A limit on the extent to which increased egg size can compensate for a poor postnatal environment revealed experimentally in the burying beetle, Nicrophorus vespilloides (original) (raw)
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Journal of Evolutionary Biology, 2012
Parents can increase the fitness of their offspring by allocating nutrients to eggs and/or providing care for eggs and offspring. Although we have a good understanding of the adaptive significance of both egg size and parental care, remarkably little is known about the co-evolution of these two mechanisms for increasing offspring fitness. Here, we report a parental removal experiment on the burying beetle Nicrophorus vespilloides in which we test whether post-hatching parental care masks the effect of egg size on offspring fitness. As predicted, we found that the parent's presence or absence had a strong main effect on larval body mass, whereas there was no detectable effect of egg size. Furthermore, egg size had a strong and positive effect on offspring body mass in the parent's absence, whereas it had no effect on offspring body mass in the parent's presence. These results support the suggestion that the stronger effect of post-hatching parental care on offspring growth masks the weaker effect of egg size. We found no correlation between the number and size of eggs. However, there was a negative correlation between larval body mass and brood size in the parent's presence, but not in its absence. These findings suggest that the trade-off between number and size of offspring is shifted from the egg stage towards the end of the parental care period and that post-hatching parental care somehow moderates this trade-off.
Increased allocation to reproduction reduces future competitive ability in a burying beetle
Journal of Animal Ecology, 2020
The existence of a trade‐off between current and future reproduction is a fundamental prediction of life history theory. Support for this prediction comes from brood size manipulations, showing that caring for enlarged broods often reduces the parent's future survival or fecundity. However, in many species, individuals must invest in competing for the resources required for future reproduction. Thus, a neglected aspect of this trade‐off is that increased allocation to current reproduction may reduce an individual's future competitive ability. We tested this prediction in the burying beetle, Nicrophorus vespilloides, a species where parents care for their offspring and where there is fierce competition for resources used for breeding. We manipulated reproductive effort by providing females with either a small brood of 10 larvae or a large brood of 40 larvae and compared the ability of these females, and virgin females that had no prior access to a carcass, to compete for a se...
Ecological Entomology, 2018
1. Burying beetles (Nicrophorus spp.) provide an excellent model system to test predictions about the relationships between environment, life-history and behaviour. All species in the genus display similar natural histories, breeding on vertebrate carcasses and providing parental care to developing offspring. However, variations in other aspects of species' ecologies provide a rich framework to examine the evolution of parental behaviours and other traits. 2. One little-studied species, N. sayi, breeds in substantially colder temperatures than its congeners, creating a potentially harsh environment for offspring. Here, we examined the timing of reproductive and developmental events in this species, and also investigated the effects of removing parents on offspring performance. 3. We find that development is not only extremely slow in this species, but it is also delayed even in comparison to other burying beetles reared at similar temperatures. However, the presence of parents reduces the time that offspring take to leave the carcass. This decrease in development time does not appear to result in a trade-off with mortality or body size. 4. From these results, we suggest that very slow development may be advantageous when living in a particularly cold environment. Additionally, one role of extended parental care may be to assist offspring in dealing with these harsh conditions, and to mitigate the potentially negative consequences of adopting such a slow life-history strategy.
Behavioral Ecology, 2009
Life-history theory suggests that offspring desertion can be an adaptive reproductive strategy, in which parents forgo the costly care of an unprofitable current brood to save resources for future reproduction. In the burying beetle, Nicrophorus vespilloides, parents commonly abandon their offspring to the care of others, resulting in female-only care, male-only care, brood parasitism, and the care of offspring sired by satellite males. Furthermore, when there is biparental care, males routinely desert the brood before larval development is complete, leaving females behind to tend their young. We attempted to understand these patterns of offspring desertion by using laboratory experiments to compare the fitness costs associated with parental care for each sex and the residual reproductive value of the 2 sexes. We also tested whether current brood size and residual reproductive value together predicted the incidence of brood desertion. We found that males and females each sustained fecundity costs as a consequence of caring for larvae and that these costs were of comparable magnitude. Nevertheless, males had greater residual reproductive value than females and were more likely than females to desert experimental broods. Our results can explain why males desert the brood earlier than females in nature and why female-only care is more common than male-only care. They also suggest that the tipping point from brood parasitism or satellite male behavior to communal breeding (and vice versa) depends on the value of the current brood relative to residual reproductive value.
Delayed benefits of paternal care in the burying beetle Nicrophorus vespilloides
Animal Behaviour, 2000
Burying beetles, Nicrophorus spp., inter the carcasses of small vertebrates as a food source for their offspring. Females can bury a carcass and rear a brood on it alone, but are frequently assisted by a male whose presence reduces the risk of the carcass being taken over by other beetles. However, the male often stays for longer than the carcass is vulnerable to take-over, and he cares for the brood without conferring any further benefits on it. In a laboratory experiment using N. vespilloides, we found that, in the absence of competitors, male assistance conferred no advantages on the brood for which he was caring, but significantly increased the subsequent reproductive success of his mate, in terms of the mass and rate of development of a second brood, reared alone. We suggest that this is due to a reduced parental effort of assisted females, who spent less time feeding offspring and more time resting than unassisted females whilst rearing their first broods. In the field, a female is unlikely to pair with the same male for consecutive broods, so we discuss the possible benefits a male may accrue from increasing his mate's reproductive success. We also discuss the relevance of these results to our understanding of the evolution of biparental care in birds.
