Morphological and genetic variation in Centrolepis paludicola and C-monogyna (Centrolepidaceae)

Centrolepis paludicola is a small cushion-forming herb which is listed as an endangered species. However, some taxonomists have questioned its species status and treat it as a subspecies of the common C. monogyna. Morphological measurements were taken on plants from 50 cushions collected from 31 sites throughout Tasmania, and included C. paludicola, C. monogyna and C. fascicularis as an outgroup to resolve this taxonomic issue. While C. fascicularis was distinct in all morphological analyses, the sympatric C. paludicola and C. monogyna could not be clearly distinguished on the basis of the reproductive and vegetative characters that are supposed to separate them. Centrolepis monogyna is henceforth interpreted as a morphologically variable species which includes C. paludicola. Once it was shown that these are best treated as one species, RAPD molecular markers were used to analyse genetic variation between populations. This analysis revealed a high level of polymorphism between cushions. As in the multivariate analysis of morphological data, C. monogyna and C. paludicola containing cushions were indistinguishable. However, there was a strong geographical structure to the genetic variation in the C. monogyna/C. paludicola group, consistent with a model in which gene flow between populations is limited and local differentiation has occurred.