Patterns of phylogeography and vicariance of Chamaerops humilis L. (Palmae)

Abstract

Chamaerops humilis L. is 1 of 2 native palms occurring in Europe and the only native palm in the West Mediterranean region. Our aims were: (1) to describe its phylogeographic structure; (2) to infer a biogeographic scenario to explain its present distribution; and (3) to assess changes in its distribution from the last interglacial period. Twenty-two populations were sampled. An amplified fragment length polymorphism analysis produced 226 fragments, which allowed recognition of 4 groups of populations: (1) E Iberian Peninsula plus Al Hoceima (NE Morocco), the Balearics, and Sardinia; (2) France, the Italian Peninsula, and Sicily; (3) SW Iberian Peninsula and NW Morocco; and (4) S Morocco (var. argentea André; the first 3 groups are currently included in var. humilis). The phylogenetic information and molecular clock-related estimates, combined with geological and fossil history from the Eocene to present, suggest that C. humilis occurred in Central Europe in the Tertiary, reaching (1) Spain and (2) Italy, with expansion from here across North Africa to (3) N Morocco and S Spain, and (4) S Morocco. Climatic changes may also help explain the fragmented current distribution of this species. The groups of populations are sufficiently genetically distinct to recommend conservation of at least some populations in each region.