Abstract
The evolution of the latitudinal diversity gra-dient(LDG),characterized by a peak in diver-sity toward the tropics,has captured significant attention in evolutionary biology and ecology.However,the inverse LDG(i-LDG)mechanism,wherein species richness increases toward the poles,remains inadequately explored.Cy-cads are among one of the oldest lineages of extant seed plants and have undergone ex-tensive diversification in the tropics.Intrigu-ingly,the extant cycad abundance exhibits an i-LDG pattern,and the underlying causes for this phenomenon remain largely elusive.Here,using 1,843 nuclear genes from a nearly com-plete sampling,we conducted comprehensive phylogenomic analyses to establish a robust species-level phylogeny for Cycas,the largest genus within cycads.We then reconstructed the spatial-temporal dynamics and integra-ted global environmental data to evaluate the roles of species ages,diversification rates,contemporary environment,and conserva-tism to ancestral niches in shaping the i-LDG pattern.We found Cycas experienced de-creased diversification rates,coupled with the cooling temperature since its origin in the Eocene from continental Asia.Different regions have distinctively contributed to the forma-tion of i-LDG for Cycas,with the northern hemisphere acting as evolutionary museums and the southern hemisphere serving as cra-dles.Moreover,water-related climate variables,specifically precipitation seasonality and po-tential evapotranspiration,were identified as paramount factors constraining Cycas species richness in the rainforest biome near the equator.Notably,the adherence to ancestral monsoonal climates emerges as a critical factor in sustaining the diversity pattern.This study underscores the imperative of integrating both evolutionary and ecological approaches to comprehensively unravel the mechanisms un-derpinning global biodiversity patterns.
基金项目
National Natural Science Foundation of China(32270246)
National Natural Science Foundation of China(31900184)
Scientific Foundation of Urban Management Bureau of Shenzhen(202019)
Scientific Foundation of Urban Management Bureau of Shenzhen(202208)
Youth Innovation Promotion Association CAS,China(2023410)
Yunnan Fundamental Research Projects(202001AT070072)
Yunnan Fundamental Research Projects(2019FD057)
NETL
NSTL
万方数据