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The burying beetle (Nicrophorus vespilloides) is thought to be predominantly sexually monomorphic. Males carry an additional abdominal segment and produce pheromones, but otherwise the sexes are alike.Both sexes bear bright orange bands on their black elytra, which probably function as part of a warning display rather than in mate choice. In wild populations, the sexes do not differ in mean body size, nor in its variation.Here we describe a form of sexual size dimorphism in wild populations that has previously been overlooked. We show that males have wider heads than females, for any given pronotum width (body size), and that the scaling relationship between head width and pronotum width is hyperallometric in males, but isometric in females. We also show how absolute head width, as well as the extent of sexual dimorphism in head width, differs among seven wild populations inhabiting different woodlands that are within c.10 km of each other.We suggest that head size dimorphism is functionally related to bite force. We hypothesise that dimorphism could be due to divergent selection arising from task specialisation during biparental care, as the duties of care favoured by males are likely to require a greater bite force. [ABSTRACT FROM AUTHOR]

Biodiversity is threatened by both climate and land‐use change. However, the synergistic impacts of these stressors and the underlying mechanisms remain poorly understood. This study seeks to bridge this knowledge gap by testing two competing hypotheses regarding the concept of the realized thermal niche. The Fixed Niche Breadth hypothesis suggests that a species' thermal niche remains constant despite fluctuations in population density resulting from land‐use changes. This hypothesis links habitat loss directly to a reduced availability of suitable climate. Conversely, the Habitat Loss‐Allee Effect hypothesis posits that land‐use changes narrow the realized thermal niche by lowering population densities, which impairs individual fitness in unfavorable temperatures due to the Allee effect—the positive impact of higher population density on individual fitness. To investigate these hypotheses, we developed an individual‐based model that integrates the Allee effect to examine how climate and land‐use changes affect population density and the thermal niche in social organisms. We empirically tested our model predictions by studying the distribution and cooperative behavior of burying beetles (Nicrophorus nepalensis), which compete with blowflies for carrion resources, along two elevational gradients in Taiwan. These gradients serve as temperature gradients, one in an intact forest and the other in a human‐altered landscape with substantial forest loss. Our results support the model predictions and show that landscape forest loss reduces beetle population densities and disrupts their dispersal dynamics, resulting in smaller cooperative groups. This, in turn, limits the beetles' ability to compete with blowflies in warmer environments, resulting in a contraction of the realized thermal niche. Together, our findings support the Habitat Loss‐Allee Effect hypothesis while rejecting the Fixed Niche Breadth hypothesis. By highlighting the effects of habitat loss and fragmentation on both intra‐ and interspecific social interactions, our study improves understanding of species' vulnerability to the combined threats of climate and land‐use change. Ultimately, our results underscore the importance of considering the demographic and behavioral consequences of land‐use change when assessing species' vulnerability to climate‐land‐use synergies. [ABSTRACT FROM AUTHOR]

The existence of life‐history trade‐offs is a fundamental assumption of evolutionary biology and behavioural ecology, yet empirical studies have found mixed evidence for this. Such trade‐offs are expected when individuals vary in how they allocate their limited resource budgets between different life‐history functions (variation in resource allocation), but they may be masked when individuals vary in how many resources they have acquired that they can later allocate to life‐history functions (variation in resource acquisition). We currently lack studies on the extent to which individual differences in behaviour reflect variation between individuals in resource acquisition and resource allocation. Here, we use parental care as a case study for exploring this question. We used the burying beetle Nicrophorus vespilloides, which exhibits facultative biparental care, comprising direct care (provisioning food or interacting with larvae) and indirect care (guarding or maintaining the carcass). We found some evidence for a positive relationship between these two components of care for both male and female parents. In addition, parents that spent more time providing care 24 h after hatching also tended to provide care for longer. Lastly, parents that provided more parental care did not experience a trade‐off of reduced lifespan after the breeding attempt. On the contrary, we found a positive relationship between the duration of care provided and parents' post‐breeding lifespan. Our finding of positive relationships between parental behaviours and between parental care and lifespan suggests that variation in care was mainly driven by differences in prior resource acquisition (i.e., parental quality) among individuals rather than differences in resource allocation. Our findings thus suggest that high intraspecific variation in parental quality can potentially mask reproductive investment trade‐offs within populations. [ABSTRACT FROM AUTHOR]

Communication plays a fundamental role in the evolution of any form of cooperative behaviour, such as parental care. However, it can be challenging to understand the specific role of certain signals and how they might have evolved into complex communication systems. To investigate what effect a lack of acoustic communication can have on brood care and offspring performance, we silenced parents of biparentally caring burying beetles with a noninvasive method and studied the effect on clutch and offspring performance. Moreover, by analysing three species with varying degrees of offspring dependency on parental care, we aimed to investigate how differing acoustic communication is related to the level of their dependency and if those two align in some way. We used Nicrophorus pustulatus , a nondependent species, Nicrophorus orbicollis , a highly dependent species and Nicrophorus vespilloides , an intermediately dependent species. We found strong effects of silencing parents on offspring performance in all three species. The lack of stridulations impacted offspring weight across all three species. However, our results point towards a difference between species in which development stage communication had the most substantial impact. Looking at larval weight at dispersal, the effects seem to be in line with the larval dependency in the way we would have expected, with N. orbicollis being the most strongly affected, N. vespilloides being also affected and N. pustulatus not being affected. However, looking more closely, we found various differences at other time points and also that larval survival was strongly affected in N. pustulatus. Few studies have looked at the exact function of acoustic signals during brood care with most of them focusing on what type of different signals are emitted rather than what effect they have. Our study is one of the first to start disentangling the interplay of communication and offspring performance. • Silencing parents has a strong effect on offspring performance in burying beetles. • Different species of Nicrophorus differ in communication during brood care. • The larvae of silenced parents are at a disadvantage. • More dependent species do not, per se, rely more on communication. [ABSTRACT FROM AUTHOR]

