Pilakouta et al. (2015) State-dependent cooperation in burying beetles: parents adjust their contribution towards care based on both their own and their partner's size. JEB, DOI: 10.1111/jeb.12712
Handicapping experiments on species with biparental care show that a focal parent increases its contribution when its partner is handicapped. Such results are interpreted as evidence for negotiation, whereby each parent adjusts its amount of care to that of its partner. However, it is currently unclear whether the focal parent responds to a change in its handicapped partner's behaviour or state. To address this gap, we conducted an experiment on the burying beetle Nicrophorus vespilloides where we first generated different-sized males and females by varying the duration of larval development. We then used a 2 × 2 factorial design in which a small or large male was paired with a small or large female. Small females provided less direct care (food provisioning and interactions with larvae) than large females, and both males and females provided less direct care when paired with a small partner. Thus, the focal parent adjusted its contribution towards care based on both its own state and that of its partner. There was also evidence for negotiation between the two parents as the focal parent adjusted its contribution based on the amount of care by its partner. However, there was no evidence that negotiation accounted for how the focal parent responded to its partner's size. Our results have important implications for our understanding of biparental cooperation as they show that each parent adjusts its contribution not only based on the amount of care provided by its partner but also based on its own state and its partner's state.
Kilner et al. (2015) Parental effects alter the adaptive value of an adult behavioural trait. eLIFE, DOI: http://dx.doi.org/10.7554/eLife.07340
The parents' phenotype, or the environment they create for their young, can have long-lasting effects on their offspring, with profound evolutionary consequences. Yet, virtually no work has considered how such parental effects might change the adaptive value of behavioural traits expressed by offspring upon reaching adulthood. To address this problem, we combined experiments on burying beetles (Nicrophorus vespilloides) with theoretical modelling and focussed on one adult behavioural trait in particular: the supply of parental care. We manipulated the early-life environment and measured the fitness payoffs associated with the supply of parental care when larvae reached maturity. We found that (1) adults that received low levels of care as larvae were less successful at raising larger broods and suffered greater mortality as a result: they were low-quality parents. Furthermore, (2) high-quality males that raised offspring with low-quality females subsequently suffered greater mortality than brothers of equivalent quality, which reared larvae with higher quality females. Our analyses identify three general ways in which parental effects can change the adaptive value of an adult behavioural trait: by influencing the associated fitness benefits and costs; by consequently changing the evolutionary outcome of social interactions; and by modifying the evolutionarily stable expression of behavioural traits that are themselves parental effects.
Gasperin & Kilner (2015) Friend or foe: inter-specific interactions and conflicts of interest within the family. Ecological Entomology, DOI: 10.1111/een.12259
1. Interactions between species can vary from mutually beneficial to evolutionarily neutral to antagonistic, even when the same two species are involved. Similarly, social interactions between members of the same species can lie on a spectrum from conflict to cooperation.
2. The aim of the present study was to investigate whether variation in the two types of social behaviour are interconnected. Is the fitness of the various classes of social partner within species (such as parent and offspring, or male and female) differently affected by interactions with a second species? Moreover, can inter-specific interactions influence the outcome of social interactions within species?
3. The present experiments focus on the interactions between the burying beetle Nicrophorus vespilloides Herbst and the phoretic mitePoecilochirus carabi G. Canestrini & R. Canestrini. The approach was to measure the fitness of burying beetle mothers, fathers, and offspring after reproduction, which took place either in the presence or absence of mites.
4. We found that male, female, and larval burying beetles derive contrasting fitness costs and benefits from their interactions with the mite, despite sharing a common family environment. From the mite's perspective, its relationship with the burying beetle can, therefore, be simultaneously antagonistic, neutral, and possibly even mutualistic, depending on the particular family member involved. We also found that mites can potentially change the outcome of evolutionary conflicts within the family.
5. We conclude that inter-specific interactions can explain some of the variation in social interactions seen within species. It is further suggested that intra-specific interactions might contribute to variation in the outcome of interactions between species.
Kuijper & Johnstone (2015) Parental effects and the evolution of phenotypic memory. JEB, DOI: 10.1111/jeb.12778
Despite growing evidence for nongenetic inheritance, the ecological conditions that favor the evolution of heritable parental or grandparental effects remain poorly understood. Here, we systematically explore the evolution of parental effects in a patch-structured population with locally changing environments. When selection favors the production of a mix of offspring types, this mix differs according to the parental phenotype, implying that parental effects are favored over selection for bet-hedging in which the mixture of offspring phenotypes produced does not depend on the parental phenotype. Positive parental effects (generating a positive correlation between parental and offspring phenotype) are favored in relatively stable habitats and when different types of local environment are roughly equally abundant, and can give rise to long-term parental inheritance of phenotypes. By contrast, unstable habitats can favor negative parental effects (generating a negative correlation between parental and offspring phenotype), and under these circumstances even slight asymmetries in the abundance of local environmental states select for marked asymmetries in transmission fidelity.
Flower et al. (2015) Dual parasitism of Fork-tailed Drongos by African and Jacobin Cuckoos. Ostrich, 86:1-2
Different species of brood parasitic birds, which lay their eggs in the nests of host foster-parents, rarely target the same host species population. We report brood parasitism of Fork-tailed Drongos Dicrurus adsimilis in the southern Kalahari Desert by both African Cuckoo Cuculus gularis and Jacobin Cuckoo Clamator jacobinus serratus. Drongos are the only known host for the African Cuckoo, and were more frequently parasitised by this species (21.8% nests). Nevertheless, parasitism rates suggest that in the Kalahari, drongos are also an important host for Jacobin Cuckoo (4.6% nests). Jacobin Cuckoos likely compete with African Cuckoos for drongo hosts, as exemplified by the occurrence of both African and Jacobin Cuckoo eggs in the same drongo clutch. The drongo's defensive adaptations to parasitism by African Cuckoos, including egg rejection, may also curtail parasitism by Jacobin Cuckoos. The extent of competition between these cuckoo species and whether they possess adaptations to prevent one another's access to drongo hosts remains to be explored.