Alpine Islands: Population genomic inference reveals high degree of isolation between freshwater spring habitats

Diversity and Distributions,115. DOI: 10.1111/ddi.13461 We observed strong genetic differentiation between individuals from different springs. Water mites from each spring qualified as well-delimited distinct populations with only little intra-spring migration, even when these were located in close geographic proximity. Furthermore, we found subtle shared genetic structure among springs within the same area, and a southwestern genotype associated with the Rhône catchment that extended into eastern populations. Effective population size estimates and standing genetic variation within springs were generally low. Main conclusions: Our findings indicate strong insularity of freshwater springs and headwater areas, likely caused by intra-alpine Pleistocene isolation and limited dispersal abilities of strictly spring-bound species like P. steinmanni. Our results support the concept of spring habitat isolation and highlight the importance of alpine protected areas to conserve springs as substantial components of freshwater biodiversity.