Evolutionary genomics analysis reveals a unique lineage of Megachile pruina found in an isolated population in Bermuda

The decline in bee diversity, largely driven by habitat loss, climate change and invasive species, is well-documented. Within this context, the genus Megachile Latreille, 1802 (Hymenoptera: Megachilidae), a diverse group of solitary leafcutter bees, lacks comprehensive species-level conservation and taxonomic assessments, potentially concealing population declines and extinctions. Megachile pruina is one of Bermuda's three bee species and possibly the last native bee on the island. Formerly distributed widely across the island, it is now restricted to a small 11.5 ha area within the Castle Harbour Islands Nature Reserve. Classified as ‘Vulnerable’ under the Bermuda Protected Species Act, its taxonomic and conservation status remains uncertain, particularly its evolutionary relationships with populations in the United States. Here, we analyse nuclear genomes and mitochondrial genomes to reveal that Bermuda's M. pruina population is genetically distinct from mainland US populations and show no close association with any sampled US population, suggesting that Bermuda's represent a unique evolutionary lineage. Our genetic diversity assessment shows lower genetic diversity in Bermuda's population compared with the United States, highlighting a higher level of vulnerability than originally thought. We recommend maintaining its current protection status and advocate for the pressing need of expanding ecological and biological studies to facilitate appropriate conservation and monitoring measures.