Vascular plant endemism in the Western Carpathians: spatial patterns, environmental correlates and taxon traits

The Western Carpathians, as part of the Carpathian mountain range, are one of the most important centres of vascular plant endemism in Europe. We analysed the distribution patterns of 85 vascular plant taxa (excluding apomictic groups) that are endemic to this region (Western Carpathian endemics) or to the whole Carpathians (pan-Carpathian endemics) across 125 operational geographic units (OGUs) delimited in the area, and assessed their niche and altitudinal breadths, habitat preferences, and life-history traits. Spatial pattern of endemic richness was not random, but was geographically structured with the highest values recorded in the OGUs from the central part of the Western Carpathians. The pan-Carpathian endemics had, on average, larger distributional ranges in the Western Carpathians than the Western Carpathian endemics and showed slightly different distribution patterns, probably affected by historical migrations from the Eastern and Southern Carpathians. A significantly higher proportion of endemics occurred in open non-forest habitats (i.e. rocks/screes and grasslands, 74%) than in forests (18%). Almost 64% of endemic taxa occurred on calcareous bedrock, while only 12% and 21% were confined to siliceous or both types of bedrocks, respectively. We found a strong positive correlation between the distribution range of endemic taxa and altitudinal and niche breadths. There were no differences between diploids and polyploids in any of tested traits, niche and altitudinal breadths and range size. The best linear model explained almost 75% of endemic richness patterns, and included maximal altitude and its interactions with the proportion of calcareous areas and total area of OGUs as the best predictors. Our data suggest that both environmental conditions and historical migrations have shaped the current pattern of endemic richness in the Western Carpathians.