Weather-related patterns of fruit abscission mask patterns of frugivory

Abstract

Previous studies on frugivory in temperate bird-dispersed plants have concluded that fleshy fruits are removed more rapidly in cold than in warm winters. However, these studies do not distinguish between fruit abscission and frugivory. The implicit assumption that fruit loss reflects frugivory may not be valid; fruit abscission may be important and respond differently to weather. During two winters, we measured fruit loss from an invasive shrub ( Lonicera maackii (Rupr.) Herder) using fruit traps. We examined the effects of temperature and precipitation on fruit retention on shrubs and fruit abscission. In the first year of our study, there was no effect of temperature or precipitation on fruit retention. In the second year, both warmer temperatures and lower precipitation resulted in more fruit retention. In both years, fruit abscission was greater during periods of cold temperatures and high precipitation. These findings suggest that weather-dependent “frugivory” reported for other bird-dispersed plants may actually reflect patterns of abscission.