Unexpected synchronous differentiation in Mediterranean and Canarian Cistus (Cistaceae)

Abstract

Diversification rates of insular oceanic lineages have been historically considered to be higher than those of mainland counterparts. In order to test this hypothesis in a group of Canarian endemics ( Cistus ), we estimated phylogeny and conducted both network analyses of haplotypes and molecular clock estimates using plastid DNA sequences of the trnS − trnG and the trnK − matK . Net differentiation rates in the Canarian purple-flowered lineage parallel those of the mainland (Mediterranean) purple-flowered sister group, as revealed by a similar number of species (five vs. three), haplotypes (seven vs. eight) and haplotype clades (four vs. four). Splitting dates in the Canarian (0.33±0.14/0.28±0.16 Ma) and Mediterranean (0.66±0.18/0.38±0.19 Ma) lineages reveal concordance in tempo of diversification. All these results are interpreted as evidence of two synchronous evolutionary histories given that Cistus ancestors had to cope with factors promoting differentiation in two hotspots of plant diversity: the Macaronesian and Mediterranean floristic regions. Analysis of Canarian populations suggests that a geographical rather than ecological differentiation was primarily responsible for early stages of a non-adaptive radiation of the Canarian lineage. Differentiation patterns of mainland populations appear to be more complex.