Genetic Diversity of Maine Offshore Island Bumble Bee (Bombus ternarius) Populations

Chris Lage¹, Sara L. Bushmann^2,3,*, and Francis A. Drummond³

¹College of Arts and Sciences, University of Maine at Augusta, Augusta, ME 04330. ²George Stevens Academy, Blue Hill, ME, 04614. ³School of Biology and Ecology, Orono, ME 04469. *Corresponding author.

Northeastern Naturalist, Volume 32, Issue 2 (2025): 303–315

First published early online: 13 June 2025

Abstract
We examined the genetic diversity of Bombus ternarius (Orange-belted Bumblebee) among offshore islands in the Gulf of Maine, Atlantic Ocean, and compared them with mainland populations from Maine. While slightly reduced genetic diversity was observed among island bees, statistical significance was not observed, and measures of genetic diversity measures were generally similar to the mainland populations. Estimates of genetic structure (F_ST) between offshore bees and coastal mainland bees were lower than that between the offshore bees and interior mainland bees, suggesting that the coastal mainland is the likely primary source population for the islands. Among offshore bees, increased genetic structure was observed at finer geographical scales, possibly due to chance dispersal and the effects of genetic drift on these small, isolated populations.

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