The evolution of paternal care: a role for microbes?

Paternal care, particularly in cases of uncertain paternity, carries significant costs. Extensive research, both theoretical and experimental, has explored the conditions in which paternal care behaviour would be favoured. Common explanations include an adjustment of care with uncertainty in paternity and limited accuracy in parentage assessment. Here, we propose a new explanation that microbes may play a role in the evolution of paternal care among their hosts. Using computational models, we demonstrate that microbes associated with increased paternal care could be favoured by natural selection. We find that microbe-induced paternal care could evolve under wider conditions than suggested by genetic models. Moreover, we show that microbe-induced paternal care is more likely to evolve when considering paternal care interactions that increase microbial transmission, such as feeding and grooming. Our results imply that factors affecting the composition of host microbiome may also alter paternal behaviour. This article is part of the theme issue ‘The role of the microbiome in host evolution’.

The evolution of paternal care: a role for microbes?

Paternal care is an evolutionary mystery. Despite extensive research, both theoretical and experimental, the reasons for its ubiquity remain unclear. Common explanations include kin selection and limited accuracy in parentage assessment. However, these explanations do not cover the breadth of circumstances in which paternal care has been observed, particularly in cases of uncertain paternity. Here we propose that microbes may play a key role in the evolution of paternal care among their hosts. Using computational models, we demonstrate that microbes associated with increased paternal care could be favoured by natural selection. We find that microbe-induced paternal care could evolve under wider conditions than suggested by genetic models. Moreover, we show that microbe-induced paternal care is more likely to evolve when considering paternal care interactions that increase microbial transmission, such as feeding and grooming. Our results imply that factors affecting the composition of host microbiome may also alter paternal behaviour.

Using a Paired-Associate Learning Task to Assess Parent-Child Phenotypic Similarity

The fact of uncertain paternity has led some researchers to hypothesize that children should more closely resemble their fathers than their mothers. The evidence in support of this hypothesis is mixed, partly because the procedures used to measure perceived phenotypic similarity may not be sensitive enough to detect small effects and partly because comparisons are made between fathers and mothers rather than random control groups. In the present experiment the viability of using a paired-associate learning paradigm to investigate parent-child phenotypic similarity is demonstrated using 15 stimulus sets of colored photographs picturing two adults and one child. Using a 2 × 2 between subjects analysis of variance for total errors across learning trials, evidence indicated genetic relatedness for both mothers and fathers influences perceived resemblance and that association of male facial features with those of children, whether paternal or not, are learned more quickly than female facial features. While the significance of genetic relatedness to facial similarity was expected, the overall sex difference was not. However, the additive combination of these variables, genetic relatedness and maleness may explain why children seem to more closely resemble their fathers.