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Data from: Effects of variation in resource acquisition during different stages of the life cycle on life-history traits and trade-offs in a burying beetle

Individual variation in resource acquisition should have consequences for life-history traits and trade-offs between them because such variation determines how many resources can be allocated to different life-history functions, such as growth, survival and reproduction. Since resource acquisition can vary across an individual's life cycle, the consequences for life-history traits and trade-offs may depend on when during the life cycle resources are limited. We tested for differential and/or interactive effects of variation in resource acquisition in the burying beetle Nicrophorus vespilloides. We designed an experiment in which individuals acquired high or low amounts of resources across three stages of the life cycle: larval development, prior to breeding and the onset of breeding in a fully crossed design. Resource acquisition during larval development and prior to breeding affected egg size and offspring survival, respectively. Meanwhile, resource acquisition at the onset of breeding affected size and number of both eggs and offspring. In addition, there were interactive effects between resource acquisition at different stages on egg size and offspring survival. However, only when females acquired few resources at the onset of breeding was there evidence for a trade-off between offspring size and number. Our results demonstrate that individual variation in resource acquisition during different stages of the life cycle has important consequences for life-history traits but limited effects on trade-offs. This suggests that, in species that acquire a fixed-sized resource at the onset of breeding, the size of this resource has larger effects on life-history trade-offs than resources acquired at earlier stages.

opencc-zeroDec 2013View details →

Data from: Trade-offs between personal immunity and reproduction in the burying beetle, N. vespilloides

We know that parental investment and immune investment are costly processes, but it is unclear which trait will be prioritized when both may be required. Here, we address this question using the burying beetle Nicrophorus vespilloides, carrion breeders that exhibit biparental care of young. Our results show that immunosuppression occurs during provision of parental care. We measured phenoloxidase (PO) on Days 1–8 of the breeding bout and results show a clear decrease in PO immediately from presentation of the breeding resource onward. Having established baseline immune investment during breeding we then manipulated immune investment at different times by applying a wounding challenge. Beetles were wounded prior to and during the parental care period and reproductive investment quantified. Different effects on reproductive output occur depending on the timing of wounding. Challenging the immune system with wounding prior to breeding does not affect reproductive output and subsequent lifetime reproductive success (LRS). LRS is also unaffected by applying an immune elicitor prior to breeding, though different arms of the immune system are up/downregulated, perhaps indicating a trade-off between cellular and humoral immunity. In contrast, wounding during breeding reduces reproductive output and to the greatest extent if the challenge is applied early in the breeding bout. Despite being immunosuppressed, breeding beetles can still respond to wounding by increasing PO, albeit not to prebreeding levels. This upregulation of PO during breeding may affect parental investment, resulting in a reduction in reproductive output. The potential role of juvenile hormone in controlling this trade-off is discussed.

Data from: Parental care and sibling competition independently increase phenotypic variation among burying beetle siblings

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 post-hatching 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.

opencc-zeroDec 2013View details →

Data from: The smell of parents: breeding status influences cuticular hydrocarbon pattern in the burying beetle Nicrophorus vespilloides

The waxy layer of the cuticle has been shown to play a fundamental role in recognition systems of insects. The biparental burying beetle Nicrophorus vespilloides is known to have the ability to discriminate between breeding and non-breeding conspecifics and also here cuticular substances could function as recognition cue. However, it has not yet been demonstrated that the pattern of cuticular lipids can reflect the breeding status of a beetle or of any other insect. With chemical analysis using coupled gas chromatography–mass spectrometry, we showed that the chemical signature of N. vespilloides males and females is highly complex and changes its feature with breeding status. Parental beetles were characterized by a higher amount of some unusual unsaturated hydrocarbons than beetles which are not caring for larvae. The striking correlation between cuticular profiles and breeding status suggests that cuticular hydrocarbons inform the beetles about parental state and thus enable them to discriminate between their breeding partner and a conspecific intruder. Furthermore, we found evidence that nutritional conditions also influence the cuticular profile and discuss the possibility that the diet provides the precursors for the unsaturated hydrocarbons observed in parental beetles. Our study underlines the fact that the cuticular pattern is rich of information and plays a central role in the burying beetles' communication systems.

