Phylogeography of cliff-dwelling relicts with a highly narrow and disjunct distribution in the western Mediterranean.
OBJECTIVE
The high biodiversity in the Baetic-Rifan hotspot of Mediterranean region is shaped by complex geological and climatic histories and has been a subject of recent intensive studies. However, very little is known about phylogenetic and biogeographic history of three rare and critically endangered cliff-dwelling species of Sonchus in section Pustulati in this region.


METHODS
We investigated the genetic variation and phylogenetic relationships of populations based on nuclear (ITS/ETS) and plastid (3'trnL-ndhJ/psaI-accD) DNA sequences, and amplified fragment length polymorphisms (AFLPs). We performed a Bayesian relaxed molecular clock analysis with ITS data to estimate divergence times for major lineages.


RESULTS
ITS/ETS and AFLP phylogenies showed high concordance and contrasted with cpDNA data. The divergence between S. masguindalii and S. fragilis was dated at 5.48 Ma, between S. fragilis and S. pustulatus at 3.89 Ma, and between the Baetic and Rifan S. pustulatus at 1.18 Ma. Within each distribution area, AFLP data showed a relatively high genetic structuring and moderate genetic diversity, the latter being impoverished in the Baetic populations.


CONCLUSIONS
Our results further confirm the hybrid origin of S. pustulatus, a critically endangered species. The origin and diversification of lineages appear to have occurred on the temporary land bridge that joined Iberian and North Africa during the Messinian Salinity Crisis (5.96-5.33 Ma) and the subsequent Zanclean flood that progressively refilled the Mediterranean Basin (5.33-3.60 Ma). The only Baetic populations of S. pustulatus most likely originated from the Rifan ones.
Departamento de Biología Vegetal y Ecología, Universidad de Sevilla, Apartado 1095 41080 Sevilla, Spain.
Jose L
JL
Silva
Departament of Biological Sciences, Sungkyunkwan University, 440-746, Suwon, Korea.
So-Yeon
SY
Lim
Departament of Biological Sciences, Sungkyunkwan University, 440-746, Suwon, Korea.
Seung-Chul
SC
Kim
Departamento de Biología Vegetal y Ecología, Universidad de Sevilla, Apartado 1095 41080 Sevilla, Spain.
José A
JA
Mejías
D002467:Cell Nucleus / Q000235:genetics; D018742:DNA, Chloroplast / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D017753:Ecosystem; D009018:Morocco; D010802:Phylogeny; D058974:Phylogeography; D063148:Plant Dispersal; D018087:Plastids / Q000235:genetics; D017422:Sequence Analysis, DNA; D031184:Sonchus / Q000235:genetics / Q000502:physiology*; D013030:Spain
D018742:DNA, Chloroplast; D018744:DNA, Plant
Baetic-Rifan region; Gibraltar arc; Messinian-Zanclean ages; Sonchus section Pustulati; cliff ecology; disjunct distribution; long-distance dispersal; relaxed Bayesian molecular clock dating; vicariance