1. Maternal effects and the evolution of sexual traits in birds
LESS IS MORE
>Order of supervisors/collaborators names?
>Addresses for all or just me?
>Picture of me, so know who to talk to?
>Size? Supposedly it can be up to A0 and either landscape or portrait.
>graphs?
>passerines, non-passerines or both?
Emma M. Birdsey1, Jonathan D. Blount1, Simon C. Griffith2, John Hunt1, Ian P.F. Owens3
1Centre for Ecology and Conservation, School of Biosciences, University of Exeter, Cornwall Campus, Penryn, Cornwall, TR10 9EZ, U.K., 2School of Biological, Earth and Environmental Sciences, UNSW, Sydney, NSW 2052, Australia. 3Department of Biological Sciences, Imperial College London, Silwood Park, Ascot, Berkshire, SL5 7PY, U.K.
RESULTS
Preliminary analyses suggest that in passerines, egg weight does not differ with the % of EPP in offspring. Female and chick weight differ with the weight of the egg.
NEXT
I will test this prediction more thoroughly using phylogenetic comparative analyses to control for other factors which may influence sexual trait expression other than maternal effects.
I will dissect eggs from different species of birds to examine yolk composition and measure the levels of hormones and antioxidants present i.e. carotenoids, vitamins A and E and androgen.
Sexual dichromatism will be used as an indicator for male sexual traits.
This will provide important data on specific maternal effects acting in the evolution of sexual ornamentation.
Male peacocks’ tail plumage and iridescence
Male House Sparrows’ black throat patch badge
Male Long-Tailed Widow Birds’ tail
Kiwi and egg
SEXUAL TRAITS
Geoffrey Dabb
Tony Faria
QUESTION
Do phenotypic maternal effects influence the evolution of sexual traits in birds?
Eggs and Ornaments
Maternal effects are a series of phenotypic effects that parents have on phenotypes of their offspring that are unrelated to the offspring's own genotype.
Maternal effects may have a large influence on sexual trait expression in many bird species and on important life-history parameters.
Phenotypic maternal effects, such as rate of extra-pair copulations, extra-pair paternity (EPP), parental care and egg size may influence the intensity of sexual selection.
Such effects are expected to drive and accelerate rates of evolutionary change within and potentially across species.
Sexual selection theory predicts that ornaments should be costly in order to be honest indicators of male quality, thus maternal effects, such as the deposition of hormones and vitamins in eggs, may be able to influence ornament development and this could be used by females to shape male offspring ornaments.
This research has the potential to be of critical importance to our understanding of evolution via sexual selection.
METHODS
Extra-pair paternity as a proxy for sexual traits, such as ornamentation, size dimorphism.
Analyses of a large data set containing many species of both passerines and non-passerines.
Carried out regressions on % EPP in offspring and egg mass, while controlling for female weight.
♀ weight
Egg
weight
Sexual selection
♀ weight*+ (p=0.000)
% EPP offspring+ (p=0.411)
% EPP broods– (p=0.275)
Life-history
♀ weight*+ (p=0.013)
Chick weight*+ (p=0.000)
Incubation period+ (p=0.099)
Fledging period+ (p=0.843)
Age at first breeding– (p=0.997)
Clutch size+ (p=0.908)
Annual fecundity- (p=0.067)
Longevity+ (p=0.691)
+ p=0.000
ANSWER
EPP, as a proxy for sexual selection, demonstrates no interaction between egg weight and extent of EPP in offspring.