Temporal variation in coffee flowering may influence the effects of bee species richness and abundance on coffee production

Abstract

Accurately estimating the contribution of pollinators to production in crop species is important but could be challenging for species that are widely cultivated. One factor that may influence the pollinator-production relationship across regions is phenology, or the timing of recurring biological events, because crop phenology can be proximately controlled by climatic variables and phenology can affect plant reproductive success. For the economically important crop, coffee (Coffea arabica), at least three aspects of flowering phenology (onset, density and frequency) are influenced by precipitation, which varies across coffee’s cultivated range. Of these aspects of flowering phenology, flower density may particularly impact production in coffee because high-density flowering can severely limit outcrossing which is a major contributor to high yields and larger, high quality beans. We studied the C. arabica coffee plant-pollinator interaction over 3 years and across two distinct types of coffee blooms: (1) low-density, synchronous flowering and (2) high-density, synchronous (mass) flowering. Bee species richness was similar for four out of five flowering periods (9.8 ± 2.7 95% CI), but nearly tripled during one high-density flowering period (26 ± 8.6 95% CI). During low-density flowering coffee fruit set rates were varied, but when coffee flowered at high-density, initial fruit set rates remained close to 60% (the rate obtained from manual self-pollination of coffee flowers in pollination experiments). We discuss how changing precipitation patterns may alter coffee flowering phenology and the coffee plant-pollinator relationship, providing insight into how climate change may influence this interaction as well as the resultant coffee production.