Hybridization hotspots at bat swarming sites

Area of Science:

• * Ecology and Evolutionary Biology
• * Mammalogy
• * Conservation Genetics

Background:

• * Bat swarming behavior in temperate Northern Hemisphere zones involves mass gatherings at caves during late summer and early autumn, primarily for mating.
• * Previous understanding suggested swarming primarily facilitated intraspecific breeding, with limited evidence for interspecific interactions.

Purpose of the Study:

• * To investigate the extent of hybridization between different species of whiskered bats (genus Myotis) during swarming events.
• * To analyze the genetic diversity and hybridization rates within sympatric Myotis species in southern Poland.
• * To identify factors contributing to interspecific hybridization at bat swarming sites.

Main Methods:

• * Analysis of 375 bat individuals from three Myotis species using 14 nuclear microsatellites.
• * Application of three genetic analysis methods: Bayesian assignment (STRUCTURE, NEWHYBRIDS) and principal coordinate analysis.
• * Study conducted at swarming sites across the sympatric range of the selected species in southern Poland.

Main Results:

• * Overall hybridization rates ranged from 3.2% to 7.2% across studied populations.
• * Species-specific hybridization rates varied significantly, with Myotis alcathoe showing the highest frequency (6.5-30.4%).
• * Hybrids were found in approximately half of the studied caves, with a male-biased sex ratio, though not statistically different from population-level ratios.

Conclusions:

• * Bat swarming sites act as significant "hybrid hotspots" promoting interspecific breeding.
• * Factors such as high bat density, male-biased sex ratios, and polygynous mating systems contribute to hybridization.
• * These sites are critical for bat biodiversity conservation and understanding evolutionary processes in mammals.