Maternal-zygotic gene conflict over sex determination: effects of inbreeding.
There is growing evidence that sex determination in a wide range of organisms is determined by interactions between maternal-effect genes and zygotically expressing genes. Maternal-effect genes typically produce products (e.g., mRNA or proteins) that are placed into the egg during oogenesis and therefore depend upon maternal genotype. Here it is shown that maternal-effect and zygotic genes are subject to conflicting selective pressures over sex determination in species with partial inbreeding or subdivided populations. The optimal sex ratios for maternal-effect genes and zygotically expressing genes are derived for two models: partial inbreeding (sibmating) and subdivided populations with local mating in temporary demes (local mate competition). In both cases, maternal-effect genes are selected to bias sex determination more toward females than are zygotically expressed genes. By investigating the invasion criteria for zygotic genes in a population producing the maternal optimum (and vice versa), it is shown that genetic conflict occurs between these genes. Even relatively low levels of inbreeding or subdivision can result in maternal-zygotic gene conflict over sex determination. The generality of maternal-zygotic gene conflict to sex determination evolution is discussed; such conflict should be considered in genetic studies of sex-determining mechanisms.
Werren
J H
JH
Biology Department, University of Rochester, Rochester, New York 14627, USA.
Hatcher
M J
MJ
D000483:Alleles; D000818:Animals; D004331:Drosophila melanogaster / Q000235:genetics; D005260:Female; D015870:Gene Expression; D005828:Genetics, Population; D018392:Genomic Imprinting / Q000235:genetics*; D007178:Inbreeding; D008297:Male; D008957:Models, Genetic; D011237:Predictive Value of Tests; D019849:Sex Determination Processes; D012737:Sex Factors; D012744:Sex Ratio; D015053:Zygote