Landscape-scale deforestation decreases gene flow distance of a keystone tropical palm, Euterpe edulis Mart (Arecaceae)

Abstract

Habitat loss represents one of the main threats to tropical forests, which have reached extremely high rates of species extinction. Forest loss negatively impacts biodiversity, affecting ecological (e.g., seed dispersal) and genetic (e.g., genetic diversity and structure) processes. Therefore, understanding how deforestation influences genetic resources is strategic for conservation. Our aim was to empirically evaluate the effects of landscape-scale forest reduction on the spatial genetic structure and gene flow of Euterpe edulis Mart (Arecaceae), a palm tree considered a keystone resource for many vertebrate species. This study was carried out in nine forest remnants in the Atlantic Forest, northeastern Brazil, located in landscapes within a gradient of forest cover (19-83%). We collected leaves of 246 adults and 271 seedlings and performed genotyping using microsatellite markers. Our results showed that the palm populations had low spatial genetic structure, indicating that forest reduction did not influence this genetic parameter for neither seedlings nor adults. However, forest loss decreased the gene flow distance, which may negatively affect the genetic diversity of future generations by increasing the risk of local extinction of this keystone palm. For efficient strategies of genetic variability conservation and maintenance of gene flow in E. edulis, we recommend the maintenance of landscapes with intermediary to high levels of forest cover, that is, forest cover above 40%.

Keywords: Conservation; functional connectivity; landscape genetics; tropical forest.

Figure 1

Location of the study region within South America (dark gray: Bahia; light gray: Brazil) and of the study sites within it. White dots indicate the study sites, the circles around them indicate the 2‐km buffers, and the numbers indicate the percentage of forest cover within each buffer. Map data: Google, TerraMetrics, 2016, obtained with the OpenLayers plugin in Quantum GIS 2.14.3 (QGIS Development Team 2016).

Figure 2

Spatial genetic structure of Euterpe edulis (N = number of individuals genotyped in each fragment and the respective forest cover, percentage ranging from 19% to 83%). The gray lines indicate 95% confidence interval for average relatedness coefficient (F _ij) observed. (A) Euterpe edulis seedlings and (B) adults sampled in nine fragments within landscapes ranging from 19% to 83% of forest.

Figure 3

Presence (A–C) and proportion (D–F) of seedlings with assigned parents overall (A, D), in the same landscape (B, E), and in another landscape (C, F) as related to forest cover in the landscape. The lines represent generalized linear models with a binomial distribution. Line type represents significance as assessed by Monte Carlo tests: P ≤ 0.05 (full black line), 0.05 < P ≤ 0.10 (full gray line), P > 0.10 (dashed gray line).

Figure 4

Gene flow distance of each seedling with an assigned parent as related to forest cover. The line represents the fit of a linear mixed model performed on the logarithm of gene flow distance and forest cover, with landscape included as random factor (P < 0.05). Please note that the y‐axis is on a logarithmic scale.