The history of Seasonally Dry Tropical Forests in eastern South America: inferences from the genetic structure of the tree Astronium urundeuva (Anacardiaceae)

CAETANO S.; D.E. PRADO; T. PENNINGTON; S. BECK; A. OLIVEIRA-FILHO; R. SPICHIGER; Y. NACIRI

MOLECULAR ECOLOGY

Blackwell Publishing

Lugar: Hoboken, New Jersey; Año: 2008 vol. 17 p. 3147 - 3159

0962-1083

Today the Seasonally Dry Tropical Forests (SDTF) of Eastern South America occur as large well-defined nuclei (e.g., Caatinga in the northeast) and as smaller enclaves within other vegetations (e.g., cerrado and chaco). In order to infer the way the present SDTF distribution was attained, the genetic structure of Astronium urundeuva, a tree confined to SDTF, was assessed using two chloroplast spacers and nine microsatellite loci. Five haplotypes were identified, whose distribution was spatially structured. The distribution of the two most common and divergent haplotypes suggested former vicariance and progressive divergence due to isolation. More recent range expansions of these two lineages subsequently occurred, leading to a secondary contact at the southern limit of the Caatinga SDTF nucleus. The multilocus-Bayesian approach using microsatellites consistently identified three groups of populations (Northeast, Central and Southwest). Isolation by distance was found in Northeast and Southwest groups whereas admixture was detected in the Central group, located at the transition between Caatinga and Cerrado domains. This further supports the existence of the range expansions and secondary contact found with the chloroplast. The former results and the lack of chloroplast patchiness within the Central group in the Cerrado domain lend support to the existence of a more continuous formation of SDTF in eastern South America.