Climate change is driving both higher mean temperatures and a greater likelihood of heatwaves, which are becoming longer and more intense. Previous work has looked at these two types of thermal stressors in isolation, focusing on the effects of either a small, long-term increase in temperature or a large, short-term increase in temperature. Yet, a fundamental gap in our understanding is the combined effect of chronic and acute thermal stressors and, in particular, its impact on vital processes such as reproduction. Here, we investigated the independent and interactive effects of higher constant temperatures and short-term heatwave events on reproductive success and offspring fitness in an insect study system, the burying beetle Nicrophorus vespilloides. We found a substantial reduction in key fitness traits (fecundity, hatching success and offspring size) after exposure to both a heatwave and higher constant temperatures, but not after exposure to only one of these thermal stressors. This indicates that the effects of chronic and acute thermal stressors are amplified when they act in combination, as is very likely to occur in natural populations. Our findings, therefore, suggest that, by not considering the potential multiplicative effects of different types of thermal stressors, we may be underestimating the effects of climate change on animal fertility. [ABSTRACT FROM AUTHOR]

Evolutionary fitness is determined by how an organism allocates energy, or other limited resources, to reproduction during its lifetime. For iteroparous organisms, two alternative patterns of lifetime reproductive allocation are terminal investment and reproductive restraint. Terminal investment maximizes an individual's current reproductive output by allocating all available resources to current reproduction at the cost of future reproduction. In contrast, the reproductive restraint strategy allocates the individual's resources toward future survival and reproductive events. We used dynamic state variable modeling to investigate the conditions under which the burying beetle, Nicrophorus orbicollis, would balance between reproductive restraint and terminal investment over their lifetime. Our model provides a formal extension, specific to burying beetle biology, of the dynamic terminal investment threshold conceptual model. For young females, we show that delayed reproduction and reproductive restraint are the optimal tactic for all individuals except for those in the highest condition. However, as age increases, terminal investment becomes the optimal tactic over an increasingly broader range of individual conditions. Surprisingly, manipulation of a variety of factors, such as survival rate, resource availability, and metabolic costs, causes only minor changes in the general pattern observed. We suggest that in burying beetles, and other similar organisms, age plays a dominant role in determining the pattern of reproductive allocation over a lifetime. Individual energetic condition is important in changing the boundaries between alternative reproductive strategies, but it does not change the overall pattern of dominance of delayed reproduction or reproductive restraint at early ages and dominance of terminal investment with increasing age. Significance statement: In this model of the dynamic terminal investment threshold, age is the dominant determinant of reproductive allocation over a lifetime. Differences in survival rate, resource availability, and metabolic costs result in only slight adjustments to the optimal reproductive allocation strategy. Our model predicts the coexistence of multiple reproductive strategies and suggests that patterns of reproductive allocation identified for burying beetles may be broadly applicable across diverse taxa (e.g., insect parasitoids, altricial birds) that share similar life history characteristics and constraints with burying beetles. Furthermore, even in species that exhibit dramatically different life histories from burying beetles (e.g., long-lived, indeterminate growth, absence of reproductive senescence) this approach of dynamic state variable modeling shows potential for characterizing and comparing lifetime reproductive allocation patterns. [ABSTRACT FROM AUTHOR]

ABSTRACT The existence of life‐history trade‐offs is a fundamental assumption of evolutionary biology and behavioural ecology, yet empirical studies have found mixed evidence for this. Such trade‐offs are expected when individuals vary in how they allocate their limited resource budgets between different life‐history functions (variation in resource allocation), but they may be masked when individuals vary in how many resources they have acquired that they can later allocate to life‐history functions (variation in resource acquisition). We currently lack studies on the extent to which individual differences in behaviour reflect variation between individuals in resource acquisition and resource allocation. Here, we use parental care as a case study for exploring this question. We used the burying beetle Nicrophorus vespilloides, which exhibits facultative biparental care, comprising direct care (provisioning food or interacting with larvae) and indirect care (guarding or maintaining the carcass). We found some evidence for a positive relationship between these two components of care for both male and female parents. In addition, parents that spent more time providing care 24 h after hatching also tended to provide care for longer. Lastly, parents that provided more parental care did not experience a trade‐off of reduced lifespan after the breeding attempt. On the contrary, we found a positive relationship between the duration of care provided and parents' post‐breeding lifespan. Our finding of positive relationships between parental behaviours and between parental care and lifespan suggests that variation in care was mainly driven by differences in prior resource acquisition (i.e., parental quality) among individuals rather than differences in resource allocation. Our findings thus suggest that high intraspecific variation in parental quality can potentially mask reproductive investment trade‐offs within populations.

Small vertebrate carcasses represent critical resources for many terrestrial organisms, including burying beetles, which rely on carcasses for survival and breeding. Carcass attributes can influence the reproduction of burying beetles, yet most studies on their breeding ecology have used laboratory-reared carcasses of limited sizes. We conducted breeding and feeding experiments using a wide size range of lab (laboratory mice) and wild carcasses (wild mammals, birds and reptiles) to investigate how carcass size, source and taxon affect various breeding outcomes (e.g. clutch size, brood size and brood mass) of the burying beetle Nicrophorus nepalensis. Our results reveal a hump-shaped relationship between carcass size and breeding performance, with optimal breeding outcomes occurring on medium-sized carcasses. Furthermore, despite the variation in carcass tissue nutritional composition, breeding outcomes and larval growth did not differ between the two carcass sources or among the three wild carcass taxa. Finally, we found a larval quality–quantity trade-off across the range of carcasses examined, with carcass size shaping the larval life-history traits. Overall, these results elucidate how carcass resources may influence the breeding performance of burying beetles. Importantly, our study provides solid evidence validating decades of research using lab carcasses to study the reproductive ecology of burying beetles.

Closely related species with ecological similarity often aggressively compete for a common, limited resource. This competition is usually asymmetric and results in one species being behaviorally dominant over the other. Trade-offs between traits for behavioral dominance and alternative strategies can result in different methods of resource acquisition between the dominant and subordinate species, with important consequences for resource partitioning and community structure. Body size is a key trait thought to commonly determine behavioral dominance. Priority effects (i.e., which species arrives at the resource first), however, can also determine the outcome of interactions, as can species-specific traits besides size that give an advantage in aggressive contests (e.g., weapons). Here, we test among these three alternative hypotheses of body size, priority effects, and species identity for what determines the outcome of competitive interactions among two species of burying beetles, Nicrophorus orbicollis and N. pustulatus. Both overlap in habitat and seasonality and exhibit aggressive competition over a shared breeding resource of small vertebrate carrion. In trials, we simulated what would happen upon the beetles' discovery of a carcass in nature by placing a carcass and one beetle of each species in a container and observing interactions over 13 h trials (n = 17 trials). We recorded and categorized interactions between beetles and the duration each individual spent in contact with the carcass (the key resource) to determine which hypothesis predicted trial outcomes. Body size was our only significant predictor; the largest species won most aggressive interactions and spent more time in contact with the carcass. Our results offer insight into the ecology and patterns of resource partitioning of N. orbicollis and N. pustulatus, the latter of which is unique among local Nicrophorus for being a canopy specialist. N. pustulatus is also unique among all Nicrophorus in using snake eggs, in addition to other carrion, as a breeding resource. Our results highlight the importance of body size and related trade-offs in ecology and suggest parallels with other coexisting species and communities. [ABSTRACT FROM AUTHOR]

