Leaf and Fruit Trait Variation in Relation to Altitude and Soil Nitrogen Among provenances of the Critically Endangered Vatica guangxiensis

Variation in leaf and fruit traits represents a key strategy for rare and endangered plants to respond to environmental changes and ensure survival and reproduction. Vatica guangxiensis , a first-class nationally protected wild plant in China, has an extremely small population size, and the relationship between its trait differentiation and environmental factors remains unclear. To investigate the variation in leaf and fruit traits among different provenances of V. guangxiensis and to identify the important environmental drivers, we systematically measured leaf and fruit traits from four wild provenances in Guangxi (Napo, NP; Ningming, NM) and Yunnan (Zijiao, ZJ; Mengdonghe, MDH). Principal component analysis (PCA) and redundancy analysis (RDA) were used to reveal patterns of trait variation and their environmental drivers. The results showed that: (1) Higher‑altitude populations exhibited more conservative leaf traits. The MDH provenance (the highest altitude) had the thickest leaves, the highest leaf dry mass per area (LMA), and the most developed palisade tissue in anatomical structure. In contrast, the NM provenance (the lowest altitude) exhibited the highest specific leaf area (SLA) and chlorophyll content (SPAD), but the thinnest leaves. (2) Fruit investment increases under more stressful environments. The MDH provenance (high altitude, seasonal flooding) significantly outperformed the others in whole fruit mass, wing development, and structural compactness. (3) Leaf and fruit traits did not fully covary along the same environmental gradient. PCA indicated clear differentiation in leaf and fruit traits among provenances. RDA further identified important environmental drivers: altitude (AL) explained 48.70% of the variation in leaf traits, while soil total nitrogen (N) and altitude (AL) together explained 49.64% of the variation in fruit traits. This study is the first to reveal the trait differentiation associated with environmental gradients among different provenances of V. guangxiensis from a functional trait perspective. Our results provide a scientific basis for formulating differentiated in situ conservation and ex situ preservation strategies. However, given the limited sample size, future common garden or genomic studies are still needed to better understand the species’ adaptive strategies and evolutionary trends.