Coadaptation of Offspring Begging and Parental Provisioning - An Evolutionary Ecological Perspective on Avian Family Life

Natalia Estramil,Wendt Müller,Marcel Eens,Tapio Mappes

doi:10.1371/journal.pone.0070463

Abstract

Offspring begging and parental provisioning are the two central social behaviours expressed during the period of parental care. Both behaviours influence each other and it is, therefore, hypothesized that they should ultimately become (genetically) correlated, stabilized by fitness costs to parents and/or offspring. By reciprocally exchanging entire clutches in canaries (Serinus canaria), we tested (1) whether there is covariation between these behaviours and (2) whether a mismatch - as introduced by cross-fostering - entails costs. Begging was scored in a standardized begging test and parental provisioning was measured via (a) the actual feeding rate and (b) using the growth rate of the foster nestlings as a proxy. Costs were established in terms of future reproductive investment in subsequent clutches and offspring growth. We found a positive and significant phenotypic covariation between offspring begging and parental feeding when using the growth rate as a proxy and, to a lesser extent, in case of the parental feeding rate. Female parents suffered no future reproductive costs when feeding foster nestlings that were more demanding than their own nestlings. Neither growth measured amongst all offspring nor the reproductive investment measured amongst the female offspring as adults was influenced by their begging behaviour. However, the reproductive investment of female offspring tended to depend on the parental qualities of their foster parents. Thus, offspring may only be able to extract resources within the limit of generosity of their foster parents. This suggests parental control of feeding, which is also supported by the positive covariation between offspring begging and parental feeding.

Highlights

The family, which is defined as a social unit consisting of one or two parents and their offspring, forms a social environment with significant consequences for individual fitness and trait evolution
Removing the term ‘‘total number of dips given by foster parents’’, which was included to control for the effect of the feeding rates of the foster parents on the begging of the focal nestlings, made little difference to the results (F1,16 = 1.12, P = 0.31)
The family life in species with parental care typically creates a social environment in which traits such as offspring begging and parental feeding that are expressed by one family member exert a selective pressure on the trait expression in another family member. These traits should become genetically correlated [1], [15]. Such genetic correlations are expected to be positive when parents control the level of parental provisioning and selection predominantly acts on offspring begging and vice versa in case of a negative correlation

Summary

Introduction

The family, which is defined as a social unit consisting of one or two parents and their offspring, forms a social environment with significant consequences for individual fitness and trait evolution. Social interactions between parents and offspring as expressed in the family context are of particular interest, since these traits are target of selection but can act as agent of selection by exerting a selective pressure on the trait expression of other family members [1]–[3] Both the social trait expressed and the social environment can evolve [2]. Offspring begging and parental feeding have a heritable basis [10]–[14] and are able to respond to selection Their evolution may not be independent, as the expression of each of these traits depends on the expression of the other. A phenotypic covariation of parental provisioning and offspring begging may depend on (prenatal) maternal effects [10], [16], [20]

Objectives

Methods

Results

Conclusion