Relative contribution of phylogeny on fruit type divergence decreases along latitudinal gradients

Many plant functional traits exhibit variations along spatial gradients, and exploring such geographical variations is of great reference value for understanding the evolutionary process of plant distribution and response mechanisms to biotic and abiotic factors. Fruit type (fleshy vs. dry fruits), a key reproductive characteristic of plants, plays an important role in seed dispersal processes. Environmental factors, plant growth form, and phylogeny are the most frequently discussed factors that explain the geographical patterns of fruit type. Disentangling the relative contribution of each factor is challenging, and previous studies have not been consistent. In the present study, we compiled a dataset of 2668 plant species from 22 ecological research stations of the Chinese Ecosystem Research Network, including diverse ecosystems across 26° latitude. The pattern of fruit type divergence (i.e., flesh vs. dry fruits) was primarily explained by phylogeny (partial R²_lik = 65.60%), whereas growth form and environmental factors revealed little variation. Interestingly, the relative contribution of phylogeny in explaining fruit-type divergence was larger in the flora at low latitudes than that at high latitudes. Temperature variables, particularly low-temperature variables, were correlated with partial R²_lik, with the results revealing that the higher the temperature, the stronger the explanatory degree of phylogeny. Our findings provide a detailed explanation for the ecological and evolutionary patterns underlying the divergence of fruit types, shedding light on understanding the geographic distribution of fruit types.