How sex-biased dispersal affects conflict over parental investment

This article is a preprint and has not been peer-reviewed. It is availble from bioRxiv via the DOI in this record.Existing models of parental investment have mainly focused on interactions at the level of the family, and have paid much less attention to the impact of population-level processes. Here we extend classical models of parental care to assess the impact of population structure and limited dispersal. We find that sex-differences in dispersal substantially affect the amount of care provided by each parent, with the more philopatric sex providing the majority of the care to young. This effect is most pronounced in highly viscous populations: in such cases, when classical models would predict stable biparental care, inclusion of a modest sex difference in dispersal leads to uniparental care by the philopatric sex. In addition, mating skew also affects sex-differences in parental investment, with the more numerous sex providing most of the care. However, the effect of mating skew only holds when parents care for their own offspring. When individuals breed communally, we recover the previous finding that the more philopatric sex provides most of the care, even when it is the rare sex. Finally, we show that sex-differences in dispersal can mask the existence of sex-specific costs of care, because the philopatric sex may provide most of the care even in the face of far higher mortality costs relative to the dispersing sex. We conclude that sex-biased dispersal is likely to be an important, yet currently overlooked driver of sex-differences in parental care.We would like to thank the other members of the Transgen group, Tom Ezard, Stuart Townley and Jonathan Wells for discussion. The Dutch Academy of Arts and Sciences (KNAW) and the Lorentz Centre at the University of Leiden, the Netherlands, funded a week-long workshop on nongenetic effects that contributed to this paper. The authors acknowledge the use of the UCL Legion High Performance Computing Facility (Legion@UCL), and associated support services, in the completion of this work. This study was funded by an EPSRC sandpit grant on transgenerational effects, grant number EP/H031928/1 awarded to RAJ and an EPSRC-funded 2020 Science fellowship awarded to BK (grant number EP/I017909/1)

Maternal effects and parent-offspring conflict

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.Maternal effects can provide offspring with reliable information about the environment they are likely to experience, but also offer scope for maternal manipulation of young when interests diverge between parents and offspring. To predict the impact of parent–offspring conflict, we model the evolution of maternal effects on local adaptation of young. We find that parent–offspring conflict strongly influences the stability of maternal effects; moreover, the nature of the disagreement between parents and young predicts how conflict is resolved: when mothers favor less extreme mixtures of phenotypes relative to offspring (i.e., when mothers stand to gain by hedging their bets), mothers win the conflict by providing offspring with limited amounts of information. When offspring favor overproduction of one and the same phenotype across all environments compared to mothers (e.g., when offspring favor a larger body size), neither side wins the conflict and signaling breaks down. Only when offspring favor less extreme mixtures relative to their mothers (something no current model predicts), offspring win the conflict and obtain full information about the environment. We conclude that a partial or complete breakdown of informative maternal effects will be the norm rather than the exception in the presence of parent–offspring conflict.B.K. has been funded by an EPSRC 2020 Science fellowship (grant number EP/I017909/1) and a Leverhulme Trust Early Career Research Fellowship (ECF 2015-273). R.A.J. was funded by an EPSRC sandpit grant on transgenerational effects, grant number EP/H031928/1 and a Leverhulme Trust Research Grant. This work has made use of the Carson computing cluster at the Environment and Sustainability Institute at the University of Exeter. In addition, the authors acknowledge the use of the UCL Legion High Performance Computing Facility (Legion@UCL) and associated support services in the completion of this work. The Dutch Academy of Arts and Sciences (KNAW) and the Lorentz Centre at the University of Leiden, the Netherlands funded a workshop on nongenetic effects that contributed to this article

How Sex-Biased Dispersal Affects Sexual Conflict over Care

This is the author accepted manuscript. The final version is available from University of Chicago Press via the DOI in this record.Existing models of parental investment have mainly focused on interactions at the level of the family and have paid much less attention to the impact of population-level processes. Here we extend classical models of parental care to assess the impact of population structure and limited dispersal. We find that sex differences in dispersal substantially affect the amount of care provided by each parent, with the more philopatric sex providing the majority of care to young. This effect is most pronounced in highly viscous populations: in such cases, when classical models would predict stable biparental care, inclusion of a modest sex difference in dispersal leads to uniparental care by the philopatric sex. In addition, mating skew also affects sex differences in parental investment, with the more numerous sex providing most of the care. However, the effect of mating skew holds only when parents care for their own offspring. When individuals breed communally, we recover the previous finding that the more philopatric sex provides most of the care even when it is the rarer sex. We conclude that sex-biased dispersal is likely to be an important yet currently overlooked driver of sex differences in parental care.BK has been funded by an EPSRC 2020 Science fellowship (grant number EP/I017909/1) and a Leverhulme Trust Early Career Research Fellowship (ECF 2015-273). RAJ has been funded by a EPSRC grant number EP/H031928/1. This work has made use of the Carson computing cluster at the Environment and Sustainability Institute at the University of Exeter. In addition, the authors acknowledge the use of the UCL Legion High Performance Computing Facility (Legion@UCL) and associated support services in the completion of this work. The Dutch Academy of Arts and Sciences (KNAW) and the Lorentz Centre at the University of Leiden, the Netherlands funded a workshop on nongenetic effects that contributed to this article

How threats influence the evolutionary resolution of within-group conflict.

