Patterns of genetic diversity in southern and southeastern Araucaria angustifolia (Bert.) O. Kuntze relict populations

Maria Isabel Ferreira De Souza,Juliana Vitoria Messias Bittencourt,Marcio Alves-Ferreira,Fabiano Salgueiro,Rogério Margis,Mariana Carnavale-Bottino,Durvalina Benedita Félix

doi:10.1590/s1415-47572009005000052

Abstract

Habitat fragmentation and a decrease in population size may lead to a loss in population genetic diversity. For the first time, the reduction in genetic diversity in the northernmost limit of natural occurence (southeastern Brazil) of Araucaria angustifolia in comparison with populations in the main area of the species continuous natural distribution (southern Brazil), was tested. The 673 AFLPs markers revealed a high level of genetic diversity for the species (Ht = 0.27), despite anthropogenic influence throughout the last century, and a decrease of H in isolated populations of southeastern Brazil (H = 0.16), thereby indicating the tendency for higher genetic diversity in remnant populations of continuous forests in southern Brazil, when compared to natural isolated populations in the southeastern region. A strong differentiation among southern and southeastern populations was detected (AMOVA variance ranged from 10%-15%). From Bayesian analysis, it is suggested that the nine populations tested form five “genetic clusters” (K = 5). Five of these populations, located in the northernmost limit of distribution of the species, represent three “genetic clusters”. These results are in agreement with the pattern of geographic distribution of the studied populations.

Highlights

Deforestation is one of the main factors leading to forest fragmentation, or in other words, the complete transformation of a large area from a continuum of habitats to a large number of small patches of vegetation isolated one from the other (Macedo, 1993; Young et al, 1996)
The main goal of the present study was to evaluate the reduction in genetic diversity of five A. angustifolia populations in southeastern Brazil, when compared with other populations from the south
In order to analyse a large part of the natural range of A. angustifolia, so as to compare genetic diversity between remnants of continuous forests in southern Brazil and isolated populations in the southeastern region, nine different populations located in the main area of distribution and in the northernmost limit of distribution of the species in Brazil, were sampled

Summary

Introduction

Deforestation is one of the main factors leading to forest fragmentation, or in other words, the complete transformation of a large area from a continuum of habitats to a large number of small patches of vegetation isolated one from the other (Macedo, 1993; Young et al, 1996). Habitat fragmentation may lead to a loss in population genetic diversity through different processes. A drastic reduction in population size can result in the loss of small frequency alleles. This usually occurs since part of the remanescent individuals may constitute an insignificant sample of the original genetic pool (Frankel and Soulé, 1981). It is extremely important to be well-aware of both the levels of reduction in forest vegetation as well as the genetic structure of natural populations present during the fragmentation process. The immediate loss of heterozigosity will only be noticed in the event of the population suffering a large reduction in size (White et al, 1999)

Objectives

Methods

Results

Conclusion