Molecular and morphological reappraisal of Spyridiocolax capixabus (Spyridiaceae, Rhodophyta), a rare endemic parasite from Brazil

Abstract

Abstract The monotypic red algal parasite genus Spyridiocolax was proposed from material from the coast of Espírito Santo to accommodate Spyridiocolax capixabus, endemic from Brazil. The species is rare, and we performed a morphological reappraisal and the first molecular characterization of S. capixabus. Parasite specimens growing on Spyridia clavata were collected in the type locality, Itaoca Beach, Espírito Santo. Spyridiocolax capixabus forms colorless warts on the branches of S. clavata, and the secondary pit connections were described for the first time. Male, female and tetrasporophytic structures were observed growing in the same host plant. The plastid rbcL sequences of parasite and host were identical. A divergence of one nucleotide was found to the nuclear SSU rRNA gene, suggesting that the parasite retains the chloroplast of its host. Both plastidial and nuclear phylogenies supported the close relationship of S. capixabus and S. clavata. The data obtained corroborate other studies with rhodophycean parasites, which show morphological and molecular similarities between parasites and hosts. To maintain the monophyly of the host genus, the transfer of S. capixabus to Spyridia is proposed here on the basis of morphological and molecular evidence. Our study constitutes a starting point for reinvestigating the red algal parasites in Brazil.