Fat-tailed dispersal shapes connectivity in a solitary bee

Dispersal-movement potentially leading to gene flow-is a fundamental ecological process yet notoriously difficult to measure. For solitary bees in particular, determining the spatial scale of dispersal movements and how landscape features influence connectivity is key to achieving conservation goals. Over 2 years, we marked 1698 females of the solitary bee Colletes validus at nesting sites, recaptured marked bees as they dispersed to build nests and as they foraged on flowers, and fit statistical kernels to observed movement distances. In total, we observed 349 dispersal events by 313 individual bees including 13 natal dispersal events (movement from emergence to the first nesting site) and 336 renesting dispersal events (movement among subsequent nesting sites). Solitary bee dispersal kernels were fat-tailed: Most bees made local movements (mean = 143 m), but a small proportion in the distributional tails made substantially longer movements (99% kernel quantile = 1.2 km) and the farthest dispersers were expected to move nearly 3 km. We also recorded 38 foraging movements from nests to flowers by 38 individual bees, allowing us to compare two ecologically distinct movement types. Mean foraging (131 m) and dispersal distances were similar, but upper foraging distances (99% kernel quantile = 554 m) were substantially lower than dispersal. Movement patterns also depended on landscape composition: Both foraging and dispersal movement propensity decreased with increasing inter-patch distance and number of road crossings. Our study highlights fundamental differences in the tails of foraging and dispersal in a central-place forager, demonstrates how landscape features constrain solitary bee movements, and contributes quantitative metrics on the spatial scale of movement for pollinator conservation planning.