High population variability and source-sink dynamics in a solitary bee species
Although solitary bees are considered to play key roles in ecosystem functions, surprisingly few studies have explored their population dynamics. We investigated the population dynamics of a rare, declining, solitary bee (Andrena humilis) in a landscape of 80 km 2 in southern Sweden from 2003 to 2011. Only one population was persistent throughout all years studied; most likely this population supp