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The Fall of the Yellow-Banded Bumblebee

The decline of the yellow-banded bumblebee may be due to inbreeding and disease, Reuters reports.

The numbers of the yellow-banded bumblebee, Bombus terricola, have fallen to the point that it is on the International Union for Conservation of Nature Red List of threatened species, despite once having been common in North America. To investigate why, a York University-led team of researchers generated draft partial B. terricola genome, while also sequencing 22 female bees with the potential of becoming queens.

As they report in Frontiers in Genetics, the researchers analyzed this dataset to find that the effective population size of B. terricola has fallen by orders of magnitude from its pre-Holocene levels and that the bees are now highly inbred.

"Inbreeding is especially bad for bees because it increases the chances of producing sterile males which then drives the decline further," York's Amro Zayed, the senior author on the paper, tells Reuters. "Inbreeding is both a consequence of the decline, but could also generate lower fitness that leads to further declines." 

They also found that some immune-linked genes are under selection in its genome, with the researchers say is consistent with the theory that pathogens have also contributed to the bees' decline.