Apomictic parthenogenesis and genotypic diversity in Cypridopsis vidua (Ostracoda: Cyprididae)

Abstract

Based on sex ratios, the crustacean subclass Ostracoda appears to have made frequent transitions from sexual to asexual reproduction. However few genetic data are available verifying their mode of reproduction. The current report provides such evidence for apomictic pathenogenesis in the cosmopolitan cypridid ostracode Cypridopsis vidua. Sex ratio analysis indicated that natural populations are exclusively female. Allozyme phenotypes in 18 of 20 natural populations showed strong departures from Hardy–Weinberg expectations at single loci, and three of four populations had non-random associations of phenotypes at MPI and PGM. Allozyme phenotypes at these loci suggested that polyploids were present in half these populations and were more common in the low arctic site than in the temperate sites. Most natural populations of C. vidua displayed high levels of genotypic diversity, with a total of 77 unique clones detected and up to 24 clones per pond. Breeding studies on 64 isofemale lines established that parthenogenesis is apomictic and that mutation rates are less than 10−3.