Outbreeding depression as a selective force on mixed mating in the mangrove rivulus fish,Kryptolebias marmoratus

Abstract

Mixed mating, a reproduction strategy utilized by many plants and invertebrates, optimizes the cost to benefit ratio of a labile mating system. One type of mixed mating includes outcrossing with conspecifics and self-fertilizing ones own eggs. The mangrove rivulus fish (Kryptolebias marmoratus) is one of two vertebrates known to employ both self-fertilization (selfing) and outcrossing. Variation in rates of outcrossing and selfing within and among populations produces individuals with diverse levels of heterozygosity. I designed an experiment to explore the consequences of variable heterozygosity across four ecologically relevant conditions of salinity and water availability (10ppt, 25ppt, and 40ppt salinity, and twice daily tide changes). I report a significant increase in mortality in the high salinity (40ppt) treatment. I also report significant effects on fecundity measures with increasing heterozygosity. The odds of laying eggs decreased with increasing heterozygosity across all treatments, and the number of eggs laid decreased with increasing heterozygosity in the 10ppt and 25ppt treatments. Increasing heterozygosity also was associated with a reduction liver mass and body condition in all treatments. My results highlight the fitness challenges that accompany living in mangrove forests ecosystem and provide the first evidence for outbreeding depression on reproductive and condition-related traits.

Microbiome and epigenetic variation in wild fish with low genetic diversity

“…This relationship would, however, fit the 'genomic coadaptation theory', according to which developmental stability can decline if coadapted gene complexes are disrupted, for example, by gene flow or introgression 79 . K. hermaphroditus is naturally highly inbred and displays no evidence of inbreeding depression 80 , thus its self-fertilising reproduction could result in a purge of deleterious alleles and in more balanced coadapted gene complexes, which would increase developmental stability and therefore decrease asymmetry 81 . Despite their different mating systems, both species are able to hybridise when occurring in sympatry, and we previously found evidence of backcrosses of the hybrids with K. ocellatus 51 .…”