title: Heritable variation in maternally derived yolk androgens, thyroid hormones and immune factors.
abstract: Maternal reproductive investment can critically influence offspring phenotype, and thus these maternal effects are expected to be under strong natural selection. Knowledge on the extent of heritable variation in the physiological mechanisms underlying maternal effects is however limited. In birds, resource allocation to eggs is a key mechanism for mothers to affect their offspring and different components of the egg may or may not be independently adjusted. We studied the heritability of egg components and their genetic and phenotypic covariation in great tits (Parus major), using captive-bred full siblings of wild origin. Egg mass, testosterone (T) and androstenedione (A4) hormone concentrations showed moderate heritability, in agreement with earlier findings. Interestingly, yolk triiodothyronine hormone (T3), but not its precursor, thyroxine hormone (T4), concentration was heritable. An immune factor, albumen lysozyme, showed moderate heritability, but yolk immunoglobulins (IgY) did not. The genetic correlation estimates were moderate but statistically nonsignificant; a trend for a positive genetic correlation was found between A4 and egg mass, T and lysozyme and IgY and lysozyme, respectively. Interestingly, phenotypic correlations were found only between A4 and T, and T4 and T3, respectively. Given that these egg components are associated with fitness-related traits in the offspring (and mother), and that we show that some components are heritable, it opens the possibility that natural selection may shape the rate and direction of phenotypic change via egg composition.
authors.affiliation: Section of Ecology, Department of Biology, University of Turku, Turku, Finland.|Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Ruuskanen
authors.affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
authors.forename: P
authors.initials: P
authors.lastname: Gienapp
authors.affiliation: Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands.
authors.forename: T G G
authors.initials: TG
authors.lastname: Groothuis
authors.affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
authors.forename: S V
authors.initials: SV
authors.lastname: Schaper
authors.affiliation: Laboratory of Comparative Endocrinology, Biology Department, KU Leuven, Leuven, Belgium.
authors.forename: V M
authors.initials: VM
authors.lastname: Darras
authors.affiliation: Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands.
authors.forename: C
authors.initials: C
authors.lastname: Pereira
authors.affiliation: Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands.
authors.forename: B
authors.initials: B
authors.lastname: de Vries
authors.affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.|Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands.
authors.forename: M E
authors.initials: ME
authors.lastname: Visser
mesh_terms: D000728:Androgens / Q000235:genetics*; D000818:Animals; D004530:Egg Yolk / Q000737:chemistry*; D005260:Female; D007136:Immunoglobulins / Q000235:genetics; D007155:Immunologic Factors / Q000235:genetics*; D040582:Inheritance Patterns; D008957:Models, Genetic; D009113:Muramidase / Q000235:genetics; D010641:Phenotype; D012641:Selection, Genetic; D020308:Songbirds / Q000235:genetics*; D013963:Thyroid Hormones / Q000235:genetics*
chemical_list: D000728:Androgens; C016512:IgY; D007136:Immunoglobulins; D007155:Immunologic Factors; D013963:Thyroid Hormones; D009113:Muramidase