From cold to warm-stage refugia for boreo-alpine plants in southern European and Mediterranean mountains: the last chance to survive or an opportunity for speciation?

During glacial phases of the Quaternary, Southern European and Mediterranean mountains (SEMms: Pyrenees, Apennines, Balkan Mountains, Maritime Alps, etc.) provided suitable habitats for numerous cold-adapted (boreo-alpine) plant species migrating from northern regions, which have been described as cold-stage refugia. Speciation events occurred in these refugia through adaptation and evolution by genetic differentiation; other species still survive as peripheral populations. In the current phase of climate change, SEMms are (macro-)refugia of great interest because they still host important populations of glacial relicts and alpine flora, often in isolated occurrences. Such species can be found in topographic niches generally linked to peculiar landforms such as fossil glacial cirques, scree slopes and gorges that may perform as warm-stage (micro-)refugia. We present a review on the boreo-alpine species living across SEMms with the aim to describe their genetic patterns evolved during Quaternary climatic oscillations as well to highlight the role of microtopographic/microgeomorphologic niches as microrefugium areas under the current scenario of climate change.