Microcnemum coralloides(Chenopodiaceae- Salicornioideae): an example of intraspecific East-West disjunctions in the Mediterranean region

[摘要] Microcnemumis a monotypic genus of Salicornioideae comprising rare, annual, hygrohalophytic herbs growing in hypersaline inland lagoons and salt pans.Microcnemum coralloidesshows an East-West disjunction in the Mediterranean region:M. coralloidessubsp.coralloidesoccurs in central and eastern Spain whileM. coralloidessubsp.anatolicumgrows in Turkey, Syria, Armenia and Iran. We studied the phylogeny, biogeography and morphological differentiation ofM. coralloides . Molecular analyses, using five western and eight eastern accessions of the species, were based on three different markers (nuclear ITS and plastidatp B- rbc L spacer andtrn T/F region) analysed with Maximum Parsimony and Maximum Likelihood. Estimates of divergence times were calculated using a Likelihood Ratio Test (LRT) and the Penalized Likelihood (PL) method. The two subspecies can be clearly distinguished by their different seed testa surface. Other diagnostic characters were not found. The molecular data (ITS and ML analysis of thetrn T/F region) indicate thatM. coralloidessubsp.coralloidesoriginated from withinM. coralloidessubsp.anatolicumwhich implies an East Mediterranean origin and subsequent westward dispersal. Age estimates for the split of the two subspecies range from 2.8�?0.5 million years ago. Considering the relatively low genetic differentiation and the low crown group age (0.7�?0.1 mya) ofM. coralloidessubsp.coralloidesin comparison toM. coralloidessubsp.anatolicumwe favour the hypothesis that the Iberian part of the species range was established during cold periods of the Early Pleistocene and that the range of the species was fragmented during a warmer period soon after its arrival in Iberia.

[学科分类] 植物学

[关键词] Biogeography;disjunction;Microcnemum;molecular clock;East Mediterranean;Spain