Tod F. Stuessy

Phylogenetic relationships and genetic divergence among endemic species of Berberis, Gunnera, Myrceugenia and Sophora of the Juan Fernandez Islands (Chile) and their continental progenitors based on isozymes and nrITS sequences

Phylogenetic relationships and genetic divergence among congeneric species endemic to the Juan Fernandez Islands and their relatives in continental Chile were estimated using percentage of divergence of ITS of nrDNA andgenetic identity (Nei) based on allozyme variability. A total of 1151 individuals in 85 populations of 17 species was analyzed belonging to the genera Berberis (four spp.), Gunnera (four spp.), Myrceugenia (five spp.), and Sophora (four spp.). ITS regions 1 and 2 ranged between 442 and 504 bp long. The number of loci resolved differed within each genus and ranged between 5 and 11 (in Gunnera and Sophora, respectively). The new data allowed testing of previous hypotheses of relationship based on morphology and secondary products chemistry. Genetic identity values among insular congeneric species ranged between 0.936 (Gunnera) and 0.670 (Myrceugenia). ITS sequence divergence ranged from 0% (Gunnera and Sophora) to 4.2% (Myrceugenia). These values are within the ranges obtained for insular endemic species in other oceanic archipelagoes. Estimates of time of divergence of endemics from progenitors, based on isozyme data, lie between 188,500 and 2,580,000 years. The oldest island, Masatierra, is approximately 4 million years old and the youngest, Masafuera, 1-2 million years old. Genetic divergence between endemic species of Masafuera and their continental relatives is in general lower than that between endemic species of Masatierra and their putative continental ancestors. Genetic divergence is also greater between continental progenitors and derivative species in Masatierra than between endemic species pairs between Masatierra and Masafuera.