DOI: 10.5061/dryad.57t89
title: Data from: Evidence of the phenotypic expression of a lethal recessive allele under inbreeding in a wild population of conservation concern

description: Deleterious recessive alleles that are masked in outbred populations are
 predicted to be expressed in small, inbred populations, reducing both
 individual fitness and population viability. However, there are few
 definitive examples of phenotypic expression of lethal recessive alleles
 under inbreeding conditions in wild populations. Studies that demonstrate
 the action of such alleles, and infer their distribution and dynamics, are
 required to understand their potential impact on population viability and
 inform management responses. The Scottish population of red-billed choughs
 (Pyrrhocorax pyrrhocorax), which currently totals &lt;60 breeding
 pairs and is of major conservation concern, has recently been affected by
 lethal blindness in nestlings. We used family data to show that the
 pattern of occurrence of blindness within and across affected families
 that produced blind nestlings was exactly 0·25, matching that expected
 given a single-locus autosomal lethal recessive allele. Furthermore, the
 observed distribution of blind nestlings within affected families did not
 differ from that expected given Mendelian inheritance of such an allele.
 Relatedness estimates showed that individuals from affected families were
 not more closely related to each other than they were to individuals from
 unaffected families that did not produce blind nestlings. Blind
 individuals tended to be less heterozygous than non-blind individuals, as
 expected if blindness was caused by the expression of a recessive allele
 under inbreeding. However, there was no difference in the variance in
 heterozygosity estimates, suggesting that some blind individuals were
 relatively outbred. These results suggest carriers of the blindness allele
 may be widely distributed across contemporary families rather than
 restricted to a single family lineage, implying that the allele has
 persisted across multiple generations. Blindness occurred at low frequency
 (affecting 1·6% of observed nestlings since 1981). However, affected
 families had larger initial brood sizes than unaffected families. Such
 high fecundity of carriers of a lethal recessive allele might reflect
 overdominance, potentially reducing purging and increasing allele
 persistence probability. We thereby demonstrate the phenotypic expression
 of a lethal recessive allele in a wild population of conservation concern,
 and provide a general framework for inferring allele distribution and
 persistence and informing management responses.
description: Genotype data for
 pair-wise relatedness estimatesThis file contains the
 microsatellite genotype data required for the analyses of pair-wise
 relatedness between affected and functionally unaffected nuclear families.
 Pair-wise relatedness estimates were calculated in the program COANCESTRY
 v.1.0.1.5 (Wang 2011).relatedness
 data.txtGenotype data for
 multi-locus heterozygosity estimatesThis file contains the
 microsatellite genotype data required for the analyses of standardized
 multi-locus heterozygosity (sMLH) estimates between blind and non-blind
 individuals. sMLH was estimated using the program Genhet (Coulon
 2010).heterozygosity
 data.txtBrood size
 dataThis file contains data
 required for the analyses of brood size in affected (where blind nestlings
 have been observed) and unaffected (where no blind nestlings have been
 observed) nuclear families, using both functionally unaffected families
 (defined in the main manuscript) or all unaffected
 families.Dyadic maximum
 likelihood relatedness dataThis file contains the
 dyadic maximum likelihood (DyadML) estimates of pair-wise relatedness
 between individuals from affected and functionally unaffected families.
 DyadML estimates were calculated in the program COANCESTRY v.1.0.1.5 (Wang
 2011).dyadML
 data.txtStandardized multi-locus
 heterozygosity dataThis file contains the
 standardized multi-locus heterozygosity (sMLH) estimates of blind and
 non-blind individuals. sMLH was estimated using the program Genhet (Coulon
 2010).sMLH
 data.txt