lineages within the Hawaiian Islands, lineage 2 is hypothesized to be the original ‘native’ lineage of this species in the Hawaiian archipelago, and lineage 4 may have arrived as recently as 1991. COI and cox2-3 spacer sequences were always in accordance for lineage assignment of A. taxiformis samples, and future studies may only need to sequence one of the two markers.