title: MHC-mediated spatial distribution in brown trout (Salmo trutta) fry.
abstract: 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.)21.03 m; one allele shared, 222.2 ± 14.49 m; two alleles shared, 124.9 ± 23.88 m; 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 ± 3.58 m; 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.
authors.affiliation: Microbial Phylogeography, Department of Microbiology, Environmental Research Institute, University College Cork, Cork, Ireland.
authors.forename: B
authors.initials: B
authors.lastname: O'Farrell
authors.forename: J A H
authors.initials: JA
authors.lastname: Benzie
authors.forename: P
authors.initials: P
authors.lastname: McGinnity
authors.forename: J
authors.initials: J
authors.lastname: Carlsson
authors.forename: E de
authors.initials: Ed
authors.lastname: Eyto
authors.forename: E
authors.initials: E
authors.lastname: Dillane
authors.forename: C
authors.initials: C
authors.lastname: Graham
authors.forename: J
authors.initials: J
authors.lastname: Coughlan
authors.forename: T
authors.initials: T
authors.lastname: Cross
mesh_terms: D000818:Animals; D003710:Demography; D004591:Electrophoresis, Polyacrylamide Gel; D005787:Gene Frequency; D005805:Genes, MHC Class I / Q000235:genetics*; D005828:Genetics, Population; D018895:Microsatellite Repeats / Q000235:genetics; D011157:Population Dynamics; D013037:Spatial Behavior / Q000502:physiology*; D018709:Statistics, Nonparametric; D014337:Trout / Q000235:genetics* / Q000502:physiology