Population structure and genetic diversity of two endangered endemic species of the Canarian laurel forest:: Dorycnium spectabile (Fabaceae) and Isoplexis chalcantha (Scrophulariaceae)

We used random amplified polymorphic DNA (RAPD) markers to assess the levels and structuring of genetic variation in the Canarian laurel forest endangered endemics Dorycnium spectabile (Fabaceae) and Isoplexis chalcantha (Scrophulariaceae). Amplification of seven primers in the only two extant populations of each species resulted in 28 (D. spectabile) and 32 (I. chalcantha) markers that exhibited a polymorphism of 78% and 100%, respectively. The estimates of population subdivision show that ca. 75% and 25% of the total genetic variability of both species is explained by the within- and between-population components, respectively. Our favored hypothesis to explain the high levels of genetic variation detected in both endemics is that they originated from multiple introductions of continental ancestors. The recent fragmentation and degradation of the Canarian laurel forest probably brought about a severe reduction of interpopulation gene flow in both species that might have disrupted the genetic cohesion of once more widespread geographic ranges. Intrapopulation spatial autocorrelation analyses indicate that the genetic variability of D. spectabile and I. chalcantha is structured in family clumps whose maintenance and enhancement is best explained by assortive mating and short-range seed dispersal capabilities. Because of the extreme vulnerability of these two endemics and their high levels of interpopulation genetic differentiation, we recommend protecting all their natural areas of occurrence and avoiding mixing individuals from different populations. Patch size estimates derived from spatial autocorrelation were used to suggest seed collection strategies that minimize the probability of sampling genetically similar individuals.