Spatial genetic structure of two conifers in a highly human-modified landscape of central Mexico

Forests have been globally reduced by unprecedented deforestation and habitat transformation rates, which can affect the species’ genetic structure. Understanding patterns of spatial genetic structure is fundamental for proposing conservation actions that contribute to their long-term persistence. This study evaluated the spatial genetic structure and the effects of landscape features on gene flow in two conifers, Abies religiosa and Pinus montezumae, with different successional affinities in the temperate forest of La Malinche National Park in central Mexico, which exhibits a complex topography and high land-use changes. We recovered 7,326 Single Nucleotide Polymorphisms for A. religiosa and 34,423 for P. montezumae across 12 sites in four mountain slopes. A weak isolation by distance pattern was found only in A. religiosa (r = 0.12, P < 0.05) and clustering analyses did not reveal genetic structure in any species. The Analysis of Molecular Variance did not show significant genetic structure at any level in A. religiosa, whereas 11% of the genetic variation was structured among slopes in P. montezumae. Only 3% of the genetic variation was spatially structured in A. religiosa while a poor adjustment (R² = -0.01) was observed in P. montezumae, based on Moran Eigenvector Maps. Landscape genetic analyses showed that geographic distance better explains genetic differentiation in A. religiosa, in contrast to P. montezumae, in which the aspect-sine surface was the top-ranked model, indicating a reduction of gene flow Eastwards. Our study contributes with information for the conservation of Mexican temperate forests.