Premium
SEX AND DEATH: CHD1Z ASSOCIATED WITH HIGH MORTALITY IN MOORHENS
Author(s) -
Lee Patricia L. M.,
Brain Paul F.,
Forman Dan W.,
Bradbury Richard B.,
Griffiths Richard
Publication year - 2002
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.0014-3820.2002.tb00180.x
Subject(s) - biology , heterogametic sex , heterozygote advantage , genetics , chromosome , gene , zoology , genotype
.— Sex ratios in clutches of moorhens (Gallinula chloropus) in Britain were measured on 83 chicks using the sex‐linked CHD1 gene (Chromo‐helicase/ATPase‐DNA binding protein 1). Among birds, the female is the hetero‐gametic sex (Z and W chromosomes), and the male is homogametic (two copies of the Z chromosome). We report variation among the PCR‐amplified fragments of the CHD1Z , and the death of nearly all heterozygous male chicks (92%). In contrast, survivorship among females and homozygote males was 54–60%. Mortality in male heterozygotes was significantly higher than that of male homozygotes (P < 0.001). Chick and egg biometrics were not significantly different between these males. The CHD1Z was unlikely to be directly responsible but may have been hitchhiked by the causal gene(s). The observations appear to follow a classic underdominance (heterozygote inferiority) pattern, but raise the paradoxical question of why one form of the Z chromosome has not been fixed, as is expected from evolutionary theory. We discuss possible explanations and include a survey of British populations based on skin specimens.