Lack of Variation in Nuclear Genes Among Isolated Populations of the Sand Dune Restricted Bee Colletes stepheni (Hymenoptera: Colletidae)

摘要

Sand dunes in the Mojave and Great Basin Deserts are unique habitats that often harbor distinct and endemic taxa (Ricketts et al., 1999). Epps et al. (1998) compared sand dunes to "habitat islands" in the desert, which provide habitat for many sand-obligate organisms. Because many of these dunes are distant from other dunes, and often flanked by mountain ranges or alkaline hardpan, isolated populations of dune-restricted organisms are often genetically distinct (e.g., Britten and Rust, 1996; Epps et al., 1998). We attempted to discover phylogeographic patterns among populations of Colletes stepheni Timberlake, a sand dune restricted, oligolectic solitary bee. Colletes stepheni nests solely in loose sandy substrates and provisions its nest with pollen only from a limited number of plant species (Hurd and Powell, 1958; Minckley et al., 2000; Andrus, 2003). Populations of C. stepheni in the Mojave Desert use pollen only from Larrea tridentata (creosote bush; Zygophylaceae), which is a common shrub in the hot deserts of North America, while populations in the Great Basin Desert, a cold desert, use pollen from Psorothamnus (indigo bush; Fabaceae) (Andrus, 2003).