Population genetics study of common (Pipistrellus pipistrellus) and soprano (Pipistrellus pygmaeus) pipistrelle bats from central Europe suggests interspecific hybridization

The discovery that the most widespread bat in Europe comprises cryptic species, Pipistrellus pipistrellus (Schreber, 1774) (common pipistrelle) and Pipistrellus pygmaeus (Leach, 1825) (soprano pipistrelle), provides a great opportunity to look at the mechanism of species coexistence. Based on eight nuclear microsatellite loci (n = 353), we observed similarities between the species in Poland with respect to heterozygosity, allelic richness, mean relatedness, and inbreeding coefficients. However, pronounced differences in migratory patterns (shown by assignment tests) suggest that P. pygmaeus is the more migratory species. The proportion of bats migrating between colonies differed significantly, with 17.1% and 41.8% individuals of P. pygmaeus and P. pipistrellus, respectively, confidently assigned to colonies of origin. Both species demonstrated a more migratory character in central Europe compared with the populations from the British Isles. Given the cryptic nature of the examined taxa, we also assessed whether they hybridize. Hybridization was confirmed by three methods-one based on genetic distance and two based on Bayesian approaches. The overall hybridization rate, depending on assumed threshold values, ranged from 1.7% to 13.3% for both species. We conclude that the population structuring in these pipistrelles is not homogenous across their range. Moreover, hybridization between them in continental Europe does occur and is not rare.