Biogeographical analyses of Batrachospermum helminthosum (Batrachospermales, Rhodophyta) in North America using molecular and morphological data

Twelve samples of Batrachospermum helminthosum were collected from stream s ites throughout the species' range in eastern North America as follows: thr ee samples from Ohio, two from Michigan, and one each from Indiana, Tenness ee, Louisiana, North Carolina, Connecticut, Rhode Island and Massachusetts. The plastid-encoded Rubisco large subunit gene (rbcL) and the nuclear regi on of ITS 1-5.8S rDNA-ITS2 were sequenced from each individual. Analysis of the rbcL sequence revealed five genotypes among the samples, with one geno type represented by seven samples. The ITS data showed unique sequences for all samples, except for one from Ohio and the North Carolina sample, which were identical. Parsimony, distance and maximum-likelihood analyses yielde d similar results, showing two clades of samples. One clade contained the m ajority of samples and the other comprised the Tennessee and Michigan sampl es. The phylogeography of the species appears to be complex, with samples f rom distant locations being genetically similar. Analysis of morphometric c haracteristics showed the species to be morphologically plastic across its range.