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Abstract
The evolution of floral traits is often attributed to plant-pollinator interactions as they serve to attract floral visitors. However, the effect of pollinator-mediated selection on floral traits is context-dependent on other biotic and abiotic agents of selection. These multiple agents of selection interact in concert to influence the evolution of floral traits maintaining variation in floral morphologies across landscapes. Global change has direct and indirect impacts that result in novel selection on these traits. Historic ranges for plants and pollinators are becoming unsuitable as climate change progresses resulting in strong novel selection regimes and range shifts to more benign conditions. Here I explore the direct effect of climate change on floral trait evolution and determine how plant pollinator assemblages may change under future conditions.I first summarized what we know about the expression and evolution of floral traits and how we expect global change to disrupt these dynamics. I also highlighted areas of research that are relatively understudied, such as selection due to abiotic factors, that should be advanced to better understand these eco-evolutionary responses (Chapter 2). I then identified pollinator assemblages of the generalist Iris missouriensis (Iridaceae) across a nearly 1000-meter elevational gradient to determine how ecological networks of generalist species will be affected by climate change. I used species distribution modeling (SDM) with future climate scenarios as predictors to determine to future co-occurrence of I. missouriensis and the potential pollinators that visited its flowers in our study. I found that I. missouriensis will likely experience significant loss of suitable habitat and it will lose large areas of co-occurrence with nearly all the floral visitors that we modeled. I found that many pollinator species that were modeled are likely to expand their range northward as climate change will significantly increase their area of suitable habitat (Chapter 3). Additionally, I measured the floral size of Iris missouriensis across an aridity gradient to identify clinal variation in flower size such that average flower size increases with moisture availability. I used artificial I. missouriensis flowers to determine that floral visitors preferentially visit larger flowers across the aridity gradient suggesting that aridity may counter the effects of pollinator-mediated selection on flower size in this system (Chapter 4). My results suggest that smaller flowers may be favored as climate change progresses and that plant-pollinator interactions will be disrupted, resulting in spatial mismatches even for generalists. This work suggests that pollinators may be more robust to the effects of climate change than plants.