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theses

Specializing on one type of resource is a strategy used by organisms throughout the natural world. This strategy can have wider ranging ecological consequences, the most notable of which is that specialist species are more vulnerable to global change. My dissertation focuses on two types of specialization found in wild bees. The first of these is foraging-bout specialization, whereby an individual bee will visit a single plant species during a foraging bout. This strategy has larger ecological importance because a bee that visits one plant species while foraging transfers more conspecific pollen and less heterospecific pollen between flowers, aiding in plant reproduction. In my first thesis chapter, I examine how common foraging-bout specialization is in communities of forest bees living in New Jersey and Pennsylvania. I find that, in most bee species, individuals exhibit foraging bout specialization some of the time, but individuals from social bee species are more likely to do so than individuals from solitary bee species. Because most bee species are solitary – but most research on this topic has focused on social bees – my research suggests that foraging-bout specialization may be less common than previously thought.

The second focus of my dissertation is on forest specialist bee species, which depend exclusively on forest habitat for their survival. Evidence from non-bee taxa suggests that, in general, forest specialists are particularly vulnerable to decline, given widespread deforestation. Though many bees reside in forests, previous research has largely ignored forest specialist bee species, and no studies have examined their response to land-use change involving forests. In my second chapter, I identify which bee species are forest specialists in eastern North America, and I show that these bees are harmed by forest loss but benefit from forest regrowth: their diversity increases with forest area, is unaffected by forest age, and has increased during a 140-year period of forest regrowth in eastern North America. In my third thesis chapter I use a simulation to examine whether forest specialist bees’ response to forest loss is mediated by forest fragmentation. I find that, in the immediate wake of forest loss, fragmented landscapes harbor more forest specialist species than continuous ones with the same area of forest habitat. This is because there is more turnover of forest specialist species within fragmented landscapes. Overall, my results suggest an optimistic outlook for the conservation of forest specialist bee species. These species are likely to benefit substantially from forest regrowth, and, at least initially, they are not likely to be harmed by the fragmentation of remaining forest habitat.

ETD_10583

Ph.D.

Includes bibliographical references

doi:10.7282/t3-p5wx-7t84

ETD doctoral

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