Abstract
Phenotypic plasticity is a key mechanism by which animals can cope with rapidly changeable environments, but the evolutionary lability of such plasticity remains unclear. The socio-sexual environment can fluctuate very rapidly, affecting both the frequency of mating opportunities and the level of competition males may face. Males of many species show plastic behavioural responses to changes in social environment, in particular the presence of rival males. For example, Drosophila pseudoobscura males respond to rivals by extending mating duration and increasing ejaculate size. Whilst such responses are predicted to be adaptive, the extent to which the magnitude of response is heritable, and hence selectable, is unknown. We investigated this using isofemale lines of the fruit fly D. pseudoobscura, estimating heritability of mating duration in males exposed or not to a rival, and any genetic basis to the change in this trait between these environments (i.e. degree of plasticity). The two populations differed in population sex ratio, and the presence of a sex ratio distorting selfish chromosome. We find that mating duration is heritable, but no evidence of population differences. We find no significant heritability of plasticity in mating duration in one population, but borderline significant heritability of plasticity in the second. This difference between populations might be related to the presence of the sex ratio distorting selfish gene in the latter population, but this will require investigation in additional populations to draw any conclusions. We suggest that there is scope for selection to produce an evolutionary response in the plasticity of mating duration in response to rivals in D. pseudoobscura, at least in some populations.
Highlights
Phenotypic plasticity, the ability of a genotype to exhibit a range of phenotypes depending on the environment, is widespread and a fundamental component of fitness [1,2]
Copulation duration when not exposed to a rival Univariate models of copulation duration in the absence of a rival revealed no significant difference between the amount of variation explained by line in the two populations (Log Likelihood ratio test, x20&1df = 0.04, p = 0.42), showing that the genetic variation in copulation duration is equal in each population
We estimated the total genetic variation and broad sense heritability of copulation duration from a model with line nested within population assuming line variances in both populations are drawn from the same distribution
Summary
Phenotypic plasticity, the ability of a genotype to exhibit a range of phenotypes depending on the environment, is widespread and a fundamental component of fitness [1,2]. Plasticity in behaviour is of particular significance to animals as it is predicted to be rapidly, even limitlessly, reversible and inexpensive [3,4], which is of critical importance if the environment is rapidly changeable. Such behaviours provide immediate responses to environmental change well before genetic adaptation can take place [5]. How such plasticity evolves is still debated, that is whether it is a by-product of directional selection on mean trait values or on the reaction norm of plasticity itself [4,6]. In order to investigate how behavioural plasticity evolves, the first step is to demonstrate that behavioural plasticity is heritable and has a genetic component upon which selection can act
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call