Anthropization as a determinant factor in the genetic structure of Copernicia prunifera (Arecaceae)

This study uses ISSR molecular markers to characterize the demographic pattern, and spatial genetic structure (SGS) at different life stages of development (cohorts) in a natural population of Copernicia prunifera in the Rio Grande do Norte State, Brazil. All individuals were sampled and georeferenced in a 0.55-ha plot. The demographic analyses showed a clustered pattern in the first-distance classes and a random or segregated pattern at higher distance classes for all cohorts. Among the three studied life stages, juveniles showed the greatest value for Nei's genetic diversity index (H_E = 0.369), while the lowest was found among reproductive adults (H_E = 0.341). Greater genetic differentiation was found within life stages (98.61%) than among stages (1.39%). The total population (N = 161) showed positive and significant kinship in the first-distance class (12.3 m). The juveniles showed significant kinship up to 10.5 m. Non-reproductive adults had a positive kinship in the first-distance class (11.0 m) and a random distribution of genotypes in the remaining classes, while reproductive adults showed a random spatial distribution of genotypes. Tests for genetic bottleneck showed that the number of loci with excess observed heterozygosity was greater than expected. The SGS results reflected the restricted seed dispersion of the species, and the genetic bottleneck reflected the reduction of genotypes as a result of the anthropization of C. prunifera natural environments.

Mating system and intrapopulational genetic diversity of Copernicia prunifera (Arecaceae): a native palm from Brazilian semiarid

The aim of this study was to investigate the mating system and genetic diversity of the palm Copernicia prunifera using inter-simple sequence repeat markers. We found that the C. prunifera has multiple inflorescences with hermaphroditic flowers and pollen viability of 62%. Outcrossing rates at the population level (N = 267) produced a multilocus outcrossing rate (t_m) of 0.878 and a single-locus outcrossing rate (t_s) of 0.738, indicating that C. prunifera has a mixed mating system that is preferentially allogamous. The rate of mating among relatives (t_m - t_s) was low, indicating limited outcrossing between closely related individuals. The fixation index between seed trees (F) was negative (0.200), suggesting an absence of inbreeding, while the correlation of selfing (r_s) was high (0.914). The values of the diversity indices among adults and progenies did not differ statistically (H_E = 0.319 and I = 0.470; H_E = 0.337 and I = 0.505, respectively). In testing for the presence of genetic bottlenecks using the infinite allele model and the stepwise mutation model, we observed a reduction in the effective population, as well as a deficit in heterozygosity (P < 0.0001). The results of this study inform management strategies for the conservation and genetic improvement of the C. prunifera palm.

Increased relatedness among the neighboring plants from seedling to adult stages in carnaúba wax palm

The objective of this study was to assess the spatial genetic structure (SGS) at different life stages (cohorts) in a remnant population (N = 101) of Copernicia prunifera in the semiarid region of northeastern Brazil. Using seven inter-simple sequence repeat molecular markers, we were able to analyze 93 loci with 100% polymorphism. Seedlings had the highest level of genetic diversity (H_E = 0.411, H_O = 0.599), followed by juveniles (H_E = 0.394, H_O = 0.579) and adults (H_E = 0.267, H_O = 0.427). Based on analysis of molecular variance, the majority of genetic variations were observed to occur within the life stages (93.42%) rather than between the life stages (6.58%). We found a recent reduction in the population size (bottleneck) based on the number of loci with heterozygosity excess for the two models used (infinite allele = 92 and stepwise = 91). All the life stages showed significant SGS, with positive and significant kinship values. Sp values were 0.040 for seedlings, 0.093 for juveniles, 0.156 for adults, and 0.053 for the total population. We found an increase in SGS from the seedling to adult stages, indicating that the plants were from related adult progenitors. Data from this study can be used in designing effective management and conservation strategies for the species.