Genetic differentiation in endemic Lobularia (Brassicaceae) in the Canary Islands

Patterns of genetic diversity were examined in five endemic subspecies of the Lobularia canariensis complex from six of the Canary Islands. The taxa are interfertile, insect-pollinated outbreeders with wind dispersal. Electrophoretic analysis revealed a high level of genetic polymorphism at ten loci coding soluble enzymes, with a mean of 2.38 alleles per locus, 73.7 % polymorphic loci, and a mean heterozygosity of 0.279. Excesses of homozygotes, indicating inbreeding, were observed in small populations. The average total diversity was high, F.,=0.518. Among-population diversity, F_ST=0.318, contributed more to the total diversity than within-population diversity, F_IS=0.222. Little geographic or taxonomic patterning of the allozyme variation was observed. The mean genetic identitity for pairwise comparisons of the 19 populations was 0.76, with a range of 0.51–0.96 and c. 17 % of the comparisons below 0.67 and c. 8 % above 0.90. The results contrast with the many cases of high genetic identities reported for populations of endemic plants on oceanic islands. High levels of allozyme divergence suggest a relatively old origin of the L. canariensis complex and a long period of isolation of some of the populations.