Diaz-Tapia P., Pasella M.M. & Verbruggen H. (2018)
Molecular analyses resolve the phylogenetic position of Polysiphonia adamsiae (Rhodomelaceae, Rhodophyta) and reveal a strong phylogeographic structure in Australia
Phycologia 57: 593-600


Polysiphonia adamsiae was originally described from Tasmania and simultaneously recorded in New Zealand. It has an unusual combination of morphological characters: rhizoids in open connection with the pericentral cells and 10-12 pericentral cells. Rhizoid anatomy resembles members of the tribe Polysiphonieae, but it differs from most species of this tribe in having more than four pericentral cells. Possessing more than four pericentral cells is much more common in the tribe Streblocladieae, which, however, was defined by having rhizoids cut off from the pericentral cells. The phylogenetic affinities of P. adamsiae were not analysed before using molecular data and at present it is uncertain whether it is a morphologically unusual member of the Polysiphonieae or Streblocladieae. We analysed phylogenetic relationships of P. adamsiae using rbcL sequences of materials collected in Tasmania and Croajingolong National Park (eastern Victoria). The phylogenetic analysis placed P. adamsiae in the Polysiphonieae. Our study further confirms rhizoidal anatomy as a key character delineating the Streblocladieae and Polysiphonieae. Conversely, the number of pericentral cells is variable in both tribes. While most species in the Polysiphonieae have four pericentral cells, at least six species evolved into multipericentral morphologies. P. adamsiae is here recorded for the first time in mainland Australia based on molecular and morphological evidence. The five haplotypes observed in our 16 rbcL sequences show that the species has strong phylogeographic structure. The Victorian haplotype is distinctive regarding Tasmanian lineages, making it is especially valuable in the conservation of this Australasian endemic species.

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