Parental care and sibling competition independently increase phenotypic variation among burying beetle siblings.

Matthew Schrader,Rebecca M Kilner,Benjamin J M Jarrett

doi:10.1111/evo.13607

Abstract

Several recent hypotheses suggest that parental care can influence the extent of phenotypic variation within populations; however, there have been few tests of these ideas. We exploited the facultative nature of posthatching parental care in the burying beetle, Nicrophorus vespilloides, to test whether parental care influences the expression of phenotypic variation in an important fitness trait (body size). We found that parental care and brood size (which influences sibling competition) had positive and independent effects on variation in body size. First, the mean coefficient of variation (CV) of body size was significantly greater in broods that received care than in those that did not. Second, CV body size increased with brood size in both parental care treatments. These results are not consistent with predictions from recent hypotheses that predict parental care will reduce phenotypic variation among siblings. The positive effects of parental care and brood size on phenotypic variation that we observed are likely due to sibling competition for access to provisioning parents and competition for limiting resources contained in the breeding carcass. Our results suggest that future theory linking parental care to the generation and maintenance of phenotypic variation must integrate the nature of interactions among family members.

Highlights

In animals with parental care, the amount, or quality of care that young receive can have an important impact on their phenotypic development and fitness (Smiseth et al 2012)
Most of the theory linking parental care to phenotypic/genetic variation predicts that the presence of parental care will reduce phenotypic variation among siblings (Table 1)
Comparisons between two O. taurus populations that differ in parental care behaviors revealed that the high care population exhibited greater phenotypic variation in body size when reared under conditions simulating low care than conditions simulating high care (Snell-Rood et al 2016)

Summary

Introduction

In animals with parental care, the amount, or quality of care that young receive can have an important impact on their phenotypic development and fitness (Smiseth et al 2012). Snell-Rood et al (2016) recently reviewed three hypotheses linking parental care to the maintenance of phenotypic and genetic variation (the environmental stress, compensation, and relaxed selection hypotheses) These three hypotheses each predict that parental care will reduce the amount of phenotypic variation expressed within a group of siblings; they focus on different mechanisms linking parental care to the maintenance of phenotypic variation. This effect of parental care on phenotypic variation could be detected experimentally by comparing phenotypic variation among groups that receive care and those that do not This environmental stress hypothesis predicts that the buffering effect of parental care will relax selection on offspring phenotype and lead to a build up of genetic variation. Populations that experience parental care may harbor more standing genetic variation than populations maintained without parental care

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Conclusion