Parental care improves offspring survival and growth in burying beetles
Animal Behaviour, 1998
Burying beetles (genus Nicrophorus) provide elaborate parental care to their offspring. Parental beetles defend a small vertebrate carcass, which constitutes the sole food source for the larvae. They also manipulate the carcass in various ways and directly regurgitate pre-digested carrion to the young. The benefits of carcass manipulation and regurgitation have been the subject of a few small-scale studies that have yielded conflicting results. In this study, we investigated the benefits of these behaviours and tested for possible beneficial effects on larval survival rates and final body mass in N. vespilloides. In this species: (1) larval survival and mass were significantly higher in broods receiving parental care throughout larval development on the carcass than in broods developing in the absence of adults; (2) parental presence immediately subsequent to larval hatching greatly improved larval survival rates; (3) continued parental presence for several days further improved larval growth, leading to a greater final mass of individual larvae; (4) larval survival and growth were improved by parental preparation of carcasses and by an excision made in the integument of the carcass surface by the parents that allows the larvae ready access to their food; (5) positive effects of parental feeding on larval survival and growth were not mediated by the transfer of symbionts. Copyright 1998 The Association for the Study of Animal Behaviour.
Entomologia Experimentalis et Applicata, 2008
During offspring growth, reduction in resource availability through competitive interactions will restrict how large individuals can become. Given that selection to mature at a large size will be greater for the sex in which large size provides the highest fitness return, sex-specific differences in response to a decrease in resource availability may be expected. Using Nicrophorus vespilloides Herbst (Coleoptera: Silphidae) we examined the sex-specific response of offspring to resource availability through sibling competition. We found that males and females were affected similarly by an increase in the level of sibling competition as brood size increased. Interestingly, although male N. vespilloides were consistently heavier than females, over a range of brood sizes, they were only significantly heavier than females at intermediate brood sizes. At present, the causes behind this finding remain unclear.
Age-related reproductive performance in the parental burying beetle, Nicrophorus orbicollis
Behavioral Ecology, 2009
Age-related improvements in reproductive performance have been explained by the selection, constraint, and restraint hypotheses (increased performance related to greater effort and a declining residual reproductive value). Using a laboratory population of the burying beetle, Nicrophorus orbicollis, 6 measures of performance were assessed. Consideration of the selection and constraint hypotheses was minimized by reducing mortality to near zero and comparing reproductive outcomes of equal-sized females with equivalent mating and breeding experience. Young and old females were provided a resource for breeding (mouse carcass) and were confronted by a potentially infanticidal intruder (young or old) after offspring were present in the nest. Younger females were more likely to experience a brood failure and were slower to oviposit eggs. Younger intruding females also were less likely to usurp a carcass from a resident female. Age, however, did not affect any measure of reproductive performance once a female had a brood. There were no differences between young and old females in the number and mass of offspring in original or replacement broods, or in the probability of successfully defending offspring against an intruder. In a follow-up experiment with smaller carcasses, there was, again, no significant difference in the ability of young and old females to defend their brood. In N. orbicollis, the reproductive restraint observed in younger females appears to inhibit the initiation but not the continuance of reproduction. The usefulness of the residual reproductive, targeted reproductive effort and the maturational limits hypotheses to explain age-related variation in reproductive performance are discussed.
Infanticide, sexual selection and task specialization in a biparental burying beetle
Animal Behaviour, 2006
Burying beetles (Nicrophorus spp.) compete for access to small vertebrate carrion, a highly valued resource. Intruders that take over a carcass will kill young of residents and use the carcass for a replacement brood. To examine whether sexual selection alters interactions with intruders, I staged encounters in which resource competition was the only important motivator for infanticide and then compared outcomes to those in which both sexual selection and resource competition might operate. On carcasses with first-instar larvae, a single resident male or female N. orbicollis was confronted with either a heterospecific or conspecific intruder of either sex (at this stage, a carcass retains 44e75% of its original value if used for a replacement brood). Single males defended their brood significantly better than did single females. Males appear to be efficient task specialists, having both a greater tendency and greater ability to guard the brood. When intruders were heterospecifics, there was no interaction between the two independent experimental variables of sex of defender and sex of intruder. When intruders were conspecifics, however, there was a significant interaction such that infanticide was more common when a defender confronted an intruder of the opposite sex. That is, when a defender had the opportunity to recoup some of its losses from infanticide by participating in a replacement brood with the intruder (opportunity for sexual selection), the probability of infanticide increased. A follow-up experiment staged at the second and early third instar indicated that infanticidal takeovers are quite common when single females defend second instars, but are infrequent when single females defend third instars, or when pairs defend second or third instars. Other measures of reproductive success (number and mass of broods in trials not including takeovers) were similar for single females and pairs. I hypothesize that the threat of infanticide and the inability of a parent to fully compensate for the absence of a partner that is a task specialist promote extended biparental care in burying beetles.
Behavioral Ecology, 2006
Alternative reproductive tactics can be maintained through different evolutionary avenues. They can be genetically or stochastically determined, in which case they must yield equal fitness, or their use can be conditional, in which case the fitness payoff of alternatives may differ. We attempted to assess the reproductive success of alternative reproductive tactics employed by wild male and female burying beetles in natural associations on carcasses placed in the field. A beetle's reproductive tactic was defined by its potential involvement in care of larvae, and parentage was assessed using oligolocus DNA fingerprinting of offspring and potential parents. Both in males and in females, alternative tactics yielded significantly different reproductive benefits: subordinate females (brood parasites) and males (satellite males) had considerably lower reproductive success than dominant or uncontested individuals. Joint breeding was too infrequent for statistical inferences, generating intermediate offspring numbers. About 15% of offspring were sired by males not present on the carcass, suggesting that mating away from reproductive resources can produce reproductive benefits to males. Our results, in concert with the observation that beetles using one tactic can be manipulated into employing the alternative, support the notion that Nicrophorus vespilloides uses alternatives conditionally, opportunistically employing lower-benefit tactics when more profitable tactics are not available, or as additional ''on-the-side'' tactics to bolster reproductive success.