PHYLOGENETIC ANALYSIS OF BATRACHOSPEMALES(FLORIDEOPHYCEAE,RHODOPHYTA) BASED ON CHLOROPLAST RBCL SEQUENCES

Batrachospermales is an order belonging to Florideophceae,Rhodophyta.It distributes all over the world,China and its adjacent regions are the distribution center.Since Batrachospermales has been reported,the studies about the order were mainly focused on their morphological characters and its flora.But the phylogenetic relationship between taxa of Batrachosperales was still hard to guarantee in terms of morphology.Chloroplast rbcL sequences from 43 species of Batrachospemales and their relative lineages were used to reconstruct the phylogenetic trees by using the PAUP* 4.0 b10 and Mr Bayes 3.0 b4 software,which contained 6 samples collected from China and 37 species abroad obtained from GenBank.The phylogenetic relationships were inferred using the neighbor-joining,maximum-parsimony and Bayesian analysis,and three methods produced trees with largely congruent topology.These trees revealed that:(1) Three kinds of phylogenetic trees based on rbcL sequences were consistent.All phylogenetic trees topology got a similar placement of Thoreales,which formed a monophyletic group with high bootstrap support(100%).According to the Bayesian analysis,the conclusion supported that the Thoreales should be classified as a separate order.Thoreales were distinguished from Batrachospemales based on having freshwater representatives with multiaxial gametophytes,a uniaxial chantransia stage,and pit plugs with two cap layers,the outer one of which was usually plate-like.(2) All phylogenetic trees,got from the three methods(MP,NJ and Bayesian),showed that the Lemaneaceae was a relatively evolutional group in Batrachospemales.Two genera(Lemanea and Paralemanea),which belonged to family Lemaneaceae,formed new branches respectively,both of which were sister group.(3) In all trees,the taxa of Sirodotia and Tuomeya clearly formed a monophyletic clade with a strong bootstrap support,showed that they were relatively evolutional group in Batrachospemales.The two species of the Nothocladus were closely related to each other and formed a sister clade with Tuomeya and Sirodotia of Batrachospertmum,which separated from the clade including most taxan of the Batrachospertmum.This result accorded with the morphologic study.(4) In Batrachospermum,Sect.Hybrida and Sect.Contorta had a relatively small sequence divergence.From the observational results of morphology,carpogonial branches of Sect.Contorta had distortion or twist more or less.So,the research result of this study was inclined to combine Sect.Hybrida as Sect.Contorta.(5) Batrachospermaceae was the largest family of Batrachospemales,contained many species and distributes broadly.So the phylogenetic relationship was more complex.Thereby,further molecular and morphological investigations are needed to determine the phylogentic position of the Batrachospermaceae.