Meeting Abstract
Seasonal environments exert strong selection on reproductive timing. Certain seasons may preclude investment in gametes, limit fitness returns of such investment, or provide favorable conditions for reproduction. Seasonality and reproductive timing might interact to drive selection on processes like developmental plasticity and phenotypic flexibility, which mediate fitness in variable environments. The mangrove rivulus fish (Kryptolebias marmoratus) is a self-fertilizing hermaphrodite that exhibits remarkable phenotypic plasticity and flexibility and exists from tropical to temperate climates. We conducted field and laboratory studies to investigate variation in reproductive timing among populations that experience varying degrees of seasonality. We hypothesized that selection would drive local adaptation in reproductive timing, with restricted reproduction in populations from highly seasonal environments and year-round reproduction in populations from less variable environments. Rivulus are being collected from nine populations in Florida and at four seasonal intervals for two consecutive years. Reproductive status has been determined by the presence/abundance of vitellogenic eggs in the gonad. Also, 398 distinct rivulus genotypes derived from 53 populations spread across their geographical range have been housed under common garden conditions. Fecundity was assessed for each genotype each week for over one year. We found different patterns of reproductive seasonality across major geographical regions. Retention of seasonality in the laboratory supports the hypothesis that selection has driven local adaptation in reproductive timing. This research establishes a foundation for generating predictions about the relative fitness advantages of developmental plasticity and phenotypic flexibility in rivulus populations.
