Mating system in Pterocarpus macrocarpus Kurz in Thailand

The mating system in 11 natural populations of Pterocarpus macrocarpus Kurz in Thailand was investigated based on the mixed mating model using 16 isozyme markers. Single-locus outcrossing rates (tm) ranged from 0.719 to 0.959. Both ts and tm revealed a geographic pattern with western populations exhibiting higher outcrossing than eastern populations. Low estimates of outcrossing rates in eastern populations could be attributed to habitat characteristic, degree of disturbance, density, and distribution of flowering mature trees. Individual tree outcrossing rates (tmi) indicated that reduced population density associated with disturbance could result in low tm in some eastern population

Isozyme analysis of a tropical forest tree, Pterocarpus macrocarpus Kurz

Genetic variation within and among 11 natural populations of Pterocarpus macrocarpus Kurz. from different forest habitats in Thailand was examined by starch gel electrophoresis of 18 loci coding for 11 enzymes. The species possesses a high level of isozyme variation. The percentage of polymorphic loci per population ranged from 66.67 to 100% with a mean of 82.32% and the number of alleles per locus per population ranged from 2.44 to 2.94, averaging 2.67. Observed average population heterozygosity, at 0.222, was lower than the expected average population heterozygosity (0.246) and the estimate of FIS, at 0.099, suggests some degree of inbreeding within populations. There was a high degree of among-population differentiation. All 18 loci exhibited allelic heterogeneity and the estimate of FST was 0.12. Cluster analysis revealed an east-west pattern of population grouping, in accordance with significant correlations between allelic frequencies and longitudes at eight loci. The correlation coefficient between genetic and geographic distance at 0.515 (P < 0.0001) suggests that isolation by distance might in part have been a contributing factor to population differentiation in this tropical forest tree

Small scale spatial genetic structure of six tropical tree species in French Guiana

The small scale spatial genetic structure of six tropical tree species (Carapa procera, Chrysophyllum sanguinolentum, Dicorynia guianensis, Eperua grandiflora, Virola michelii, Vouacapoua americana) was studied for populations located within a sylvicultural trial in French Guiana. The analysed species have different biological and ecological characteristics with respect to spatial distribution, sexual system, pollen and seed dispersal agents, flowering phenology, and they differ in their environmental demands. The spatial position of trees and at least one data set on the genetic information for allozymes, cp-DNA marker, RAPDs and AFLPs served as basis for the analysis. As estimator for spatial genetic structure, Moran's index was computed for allozymes and cp-DNA markers, while for RAPDs and AFLPs mean Tanimoto distances between pairs of trees in different spatial distance classes were calculated. Each species showed significant spatial structure for at least one type of gene marker. The expansion of significant spatial genetic structures was relatively large and varied between 60m up to 800m. The strongest spatial autocorrelation was found for maternally inherited cp-DNA marker. Due to distinctly higher level of genetic variation, AFLPs and RAPDs were more sensitive to detect spatial structure than allozymes. Relations between the spatial genetic structures and the species' life characteristics are discussed

Mating system in a neotropical tree species, Senna multijuga (Fabaceae)

Senna multijuga is a pioneer tropical tree species that occurs mainly in the Brazilian Atlantic forest. We investigated the mating system of two populations of S. multijuga, one located in a reserve area (RD1) and the other (RD2) about 15 km away. The mating system parameters were estimated using the mixed mating model (software MLTR). The two populations had significantly different outcrossing rates, with population RD2 having a high rate (t m = 0.838) and population RD1, a lower rate (t m = 0.540). The values of t s were different between the two populations and also lower than those of t m. Significant t m - t s estimates indicated that biparental inbreeding contributed to the apparent selfing rate in these populations. The correlation of paternity was significant in population RD2 (r p = 0.309), suggesting that the progeny were more closely related than inferred by the observed outcrossing rate. The estimates of correlation of paternity, biparental inbreeding and the significant differences in pollen and ovule allele frequencies indicated that population RD2 is genetically substructured. For a pioneer species such as S. multijuga, selfing can be an important strategy for occupying open areas