Data from: No evidence for parent-offspring competition in the burying beetle Nicrophorus vespilloides

In species where family members share a limited pool of resources, there may be competition between parents and their dependent offspring for access to these resources. Parent-offspring competition may impose a cost to family living that would constrain the evolution of parental care and family living. Yet, few studies have tested for evidence of parent-offspring competition. Here we test for parent-offspring competition in the burying beetle Nicrophorus vespilloides. This species breeds on carcasses of small vertebrates that serve as food for both parents and offspring. We used a two-by-two factorial design, where we manipulated female nutritional state (food-deprivation versus control treatments) and the amount of resources (small versus large mouse carcasses). We find that food-deprived females lost more mass than controls over the 9-day long food deprivation treatment, confirming that food-deprivation caused a substantial decline in female nutritional state at the start of breeding. However, we find no evidence that increased food consumption by food-deprived females had a greater impact on offspring growth or survival when breeding on small carcasses. Instead, poor female nutritional state had a negative impact on offspring survival when females bred on large carcasses. There was more mould on the carcass when food-deprived females bred on a large carcass, suggesting that such females provided less indirect care serving to suppress microbial growth. We conclude that parent-offspring competition is associated with relatively minor costs to family members in this species, suggesting that it may not necessarily constrain the evolution of parental care and family living.

opencc-zeroDec 2012View details →

Data from: Nutrition during sexual maturation affects competitive ability but not reproductive productivity in burying beetles

1. Food availability can be unpredictable. When food becomes more abundant following a period of low food availability, developing larvae or juveniles often allocate resources preferentially towards increasing growth. This has important long-term effects on adult phenotypes and longevity. Despite the importance of strategic resource allocation during early development, few studies have examined how changes in resource availability during other windows of development affect reproductive strategies and fitness independent of growth. 2. We manipulated food availability in a burying beetle, Nicrophorus vespilloides, during a subadult period of sexual maturation when individuals cannot increase structural size but are still undergoing reproductive maturation. 3. In contrast to the trade-offs during larval or juvenile growth, beetles that experienced delayed feeding during reproductive maturation allocated resources preferentially towards maintaining both reproductive function and longevity. 4. In both sexes, delayed feeding beetles were much less successful in competition for carcasses. However, delayed feeding males and females provided similar amounts of parental care and did not differ in reproductive success or longevity. 5. These results indicate that the nutritional environment experienced during a key developmental window may be an important determinant of the expression of alternative reproductive strategies in adulthood, independent of body size.

Data from: Interplay between age-based competitive asymmetries within the brood and direct competition between inbred and outbred offspring in a burying beetle

Theory suggests that intraspecific competition associated with direct competition between inbred and outbred individuals should be an important determinant of the severity of inbreeding depression. The reason is that, if outbred individuals are stronger competitors than inbred ones, direct competition should have a disproportionate effect on the fitness of inbred individuals. However, an individual's competitive ability is not only determined by its inbreeding status but also by competitive asymmetries that are independent of an individual's inbreeding status. When this is the case, such competitive asymmetries may shape the outcome of direct competition between inbred and outbred individuals. Here we investigate the interface between age-based competitive asymmetries within broods and direct competition between inbred and outbred offspring in the burying beetle Nicrophorus vespilloides. We found that inbred offspring had lower survival than outbred ones confirming that there was inbreeding depression. Furthermore, seniors (older larvae) grew to a larger size and had higher survival than juniors (younger larvae), confirming that there were age-based competitive asymmetries. Nevertheless, there was no evidence that direct competition between inbred and outbred larvae exacerbated inbreeding depression, no evidence that inbreeding depression was more severe in juniors, and no evidence that inbred juniors suffered disproportionately due to competition from outbred seniors. Our results suggest that direct competition between inbred and outbred individuals does not necessarily exacerbate inbreeding depression and that inbred individuals are not always more sensitive to poor and stressful conditions than outbred ones.

