Papers
Phylogeographic structure of Pinus strobiformis Engelm. across the Chihuahuan Desert filter-barrier
Journal of Biogeography DOI 10.1111/j.1365-2699.2008.02001.x
Aim: To explore the genetic and phylogeographic structure of a temperate forest species, Pinus strobiformis Englem., in a subtropical region in the context of climate change during the Pleistocene. It is expected that the colder conditions during glacial stages favoured range expansions of P. strobiformis, thus promoting gene flow.
Location: Mexico and the United States.
Methods: Estimates of genetic diversity and structure were obtained using chloroplast microsatellite loci of 23 populations of P. strobiformis across its entire range, seven neighbouring populations of Pinus ayacahuite Ehrenb. ex. Schtdl, and one population of Pinus flexilis James.
Results: The genetic diversity of P. strobiformis (He = 0.856) was found to be high, especially in western populations, whereas eastern populations were less variable and more genetically similar to P. ayacahuite of central Mexico. We found evidence of significant phylogeographic structure (NST = 0.444; P = 0.026), high genetic structure (RST = 0.270), and isolation by distance. Pairwise RST and samova (spatial analysis of molecular variance) results indicated an east–west partition of genetic variation, with populations within each group showing little differentiation and no isolation by distance.
Main conclusions: The phylogeographic structure of P. strobiformis across the entire range was pronounced, with two main genetic and geographic groups separated by the Chihuahuan Desert. However, within each of the two groups there was little population differentiation and no isolation by distance, suggesting genetic connectivity as a result of population expansions within these areas during glacial stages.
Like (4)Framentación y expansión demográfica en las poblaciones mexicanas de Pinus ayacahuite var. ayacahuite
Ortiz-Medrano A., Moreno-Letelier, A. and Piñero D.
This study explores the phylogeographic structure and the demographic history of the Mexican populations of Pinus ayacahuite var. ayacahuite. Three chloroplast microsatellites were aplified in 198 invidivuals form 14 populations. Twelve haplotypes were found and an average genetic diversity (He) of 0.705. Two maximally differentiated groups were determined with a spatial analysis of molecular variance. A significant correlation was detected between the genetic and geographic distances between there two groups, but not within them. A significant phylogeographic structure was found, produced by the existence of two groups. Two demographic expansions were detected, the first in the entire species, the second only in the southernmost populations. Aditionally, a nested clade analysis was perfomed to complement our observations. The results showed that the tehuantepec Isthmus was a corridor for species of temperate affinities in a cold period in ealy Pleistocene, and later acted as a barrier.
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