ABSTRACT In the central plains of North America, the beetle family Silphidae comprised two subfamilies, Silphinae and Nicrophorinae, differentiated by reproductive behaviors. Silphinae, known as carrion beetles, feed on carrion and fly larvae and produce free-living larvae that receive no parental care. Adult Nicrophorinae, known as burying beetles, prepare a vertebrate carcass into a brood ball and provide biparental care to their offspring. Preparation of a brood ball involves coating the carcass in antimicrobial oral and anal secretions. These secretions contain a community of microbes, referred to as the secretion microbiome, which inhibit carcass microbe succession, preventing normal decomposition. Here, the secretion microbiomes of five species of Nicrophorinae and two species of Silphinae, both sampled from Oklahoma, with additional Nicrophorinae from Nebraska, were characterized using culture-independent analyses to understand and decipher factors shaping diversity and community structure. We identify the core secretion microbiome across Silphidae and show that, while the host subfamily, secretion type, and collection locality had no significant effect on the bacterial community alpha diversity, these factors significantly influenced bacterial community structure. Global and local tests of phylogenetic associations identified 14 genera with phylogenetic signals to the host subfamily and species. Description of the bacterial communities present in silphid secretions furthers our understanding of how these beetles interact with microbes for carcass nutrient processing. Future culture-dependent studies from silphid secretions may identify novel antimicrobials and nontoxic compounds that can act as meat preservatives or sources for antimicrobials. IMPORTANCE The manuscript explores the secretion bacterial community of carrion and burying beetles of the central plains of North America. A core secretion microbiome of 11 genera is identified. The host subfamily, secretion type, and collection locality significantly affects the secretion microbiome. Future culture-dependent studies from silphid secretions may identify novel antimicrobials and nontoxic compounds that can act as meat preservatives or sources for antimicrobials.

Parental care is thought to evolve through modification of behavioral precursors, which predicts that mechanistic changes occur in the genes underlying those traits. The duplicated gene system of oxytocin/vasopressin has been broadly co-opted across vertebrates to influence parenting, from a preduplication ancestral role in water balance. It remains unclear whether co-option of these genes for parenting is limited to vertebrates. Here, we experimentally tested for associations between inotocin gene expression and water balance, parental acceptance of offspring, and active parenting in the subsocial beetle Nicrophorus orbicollis , to test whether this single-copy homolog of the oxytocin/vasopressin system has similarly been co-opted for parental care in a species with elaborate parenting. As expected, inotocin was associated with water balance in both sexes. Inotocin expression increased around sexual maturation in both males and females, although more clearly in males. Finally, inotocin expression was not associated with acceptance of larvae, but was associated with a transition to male but not female parenting. Moreover, level of offspring provisioning behavior and gene expression were positively correlated in males but uncorrelated in females. Our results suggest a broad co-option of this system for parenting that may have existed prior to gene duplication. [ABSTRACT FROM AUTHOR]

The use of recovered DNA ingested by necrophagous or hematophagous insects has increased in forensic sciences, mainly with representatives of flies. However, some beetles are also important for medico-legal forensic entomology because they feed on carcasses until advanced decomposition. This study evaluated whether the Neotropical carrion beetle Oxelytrum discicolle (Silphidae) has the potential for the detection of exogenous DNA into the gut. The whole gut or the gut contents were extracted from O. discicolle larvae and adult previously fed on pig carcass. The pig DNA recovery rate was 33.3% in larvae and 25% in adults, indicating that the carrion beetle's gut may be useful for DNA identification of ingested food. Samples with the whole gut or only gut contents showed the same DNA recovery rate. Exogenous DNA from the whole gut was recovered from samples stored in ethanol at -20 ºC for 11 days, showing that samples of O. discicolle can be stored in the forensic laboratory without loss in DNA recovery rate. [ABSTRACT FROM AUTHOR]

Inbreeding depression occurs when individuals who are closely related mate and produce offspring with reduced fitness. Although inbreeding depression is a genetic phenomenon, the magnitude of inbreeding depression can be influenced by environmental conditions and parental effects. In this study, we tested whether size‐based parental effects influence the magnitude of inbreeding depression in an insect with elaborate and obligate parental care (the burying beetle, Nicrophorus orbicollis). We found that larger parents produced larger offspring. However, larval mass was also influenced by the interaction between parental body size and larval inbreeding status: when parents were small, inbred larvae were smaller than outbred larvae, but when parents were large this pattern was reversed. In contrast, survival from larval dispersal to adult emergence showed inbreeding depression that was unaffected by parental body size. Our results suggest that size‐based parental effects can generate variation in the magnitude of inbreeding depression. Further work is needed to dissect the mechanisms through which this might occur and to better understand why parental size influences inbreeding depression in some traits but not others. [ABSTRACT FROM AUTHOR]

Burying beetles of the genus Nicrophorus have become a model for studying the evolution of complex parental care in laboratory studies. Nicrophorus species depend on small vertebrate carcasses to breed, which they process and provision to their begging offspring. However, vertebrate carcasses are highly sought after by a wide variety of species and so competition is expected to be critical to the evolution of parental care. Despite this, the competitive environment for Nicrophorus is rarely characterized in the wild and remains a missing factor in laboratory studies. Here, we performed a systematic sampling of Nicrophorus orbicollis living near the southern extent of their range at Whitehall Forest in Clarke County, Georgia, USA. We determined the density of N. orbicollis and other necrophilous species that may affect the availability of this breeding resource through interference or exploitation competition. In addition, we characterize body size, a key trait involved in competitive ability, for all Nicrophorus species at Whitehall Forest throughout the season. Finally, we compare our findings to other published natural history data for Nicrophorines. We document a significantly longer active season than was observed 20 years previously at Whitehall Forest for both N. orbicollis and Nicrophorus tomentosus, potentially due to climate change. As expected, the adult body size of N. orbicollis was larger than N. tomentosus, the only other Nicrophorus species that was captured in 2022 at Whitehall Forest. The other most prevalent insects captured included species in the families Staphylinidae, Histeridae, Scarabaeidae, and Elateridae, which may act as competitors or predators of Nicrophorus young. Together, our results indicate significant variation in intra‐ and interspecific competition relative to populations within the N. orbicollis range. These findings suggest that the competitive environment shows extensive spatiotemporal variation, providing the basis to make predictions for how ecology may influence parenting in this species. [ABSTRACT FROM AUTHOR]

