Evolutionary genetics and ecology of sperm-dependent parthenogenesis

Sperm-dependent (or pseudogamous) forms of parthenogenetic reproduction occ ur in a wide variety of animals. Inheritance is typically clonal and matroc linous (of female descent), but sperm are needed to initiate normal develop ment. As opposed to true parthenogenesis (i.e., sperm-independent reproduct ion), pseudogamous parthenogenetic lineages must coexist with a 'sperm dono r' - e.g., males from a conspecific sexual lineage, conspecific hermaphrodi tes, or males from a closely related sexual species. Such sperm donors do n ot contribute genetically to the next generation. The parasitic nature of s perm-dependent parthenogenesis raises numerous ecological and evolutionary questions. How do they arise? What factors help stabilize coexistence betwe en the pseudogamous parthenogens and their sperm donors (i.e.,'sexual hosts ')? Why do males waste sperm on the asexual females? Why does true partheno genesis not evolve in pseudogamous lineages and free them from their depend ency on sperm donors? Does pseudogamous parthenogenesis provide compensator y benefits that outweigh the constraints of sperm-dependence? Herein, we co nsider some genetic, ecological, and geographical consequences of sperm-dep endent parthenogenesis in animals.