Unravelling the habitat preferences of two closely related bumble bee species in Eastern Europe

Co-occurrence of closely related species is often explained through resource partitioning, where key morphological or life-history traits evolve under strong divergent selection. In bumble bees (genus Bombus), differences in tongue lengths, nest sites, and several life-history traits are the principal factors in resource partitioning. However, the buff-tailed and white-tailed bumble bee (Bombus terrestris and B. lucorum respectively) are very similar in morphology and life-history, but their ranges nevertheless partly overlap, raising the question how they are ecologically divergent. What little is known about the environmental factors determining their distributions stems from studies in Central and Western Europe, but even less information is available about their distributions in Eastern Europe, where different subspecies occur. Here, we aimed to disentangle the broad habitat requirements and associated distributions of these species in Romania and Bulgaria. First, we genetically ide...