A diversity of all-female fishes of the genus Poeciliopsis coexists with their sexual ancestor species in streams of western Mexico. All-females are hybrids that depend on the sperm of paternal species to reproduce. Rare-female advantage is one of several hypotheses that attempt to explain how the diversity of all-female biotypes is maintained within the Poeciliopsis reproductive complexes. According to this hypothesis, the uncommon all-female biotype has a mating advantage over the common ones and has been maintained by a dynamic equilibrium process. In the P. monacha reproductive complex at Arroyo de los Platanos the density of two all-female biotypes (P. 2monacha-lucida I and II) varies across pools. The objective of this study was to analyse fecundity and mating success of females from this arroyo to test the hypothesis. Female mating success was inversely correlated to their density, supporting this hypothesis.
All-females; mating success; Poeciliopsis monacha; rare-female advantage