Seed traits predict elevational range size in Impatiens species across a biodiversity hotspot in southwest China

Seed traits play a critical role in shaping plant elevational range size through their influence on dispersal and establishment, yet their contribution remains poorly quantified. This study investigated the extent to which seed traits predict elevational range size in 27 Impatiens species (Balsaminaceae) from the Gaoligong Mountains in southwest China, including 10 endemic species. Nine seed traits were measured for each species, including seed mass (SM), seed number (SN), seed area (SA), seed circularity (SC), seed fat content (SFC), germination percentage (GP), duration of cold stratification required for dormancy break (DCSRD), mean germination time (MGT), and optimum germination temperature (OGT). Species elevational range sizes were modeled using 729 specimens. Linear regression and structural equation modeling (SEM) were performed to estimate the effects of seed traits on species elevational range size. Results showed that SM, SN, SA, SFC, and MGT were significantly associated with elevational range size. Constraints imposed by seed traits were stronger in endemic species than in non-endemic species. Among all traits, MGT, SM, SA, and SFC were most strongly linked to dispersal and establishment capacity, explaining substantial variation in elevational range size. These findings demonstrate that seed traits associated with dispersal and establishment ability are key predictors of elevational range size variation and provide a valuable framework for anticipating plant range shifts under climate change in montane ecosystems.