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.

Naturally fragmented but not genetically isolated populations of Podocarpus sellowii Klotzsch (Podocarpaceae) in southeast Brazil

In southeastern Brazil, the majority of the riparian ecosystems are fragmented and degraded mainly due to human activities. The perennial gymnosperm Podocarpus sellowii Klotzch is a typical tree species from a gallery forest in the rupestrian area. Ten alloenzymatic loci were used to estimate the allelic frequency of 232 individuals distributed in eight subpopulations naturally divided by rock outcrops. The results indicated high genetic variability for the species in all subpopulations, with H_O varying from 0.593 to 0.658, and H_E, from 0.484 to 0.502. No endogamy was observed within (f = -0.292) and for the population set (f = -0.264). Genetic divergence of the species between subpopulations was 2.1%. Historic gene flow was low between subpopulations located in different water streams, corroborating the positive and significant correlation between genetic and geographical distance (r_m = 0.496, P = 0.022). Co-ancestry revealed that only population A presents continuous distribution of the genotypes up to 94 m. Sp statistics did not indicate significant spatial genetic structure in the populations. In all the subpopulations, values of effective sizes were higher than the numbers of sampled individuals. The balance between mutation and drift was not verified, indicating the occurrence of a recent population bottleneck. These data can be used to determine the most effective strategies for the genetic conservation of this species.

Divergent responsiveness of the dentary and vertebral bone to a selective estrogen-receptor modulator (SERM) in the teleost Sparus auratus

In teleosts the regulation of skeletal homeostasis and turnover by estrogen is poorly understood. For this reason raloxifene, a selective estrogen-receptor modulator (SERM), was administered to sea bream (Sparus auratus) and its effect on plasma calcium balance and transcript expression in dentary (dermal bone) and vertebra (perichondral bone) was studied. The concentration of total calcium or phosphorus in plasma was unchanged by raloxifene treatment for 6days. The activity of alkaline phosphatase (ALP) in dentary bone of raloxifene treated fish was significantly (p<0.05) higher than control fish but it was not changed in vertebral bone. Transcripts for estrogen receptor (ER) α were in very low abundance in the sea bream dentary and vertebra and were unchanged by raloxifene treatment. In contrast, raloxifene caused significant (p<0.05) up-regulation of the duplicate ERβ transcripts in the dentary but did not affect specific transcripts for osteoclast (TRAP), osteoblast (ALP, Runx2, osteonectin) or cartilage (IGF1, CILP2, FN1a). In the vertebra ERβb was not changed by raloxifene but ERβa was significantly (p<0.05) down-regulated as was the skeletal specific transcripts, TRAP, ALP, CILP2, FN1a. In summary, ERβs regulate estrogen sensitivity of the skeleton in sea bream, which responds in a non uniform manner. In common with mammals raloxifene appears to have an anti-resorptive role (in sea bream vertebra), but also an osteoblast stimulatory role, inducing ALP activity in the dentary of sea bream. Overall, the results indicate bone specific responsiveness to raloxifene in the sea bream. Further work will be required to understand the basis of bone responsiveness and the role of E(2) and ERs in teleost bone homeostasis.