Small vertebrate carcasses represent critical resources for many terrestrial organisms, including burying beetles, which rely on carcasses for survival and breeding. Carcass attributes can influence the reproduction of burying beetles, yet most studies on their breeding ecology have used laboratory-reared carcasses of limited sizes. We conducted breeding and feeding experiments using a wide size range of lab (laboratory mice) and wild carcasses (wild mammals, birds and reptiles) to investigate how carcass size, source and taxon affect various breeding outcomes (e.g. clutch size, brood size and brood mass) of the burying beetle Nicrophorus nepalensis . Our results reveal a hump-shaped relationship between carcass size and breeding performance, with optimal breeding outcomes occurring on medium-sized carcasses. Furthermore, despite the variation in carcass tissue nutritional composition, breeding outcomes and larval growth did not differ between the two carcass sources or among the three wild carcass taxa. Finally, we found a larval quality-quantity trade-off across the range of carcasses examined, with carcass size shaping the larval life-history traits. Overall, these results elucidate how carcass resources may influence the breeding performance of burying beetles. Importantly, our study provides solid evidence validating decades of research using lab carcasses to study the reproductive ecology of burying beetles., Competing Interests: We declare we have no competing interests., (© 2024 The Author(s).)

Abstract Understanding the genetic influences of traits of nonmodel organisms is crucial to understanding how novel traits arise. Do new traits require new genes or are old genes repurposed? How predictable is this process? Here, we examine this question for gene expression influencing parenting behavior in a beetle, Nicrophorus vespilloides. Parental care, produced from many individual behaviors, should be influenced by changes of expression of multiple genes, and one suggestion is that the genes can be predicted based on knowledge of behavior expected to be precursors to parental care, such as aggression, resource defense, and mating on a resource. Thus, testing gene expression during parental care allows us to test expectations of this “precursor hypothesis” for multiple genes and traits. We tested for changes of the expression of serotonin, octopamine/tyramine, and dopamine receptors, as well as one glutamate receptor, predicting that these gene families would be differentially expressed during social interactions with offspring and associated resource defense. We found that serotonin receptors were strongly associated with social and aggression behavioral transitions. Octopamine receptors produced a complex picture of gene expression over a reproductive cycle. Dopamine was not associated with the behavioral transitions sampled here, while the glutamate receptor was most consistent with a behavioral change of resource defense/aggression. Our results generate new hypotheses, refine candidate lists for further studies, and inform the genetic mechanisms that are co‐opted during the evolution of parent–offspring interactions, a likely evolutionary path for many lineages that become fully social. The precursor hypothesis, while not perfect, does provide a starting point for identifying candidate genes.

Recent studies have shown that intraspecific patterns of phenotypic plasticity can mirror patterns of evolutionary diversification among species. This appears to be the case in Nicrophorus beetles. Within species, body size is positively correlated with the size of carrion used to provision larvae and parental performance. Likewise, among species, variation in body size influences whether species exploit smaller or larger carrion and the extent to which larvae depend on parental care. However, it is unclear whether developmental plasticity in response to carcass size, parental care, or both underlie transitions to new carcass niches. We examined this by testing whether variation in the conditions experienced by Nicrophorus vespilloides larvae influenced their ability to breed efficiently upon differently sized carcasses as adults. We found that the conditions experienced by larvae during development played a critical role in determining their ability to use large carcasses effectively as adults. Specifically, individuals that developed with parental care and on large carcasses were best able to convert the resources on a large carcass into offspring when breeding themselves. Our results suggest that parentally induced plasticity can be important in the initial stages of niche expansion. [ABSTRACT FROM AUTHOR]

The widely spread evolutionary strategy of parental care is considered an important driver of social evolution. Although offspring were long thought to primarily interact competitively, recent studies revealed the potential importance of sibling cooperation. Theories suggest that the degree of cooperation in offspring interactions depends on the degree of offspring dependence on parental care: offspring unable to forage on their own should compete more, whereas more independent juveniles may increase the degree of cooperation. In this study, we tested the occurrence of sibling cooperation in the absence of posthatching care in several burying beetle species exhibiting varying degrees of offspring dependence. To this end, we measured larval growth rate and survival in the presence and absence of prehatching care using different brood sizes. We found that sibling cooperation cannot be exclusively explained by offspring dependence on parental care. Although only species with more independent larvae cooperated when receiving prehatching care, larval cooperation occurred across species in the absence of care. The latter result suggests that sibling cooperation was already present in an early ancestor of the genus Nicrophorus. Overall, these findings give important insights into the transition from facultative to obligate family life. [ABSTRACT FROM AUTHOR]

Abstract The sharing of the same food source among parents and offspring can be a driver of the evolution of family life and parental care. However, if all family members desire the same meal, competitive situations can arise, especially if resource depletion is likely. When food is shared for reproduction and the raising of offspring, parents have to decide whether they should invest in self‐maintenance or in their offspring and it is not entirely clear how these two strategies are balanced. In the burying beetle Nicrophorus vespilloides, parents care for their offspring either bi‐ or uniparentally at a vertebrate carcass as the sole food source. The question of whether biparental care in this species offers the offspring a better environment for development compared with uniparental care has been the subject of some debate. We tested the hypothesis that male contribution to biparental brood care has a beneficial effect on offspring fitness but that this effect can be masked because the male also feeds from the shared resource. We show that a mouse carcass prepared by two Nicrophorus beetles is lighter compared with a carcass prepared by a single female beetle at the start of larval hatching and provisioning. This difference in carcass mass can influence offspring fitness when food availability is limited, supporting our hypothesis. Our results provide new insights into the possible evolutionary pathway of biparental care in this species of burying beetles.

