Effects of different mating scenarios on embryo viability in brown trout

Abstract

Mating with attractive or dominant males is often predicted to offer indirect genetic benefits to females, but it is still largely unclear how important such non-random mating can be with regard to embryo viability. We sampled a natural population of adult migratory brown trout (Salmo trutta), bred them in vitro in a half-sib breeding design to separate genetic from maternal environmental effects, raised 2098 embryos singly until hatching, and exposed them experimentally to different levels of pathogen stress at a late embryonic stage. We found that the embryos' tolerance to the induced pathogen stress was linked to the major histocompatibility complex (MHC) of their parents, i.e. certain MHC genotypes appeared to provide better protection against infection than others. We also found significant additive genetic variance for stress tolerance. Melanin-based dark skin patterns revealed males with 'good genes', i.e. embryos fathered by dark coloured males had a high tolerance to infection. Mating with large and dominant males would, however, not improve embryo viability when compared to random mating. We used simulations to provide estimates of how mate choice based on MHC or melanin-based skin patterns would influence embryos' tolerance to the experimentally induced pathogen stress.

Pathogen-induced hatching and population-specific life-history response to waterborne cues in brown trout (Salmo trutta)

“…However, significant gene by environment interactions on larval survival could be found in other salmonids, e.g., in the Chinook salmon (Oncorhynchus tshawytscha) (Evans et al 2010) or in whitefish (Coregonus sp.) (von Siebenthal et al 2009), and even in other populations of brown trout (Wedekind et al 2008;Jacob et al 2010). Genetic variability in reaction norms may therefore depend on the kind of stressor, the developmental stage, and the species or population in question.…”

Selection and genetic drift in captive versus wild populations: an assessment of neutral and adaptive (MHC-linked) genetic variation in wild and hatchery brown trout (Salmo trutta) populations

“…We amplified, cloned and sequenced a 254-257 bp fragment of exon 2 of the MHC II β (Satr-DAB) locus, which exists as a single copy in salmonids, including brown trout (Hordvik et al 1993;Jacob et al 2010). The MHC II β locus is called Satr-DAB in S. trutta, but in the interest of uniformity with other cross-taxa studies, we will refer to it as MHC II β.…”

“…However, only about 13% of captive breeding and reintroduction efforts are successful, whereas reintroductions not involving captive breeding (termed relocations) have a higher success rate (31%; Fischer and Lindenmayer 2000;Williams and Hoffman 2009). The causes of reintroduction failures have been linked to ecological factors or mismanagement, but genetic factors have also been suggested (Fischer and Lindenmayer 2000;Jiménez et al 1994).…”

“…For salmonids, the genetic variability of MHC loci has been linked to kin discrimination (Olsén et al 1998), mate choice (Landry et al 2001;Forsberg et al 2007), embryo viability (Jacob et al 2010) and pathogen infections (Consuegra and Garcia de Leaniz 2008; Lamaze et al 2014), and also play an important role in the viability of invasive species or non-native strains (O'Farrell et al 2013;Monzón-Argüello et al 2014). The negative effects that stocking can have on immunogenetic traits (including MHC variability and expression) have also been documented in salmonids (Currens et al 1997;Lamaze et al 2014).…”

Managing Population Sex Ratios in Conservation Practice: How and Why?

“…There are a number of potential risks that need to be considered in such programs. These risks include, among others, a general increase in the variance in reproductive success and hence a reduction in overall N e (Ryman and Laikre 1991), potential negative effects of circumventing natural mate preferences (Grahn et al 1998, Wedekind et al 2001, Wedekind 2002b, Jacob et al 2010, and artificial selection favoring certain life-history characteristics (Heath et al 2003). However, if we can assume that offspring have an enhanced survival in captivity and that the subsequent release of captive bred individuals into the wild has a positive effect of the long-term survival of the population, artificially changing family sex ratios towards a female bias could sometimes even further increase population growth rate.…”