Abstract
In phylogeography, DNA sequence and fingerprint data at the population level are used to infer evolutionary histories of species. Phylogeography above the species level is concerned with the genealogical aspects of divergent lineages. Here, we present a phylogeographic study to examine the evolutionary history of a western Mediterranean composite, 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 relationships among populations throughout the distributional range of the group. Interpretation is aided by biogeographic and molecular clock analyses. Four coherent entities are revealed by Bayesian mixture clustering of AFLP data, which correspond to taxa previously recognized at the rank of subspecies. The origin of the group was in western North Africa, from where it expanded across the Strait of Gibraltar to the Iberian Peninsula and across the Strait of Sicily to Sicily. Pleistocene lineage divergence is inferred within western North Africa as well as within the western Iberian region. The existence of 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.
Highlights
Intraspecific phylogeography as originally defined by Avise et al (1987) is concerned with the geographic distribution of genealogical lineages at the level of conspecific populations
The origin of the group was in western North Africa, from where it expanded across the Strait of Gibraltar to the Iberian Peninsula and across the Strait of Sicily to Sicily
Using molecular makers from the nuclear and plastid genomes, we addressed the following questions: (i) Does genetic grouping correlate with the present taxonomic treatment? (ii) Where did perennial species of Helminthotheca originate? (iii) Along which routes did they spread to occupy their present areas? The inferred evolutionary history is discussed with respect to the evolutionary forces that might have been relevant for speciation
Summary
Intraspecific phylogeography as originally defined by Avise et al (1987) is concerned with the geographic distribution of genealogical lineages at the level of conspecific populations. Based upon animal mitochondrial DNA sequence data, phylogeographic studies today make use of a variety of molecular techniques and are based upon DNA sequence and fingerprint data from the mitochondrial, plastid and nuclear genomes. The field of phylogeography today extends from the level of conspecific populations to the supraspecific level (Avise 2000) and targets organisms from the bacteria and eukaryote domains of life as well as viruses. Phylogeography of closely related species spans the boundary between reticulate and divergent relationships, where a partially braided collection of allelic pathways of interbreeding individuals bifurcates
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