Unexpected but welcome. Artificially selected traits may increase fitness in wild boar

Abstract

Artificial selection affects phenotypes differently by natural selection. Domestic traits, which pass into the wild, are usually negatively selected. Yet, exceptionally, this axiom may fail to apply if genes, from the domestic animals, increase fertility in the wild. We studied a rare case of a wild boar population under the framework of Wright's interdemic selection model, which could explain gene flow between wild boar and pig, both considered as demes. We analysed the MC1R gene and microsatellite neutral loci in 62 pregnant wild boars as markers of hybridization, and we correlated nucleotide mutations on MC1R (which are common in domestic breeds) to litter size, as an evaluation of fitness in wild sow. Regardless of body size and phyletic effects, wild boar sows bearing nonsynonymous MC1R mutations produced larger litters. This directly suggests that artificially selected traits reaching wild populations, through interdemic gene flow, could bypass natural selection if and only if they increase the fitness in the wild.

High domestic pig contribution to the local gene pool of free-living European wild boar: a case study in Poland

“…In fact, introgression of domestic genes may reach much higher levels at very local scale (Fulgione et al 2016), especially in regions where open-air pig farming (Canu et al 2016) and/or hybridization in captivity (Gongora et al 2003;Canu et al 2014) and/or restocking with farmed WB that had been cross-bred with DS (Frantz et al 2012McDevitt et al 2013), are practiced.…”

“…This may unintentionally promote the spread of Bdomestic genes^by reducing the size of local populations to the extent that DS alleles have a greater chance of being fixed. This is most likely to occur at the local scale where there is open-air pig farming, hybridization in captivity, or restocking of farms with WB cross-bred with DS (Gongora et al 2003;Frantz et al 2012Frantz et al , 2013McDevitt et al 2013;Canu et al 2014;Fulgione et al 2016). Disruption of WB population structure could also favor migration of individuals with DS alleles.…”

“…For example, evidence is accumulating that rates of hybridization between wild species and their domestic relatives are increasing (Randi 2008;Canu et al 2014). This hybridization may occur intentionally or accidentally (Fulgione et al 2016). Domestic genes may provide a fitness advantage for individuals of some species (Anderson et al 2009;Goedbloed et al 2013a;Fulgione et al 2016).…”

“…This hybridization may occur intentionally or accidentally (Fulgione et al 2016). Domestic genes may provide a fitness advantage for individuals of some species (Anderson et al 2009;Goedbloed et al 2013a;Fulgione et al 2016). However, there is growing concern that introgression from domestic into wild animals may compromise the genetic integrity of the latter (Largiadèr 2008).…”

Mixed ancestry from wild and domestic lineages contributes to the rapid expansion of invasive feral swine

“…Furthermore, increases in wild boar ancestry among newly emergent feral swine populations could result from the intensification of environmental selective pressures if the fitness advantages of individuals with wild boar phenotypic attributes become greater as limiting factors, such as winter severity, become more restrictive with northward and inland range expansion (McClure et al, 2015; Snow et al, 2017). Support for the assertion that domestic pig–wild boar hybrids may be highly invasive can be drawn from the observed introgression of domestic pigs into native European wild boar populations and subsequent proliferation of admixed genotypes among wild populations in Europe (Fulgione et al, 2016; Goedbloed, Hooft, et al, 2013; Goedbloed, Megens, et al, 2013). Intensive artificial selection imposed during the domestication process has served to dramatically increase the fecundity of domestic pigs relative to wild boar (Miller, 2017).…”