Climate change is expected to alter many natural processes. One way in which plants will respond is through changes in the timing of seasonal events, also known as phenology. Studies have found that as temperatures increase, some plants have begun flowering earlier, with the potential to disrupt plant-pollinator interactions. Mismatched timing between flowering and pollinator emergence (i.e. pollinator mismatch) could cause a reduction in fitness in both plant and pollinator. Investigating the relationship between flowering time and pollination is important to understanding how not just individual species, but plant-pollinator relationships, will respond to changes in climate. In 2013, common milkweed seed was sourced from northern, local, and southern populations in the Midwest, and planted in a common garden at the Chicago Botanic Garden to study ecotypic variation. This summer we used phenology surveys and pollinator observations to answer the following questions: 1) Do local and non-local populations differ in flowering phenology? 2) Does variation in flowering time affect pollination?
Results/Conclusions
Variation in flowering schedule adhered to expectations based on source climate. As source latitude increased, flowering time occurred earlier. However, flowering period lengthened as source latitude decreased. Flowering periods for local and southern populations were largely overlapping. Average insect visitation length was slightly longer in the local population (+24-37%), although this trend was marginally significant (p=0.07). Increased sampling may provide greater evidence supporting the relationship between population, flowering phenology, and length of visit. The highest proportion of visitors seen among all three populations were bees, with declining abundance throughout the summer. Given the later flowering period of the local and southern ecotypes, decreased bee abundance may result in reduced reproductive fitness for these populations.