Development of 12 polymorphic microsatellite loci for the endangered Seychelles palm Lodoicea maldivica (Arecaceae).

PREMISE OF THE STUDY: The evolutionarily and ecologically distinct coco de mer palm Lodoicea maldivica (Arecaceae) is endemic to two islands in the Seychelles. Before colonization of the islands by man, the endangered palm formed large monodominant stands, but its natural range is now restricted to four main populations and several patches of isolated individuals. Microsatellite markers were designed to investigate the genetic structure of the remaining natural populations of L. maldivica. METHODS AND RESULTS: We developed 12 polymorphic and three monomorphic microsatellite markers for this species, with a mean number of alleles per locus of 13.2 (range 5-21) and expected heterozygosity values ranging from 0.31-0.91 for the polymorphic loci. CONCLUSIONS: These markers enable us to study the patterns of genetic diversity, contemporary seed dispersal, and the fine-scale spatial genetic structure of this important conservation flagship species.

Eleven microsatellite markers for the mountain clover Trifolium montanum (Fabaceae).

PREMISE OF THE STUDY: Microsatellite markers were developed in Trifolium montanum to investigate pollen dispersal patterns at landscape scale with a pollen-pool analysis (indirect parentage analysis) as well as in an experimental set-up with a direct paternity analysis. METHODS AND RESULTS: Screening 46 microsatellites developed for T. repens yielded four markers usable in T. montanum. Seven additional ones have been developed specifically for the target species using a 454-sequencing approach. All markers were polymorphic, with an allele number ranging from two to 45 based upon 254 individuals sampled from four populations, and an exclusion probability of 0.999. CONCLUSIONS: These markers proved a useful and reliable molecular tool for use in population genetics and parentage studies of this common grassland herb.

The relative importance of factors determining genetic drift: mating system, spatial genetic structure, habitat and census size in Arabidopsis lyrata.

• The mating system, dispersal and census size are predicted to determine the magnitude of genetic drift, but little is known about their relative importance in nature. • We estimated the contributions of several population-level features to genetic drift in 18 populations of Arabidopsis lyrata. The factors were outcrossing rate, within-population spatial genetic structure, census size and substrate type. The expected heterozygosity (H(E)) at 10 microsatellite loci was taken to reflect the effective population size (N(e)) and the strength of genetic drift. • The mating system explained most of the variation in H(E) (60%), followed by substrate (10%), genetic structure (9%) and census size (6%). The most outcrossing population had a +0.32 higher predicted H(E) than the most selfing population; the estimated N(e) of selfing populations was less than half that of outcrossing populations. Rocky outcrops supported populations with a +0.14 higher H(E) than did sandy substrates. The most structured population had a +0.24 higher H(E) than the least structured population, and the largest population had a +0.18 higher H(E) than the smallest population. • This study illustrates the importance of outcrossing, genetic structure and the physical environment--together with census size--in maintaining H(E), and suggests that multiple population-level characteristics influence N(e) and the action of genetic drift.