The Mid-Domain Effect Shapes a Unimodal Latitudinal Pattern in Fruiting Phenology.

The mid-domain effect (MDE) has been used to explain spatial diversity patterns and flowering phenology, but its role in fruiting phenology has received limited attention to date. This study investigates whether the MDE shapes fruiting phenology and whether its influence varies with latitude. We integrated fruiting phenology data for 12,179 plant species across 28 Chinese provinces and used a null model to simulate expected fruiting richness patterns. Our results suggest that the MDE plays a significant role in explaining fruiting phenology patterns in most provinces. Crucially, the variance explained by the MDE exhibited a significant unimodal relationship with latitude across all groups, peaking at mid-latitudes (39.6° N for all species, 37.1° N for herbaceous plants, and 36.8° N for woody plants). Unlike flowering phenology-which tends to show a simple linear increase in MDE strength with latitude-fruiting exhibited a distinct peak, highlighting different ecological pressures acting on these two reproductive stages. The MDE was the primary contributor explaining fruiting richness, providing a markedly stronger fit to the data than key climate variables like temperature and precipitation, although woody plants showed a stronger secondary response to precipitation. These findings demonstrate that geometric constraints are a key driver of fruiting phenology, deepening our understanding of temporal niches and the ecological processes shaping plant reproductive phenology.