Outbreeding depression in hybrids between spatially separated pink salmon, Oncorhynchus gorbuscha, populations: marine survival, homing ability, and variability in family size

Abstract

Hybridization between distinct populations of salmon can cause fitness loss (outbreeding depression), and may result in reduced survival. The erosion of fitness-related traits such as homing ability and change in family size distribution may underlie reduced survival. Outbreeding depression was investigated in two independent experiments that made hybrids between geographically separated and genetically divergent pink salmon populations. Control crosses were made from male and female Auke Creek (Southeast Alaska) pink salmon and hybrid crosses were between Auke Creek females and Pillar Creek (Kodiak Island, about 1000km away) males. Parentage assignment from microsatellite analysis improved estimates of survival and straying, and was used to examine variation in family size. The return rates of even-broodyear Fi control and hybrid fish were similar, but the odd-broodyear Fj control returns exceeded hybrid returns. The F2 control returns exceeded hybrid returns in both the even-and oddbroodyears. Hybridization did not impair homing ability; weekly surveys in nearby (~ 1km) Waydelich Creek revealed similar straying rates from Auke Creek by both hybrid and control fish in all years. Family data were available only for even-broodyear returns; hybridization did not increase the index of variability (ratio of variance to mean) in family size in these years. Outbreeding depression in hybrids of geographically separated populations demonstrates the potential for introgression of normative fish to erode natural production.

Fast Transcriptional Responses to Domestication in the Brook CharrSalvelinus fontinalis

“…The fact that artificially selected brook charr are intensively used for stocking wild populations raises the issue of potentially negative consequences associated with reduction in genomic integrity and adaptative capacity of wild populations (Leary et al 1983;Gharrett et al 1999;Gilk et al 2004;Roberge et al 2006). For example, it has been shown in Atlantic salmon that genetic introgressive hybridization between farmed and wild fish substantially alters the genetic control of gene transcription within natural populations.…”

Fluctuating Asymmetry of Human Populations: A Review

“…If it has positive fitness consequences (e.g., if both populations were highly inbred before hybridization), it is referred to as hybrid vigor or heterosis. In most cases, outbreeding depression occurs when populations are separated at the species or subspecies levels, having been isolated for thousands of generations, though several studies have observed outbreeding depression within a single species of copepods in neighboring tidal pools [204][205][206] and among breeding stocks of salmon [207][208][209]. Heterosis is expected when small, inbred populations meet and hybridize.…”

Site fidelity of farmed gilthead seabream Sparus aurata escapees in a coastal environment of the Adriatic Sea

“…The genetic introgression of farmed escapees into native populations (Glover et al 2012) can lead to reduced overall fitness of wild populations (Fleming et al 2000, Gilk et al 2004, Tymchuk et al 2007) and competition for food and habitat (Jonsson & Jonsson 2006, Šegvić-Bubić et al 2011a. Post-escape behaviour of coldwater-aquaculture species, such as Atlantic salmon Salmo salar or Atlantic cod, has been extensively studied (Olsen & Skilbrei 2010, Skilbrei 2010, Chittenden et al 2011, Zimmermann et al 2013).…”