Publications

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Patterns of range-wide genetic variation in six North American bumble bee (Apidae: Bombus) species.The increasing evidence for population declines in bumble bee (Bombus) species worldwide has accelerated research efforts to explain losses in these important pollinators. In North America, a number of once widespread Bombus species have suffered serious reductions in range and abundance, although other species remain healthy. To examine whether declining and stable species exhibit different levels of genetic diversity or population fragmentation, we used microsatellite markers to genotype popul ...201122035452
interspecific geographic distribution and variation of the pathogens nosema bombi and crithidia species in united states bumble bee populations.several bumble bee (bombus) species in north america have undergone range reductions and rapid declines in relative abundance. pathogens have been suggested as causal factors, however, baseline data on pathogen distributions in a large number of bumble bee species have not been available to test this hypothesis. in a nationwide survey of the us, nearly 10,000 specimens of 36 bumble bee species collected at 284 sites were evaluated for the presence and prevalence of two known bombus pathogens, th ...201122119631
nest initiation in three north american bumble bees (bombus): gyne number and presence of honey bee workers influence establishment success and colony size.three species of bumble bees, bombus appositus cresson, bombus bifarius, cresson and bombus centralis cresson (hymenoptera: apidae) were evaluated for nest initiation success under three sets of initial conditions. in the spring, gynes of each species were caught in the wild and introduced to nest boxes in one of three ways. gynes were either introduced in conspecific pairs, singly with two honey bees, apis mellifera l. (hymenoptera: apidae) workers, or alone. nesting success and colony growth p ...201020879924
altitudinal variation in bumble bee (bombus) critical thermal limits.organism critical thermal limits are often tightly linked to current geographic distribution and can therefore help predict future range shifts driven by changing environmental temperatures. thermal tolerance of diverse organisms often varies predictably with latitude, with upper thermal limits changing little and lower thermal limits decreasing with latitude. despite similarly steep gradients in environmental temperatures across altitude, few studies have investigated altitudinal variation in c ...201627264888
optimal foraging: random movement by pollen collecting bumblebees.two bumblebee species, bombus bifarius and b. flavifrons, forage randomly with respect to direction when gathering pollen on potentilla gracilis. bees avoid revisiting flowers by being able to differentiate recently visited from unvisited flowers. this recognition occurs while bees are flying over open flowers and appears to be a response to the amount of available pollen within flowers. random foraging with respect to direction is the optimal strategy when the probability of flower revisitation ...198228311747
population genomics of divergence among extreme and intermediate color forms in a polymorphic insect.geographic variation in insect coloration is among the most intriguing examples of rapid phenotypic evolution and provides opportunities to study mechanisms of phenotypic change and diversification in closely related lineages. the bumble bee bombus bifarius comprises two geographically disparate color groups characterized by red-banded and black-banded abdominal pigmentation, but with a range of spatially and phenotypically intermediate populations across western north america. microsatellite an ...201626811748
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