Phylogeny and genetic structure of Erophaca (Leguminosae), a East–West Mediterranean disjunct genus from the Tertiary

The genus Erophaca comprises a single herbaceous perennial species with two subspecies distributed at opposite ends of the Mediterranean region. We used nrDNA ITS to investigate the phylogeny of the genus, and AFLP markers (9 primers, 20 populations) to establish the genetic relationship between subspecies, and among populations at each side of the Gibraltar Strait. According to nrDNA ITS, Erophaca is monophyletic, old (Miocene), and sister to the Astragalean clade. Life form attributes and molecular clock estimates suggest that Erophaca is one of the many Tertiary relicts that form part of the present Mediterranean flora. Within the occidental subspecies, European plants are clearly derived from North-African populations (Morocco) which, despite being rare on a regional scale, present the highest genetic diversity (as estimated by private and rare fragment numbers). In general, genetic diversity decreased with increasing distance from Morocco. AFLP and nrDNA ITS markers evidenced that the Eastern and the Western subspecies are genetically distinct. Possible causes for their disjunct distribution are discussed.