Data from: Differential effects of offspring and maternal inbreeding on egg laying and offspring performance in the burying beetle Nicrophorus vespilloides

We investigate the effect of offspring and maternal inbreeding on maternal and offspring traits associated with early offspring fitness in the burying beetle Nicrophorus vespilloides. We conducted two experiments. In the first experiment, we manipulated maternal inbreeding only (keeping offspring outbred) by generating mothers that were outbred, moderately inbred or highly inbred. Meanwhile, in the second experiment, we manipulated offspring inbreeding only (keeping females outbred) by generating offspring that were outbred, moderately inbred or highly inbred. In both experiments, we monitored subsequent effects on breeding success (number of larvae), maternal traits (clutch size, delay until laying, laying skew, laying spread and egg size) and offspring traits (hatching success, larval survival, duration of larval development, and average larval mass). Maternal inbreeding reduced breeding success, and this effect was mediated through lower hatching success and greater larval mortality. Furthermore, inbred mothers produced clutches where egg laying was less skewed towards the early part of laying than outbred females. This reduction in the skew in egg laying is beneficial for larval survival, suggesting that inbred females adjusted their laying patterns facultatively, thereby partially compensating for the detrimental effects of maternal inbreeding on offspring. Finally, we found evidence of a nonlinear effect of offspring inbreeding coefficient on number of larvae dispersing. Offspring inbreeding affected larval survival and larval development time but also unexpectedly affected maternal traits (clutch size and delay until laying), suggesting that females adjust clutch size and the delay until laying in response to being related to their mate.

opencc-zeroDec 2016View details →

Data from: Staying with the young enhances the fathers' attractiveness in burying beetles

Studying the relationship between parental and mating effort helps us to understand the evolution of parental care and, consequently, has been the subject of many theoretical and empirical investigations. Using burying beetles as a model, we found no correlation between the intensity of a sexual signal (sex pheromone quantity) and the amount of care provided by males. However, males that were given the opportunity to breed and care for young went on to produce a higher amount of their sexual signal and attracted three times more females in the field than control males that were not given the opportunity to breed. The likely explanation for our finding is that specific aspects of care in burying beetles, that is the defense and preservation of a nutrient rich breeding resource, a small vertebrate cadaver, is not only beneficial for the offspring but also for the adults themselves. Obtaining a good carrion meal possibly enables males to store resources that they can subsequently allocate toward sexual signaling. Collectively, our results highlight that conditions can exist where male participation in brood care has a positive effect on its sexual attractiveness. This in turn might have facilitated the evolution of male assistance in parental care.

opencc-zeroDec 2014View details →

Data from: Male burying beetles extend, not reduce, parental care duration when reproductive competition is high

Male parents spend less time caring than females in many species with biparental care. The traditional explanation for this pattern is that males have lower confidence of parentage, so they desert earlier in favor of pursuing other mating opportunities. However, one recent alternative hypothesis is that prolonged male parental care might also evolve if staying to care actively improves paternity. If this is the case, an increase in reproductive competition should be associated with increased paternal care. To test this prediction we manipulated the level of reproductive competition experienced by burying beetles, Nicrophorus vespilloides (Herbst, 1783). We found that caregiving males stayed for longer and mated more frequently with their partner when reproductive competition was greater. Reproductive productivity did not increase when males extended care. Our findings provide support for the increased paternity hypothesis. Extended duration of parental care may be a male tactic both protecting investment (in the current brood) and maximising paternity (in subsequent brood(s) via female stored sperm) even if this fails to maximise current reproductive productivity and creates conflict of interest with their mate via costs associated with increased mating frequency.