Communal breeding, wherein multiple conspecifics live and reproduce together, may generate short-term benefits in terms of defence and reproduction. However, its carry-over effects remain unclear. We experimentally tested the effects of communal breeding on parental care and reproduction in burying beetles (Nicrophorus vespilloides), which use carcasses as breeding resources and provide parental care to offspring. We subjected individuals to communal or non-communal breeding (i.e. pair breeding) during their first breeding event and to non-communal breeding during their second breeding event. We measured the parental care of individuals and of groups and the reproductive success of groups during both breeding events. In communal groups, large individuals became dominant and largely monopolized the carcass, whereas small individuals (i.e. subordinates) had restricted access to the carcass. At the first breeding event, large males in communal groups spent more time providing care than large males in non-communal groups, whereas such an effect was not observed for large females and small individuals. Reproductive successes were similar in communal and non-communal groups, indicating no short-term benefits of communal breeding in terms of reproduction. Compared with males from non-communal groups, males originating from communal groups produced a larger size of brood during their second breeding event, whereas such an effect was not observed for females. Our results demonstrate the sex-specific effects of communal breeding experience on parenting performance and fitness.

1. Understanding how organisms respond to thermal stress can help predict long‐term population viability under projected climate change models. Behavioural plasticity can mediate the impact of thermal stress; however, some behavioural modifications in response to novel environments act maladaptively and could implicate population persistence. 2. Burying beetles (Silphidae: Nicrophorus) have been found to modify traits related to individual fitness to be favourable in their perceived environments. To reproduce, breeding individuals of the nicrophorine genus work together to bury and prepare a suitable vertebrate carcass as food for their developing larvae. 3. Here, we explore how sustained temperature treatments influence traits that closely tie to individual fitness in Nicrophorus marginatus. We measure carcass handling, reproductive output, and activity levels in controlled and elevated temperature treatments. 4. At only 27.5 °C, we observed significantly reduced reproductive success rates, extended carcass handling time, and increased levels of activity when compared to the baseline temperature treatment of 26 °C. Additionally, at 26.5 °C, we document reduced brood size. 5. These findings indicate that slight incremental increases in temperature could have profound effects on burying beetle fitness when experienced for extended periods. [ABSTRACT FROM AUTHOR]

Parental care can be partitioned into traits that involve direct engagement with offspring and traits that are expressed as an extended phenotype and influence the developmental environment, such as constructing a nursery. Here, we use experimental evolution to test whether parents can evolve modifications in nursery construction when they are experimentally prevented from supplying care directly to offspring. We exposed replicate experimental populations of burying beetles (Nicrophorus vespilloides) to different regimes of posthatching care by allowing larvae to develop in the presence (Full Care) or absence of parents (No Care). After only 13 generations of experimental evolution, we found an adaptive evolutionary increase in the pace at which parents in the No Care populations converted a dead body into a carrion nest for larvae. Cross-fostering experiments further revealed that No Care larvae performed better on a carrion nest prepared by No Care parents than did Full Care larvae. We conclude that parents construct the nursery environment in relation to their effectiveness at supplying care directly, after offspring are born. When direct care is prevented entirely, they evolve to make compensatory adjustments to the nursery in which their young will develop. The rapid evolutionary change observed in our experiments suggests there is considerable standing genetic variation for parental care traits in natural burying beetle populations— for reasons that remain unclear. [ABSTRACT FROM AUTHOR]

Comparative experimental study of species can provide insight into behavioral transitions in evolution. The insects offer many such examples for the analysis of parental care. We examined three distantly related species of Nicrophorus and two non‐Nicrophorus silphid beetles for their ability to conceal odors from a carcass that cue competitors that attempt to usurp the resource. We predicted that species with well‐developed parental care would exhibit a heightened ability to conceal a resource from competitors, even when differences in burying behavior and direct defense were experimentally eliminated. Carcasses were provided to male–female pairs in the laboratory for 3 days and then experimentally buried in the field, without parents, to assess discovery by Nicrophorus and vertebrate scavengers. The burying beetles Ni. orbicollis, Ni. sayi and Ni. pustulatus were far more successful in hiding a prepared resource (>76%) from free‐flying Nicrophorus than the less parental Ptomascopus morio or Necrophila americana (<25%). Carcasses provided to P. morio and Ne. americana were also more likely to be discovered by Nicrophorus than non‐prepared control carcasses, suggesting that microbially derived odor cues available to competitors were increased by non‐Nicrophorus interaction with carcasses. In the absence of burial, carcass preparation had no effect on vertebrate scavenging. We hypothesize that the evolution of burying and carcass modification to conceal a discovered resource from diverse competitors, more so than control of microbial decay, was a critical step in the evolutionary transition to monopolization of a small carcass, nesting and extended parental care in the Silphidae. [ABSTRACT FROM AUTHOR]

Understanding the genetic influences of traits of nonmodel organisms is crucial to understanding how novel traits arise. Do new traits require new genes or are old genes repurposed? How predictable is this process? Here, we examine this question for gene expression influencing parenting behavior in a beetle, Nicrophorus vespilloides. Parental care, produced from many individual behaviors, should be influenced by changes of expression of multiple genes, and one suggestion is that the genes can be predicted based on knowledge of behavior expected to be precursors to parental care, such as aggression, resource defense, and mating on a resource. Thus, testing gene expression during parental care allows us to test expectations of this "precursor hypothesis" for multiple genes and traits. We tested for changes of the expression of serotonin, octopamine/tyramine, and dopamine receptors, as well as one glutamate receptor, predicting that these gene families would be differentially expressed during social interactions with offspring and associated resource defense. We found that serotonin receptors were strongly associated with social and aggression behavioral transitions. Octopamine receptors produced a complex picture of gene expression over a reproductive cycle. Dopamine was not associated with the behavioral transitions sampled here, while the glutamate receptor was most consistent with a behavioral change of resource defense/aggression. Our results generate new hypotheses, refine candidate lists for further studies, and inform the genetic mechanisms that are co‐opted during the evolution of parent–offspring interactions, a likely evolutionary path for many lineages that become fully social. The precursor hypothesis, while not perfect, does provide a starting point for identifying candidate genes. [ABSTRACT FROM AUTHOR]

