Anthropogenic deforestation and climate dryness as drivers of demographic decline and genetic erosion in the southernmost European fir forests

A better understanding of long-term effects of climate and historical anthropogenic changes is needed to define effective conservation measures of endangered forest inhabiting managed landscapes. Diversification and distribution of Mediterranean firs are attributed to the global climate change during the Miocene and Quaternary as well as to the effects of human-driven deforestation. We evaluated the impact of climate change and anthropogenic activities in shaping the genetic diversity and structure of Abies pinsapo Boiss. (Pinaceae), a relict fir endemic from SW Spain. We genotyped a total of 440 individuals from 44 populations by using two different molecular markers (cpSSRs and nSSRs). Overall, low genetic structure was found; however, incipient differentiation appeared within mountain ranges. Analyses suggest that the effects of isolation by distance and lithological or topographical diversity were not enough to structure the populations of the different mountain ranges. The combined role of genetic drift in the small populations and the anthropogenic action associated with forest management has shaped the current genetic pattern of this fir species in the study area. Demographic inference analyses pointed to a very recent synchronic divergence (eleventh–sixteenth century) of the ancestral A. pinsapo population into its current scattered distribution range. Although population bottlenecks were supported by several analyses, the conservation of this endangered species seems not to be limited by lacking genetic diversity, while threats of current climate change and habitat loss must be regarded.