• A genetic marker for the maternal identification of Atlantic salmon × brown trout hybrids

      Karlsson, S.; Hagen, M.; Eriksen, L.; Hindar, K.; Jensen, A.; De Leaniz, C.; Cotter, D.; Guobergsson, G.; Kahilainen, K.; Guojonsson, S.; et al. (Springer Netherlands, 2013)
      Interspecific hybridization between Atlantic salmon and brown trout is well documented, but why it should vary so much among populations is not clear. Determining the maternal origin of hybrids can provide insights into the mechanisms underlying interspecific hybridization, but this information is lacking in many studies. Here we present a species-specific mitochondrial DNA marker for the identification of the maternal origin of hybrids. This marker involves only one PCR step followed by fragment analysis, can be integrated within PCR multiplexing for existing nuclear markers for hybrid identification, and is therefore faster and more cost-effective than previous methods.
    • MHC-mediated spatial distribution in brown trout (Salmo trutta) fry

      O'Farrell, Brian; Benzie, John A. H.; McGinnity, Philip; Carlsson, Jens; De Eyto, Elvira; Dillane, Eileen; Graham, Conor; Coughlan, James; Cross, Tom (Nature Publishing Group, 2011-09)
      Major histocompatibility complex (MHC) class I-linked microsatellite data and parental assignment data for a group of wild brown trout (Salmo trutta L.) provide evidence of closer spatial aggregation among fry sharing greater numbers of MHC class I alleles under natural conditions. This result confirms predictions from laboratory experiments demonstrating a hierarchical preference for association of fry sharing MHC alleles. Full-siblings emerge from the same nest (redd), and a passive kin association pattern arising from limited dispersal from the nest (redd effect) would predict that all such pairs would have a similar distribution. However, this study demonstrates a strong, significant trend for reduced distance between pairs of full-sibling fry sharing more MHC class I alleles reflecting their closer aggregation (no alleles shared, 311.5±(s.e.)21.03m; one allele shared, 222.2±14.49m; two alleles shared, 124.9±23.88m; P<0.0001). A significant trend for closer aggregation among fry sharing more MHC class I alleles was also observed in fry pairs, which were known to have different mothers and were otherwise unrelated (ML-r=0) (no alleles: 457.6±3.58m; one allele (422.4±3.86 m); two alleles (381.7±10.72 m); P<0.0001). These pairs are expected to have emerged from different redds and a passive association would then be unlikely. These data suggest that sharing MHC class I alleles has a role in maintaining kin association among full-siblings after emergence. This study demonstrates a pattern consistent with MHC-mediated kin association in the wild for the first time.