Molecular phylogeny of Rhodochaete parvula (Bangiophycidae, Rhodophyta)

Abstract

Rhodochaete parvula Thuret (Rhodochaetales) was isolated from a culture of the marine green alga, Palmophyllum sp., from Point Lonsdale, Victoria, Australia. Previously known only from France and Jamaica, this is the first record of Rhodochaete parvula from the southern hemisphere. Rhodochaete is an enigmatic marine red alga believed by some to occupy a pivotal evolutionary position in the Rhodophyta. Monosporangia are common in the culture isolate, and monospores germinate readily, forming a new monosporangiate generation. No sexual reproduction was observed. Phylogenetic analysis based on DNA sequence of the small subunit of the ribosomal RNA reveals that R. parvula forms a well-supported clade with Erythrotrichia carnea and Erythrocladia sp. of the Erythropeltidales. Some phylogenetic support is found for grouping these two previous orders and the Compsopogonales (Compsopogon and Boldia), but this clade also contains Porphyridium aerugineum and Stylonema alsidii of the Porphyridiales. Certain morphological, cytological, and life history characters support grouping of the Rhodochaetales, Erythropeltidales, and Compsopogonales. Previous workers have shown that members of the Rhodochaetales and Erythropeltidales produce spores by lenticular divisions of vegetative cells, and several of these taxa display similar patterns of sexual reproduction. Unlike most other red algae, the mitochondria in Rhodochaetales, Erythropeltidales, and Compsopogonales are not associated with the cis-region of the Golgi or nuclei.