LAUSR

Drought is an increasingly important consequence of climate change. Drought often causes plants to alter patterns of resource allocation that in turn can affect how plants interact with other species. How these altered interactions subsequently influence plant reproductive success remains incompletely understood and may depend on the degree of specialization exhibited by antagonists and mutualists. Specialist pollinators, for example, are dependent on floral resources from their obligate hosts, and under drought conditions may thus indiscriminately visit these hosts (at least in certain circumstances). Generalist pollinators, in contrast, may only forage on host plants in good condition, given that they can forage on other plant species. We tested this hypothesis and its consequences for plant reproduction in squash (Cucurbita pepo) grown along an experimental moisture gradient ranging from dry conditions (growth and flowering compromised) to wet conditions. Floral visitation increased with plant soil moisture for generalist honey bees but was independent of plant soil moisture for specialist squash bees. Pollen production increased with plant soil moisture, and fluorescent pigments placed on flowers revealed that pollinators primarily moved pollen from male flowers on well-watered plants to the stigmas of female flowers on well-watered plants. Seed set increased with increasing plant soil moisture, but, notably, was higher in bee-pollinated plants compared to plants pollinated by hand with an even mix of pollen from plants grown at either end of the experimental moisture gradient. These results suggest that superior pollen rewards, perhaps combined with selective foraging by generalists, enhanced reproductive success in C. pepo when plant soil moisture was high and more generally illustrate that pollinator behavior may contribute to how drought conditions affect plant reproduction. This article is protected by copyright. All rights reserved.