Meeting Abstract
Mangrove rivulus fish (Kryptolebias marmoratus) exist predominantly as self-fertilizing hermaphrodites but males occur in varying abundances across their expansive geographical range. As follows, levels of outcrossing between hermaphrodites and males and heterozygosity also differ dramatically among populations, which raises the question of why males would be favored in some areas more than others. We hypothesized that heterozygous progeny derived from outcrossing would have higher fitness than homozygous offspring derived from selfing, especially under stressful environmental conditions. We predicted that more heterozygous fish would have lower mortality rates, higher growth rates, and greater reproductive success than homozygous fish, and that this fitness asymmetry would be amplified under suboptimal environmental conditions. To test this hypothesis, fish with varying levels of heterozygosity were exposed to control conditions and to high/low salinity and variable water availability, environmental stressors that characterize their native habitat. We report preliminary data on variation among genotypes in a number of fitness-related life history characteristics, including growth rate, fecundity, and offspring survival.
