Domestication of plant species results in phenotypic modifications and influences changes in biotic interactions. Most studies have analyzed ecological and evolutionary relationships of plant-herbivore interactions of cultivated plants and their wild relatives, but little attention has been given to how domestication may also influence the mutualistic interaction of plant-pollinator. This study investigates the potential changes to floral characteristics and interactions of floral visitors of domesticated squash with its wild relatives in its place of origin. We expect artificial selection modifies floral morphology from wild to domesticated forms, and these changes, in turn, may influence floral visitation rates and behavior as well as the diversity floral visitors. Our study was conducted in two regions along the west coast in México where we studied three sister species of squash (Cucurbita: Cucurbitaceae), Cucurbita argyrosperma ssp. sororia (wild ancestor), C. argyrosperma spp. argyrosperma (domesticated) and C. moschata (domesticated). We identified four wild populations of C. sororia and four cultivated plots. For each squash species we quantified variation of floral traits including morphological measurements and quantity and quality of floral rewards. Additionally, we conducted video recordings of flowers and described floral visitor communities and behavior.
Results/Conclusions
Our results indicate that floral morphological characteristics of pistillate and staminate flowers of domesticated species were more distinct from that of the wild. All traits were larger in the domesticated squash than in the wild squash expect for the length of the anthers which were longer only for C. moschata. Floral traits of staminate and pistillate flowers covaried significantly differently between all 3 species. The floral integration values for staminate flowers in the domesticated species was higher than in the wild species, while in the pistillate flowers, the wild species had a higher integration value than the domesticates. Additionally, in domesticated species there was a larger amount of floral rewards but no difference in nectar sugar concentration. We recorded 9710 visits from approximately 31 visitor types. The most abundant visitors were bees from the genera Eucera subg. Peponapis and the tribes Meliponini and Augcholorini. Diversity of floral visitors was greater in flowers of wild squash, but the visitation rate was higher in the domesticated. Pollen was more frequently collected from staminate flowers of wild plants while nectar was more frequently collected from pistillate domesticated plants. These results suggest that although floral traits were not directly selected upon, indirect effects of plant domestication can result in modification to plant-pollinator relationships.