Brood parasites lay their eggs in the nests of other females, thereby shifting the costs of offspring care onto others. Given that care is costly, potential hosts should evolve mechanisms to avoid brood parasitism. Meanwhile, brood parasites should evolve mechanisms to circumvent host defences. Here we investigate whether hosts or intraspecific brood parasites adjust their egg laying behaviour as a mechanism to reduce or increase the effectiveness of brood parasitism. We use the burying beetle Nicrophorus vespilloides as our study system, in which hosts and brood parasites lay their eggs in the soil around a carcass controlled by the host. To test whether females adjust their egg laying behaviour when breeding as a host or brood parasite, we used an experimental design with three treatments: hosts, where focal females bred alongside a smaller female; brood parasites, where focal females bred alongside a larger female; and controls, where focal females bred alone. We used focal females from a narrowly defined size range to control for potential effects of body size. We found that hosts delayed the start of egg laying, which may allow them to recognise brood parasitic offspring that arrive too early. Meanwhile, brood parasites laid their eggs over an extended period, which may increase the chances that their egg laying overlapped with the host. Our results suggest that adjusting egg laying behaviour is a mechanism used by both hosts and brood parasites that may contribute to the differences in reproductive success shown in prior studies. [ABSTRACT FROM AUTHOR]

Parental care is predicted to evolve to mitigate harsh environments, thus adaptive plasticity of care may be an important response to our climate crisis. In biparental species, fitness costs may be reduced by resolving conflict and enhancing cooperation among partners. We investigated this prediction with the burying beetle, Nicrophorus orbicollis, by exposing them to contrasting benign and harsh thermal environments. Despite measurable fitness costs under the harsh environment, sexual conflict persisted in the form of sex‐specific social plasticity. That is, females provided equivalent care with or without males, whereas males with partners deserted earlier and reduced provisioning effort. The interaction of social condition and thermal environment did not explain variation in individual behavior, failing to support a temperature‐mediated shift from conflict to cooperation. Examining selection gradients and splines on cumulative care revealed a likely explanation for these patterns. Contrary to predictions, increased care did not enhance offspring performance under stress. Rather, different components of care were under different selection regimes, with optimization constrained due to lack of coordination between parents. We suggest that the potential for parenting to ameliorate the effects of our climate crisis may depend on the sex‐specific evolutionary drivers of parental care, and that this may be best reflected in components of care. [ABSTRACT FROM AUTHOR]

Parental care has evolved to increase offspring fitness. Burying beetles, which breed on small vertebrate carcasses, engage in extensive parental care, including prehatch carcass preservation using oral and anal secretions and direct posthatch care by regurgitating food for offspring. Aspects of parental care, such as regurgitation, may also act as a means of transmitting beneficial microbes to offspring. To explore the contributions of parental care to microbial transmission, we used Illumina high-throughput sequencing of the 16S rRNA gene to characterize bacterial communities found on prepared carcasses and in the digestive tracts of wild-caught and laboratory-reared adults and in the digestive tracts of larvae that either received or did not receive parental care. We found that the digestive tract bacterial communities of larvae receiving parental care were similar to those of their parents, whereas digestive tract bacterial communities of larvae not receiving parental care were dissimilar to those of their parents. All larval digestive tract bacterial communities were dissimilar from those found on prepared carcasses. Furthermore, we found that the digestive tract bacterial communities did not differ significantly between wild-caught nonreproductive adults and F1 and F2 laboratory-reared nonreproductive adults or between laboratory-reared nonreproductive and reproductive adults. While previous work showed that a prepared carcass may serve to inoculate some larval digestive tract bacteria, the results of the present study suggest that this role may be relatively minor and that parental care is crucial in shaping the gut microbiome of offspring, with aspects of this care, such as parental regurgitation, likely being an important component of the transmission process. Furthermore, as wild-reared and laboratory-reared adults did not vary significantly in their digestive tract bacterial communities, our findings suggest that gut microbiome transmittance within our Nicrophorus defodiens model is likely germane to the natural system. • Parental care plays a role in transmitting gut bacteria to larvae in Nicrophorus defodiens. • Larval gut bacterial communities differ when receiving parental care or not. • Core gut bacteria persist throughout the N. defodiens life cycle. • Reproductive and nonreproductive adults have similar gut bacterial communities. [ABSTRACT FROM AUTHOR]

Asymmetric interference competition, where one species is behaviorally dominant over another, appears widespread in nature with the potential to structure ecological communities through trade-offs between competitive dominance and environmental tolerance. The details of how species interact and the factors that contribute to behavioral dominance, however, are poorly known for most species, yet such details are important for understanding when and why trade-offs occur. Here, we examine behavioral interactions between two species of burying beetles (Coleoptera: Silphidae) that compete for limited breeding resources (i.e., small vertebrate carcasses) in nature, to identify behaviors involved in interference competition and to test if large body size, species identity, or time of arrival best predict behavioral dominance among species. To test these ideas, we placed samesex individuals of Nicrophorus orbicollis (early to mid-summer breeder) and N. tomentosus (late summer to fall breeder) into an enclosure together with a 25-30 g mouse carcass (Mus musculus). We then video-recorded all behaviors, including neutral and aggressive interactions, for 13 h per trial (N = 14 trials). For each interaction, we assigned a winner based on which beetle retained its position instead of fleeing or retained possession of the carcass; the overall behavioral dominant was determined as the individual that won the most interactions over the length of the trial. We found that large body size was the best predictor of behavioral dominance. In most interactions, N. orbicollis was larger and dominant over N. tomentosus; however, when N. tomentosus was larger they outcompeted smaller N. orbicollis, illustrating the importance of body size in aggressive contests. The order of arrival to the carcass (priority effects) did not predict behavioral dominance. The larger size and abundance of N. orbicollis in nature suggest a competitive asymmetry between the species, supporting the idea that N. orbicollis constrains the ability of N. tomentosus to breed earlier in the summer. [ABSTRACT FROM AUTHOR]

Burying beetles (Coleoptera: Silphidae: Nicrophorus) occasionally bury small vertebrate carcasses in animal burrows for use in reproduction. However, few studies have examined how often this burying behavior occurs under natural conditions. Here, I determined the frequency of animal burrow utilization by Nicrophorus concolor by placing rat carcasses in a field without consideration of animal burrow proximity. I observed that 36% of the carcasses were buried in animal burrows. The results suggest that Nicrophorus concolor may frequently utilize animal burrows, which may be important for its reproduction. [ABSTRACT FROM AUTHOR]

