Biogeography of 'tropical Anagallis' (Myrsinaceae) inferred from nuclear and plastid DNA sequence data.

'Tropical Anagallis' corresponds to one of two evolutionary lineages within the genus Anagallis L. Generally, species within this lineage have a limited distribution in (sub-)tropical regions in Africa or Madagascar. Two species, however, are endemic to South America, and exhibit a trans-Atlantic disjunction with the rest of the species within the lineage. To investigate this disjunct distribution, as well as other dispersal events, the distribution of extant taxa was used to hypothesize the ancestral area(s) of distribution. Africa, Madagascar, Europe and South America. Dispersal-vicariance analysis (DIVA) was used to optimize distribution areas onto parsimony and Bayesian phylogenies based on sequence data from four chloroplast loci and the nuclear internal transcribed spacers (ITS). Parsimony analysis gave one most parsimonious tree while Bayesian analysis resulted in a collapsed node due to alternative placements of Anagallis nummularifolia Baker, endemic to Madagascar. Optimization of the present distribution using DIVA and the most parsimonious tree and six alternative topologies of the Bayesian analysis, show an origin of the lineage in Europe as most likely, although one topology indicates a broader ancestral distribution area. Dispersal to Africa appears to have been a single event, while two parallel dispersal events seem to have resulted in the American as well as Madagascan distributions. The lineage 'tropical Anagallis' evolved in Europe and may have been present in the Eocene boreotropical forests, although scarcity of fossils makes assessment of age difficult. Dispersal to South America is proposed to have been via the North Atlantic land bridge, or, more likely, through transport by the North Equatorial Current. Dispersal from Europe to Africa represents a single event, while dispersal to Madagascar from mainland Africa has occurred twice. [ABSTRACT FROM AUTHOR]