Field estimates of reproductive success in a model insect: behavioural surrogates are poor predictors of fitness

David J Thompson,Christopher Hassall,Phillip C Watts,Chris D Lowe

doi:10.1111/j.1461-0248.2011.01655.x

David J Thompson, Christopher Hassall + Show 2 more

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https://doi.org/10.1111/j.1461-0248.2011.01655.x

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Journal: Ecology Letters	Publication Date: Jul 12, 2011
Citations: 66	License type: cc-by

Affiliation: Carleton University, University of Liverpool

Abstract

Understanding, and therefore measuring, factors that determine fitness is a central problem in evolutionary biology. We studied a natural population of Coenagrion puella (Odonata: Zygoptera) over two entire breeding seasons, with over a thousand individuals uniquely marked and genotyped, and all mating events at the rendezvous site recorded. Using a parentage analysis, fitness of individuals in the first generation was quantified as the numbers of offspring that survived to maturity. Although mating behaviour can be predicted by environmental and demographical variables, the numbers of mature offspring produced (fitness) cannot, and crucially, are poorly correlated with behavioural observations of mating. While fitness of both sexes was positively related to mating behaviour and to female's ectoparasite burden, these behavioural observations explained little more variance in offspring production than environmental and demographical variables. Thus, we demonstrate that behavioural measures of reproductive success are not necessarily reliable estimates of fitness in natural populations.

Highlights

Evolution acts upon the pool of available genetic variation, with the reproductive performances of different individuals determining their genetic representation in future generations: the central concept in natural and sexual selection
Long-term field studies are rare (Clutton-Brock & Sheldon, 2010) and a spectrum of surrogates have been used to study fitness; these range from morphological traits that correlate with the probability of obtaining a mate, such as body condition (Jakob et al, 1996) or body size (Simmons, 1988; Sokolovska et al, 2000), to behavioural measures of copulatory success that are assumed to correlate with offspring number, such as daily mating rate (DMR) and lifetime mating success (LMS)
Using an insect model that is tractable to in situ observations of mating behaviour, we genotyped a large (n>400) population to determine individual variation in fitness and quantify the relationship between surrogate measures of fitness based on observed reproductive behaviour and fitness: while mating behaviour is predicted well by environmental and demographic variables, a substantial proportion of the variance in fitness, i.e. numbers of offspring surviving to maturity, is left unexplained

Summary

Introduction

Evolution acts upon the pool of available genetic variation, with the reproductive performances of different individuals determining their genetic representation in future generations: the central concept in natural and sexual selection. Through a thorough genetic analysis can parentage be determined unequivocally, an essential requirement in bridging the gap between fitness surrogates and fitness itself Such an approach has been demonstrated for a range of vertebrates, with studies on ungulates in particular illustrating the importance of factors such as body size, population density, lifespan, time during the season and environmental conditions upon successful production of offspring (Albon et al, 1987; Coltman et al, 1999; Kruuk et al 1999; Gaillard et al, 2000)

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