Testing the biogeographical congruence of palaeofloras using molecular phylogenetics: snapdragons and the Madrean–Tethyan flora
The biogeographical congruence hypothesis, that similar spatiotemporal patterns of geographical distribution exist across lineages, is revisited in this study, and biogeographical processes in presumed Madrean–Tethyan plants are investigated by employing phylogenetic analyses.
Mediterranean and Californian floristic regions.
The snapdragons (tribe Antirrhineae, Plantaginaceae) are one of the plant groups that best illustrate disjunctions between the New World (14 genera) and the Old World (15 genera). A time-calibrated phylogeny (ndhF sequences) and ancestral-area reconstructions were used to test the hypothesis of biogeographical congruence. We estimated support for sister-group relationships together with the probability of temporal congruence of snapdragons and five additional angiosperm groups using a biogeographical approach based on Bayesian inference, parsimony and maximum-likelihood methods.
Synchronous divergences of four phylogenetically independent Mediterranean/Californian lineages within Antirrhineae were inferred for the Miocene. This result constitutes the first example of high biogeographical congruence within the same plant group. Analyses of five additional angiosperm groups previously considered exemplars of Madrean–Tethyan disjunctions revealed a total of 10 Mediterranean/Californian sister-group lineages, mostly with Miocene divergence times. In particular, our contrasting biogeographical analysis favoured a prevalent colonization process post-dating the separation of America and Eurasia (Eocene) for at least eight angiosperm lineages.
Explicit testing of the Madrean–Tethyan hypothesis did not support predominant vicariance for Mediterranean/Californian sister groups as previously proposed. Instead, eight Mediterranean/Californian sister-group lineages displayed a Miocene divergence, including considerable biogeographical congruence within Antirrhineae (four independent lineages) and Cistaceae (two lineages).