Genetic and growth differences in the outcrossings between two clonal strains of the self-fertilizing mangrove killifish

Abstract

The populations of the only known self-fertilizing vertebrate Kryptolebias marmoratus (Poey, 1880) (formerly known as Rivulus marmoratus Poey, 1880; Cyprinodontiformes: Aplocheilidae) usually consist of different homozygous lineages; however, heterozygous individuals are found occasionally and ratios of homozygosity and heterozygosity in populations are dependent on the proportion of males. However, it is still unclear what impact male-mediated genetic diversity has on the phenotype of K. marmoratus. To clarify this, we attempted outcrossing between male and hermaphrodite of two different clonal strains with different life-history traits using artificial insemination, and examined the genotypes and growth of the hybrid F 2 generation. We detected genetic differences between the two clonal strains using amplified fragment length polymorphism (AFLP) analysis with 3 primer combinations, and then obtained 11 AFLP markers. From a total of 31 artificial inseminations with two clonal strains, 1 of 13 hatched fish clearly indicated heterozygosity. The hybrid F 2 generations were also heterozygous. Moreover, the growths of the hybrid F 2 generation were intermediate of the parental strains from days 0 to 30. Therefore, outcrossing changes genetic architecture and the new genotypes potentially result in new phenotypes of the subsequent generations of K. marmoratus. It may also play a role in adaptation to new environments and the facilitation of local adaptation.