Alternative Mating Strategies in Atlantic Salmon and Brown Trout

Abstract

By screening variable number of tandem repeat (VNTR) loci, multiple paternity within clutches has been found in wild populations of southern European Atlantic salmon (Salmo salar) and brown trout (Salmo trutta). For Atlantic salmon, we determined the relative contribution of alternative male phenotypes to the next generation. Individual males that are morphologically juvenile yet sexually mature fertilized a large proportion of eggs, and they thereby contributed to an increase of genetic variability in wild populations via (1) balancing the sex ratio, (2) increasing outbreeding, and (3) enlarging the effective population size, in part a consequence of (1) and (2). In addition, these precocious males ensured that interspecific spawns involving Atlantic salmon females and brown trout males (a fairly common occurrence in southern Europe where the two species are sympatric) resulted mostly in Atlantic salmon progeny. For brown trout, preliminary genetic results indicated that multiple paternity, when present, was not due to alternative mating strategies by males, but rather to successive fertilizations by adult suitors.

Interspecific barriers between salmonids when hybridisation is due to sneak mating

“…In rivers flowing into the Bay of Biscay from northern Spain and southern France, where most Atlantic salmon parr mature in freshwater, hybrids issued from sneaking Atlantic salmon are likely to occur. However, all juvenile and adult hybrids found in the wild were offspring of Atlantic salmon females in this area (Beall et al, 1997;Garcia-Vazquez et al, 2001), contrarily to what would be expected if sneaker salmon contributed to interspecific hybridisation. We investigated possible interspecific barriers in a controlled stream, where mature individuals of both species in different situations were released.…”

“…Heredity (2002) 89, 288-292. doi:10.1038/sj.hdy.6800134 very important; they increase population size (Myers, 1984;L'Abée-Lund 1989), which maintains genetic variability (Garcia-Vazquez et al, 2001).…”

“…The maternal species has been determined in a few cases. In hybrids from European rivers the mother was Atlantic salmon in some cases (Youngson et al, 1992(Youngson et al, , 1993Garcia-Vazquez et al, 2001) and brown trout in others (Hartley, 1996;Jansson and Ost, 1997). American wild hybrids were reported to be the product of a cross between female brown trout and male Atlantic salmon (McGowan and Davidson, 1992a;Gephard et al, 2000).…”

The reproductive traits of brown trout (Salmo trutta fario L.) from the Yadong River, Tibet

“…The reproductive traits of brown trout have been described in geographically different populations previously (Hegge et al 1991;Crisp 1994;Sorensen et al 1995;Garcia-Vazquez et al 2001;Nicola and Almodovar 2002;Pender and Kwak 2002;Alp et al 2003;Estay et al 2004;Olsen and Vollestad 2005;Rubin et al 2005;Arslan and Aras 2007).…”

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“…As a result, sperm from different males may compete to 54 fertilize a single clutch of eggs. This is the case in many species of insects, gastropods, fish, amphibian, 55 birds and reptiles (FitzSimmons, 1998;Garcia-Vazquez, 2001;Jones & Clark, 2003; Garcıá-González 56 & Simmons, 2005;Chandler & Zamudio, 2008;Beese et al, 2008;Noble, Keogh & Whiting, 2013; 57 LaBrecque et al, 2014); or in progeny from the same brood in mammals (Clapham & Palsbøll, 1997; 58 Shurtliff, Pearse & Rogers, 2005). Thus, sperm competition may be an important factor in the 59 evolution of reproduction of many organisms, although the precise mechanism that determines sperm 60 success is not fully understood (Jones & Clark, 2003).…”