Wings or winds: inferring bat migration in a stepping-stone archipelago

Area of Science:

• Evolutionary Biology
• Island Biogeography
• Paleoceanography

Background:

• Eocene ocean currents facilitated mammal dispersal from Africa to Madagascar.
• Since the Early Miocene, currents reversed, flowing from the Indian Ocean to Africa.
• Comoro Islands harbor endemic fauna with Malagasy ancestry, suggesting past dispersal events.

Purpose of the Study:

• To investigate gene flow in endemic Miniopterus bat species between Comoros and Madagascar.
• To correlate bat dispersal patterns with prevailing wind and ocean current directions.
• To utilize uni- and bi-parentally inherited markers with varying evolutionary rates.

Main Methods:

• Coalescence-based analyses of mitochondrial DNA (mtDNA) for matrilineal inheritance.
• Analysis of nuclear microsatellites for bi-parental inheritance.
• Comparison of genetic data with paleoceanographic and paleoclimatic reconstructions.

Main Results:

• Mitochondrial DNA data support a Pleistocene colonization from Madagascar to the Comoros (300 km), aligning with predicted dispersal.
• Nuclear microsatellites indicate recent, limited gene flow from Grande Comore to Anjouan (80 km), against prevailing winds.
• Dispersal patterns differ between maternal and biparental lineages, suggesting varied migratory behaviors.

Conclusions:

• Ancient bat colonization likely followed prevailing wind and ocean current directions.
• Recent gene flow demonstrates the capacity for bats to migrate against prevailing winds over shorter distances.
• The study highlights the complex interplay of geological history, climate, and behavioral adaptations in shaping island vertebrate faunas.