© University of Chicago Press. This is the final published version of the article, deposited in accordance with SHERPA RoMEO guidelines. Also available from: http://www.jstor.org/stable/10.1086/598489Most examples of cooperation in nature share a common feature: individuals can interact to produce a productivity benefit or fitness surplus, but there is conflict over how these gains are shared. A central question is how threats to exercise outside options influence the resolution of conflict within such cooperative associations. Here we show how a simple principle from economic bargaining theory, the outside option principle, can help to solve this problem in biological systems. According to this principle, outside options will affect the resolution of conflict only when the payoff of taking up these options exceeds the payoffs individuals can obtain from bargaining or negotiating within the group; otherwise, threats to exercise outside options are not credible and are therefore irrelevant. We show that previous attempts to incorporate outside options in synthetic models of reproductive conflict fail to distinguish between credible and incredible threats, and then we use the outside option principle to develop credible synthetic models in two contexts: reproductive skew and biparental care. A striking prediction of our analysis is that outside options are least relevant to the resolution of conflict in cooperative groups of kin and are most relevant in transient associations or interactions among nonrelatives. Our analysis shows a way to link the resolution of within-group conflict to the environmental setting in which it occurs, and it illuminates the role of threats in the evolution of social behavior

Intra-group relatedness affects parental and helper investment rules in offspring care

In any system where multiple individuals jointly contribute to rearing offspring, conflict is expected to arise over the relative contributions of each carer. Existing theoretical work on the conflict over care has: (a) rarely considered the influence of tactical investment during offspring production on later contributions to offspring rearing; (b) concentrated mainly on biparental care, rather than cooperatively caring groups comprising both parents and helpers; and (c) typically ignored relatedness between carers as a potential influence on investment behavior. We use a game-theoretical approach to explore the effects of female production tactics and differing group relatedness structures on the expected rearing investment contributed by breeding females, breeding males, and helpers in cooperative groups. Our results suggest that the breeding female should pay higher costs overall when helpful helpers are present, as she produces additional offspring to take advantage of the available care. We find that helpers related to offspring through the breeding female rather than the breeding male should contribute less to care, and decrease their contribution as group size increases, because the female refrains from producing additional offspring to exploit them. Finally, within-group variation in helper relatedness also affects individual helper investment rules by inflating the differences between the contributions to care of dissimilar helpers. Our findings underline the importance of considering maternal investment decisions during offspring production to understand investment across the entire breeding attempt, and provide empirically testable predictions concerning the interplay between maternal, paternal and helper investment and how these are modified by different relatedness structures.This work was supported by a Natural Environment Research Council Studentship to the University of Cambridge (J.L.S.) and by a Royal Society University Research Fellowship (A.F.R.)This is the author accepted manuscript. The final version can be found on the publisher's website at: http://link.springer.com/article/10.1007%2Fs00265-013-1595-5# © Springer-Verlag Berlin Heidelberg 201

The evolution of multivariate maternal effects.

Published onlineJournal ArticleResearch Support, Non-U.S. Gov'tThere is a growing interest in predicting the social and ecological contexts that favor the evolution of maternal effects. Most predictions focus, however, on maternal effects that affect only a single character, whereas the evolution of maternal effects is poorly understood in the presence of suites of interacting traits. To overcome this, we simulate the evolution of multivariate maternal effects (captured by the matrix M) in a fluctuating environment. We find that the rate of environmental fluctuations has a substantial effect on the properties of M: in slowly changing environments, offspring are selected to have a multivariate phenotype roughly similar to the maternal phenotype, so that M is characterized by positive dominant eigenvalues; by contrast, rapidly changing environments favor Ms with dominant eigenvalues that are negative, as offspring favor a phenotype which substantially differs from the maternal phenotype. Moreover, when fluctuating selection on one maternal character is temporally delayed relative to selection on other traits, we find a striking pattern of cross-trait maternal effects in which maternal characters influence not only the same character in offspring, but also other offspring characters. Additionally, when selection on one character contains more stochastic noise relative to selection on other traits, large cross-trait maternal effects evolve from those maternal traits that experience the smallest amounts of noise. The presence of these cross-trait maternal effects shows that individual maternal effects cannot be studied in isolation, and that their study in a multivariate context may provide important insights about the nature of past selection. Our results call for more studies that measure multivariate maternal effects in wild populations.This work was supported by EPSRC grant EP/H031928/1. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscrip

