ABSTRACT
Three species of the asteroid genus Patiriella occur sympatrically in New South Wales and the possibility for hybridization between them was examined through a series of cross-fertilization experiments. P. calcar and P. gunnii are morphologically distinct as adults, but indistinguishable as larvae. P. exigua is morphologically distinct in both its adult and larval morphologies. The gametes of P. calcar and P. gunnii are reciprocally compatible and crosses between these species produced viable hybrid juveniles. Successful rearing of P. calcar and P. gunnii hybrids eliminates the possibilities that gametic incompatibility or hybrid inviability serve as mechanisms of reproductive isolation between these species. It is suggested that ecological or habitat segregation and temporal separation in breeding isolates these species in the field. The results demonstrate that if gamete surface recognition molecules are involved in fertilization of P. calcar and P. gunnii, then they are not strongly species-specific.
