Genetic uniformity of a widespread mediterranean tree, Pinus pinea

Phylogeographic studies have used current geographical patterns of genetic diversity to infer the post-glacial history of many tree species. For domesticated species, this inference may be incorrect as a result of human practices in a more recent past. We used 12 chloroplast microsatellites (cpSSRs) to estimate the among and within population genetic variation of 50 Pinus pinea L. populations representing the species’ current Mediterranean distribution area. A single haplotype was detected in all populations studied except in Lebanon and in two populations from Spain, where 3 and 1 additional haplotypes at very low frequencies were found, respectively. The results found in P. pinea are therefore unique and may reflect the recent diffusion of the species westward across the Mediterranean, along with the beginning of offshore sailing and of long-distance trade in the Basin. Confined to a narrow distribution range during successive glacial-interglacial cycles, P. pinea may (or not) have experienced further reduction of its genetic diversity with the emergence of traditional agriculture and long distance trading. In order to deeply investigate the genetic uniformity of P. pinea new nuclear markers were developed. Since expressed sequence tags (ESTs) offer an interesting source for marker discovery, a non-normalized cDNA library was constructed from mRNA of young P. pinea needles. 1000 ESTs were sequenced to characterize the gene content of the library and a set of EST-SSR were developed and optimised and then used to screen diversity in the same populations