Genetic diversity was measured by allozyme electrophoresis in eight natural populations of the threatened Canarian endemic Viola palmensis Webb & Berth. (Violaceae). Nineteen alleles corresponding to 11 gene loci were detected. High levels of genetic diversity were found, ranging from 36.3 to 45.4 % for the percentage of polymorphic loci (P), from 1.45 to 1.60 for the average number of alleles per locus (A) and from 0.128 to 0.200 for the expected heterozygosity (H(e)). Between 85.5 and 96.6 % of genetic variability was apportioned within populations. As a whole, populations were not at Hardy-Weinberg equilibrium, with a deficit of heterozygous individuals attributable to the existence of genetic structuring in the populations analysed. The levels of interpopulation genetic differentiation were low (mean F(ST) = 0.100), while genetic identity pair-wise comparisons were high (mean I = 0.973) suggesting considerable levels of gene flow among populations. No relationship was detected between genetic differentiation and geographical distances between populations. An outcrossing insect-mediated breeding system might contribute to pollen dispersion of this species. For conservation genetics we suggest in situ preservation areas are defined that are free of disturbance and that include populations with the highest genetic diversity.
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.
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