Pollinator community composition and ecosystem service provision across human-altered landscapes

Ecosystem services and the underlying biodiversity that support them are critical to the functioning of natural and human-dominated landscapes. However, across the globe, land cover change is rapidly altering the availability of semi-natural habitats in these ecosystems, with unknown consequences for biodiversity and services. This is particularly worrisome given the multiple temporal and spatial scales that likely drive successional change following a disturbance. Though both contemporary and historic processes likely mediate biodiversity and ecosystem service patterns, most studies focus primarily on contemporary and local factors. Identifying how both the current and historic land cover drive ecosystem services in human-altered landscapes across spatial scales and agro-ecosystems may reveal key governing principles that transcend a single region, target taxon, or type of human disturbance. Ecosystem services provided by mobile organisms, such as pollinators, may respond to land cover change through two major mechanisms. First, land cover change may alter ecosystem services through changes in pollinator community composition (Chapters 1, 2, 3, 4). Second, land cover change may alter ecosystem services through changes in pollinator behavior (Chapter 5). To examine these mechanisms, we conducted an extensive survey of the wild pollinators of the peach (Chapter 1) and cotton agro-ecosystems across Texas, USA (Chapter 2) and conducted a comparative study of cotton in Mato Grosso, Brazil (Chapter 3). We also examined the consequent changes in ecosystem services in cotton due to land cover and community change (Chapter 4). Lastly, to understand how land cover alters pollinator foraging behavior, we built quantitative plant-pollinator networks, focused on the two most common cotton pollinator species in the region (Chapter 5). Our results reveal that the overall composition of the wild pollinator community is closely related to the abundance and heterogeneity of semi-natural land cover both currently and historically (Chapter 1, 2, 3). Further, changes in community composition were closely related to ecosystem service provision in the cotton agro-ecosystem (Chapter 4). Lastly, beyond composition, pollinator behavior was found to respond to land cover through changes in generalization (Chapter 5).