Parents and offspring have different optima for the level of parental resource allocation and the timing of nutritional independence. Theoretical models assume that either parents or offspring control the allocation of resources within a brood; however, control may also be mutual. Here, we investigate whether the resolution of parent–offspring conflict is biased towards cues from either the parents' or the offspring's behaviour, or whether the conflict is under mutual control. Importantly, we considered potential shifts in the power continuum over the entire period of juvenile dependency. The burying beetle Nicrophorus vespilloides parents provision food for the larvae, and the larvae solicit food from their parents with conspicuous begging displays. Both parental and larval behaviours change as larvae age. We repeatedly manipulated the age of the brood females care for, thereby creating mismatch between the age of the foster brood and expected age of the brood from the female parent's perspective, over the period of dependency in juvenile development. We found that females adjusted the total amount of provisioning based on the actual age of the brood. However, both the parent and the offspring influenced the levels of food provisioning, which followed neither the expected age of the brood from the parent's perspective nor offspring age. Our results suggest that there is mutual control over parental care, thus contradicting the dichotomous view of control over parental care. We suggest that the mutual influence of both parents and the offspring should be taken into account in development of future theory, as well as empirical studies. [ABSTRACT FROM AUTHOR]

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 second carcass against a virgin competitor.We found that increased allocation to current reproduction reduced future competitive ability, as females that had cared for a small brood were more successful when competing for a second carcass against a virgin competitor than females that had cared for a large brood. In addition, the costs of reproduction were offset by the benefits of feeding from the carcass during an initial breeding attempt, as females that had cared for a small brood were better competitors than virgin females that had no prior access to a carcass, whilst females that had cared for a large brood were similar in competitive ability to virgin females.Our results add to our understanding of the trade‐off between current and future reproduction by showing that this trade‐off can manifest through differences in future competitive ability and that direct benefits of reproduction can offset some of these costs. [ABSTRACT FROM AUTHOR]

The ecology of Pustulated Burying Beetle (Nicrophorus pustulatus, Coleoptera: Silphidae) appears distinct among Nicrophorus species, with evidence of it parasitizing snake eggs and foraging primarily above the ground and into the forest canopy. Here we document an extension of its aberrant ecology and behaviour: a case of N. pustulatus burying 2-day-old live and dead nestlings of Tree Swallow (Tachycineta bicolor, Passeriformes: Hirundinidae) under the nest, behaviour consistent with the early stages of breeding in N. pustulatus. Based on different levels of decomposition, we suspect that N. pustulatus responded to one dead swallow nestling in the brood of five and went on to bury all of the nestlings at the bottom of the nest box. The observation provides the first evidence, to our knowledge, of Nicrophorus burying live vertebrates. [ABSTRACT FROM AUTHOR]

The dynamic terminal investment threshold model posits that the propensity of an individual to terminally invest in response to an immediate survival threat, such as an infection, depends on other factors that alter an individual's residual reproductive value. Here, we explore the potential for dynamic terminal investment in burying beetles, insects that inter small vertebrate carcasses as the sole source of food for their offspring and that exhibit extensive biparental care. We injected males at two different ages with heat-killed bacteria and measured their reproductive output, predicting that immune-challenged males would show a longer period of parental care, consume less of the carcass and produce a greater number of larvae in the current reproductive attempt compared with control males. We further predicted that terminal investment would be more evident in older males than in younger ones. Males challenged with heat-killed bacteria as virgins prior to their first reproductive attempt showed no evidence of terminal investment, whereas these same individuals when challenged at a later age as reproductively experienced breeders in a subsequent reproductive attempt showed increased reproductive output. Older, immune-challenged individuals gained less mass during the time on the carcass than control males, suggesting that this terminal investment was subsidized, at least in part, by males refraining from eating as much of the carcass as they might have otherwise done in the absence of an immune challenge, leaving more carrion for their offspring to consume at the expense of their own maintenance and future reproduction. Because it seems likely than an individual's residual reproductive value decreases with both increasing age and reproductive experience, the context-specific terminal investment shown by immune-challenged males in the current study aligns with theory. • Older male burying beetles terminally invest, but younger males do not. • Older immune-challenged males produced more young than control males. • Older immune-challenged males consumed less of the carcass than control males. • Terminal investment was thus subsidized by older males forgoing feeding. • These results align with the dynamic terminal investment threshold model. [ABSTRACT FROM AUTHOR]

The sharing of the same food source among parents and offspring can be a driver of the evolution of family life and parental care. However, if all family members desire the same meal, competitive situations can arise, especially if resource depletion is likely. When food is shared for reproduction and the raising of offspring, parents have to decide whether they should invest in self‐maintenance or in their offspring and it is not entirely clear how these two strategies are balanced. In the burying beetle Nicrophorus vespilloides, parents care for their offspring either bi‐ or uniparentally at a vertebrate carcass as the sole food source. The question of whether biparental care in this species offers the offspring a better environment for development compared with uniparental care has been the subject of some debate. We tested the hypothesis that male contribution to biparental brood care has a beneficial effect on offspring fitness but that this effect can be masked because the male also feeds from the shared resource. We show that a mouse carcass prepared by two Nicrophorus beetles is lighter compared with a carcass prepared by a single female beetle at the start of larval hatching and provisioning. This difference in carcass mass can influence offspring fitness when food availability is limited, supporting our hypothesis. Our results provide new insights into the possible evolutionary pathway of biparental care in this species of burying beetles. [ABSTRACT FROM AUTHOR]

Sibling rivalry is commonplace within animal families, yet offspring can also work together to promote each other's fitness. Here we show that the extent of parental care can determine whether siblings evolve to compete or to cooperate. Our experiments focus on the burying beetle Nicrophorus vespilloides, which naturally provides variable levels of care to its larvae. We evolved replicate populations of burying beetles under two different regimes of parental care: Some populations were allowed to supply posthatching care to their young (Full Care), while others were not (No Care). After 22 generations of experimental evolution, we found that No Care larvae had evolved to be more cooperative, whereas Full Care larvae were more competitive. Greater levels of cooperation among larvae compensated for the fitness costs caused by parental absence, whereas parental care fully compensated for the fitness costs of sibling rivalry. We dissected the evolutionary mechanisms underlying these responses by measuring indirect genetic effects (IGEs) that occur when different sibling social environments induce the expression of more cooperative (or more competitive) behavior in focal larvae. We found that indirect genetic effects create a tipping point in the evolution of larval social behavior. Once the majority of offspring in a brood start to express cooperative (or competitive) behavior, they induce greater levels of cooperation (or competition) in their siblings. The resulting positive feedback loops rapidly lock larvae into evolving greater levels of cooperation in the absence of parental care and greater levels of rivalry when parents provide care. [ABSTRACT FROM AUTHOR]

