Cladistic and phenetic analysis of allozyme data for nine species of sea anemones of the family Actiniidae (Cnidaria: Anthozoa)

The aim of this study was to infer from allozyme data the phylogenetic relationships of nine species of actiniid sea anemones, and also use these data to assess the various methods (phenetic and cladistic) available for phylogenetic analysis. Starch gel electrophoresis was used to obtain genetic data from 13 gene loci. The anemone Metridium senile, from the family Metridiidae, was used as an outgroup. For the phenetic analysis a matrix of pairwise unbiased genetic distances was computed and, from this, dendrograms were produced both by the Wagner distance and the UPGMA methods. For the cladistic analyses three different approaches were used: the first was to treat the allele as a binary character; this was investigated using a Wagner parsimony algorithm. Another approach used was to consider the locus as an unordered character, using the alleles as states. Finally, we used the locus as an ordered multistate character, where mutation, fixation and elimination of each allele were treated as evolutionary novelties, and the heterozygotes were used as cues for the construction of transformation series. The trees produced by the phenetic and cladistic methods were highly congruent. This result suggests that allozymes can be used to produce phylogenetic hypotheses at higher taxonomic levels than those at which they are more usually employed. The Solé difference between the various trees was the relative positions of Bunodosoma caissarum and Bunodactis verrucosa in relation to the two species of Urticina. This difference was probably due to a high rate of anagenic change in B. verrucosa, which distorted the UPGMA dendrogram. The genera Actinia and Urticina appeared monophyletic in all of the trees produced. Also, the sea anemones with specialized column structures such as verrucae and vesicles (U.felina, U. eques, B. verrucosa, B. caissarum) formed a monophyletic cluster, a result compatible with the suggestion that these structures may have appeared only once in the evolutionary history of the Actiniidae.