Biology ETDs

Publication Date

4-15-2022

Abstract

Recent declines in terrestrial arthropod biodiversity highlight the need to pinpoint which taxa and ecosystem services are most threatened, and why. But, for most of the world’s ~20,000 bee species, we lack robust evidence of population trends, and the role of climate change remains surprisingly little studied. I used long-term bee monitoring data from the Sevilleta Long-Term Ecological Research Program (Socorro, NM, USA), along with complementary experimental and observational data, to examine how climate relates to bee abundance and diversity patterns over time and space, and to identify the traits that govern bees’ climate sensitivities. Under climate change, drylands worldwide are experiencing ecosystem transitions: the expansion of some ecosystem types at the expense of others. In chapter 1, to understand how these transitions could influence bees, I compared bee assemblages and their seasonality among three dryland ecosystem types. Bee abundance, composition, and seasonal turnover differed among ecosystems, indicating that predicted ecosystem transitions could alter assemblage composition and phenology. Predicting the consequences of global change for bee assemblages thus requires accounting for both within-year and among-ecosystem variation. Climate change could pose a direct threat to insect pollinators, but for most species, we lack the long-term data and mechanistic evidence necessary to identify climate-driven declines and predict future trends. In chapter 2, I combined bee abundance data with experimentally determined heat and desiccation tolerances to predict which bee species will “win” vs. “lose” under climate change. Aridity strongly predicted bee abundance, and taxa that best tolerated heat and desiccation in physiological experiments increased the most over time. Models forecasted declines for 44% of species and predicted more homogeneous future communities, suggesting that bee conservation efforts should account for the direct stress imposed by climate. Behavioral thermoregulation could buffer ectotherms against climate stress, enabling population persistence and preserving ecosystem services. But evidence supporting this hypothesis for insects is sparse. In chapter 3, I assessed whether activity periods and physiological tolerances jointly predicted temporal trends in bee abundance under increasing aridity. Bee populations with weak thermal and desiccation tolerances declined if the bees were active during dry times of day, but populations were stable or grew if bees were active during less stressful daily periods. These results advance the prediction that animal behavior and physiology will jointly determine insect abundances under future climate change.

Language

English

Keywords

pollinators, global change, biodiversity, traits, physiology, behavior

Document Type

Dissertation

Degree Name

Biology

Level of Degree

Doctoral

Department Name

UNM Biology Department

First Committee Member (Chair)

Kenneth D. Whitney

Second Committee Member

Jennifer A. Rudgers

Third Committee Member

Helen J. Wearing

Fourth Committee Member

Michael E. Dillon

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