干旱区生态环境知识资源中心

Ephedra (Gymnosperma, Gnetales, Ephedraceae) includes 13 species in the arid American Southwest that have three morphological types of propagules. We performed field and laboratory experiments on five species (E. torreyana, E. antisyphilitica, E. viridis, E. funerea, and E. nevadensis) that represent the three morphological types (dispersal syndromes) and two intermediate forms. Ephedra torreyana has large, winged cone bracts and small seeds that are largely ignored by animals and that are dispersed by the wind. Ephedra antisyphilitica has succulent cone bracts that are eaten by birds that disperse the seeds in their feces. Ephedra viridis has large, conspicuous seeds that are attractive to some rodents, which gather the seeds and scatter hoard them in soil. Ephedra funerea and E. nevadensis are also dispersed by seed-caching rodents but share traits with wind-dispersed and bird-dispersed species, respectively. Most North American species of Ephedra are dispersed by seed-caching rodents, and this mode of dispersal is not represented in Ephedra from other continents (i.e., arid portions of South America, North Africa, Europe, Asia), perhaps because of a more diverse assemblage of seed-caching rodents in North America than in these other regions.