Phylogenetic relationships among lineages of the Ceramiaceae (Ceramiales, Rhodophyta) based on nuclear small subunit rDNA sequence data

Abstract

Phylogenetic relationships among 69 species of the Ceramiales (51 Ceramiaceae, six Dasyaceae, seven Delesseriaceae and five Rhodomelaceae) were determined based on nuclear small subunit (SSU) rDNA sequence data. We resolved five strongly supported but divergent lineages among the included Ceramiaceae: i) the genus Inkyuleea, which weakly joins other orders of the Rhodymeniophycidae rather than the Ceramiales in our analyses;ii) the tribe Spyridieae, which is sister to the remainder of the included ceramialean taxa;iii) the subfamily Ceramioideae, weakly including the tribe Warrenieae;iv) the subfamily Callithamnioideae;and v) the subfamily Compsothamnioideae, which emerges as sister to the Dasyaceae/ Delesseriaceae/Rhodomelaceae complex, thus rendering the Ceramiaceae sensu lato unequivocally paraphyletic, as has been separately argued on anatomical grounds by Kylin and Hommersand. Our data support a restricted concept of the Ceramiaceae that includes only one of the five lineages (Ceramioideae) that we have resolved. In addition to failing to ally with the Ceramiales in our molecular analyses, species of Inkyuleea also differ substantially from other Ceramiaceae sensu lato in details of pre- and postfertilization development. The genus Inkyuleea is here assigned to the Inkyuleeaceae fam. nov., which we provisionally retain in the Ceramiales. Species of Spyridia also differ from the remaining Ceramiaceae in their postfertilization development and, in light of our molecular data, the genus Spyridia is assigned to the Spyridiaceae J. Agardh. The Callithamnioideae is strongly monophyletic (100% in all analyses), which, in combination with key anatomical differences, supports elevation to family status for this lineage as the Callithamniaceae K？tzing. Similarly, the Compsothamnioideae is solidly monophyletic in our molecular trees and has a unique suite of defining anatomical characters that supports family status for a complex that we consider includes