Phylogeography above the species level for perennial species in a composite genus

Abstract

In phylogeography, DNA sequence and fingerprint data at the population level are used to infer evolutionaryhistories of species. Phylogeography above the species level is concerned with the genealogical aspects of divergentlineages. Here, we present a phylogeographic study to examine the evolutionary history of a western Mediterraneancomposite, focusing on the perennial species of Helminthotheca (Asteraceae, Cichorieae). We used molecular markers(amplified fragment length polymorphism (AFLP), internal transcribed spacer and plastid DNA sequences) to infer relationshipsamong populations throughout the distributional range of the group. Interpretation is aided by biogeographicand molecular clock analyses. Four coherent entities are revealed by Bayesian mixture clustering of AFLP data, whichcorrespond to taxa previously recognized at the rank of subspecies. The origin of the group was in western North Africa, fromwhere it expanded across the Strait of Gibraltar to the Iberian Peninsula and across the Strait of Sicily to Sicily. Pleistocenelineage divergence is inferred within western North Africa as well as within the western Iberian region. The existenceof the four entities as discrete evolutionary lineages suggests that they should be elevated to the rank of species, yielding H. aculeata, H. comosa, H. maroccana and H. spinosa, whereby the latter two necessitate new combinations.