Phylogeography of Pinus subsection Australes in the Caribbean Basin.
OBJECTIVE
Four species of Pinus subsection Australes occur in the Caribbean Basin: P. caribaea, P. cubensis, P. maestrensis and P. occidentalis. This study analyses the phylogeography of these species to assess possible colonization events from Central America to the islands and subsequent population expansions during glacial periods driven by both drier climate and larger emerged land areas.


METHODS
Allele size data were obtained for plastid microsatellites for 314 individuals from 24 populations, covering the distribution range of subsection Australes in the Caribbean Basin.


RESULTS
In total, 113 plastid haplotypes were identified. The highest genetic diversity was found in populations of P. caribaea. Overall, Caribbean Basin populations fit the isolation by distance model. Significant phylogeographical structure was found (R(ST) = 0·671 > permuted R(ST) = 0·101; P < 0·0001). The haplotype network and a Bayesian analysis of population structure (BAPS) indicated different Central American origins for P. caribaea var. bahamensis and P. caribaea var. caribaea plastids, with Central America populations in northern and south-eastern groups. Sudden expansion times for BAPS clusters were close to three glacial maxima.


CONCLUSIONS
Central America contains ancestral plastid haplotypes. Population expansion has played a major role in the distribution of genetic diversity in P. caribaea var. hondurensis. Two colonization events gave rise to the P. caribaea var. bahamensis and P. caribaea var. caribaea lineages. Plastid variation in the eastern species (P. cubensis, P. maestrensis and P. occidentalis) evolved independently from that in P. caribaea var. caribaea. Incomplete lineage sorting between P. cubensis and P. maestrensis is apparent. Inferred expansion times for P. caribaea var. bahamensis and for the eastern lineages correspond to glacial maxima, whereas those for P. caribaea var. hondurensis correspond to the beginning of the temperature decrease that led to Marine Isotope Stage 8.
Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México (UNAM), Apartado Postal 70-275, Mexico D.F. 04510, Mexico. levjardon@yahoo.com.mx
Lev
L
Jardón-Barbolla
Patricia
P
Delgado-Valerio
Gretel
G
Geada-López
Alejandra
A
Vázquez-Lobo
Daniel
D
Piñero
D005075:Biological Evolution; D017691:Caribbean Region; D002489:Central America; D018744:DNA, Plant / Q000235:genetics; D014644:Genetic Variation; D006239:Haplotypes; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D010802:Phylogeny; D058974:Phylogeography; D028223:Pinus / Q000235:genetics*; D018087:Plastids / Q000235:genetics*; D017422:Sequence Analysis, DNA
D018744:DNA, Plant