Pliocene-Pleistocene ecological niche evolution shapes the phylogeography of a Mediterranean plant group.

Estimating species ability to adapt to environmental changes is crucial to understand their past and future response to climate change. The Mediterranean Basin has experienced remarkable climatic changes since the Miocene, which have greatly influenced the evolution of the Mediterranean flora. Here, we examine the evolutionary history and biogeographic patterns of two sedge sister species (Carex, Cyperaceae) restricted to the western Mediterranean Basin, but with Pliocene fossil record in central Europe. In particular, we estimated the evolution of climatic niches through time and its influence in lineage differentiation. We carried out a dated phylogenetic-phylogeographic study based on seven DNA regions (nDNA and ptDNA) and fingerprinting data (AFLPs), and modelled ecological niches and species distributions for the Pliocene, Pleistocene and present. Phylogenetic and divergence time analyses revealed that both species form a monophyletic lineage originated in the late Pliocene-early Pleistocene. We detected clear genetic differentiation between both species with distinct genetic clusters in disjunct areas, indicating the predominant role of geographic barriers limiting gene flow. We found a remarkable shift in the climatic requirements between Pliocene and extant populations, although the niche seems to have been relatively conserved since the Pleistocene split of both species. This study highlights how an integrative approach combining different data sources and analyses, including fossils, allows solid and robust inferences about the evolutionary history of a plant group since the Pliocene.

Narrow endemics on coastal plains: Miocene divergence of the critically endangered genus Avellara (Compositae).

Critically endangered species representing ancient, evolutionarily isolated lineages must be given priority when allocating resources for conservation projects. Sound phylogenetic analyses and divergence time estimations are required to detect them, and studies on their population genetics, ecological requirements and breeding system are needed to understand their evolutionary history and to design efficient conservation strategies. Here we present the paradigmatic case of Avellara, a critically endangered monotypic genus of Compositae inhabiting a few swamps in the west-southwest Iberian coastal plains. Our phylogenetic and dating analyses based on nuclear (ITS) and plastid (matK) DNA sequences support a Miocene (>8.6 Ma) divergence between Avellara and closely related genera, resulting in marked morphological and ecological differentiation. We found alarmingly low levels of genetic diversity, based on AFLPs and plastid DNA sequences, and confirmed the prevalence of clonal reproduction. Species distribution modelling suggested a large macroclimatically suitable area for Avellara in the western Iberian Peninsula, but its apparently narrow microecological requirements restrict its distribution to peatlands with low-mineralised waters. Although five populations have been recorded from Spain and Portugal in the past, its current distribution may be reduced to only one population, recurrently found in the last decade but threatened by herbivory and habitat degradation. All this confirms the consideration of Avellara as a threatened species with high phylogenetic singularity, and makes it a flagship species for plant conservation in both Spain and Portugal that should be given priority in the design of in situ and ex situ conservation programmes.