The European Alps are highly rich in species, but their future may be threatened by ongoing changes in human land use and climate. Here, we reconstructed vegetation, temperature, human impact and livestock over the past ~12,000 years from Lake Sulsseewli, based on sedimentary ancient plant and mammal DNA, pollen, spores, chironomids, and microcharcoal. We assembled a highly-complete local DNA reference library (PhyloAlps, 3923 plant taxa), and used this to obtain an exceptionally rich sedaDNA record of 366 plant taxa. Vegetation mainly responded to climate during the early Holocene, while human activity had an additional influence on vegetation from 6 ka onwards. Land-use shifted from episodic grazing during the Neolithic and Bronze Age to agropastoralism in the Middle Ages. Associated human deforestation allowed the coexistence of plant species typically found at different elevational belts, leading to levels of plant richness that characterise the current high diversity of this region. Our findings indicate a positive association between low intensity agropastoral activities and precipitation with the maintenance of the unique subalpine and alpine plant diversity of the European Alps.

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With five currently recognized species that form several secondary contact zones, slow worms (Anguidae: Anguis) offer a valuable model to study the fate of evolutionary lineages in the face of hybridization and genetic introgression. The relationships between the Western Slow Worm Anguis fragilis and the Italian Slow Worm Anguis veronensis are particularly puzzling. Their respective distributions remain poorly known on the edges of their parapatric ranges, as both species lack external differentiation. Contra earlier mitochondrial phylogenies, new phylogenomic inferences have shown that A. fragilis and A. veronensis are sister taxa, thus casting doubts on their specific status. In this study, we analyze the A. fragilis/veronensis transition in southeastern France, based on one mitochondrial (ND2) and two nuclear (PRLR and HA1) genetic markers in 81 specimens from 61 localities. The ranges of A. fragilis and A. veronensis roughly extends northwest and southeast of the Rhône-Durance valleys, respectively, with clear signs of introgressive hybridization in the areas of contact (notably the eastern parts of the lower Rhône valley). Based on the three molecular markers analyzed, gene flow does not seem to reach outside the narrow hybrid zone, which likely indicates (incomplete) intrinsic reproductive isolation. Hence, we provisionally suggest maintaining A. veronensis as a separate species from A. fragilis. More generally, patterns of genetic divergence, external differentiation, and hybridization (both historical and contemporary) in Anguis ssp. supports a speciation continuum spanning from cryptic, genetically compatible alloparapatric lineages to phenotypically distinct, deeply diverged and fully reproductively isolated taxa able to coexist in sympatry.