High levels of genetic diversity through pollen flow of the coniferous Araucaria angustifolia: a landscape level study in Southern Brazil

Abstract

In this study, genetic diversity, inbreeding, spatial genetic structure (SGS), and pollen dispersal are analyzed using ten microsatellite loci from two populations of the dioecious, wind-pollinated, coniferous tree Araucaria angustifolia in Southern Brazil. The study populations include an undisturbed 7 ha A. angustifolia cluster, where all adult trees were mapped and sampled, and an adjacent, long-abandoned, open agricultural area with an aggregated A. angustifolia population. Seeds were collected from 13 seed trees inside the forest cluster and from eight seed trees in the open forest. Our results showed that the adults present high levels of heterozygosity (H o = 0.91) and an absence of inbreeding. However, significant SGS was detected up to 90 m in the forest cluster suggesting that near-neighbor trees are related. The estimate of effective population size was lower than the total number of trees in the cluster (N e/N = 0.19), which can be explained by the presence of SGS in the stand. Substantial external pollen flow was detected in the forest cluster (26 %) and open forest (20 %), indicating that the reproductive population size is greater than the sampled populations, explaining the high genetic diversity in this population. Our results indicate that this site has potential for in and ex situ conservation due to high levels of genetic diversity and gene immigration resulting from pollen flow. Conservation strategies for A. angustifolia should focus not only on forest fragments but should also include the preservation of isolated trees throughout the landscape.