opennotspecifiedSep 2012View details →

Fig. 3. Standard pitfall trap design. A in Efficient New Above-Ground Bucket Traps Produce Comparable Data to that of Standard Transects for the Endangered American Burying Beetle,Nicrophorus AmericanusOlivier (Coleoptera: Silphidae)

Fig. 3. Standard pitfall trap design. A standard transect consisted of eight traps spaced 20 m.

opennotspecifiedMar 2005View details →

Fig. 1. a in Predatory Hypogaeic Beetles are Attracted to Buried Winter Moth (Lepidoptera: Geometridae) Pupae: Evidence Using a New Trap Design

Fig. 1. a) Exclusion cage and b) hypogaeic trap.

Figure 3 from: Knee W (2017) New Macrocheles species (Acari, Mesostigmata, Macrochelidae) associated with burying beetles (Silphidae, Nicrophorus) in North America. ZooKeys 721: 1-32. https://doi.org/10.3897/zookeys.721.21747

Figure 3 - Female Macrocheles willowae sp. n. A subcapitulum and palp, ventral aspect B chelicera, antiaxial aspect C epistome D tritosternum.

Figure 8 from: Knee W (2017) New Macrocheles species (Acari, Mesostigmata, Macrochelidae) associated with burying beetles (Silphidae, Nicrophorus) in North America. ZooKeys 721: 1-32. https://doi.org/10.3897/zookeys.721.21747

Figure 8 - Female Macrocheles pratum sp. n. legs I–IV, coxae omitted; leg I anterolateral, II posterolateral, III posterolateral, IV femur dorsal, genu, tibia, tarsus anterolateral.

Figure 14 from: Knee W (2017) New Macrocheles species (Acari, Mesostigmata, Macrochelidae) associated with burying beetles (Silphidae, Nicrophorus) in North America. ZooKeys 721: 1-32. https://doi.org/10.3897/zookeys.721.21747

Figure 14 - Majority rule consensus tree of 19502 trees generated by Bayesian MCMC analysis (10 million generations) of 689bp fragment of COI from 14 ingroup specimens representing six Macrocheles species, and two outgroup specimens representing two species, posterior probabilities >50% shown above branches.

Figure 12 from: Knee W (2017) New Macrocheles species (Acari, Mesostigmata, Macrochelidae) associated with burying beetles (Silphidae, Nicrophorus) in North America. ZooKeys 721: 1-32. https://doi.org/10.3897/zookeys.721.21747

Figure 12 - Female Macrocheles kaiju sp. n. legs I–IV, coxae omitted; leg I anterolateral, II posterolateral, III and IV dorsal.

Figure 11 from: Knee W (2017) New Macrocheles species (Acari, Mesostigmata, Macrochelidae) associated with burying beetles (Silphidae, Nicrophorus) in North America. ZooKeys 721: 1-32. https://doi.org/10.3897/zookeys.721.21747

Figure 11 - Female Macrocheles kaiju sp. n. A subcapitulum and palp, ventral aspect B chelicera, antiaxial aspect C epistome D tritosternum.

Figure 7 from: Knee W (2017) New Macrocheles species (Acari, Mesostigmata, Macrochelidae) associated with burying beetles (Silphidae, Nicrophorus) in North America. ZooKeys 721: 1-32. https://doi.org/10.3897/zookeys.721.21747

Figure 7 - Female Macrocheles pratum sp. n. A subcapitulum and palp, ventral aspect B chelicera, antiaxial aspect C epistome D tritosternum.

Figure 4 from: Knee W (2017) New Macrocheles species (Acari, Mesostigmata, Macrochelidae) associated with burying beetles (Silphidae, Nicrophorus) in North America. ZooKeys 721: 1-32. https://doi.org/10.3897/zookeys.721.21747

Figure 4 - Female Macrocheles willowae sp. n. legs I–IV, coxae omitted; leg I anterolateral, II posterolateral, III dorsal, IV anterolateral.