Contemporary pollen flow, mating patterns and effective population size inferred from paternity analysis in a small fragmented population of the Neotropical tree Copaifera langsdorffii Desf. (Leguminosae-Caesalpinioideae)

Abstract

Pollen flow and dispersal patterns were investigated in a small, isolated forest fragment of the Neotropical insect pollinated tree Copaifera langsdorffii, using paternity analysis and eight microsatellite loci. We also investigated the coancestry and effective population size of progeny arrays for conservation and environmental restoration purposes. Open-pollinated seeds were collected from 15 seed trees within the forest fragment, in which all adult trees were mapped, measured and genotyped. Twenty seeds were also collected from the nearest neighbor tree located 1.2 km from the forest fragment. Our results show that levels of genetic diversity were significantly higher in adults than offspring and significant levels of inbreeding were detected in offspring (F = 0.226). From paternity analysis, we observed low levels of selfing (s = 8%) and pollen immigration (m = 8%) in the fragment, but very high levels were detected for the isolated tree (s = 20%; m = 75%), indicating that the population and the tree are not reproductively isolated and are connected by patterns of long distance pollen dispersal (maximum detected 1,420 m). Within the forest fragment, the pattern of pollen dispersal was a near neighbor pattern with 49% of the pollen being dispersed within 50 m. The effective population size of the progeny array was low, indicating the need to collect seeds from a large number of seed trees (at least 76) for conservation purposes. The results show that the spatial isolation of the population and isolated tree due to forest fragmentation has not disrupted genetic connectivity; however, spatial isolation does seem to increase selfing and correlated mating.

Research Article Contemporary pollen and seed dispersal in natural populations of Bertholletia excelsa (Bonpl.).

“…In populations with SGS due to short distance seed dispersal low levels of pollen immigration along with short distance pollen dispersal, can lead to mating between relatives, resulting in inbreeding (Degen and Sebbenn, 2014). Pollen flow can mitigate the negative effects of genetic drift, such as the loss of alleles, increased inbreeding and coancestry, and reduced heterozygosity (Burczyk et al, 2004), thereby increasing genetic diversity, the effective number of pollen donors, and population size within families (Manoel et al, 2012). These aspects of pollen dispersal are particularly important regarding genetic conservation, environmental restoration, and mating since crossing patterns determine the relationships between and among families, and thus the effective population size.…”

Genetic diversity and spatial genetic structure in populations of Orbignya phalerata Mart. under different exploitation intensities in the Brazilian savanna

“…Studies of tropical tree species have found signs of decreased genetic diversity and increased inbreeding in fragmented forest populations (AGUILAR et al, 2008). However, such changes may take several generations to manifest because the remaining adults still represent the pre-disturbance population (HAMRICK, 2004;AGUILAR et al, 2008;MANOEL et al, 2012).…”

Detecting the Early Genetic Effects of Habitat Degradation in Small Size Remnant Populations ofMachilus thunbergiiSieb. et Zucc. (Lauraceae)

“…The most likely explanation for these results is that human exploitation and habitat degradation have reduced the effective population size of adult trees in remnant populations, thus decreasing pollen availability and increasing the level of either self-fertilization or biparental inbreeding in the small, disturbed populations. Some previous researches indicate habitat degradation increases mating with relatives and genetic differentiation of future generations [7,[41][42][43]. On the other hand, result of (null) and frequency of null allele indicate some populations contain substantial proportion of null alleles and this also contributed to the excessive homozygosity.…”