Northwestward range expansion of the bumblebee Bombus haematurus into Central Europe is associated with warmer winters and niche conservatism.

Species range expansions are crucial for understanding niche formation and the interaction with the environment. Here, we studied the bumblebee Bombus haematurus Kriechbaumer, 1870, a species historically distributed from northern Serbia through northern Iran which has very recently started expanding northwestward into Central Europe without human-mediated dispersal (i.e.