Climate Alters the Effects of Altitude and Phylogenetic Diversity on Plant Structure in Tropical Forests

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Understanding how climate, altitude and evolutionary diversity affect regeneration is crucial for predicting species persistence in changing environments. Yet, in tropical forests, most research has focused on timber trees. This limits our understanding of how small-statured yet socio-ecologically important species respond to environmental gradients and evolutionary diversity. We investigated the regeneration and structural patterns of Pavetta crassipes K. Schum, a widely used shrub, across the Sudanian and Sudano-Guinean zones of West Africa. We used generalized mixed-effects models to assess the effects of climate, altitude, and phylogenetic diversity on seedling occurrence, density, and adult structure. Although altitude exerted contrasting effects depending on climatic zone, seedling probability increased with altitude in the Sudano-Guinean zone but decreased with altitude in the Sudanian zone. Across both climatic zones, higher evolutionary diversity enhanced the occurrence and density of seedlings. Adult structure also varied with environment. Phylogenetic diversity further promoted crown development, suggesting long-term structural advantages in diverse communities. These findings reveal that regeneration in P. crassipes is not solely governed by climate or altitude but is strongly reinforced by evolutionary breadth. Conservation strategies that maintain phylogenetic diversity will therefore be central to sustaining regeneration dynamics and ensuring the persistence of P. crassipes in fragmented landscapes.