Investigation of two species complexes in Batrachospermum section Batrachospermum (Batrachospermales, Rhodophyta)

Abstract

S.A. Stewart and M.L. Vis. 2007. Investigation of two species complexes in Batrachospermum section Batrachospermum (Batrachospermales, Rhodophyta). Phycologia 46:380–385. DOI: 10.2216/06-86.1

Within Batrachospermum section Batrachospermum, there are two putative species complexes with members that only differ by breeding system alone or this trait with a single vegetative character. New sequence data for the rbcL gene were generated from specimens of B. anatinum, B. arcuatum, B. boryanum, B. confusum and B. heterocorticum in order to assess the phylogenetic value of heterocortication on the main axis of the thallus and further explore the taxonomic utility of breeding system. The presence of heterocortication in B. involutum was confirmed, and this character served as a synapomorphy for a clade containing this taxon and B. anatinum, B. boryanum, B. confusum and B. heterocorticum. The rbcL sequences were identical for the two monoecious species: B. anatinum with spermatangia confined to the tips of vegetative branches and B. confusum with spermatangia on involucral filaments of the carpogonial branches as well as the vegetative ones. It is argued that knowledge of spermatangia placement is of ecological importance, and B. anatinum f. confusum is proposed rather than simply placing the two entities in synonymy. There was no clear support for or against the use of breeding system as a taxonomic character, with pairs of morphologically similar species differing primarily by breeding system grouped together. Batrachospermum gelatinosum and B. gelatinosum f. spermatoinvolucrum from North America were not part of the clade formed by the other taxa studied. In fact, they were nested distantly in a clade containing other genera in the Batrachospermaceae. Among the taxa with heterocortication, B. anatinum, B. boryanum, B. heterocorticum and B. involutum, each was at least 1.4% different in its rbcL sequence from its closest neighbor. The present research provides more evidence that section Batrachospermum will need to be split with the potential of resurrecting section Helminthoidea and that the generic classification needs revision.

Key Words::

• Batrachospermum
• Breeding system
• Freshwater
• Heterocortication
• Morphology
• Phylogeny
• rbcL gene
• Rhodophyta

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Corrigendum

ACKNOWLEDGMENTS

The authors thank J.-Y. Chou for providing his prepublication data on B. arcuatum from Taiwan. In addition, collection of materials by Wayne Chiasson, Tim Entwisle, Melissa Hall, Rosalina Stancheva, Robert Verb and Brian Whitton is much appreciated. Help in laboratory research by Kevin Snyder is gratefully acknowledged. The authors are indebted to Robert Sheath and Kirsten Müller for loan of the B. involutum specimen for morphological examination. Funding for this research from the National Science Foundation (DEB 0235676 to M.L.V.) is most appreciated.