COMPARATIVE EVOLUTIONARY GENETICS OF TREMATODE PARASITES (PLAGIORCHIIDAE) AND THEIR ANURAN HOSTS

A study of five trematode species of the genera Glypthelmins and Haplometrana inhabiting anurans produced allozyme-based estimates of Nei's (1978) genetic distance ranging from 0. 126 to 1. 867. An estimate of trematode phylogeny is in agreement with earlier morphologically based phylogenetic hypotheses and is similar to the phylogeny for associated host ranid and hylid frogs based on rDNA and morphology. A comparison of the genetic distances observed among trematodes with those of their respective hosts suggests that host and parasite genetic distances are not significantly correlated. This is counter to expectations based on a molecular clock for protein evolution in hosts and parasites. These results may reflect (i) the effects of sampling error on genetic distance estimates, (ii) a non-clocklike rate of protein evolution in hosts and (or) parasites, (iii) temporally independent speciation events in associated host and parasite lineages, or (iv) the effects of host hybridization.