Maternal costs in offspring production affect investment rules in joint rearing

When multiple individuals contribute to rearing the same offspring, conflict is expected to occur over the relative amounts invested by each carer. Existing models of biparental care suggest that this conflict should be resolved by partially compensating for changes by co-investors, but this has yet to be explicitly modeled in cooperative breeders over a range of carer numbers. In addition, existing models of biparental and cooperative care ignore potential variation in both the relative costs of offspring production to mothers and in maternal allocation decisions. If mothers experience particularly high costs during offspring production, this might be expected to affect their investment strategies during later offspring care. Here we show using a game-theoretical model that a range of investment tactics can result depending on the number of carers and the relative costs to the mother of the different stages within the breeding attempt. Additional carers result in no change in investment by individuals when production costs are low, as mothers can take advantage of the greater potential investment by increasing offspring number; however this tactic ultimately results in a decrease in care delivered to each offspring. Conversely, when production costs prevent the mother from increasing offspring number, our model predicts that other individuals should partially compensate for additional carers and hence offspring should each receive a greater amount of care. Our results reinforce the importance of considering investment across all stages in a breeding attempt, and provide some explanatory power for the variation in investment rules observed across cooperative species.This work was supported by a Natural Environment Research Council studentship to JLS, and by a Royal Society University Research Fellowship to AFR.This is the author accepted manuscript. The final version can be found on the publisher's website at: http://beheco.oxfordjournals.org/content/early/2012/11/20/beheco.ars203 © The Author 2012. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved

Modeling Developmental Plasticity in Human Growth: Buffering the Past or Predicting the Future?

Substantial variation in adult body size between human populations is widely assumed in part to represent adaptation to local ecological conditions. Developmental plasticity contributes to such variability; however, there is debate regarding how this early-life process can produce adaptation when environments change within the life span. We developed a simple mathematical simulation model, testing how human fetuses could tailor their growth to ecological conditions without being oversensitive and hence prone to extremes of growth. Data on Indian rainfall (1871–2004) were used as an index of ecological conditions. The simulation model allowed the comparison of different strategies for processing these time-series data regarding (a) the toleration of short-term ecological variability and (b) the prediction of conditions in adulthood. We showed that ecological information processing is favored in environments prone to long-term ecological trends. Once this strategy is adopted, resistance to short-term ecological perturbations can be achieved either by lengthening the duration of developmental plasticity or by accumulating multigenerational influences. A multigenerational strategy successfully dampens the transmission of the effects of ecological shocks to future generations, but it does not predict or enable offspring to respond to longer-term conditions. However, this strategy does allow fetal growth to be tailored to the likely supply of nutrition from the mother in the period after birth, during when extrinsic mortality risk is high. Our model has implications for public health policies aimed at addressing chronic malnutrition

Evolution of epigenetic transmission when selection acts on fecundity versus viability

This is the author accepted manuscript. The final version is available from the Royal Society via the DOI in this recordExisting theory on the evolution of parental effects and the inheritance of nongenetic factors has mostly focused on the role of environmental change. By contrast, how differences in population demography and life history affect parental effects is poorly understood. To fill this gap, we develop an analytical model to explore how parental effects evolve when selection acts on fecundity versus viability in spatiotemporally fluctuating environments. We find that regimes of viability selection, but not fecundity selection, are most likely to favour parental effects. In case of viability selection, locally adapted phenotypes have a higher survival than maladapted phenotypes and hence become enriched in the local environment. Hence, simply by being alive, a parental phenotype becomes correlated to its environment (and hence informative to offspring) during its lifetime, favouring the evolution of parental effects. By contrast, in regimes of fecundity selection, correlations between phenotype and environment develop more slowly: this is because locally adapted and maladapted parents survive at equal rates (no survival selection), so that parental phenotypes, by themselves, are uninformative about the local environment. However, because locally adapted parents are more fecund, they contribute more offspring to the local patch than maladapted parents. In case these offspring are also likely to inherit the adapted parents’ phenotypes (requiring pre-existing inheritance), locally adapted offspring become enriched in the local environment, resulting in a correlation between phenotype and environment, but only in the offspring’s generation. Because of this slower build-up of a correlation between phenotype and environment essential to parental effects, fecundity selection is more sensitive to any distortions due to environmental change than viability selection. Hence, we conclude that viability selection is most conducive to the evolution of parental effects.Leverhulme Trus