With growing numbers of sequenced genomes, increasing numbers of duplicate genes are being uncovered. Here we examine Malvolio, a gene in the natural resistance-associated macrophage protein (Nramp) family, that has been duplicated in the subsocial beetle, Nicrophorus vespilloides, which exhibits advanced parental behavior. There is only one copy of Mvl in honey bees and Drosophila, whereas in vertebrates there are two copies that are subfunctionalized. We first compared amino acid sequences for Drosophila, beetles, mice, and humans. We found a high level of conservation between the different species, although there was greater variation in the C-terminal regions. A phylogenetic analysis across multiple insect orders suggested that Mvl has undergone several independent duplications. To examine the potential for different functions where it has been duplicated, we quantified expression levels of Mvl1 and Mvl2 in eight tissues in N. vespilloides. We found that while Mvl1 was expressed ubiquitously, albeit at varying levels, expression of Mvl2 was limited to brain and midgut. Because Mvl has been implicated in behavior, we examined expression during different behavioral states that reflected differences in opportunity for social interactions and expression of parental care behaviors. We found differing expression patterns for the two copies, with Mvl1 increasing in expression during resource preparation and feeding offspring, and Mvl2 decreasing in these same states. Given these patterns of expression, along with the protein analysis, we suggest that Mvl in N. vespilloides has experienced sub/neofunctionalization following its duplication, and may be evolving differing and tissue-specific roles in behavior and physiology.

The increasing prevalence of antibiotic-resistant human pathogens is a growing public concern and there is intense pressure to identify new antibacterial compounds that can be developed into antibiotics with novel mode of action. Evolutionary theory predicts that insects that have evolved to occupy sophisticated ecological niches by feeding and reproducing on carcasses will depend on their gut microbiome to prevent colonization by invading pathogens taken up with the diet. This inspired our hypothesis that the complex interactions between the core microbiome and the more flexible microbial communities dependent on the environment may promote the outsourcing of antibiotic synthesis to beneficial microbes. We tested this hypothesis by cultivating and characterizing bacteria isolated from the gut of the burying beetle Nicrophorus vespilloides, which feeds and reproduces on small vertebrate carcasses buried in the soil to avoid competitors such as fly maggots. The extracts of isolated bacteria were screened for activity against human pathogens such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans. More than 400 strains were isolated, among which the crude extract of Serratia marcescens 2MH3-2 displayed promising activity against Staphylococcus aureus. Bioactivity-guided fractionation enabled purification of the primary antimicrobial compound of the extract. By LC-MS and NMR experiments, it was identified as serrawettin W2 (C38H61N5O9), the antibacterial and nematostatic activity of which was corroborated in our study. We postulate that this antibiotic could contribute to the control of both bacteria and phoretic nematodes in the gut, which compete for food when transferred to the carcass. Our study shows that the gut microbiome of N. vespilloides is a promising resource for the screening of antibiotic-producing bacteria.

Understanding how animals respond to and cope with variation in ambient temperature is an important priority. The reason for this is that ambient temperature is a key component of the physical environment that influences offspring performance in a wide range of ectotherms and endotherms. Here, we investigate whether posthatching parental care provides a behavioral mechanism for buffering against the effects of ambient temperature on offspring in the burying beetle Nicrophorus vespilloides. We used a 3 × 2 factorial design where we manipulated ambient temperature (15, 20, or 25 °C) and parental care (presence or absence of a female parent after hatching). We found that the effect of ambient temperature on offspring performance was conditional upon the presence or absence of a caring female. Fewer larvae survived in the absence than in the presence of a caring female at 15 °C while there was no difference in larval survival at 20 and 25 °C. Our results show that parental care buffers against some of the detrimental effects of variation in ambient temperature on offspring. We suggest that posthatching parental care may buffer against such effects by creating a more benign environment or by boosting offspring resilience toward stressors. Our results have important implications for our understanding of the evolution of parental care because they suggest that the evolution of parental care could allow species to expand their geographical range to colonize areas with harsher climatic conditions than they otherwise would tolerate. [ABSTRACT FROM AUTHOR]

The increasing prevalence of antibiotic-resistant human pathogens is a growing public concern and there is intense pressure to identify new antibacterial compounds that can be developed into antibiotics with novel mode of action. Evolutionary theory predicts that insects that have evolved to occupy sophisticated ecological niches by feeding and reproducing on carcasses will depend on their gut microbiome to prevent colonization by invading pathogens taken up with the diet. This inspired our hypothesis that the complex interactions between the core microbiome and the more flexible microbial communities dependent on the environment may promote the outsourcing of antibiotic synthesis to beneficial microbes. We tested this hypothesis by cultivating and characterizing bacteria isolated from the gut of the burying beetle Nicrophorus vespilloides , which feeds and reproduces on small vertebrate carcasses buried in the soil to avoid competitors such as fly maggots. The extracts of isolated bacteria were screened for activity against human pathogens such as Escherichia coli , Pseudomonas aeruginosa , Staphylococcus aureus , and Candida albicans. More than 400 strains were isolated, among which the crude extract of Serratia marcescens 2MH3-2 displayed promising activity against Staphylococcus aureus. Bioactivity-guided fractionation enabled purification of the primary antimicrobial compound of the extract. By LC-MS and NMR experiments, it was identified as serrawettin W2 (C38H61N5O9), the antibacterial and nematostatic activity of which was corroborated in our study. We postulate that this antibiotic could contribute to the control of both bacteria and phoretic nematodes in the gut, which compete for food when transferred to the carcass. Our study shows that the gut microbiome of N. vespilloides is a promising resource for the screening of antibiotic-producing bacteria. [ABSTRACT FROM AUTHOR]

Theory predicts that the outcome of mating interactions should be influenced by the condition of both males and females. First, females should base their mating decisions on reliable cues about male quality, which are often condition dependent. Second, the costs and/or benefits of being choosy during mating may depend on the female's own condition. Finally, when males divide their time between different mating tactics, investment in alternative mating tactics may depend on male condition. Here we examined the effects of male and female nutritional condition on mating behaviour in the burying beetle Nicrophorus vespilloides. We manipulated male and female nutritional condition either during sexual maturation or at the time of mating and monitored female mate choice and male mating tactics. We found that females in poor condition (i.e. starved either during sexual maturation or at the time of mating) preferred to mate with males in good condition over males that were starved at the time of mating. In contrast, well-fed females showed no such preference. Furthermore, males that were starved during sexual maturation increased their investment in alternative mating tactics by spending more time signalling for females. Our results add to evidence suggesting that females in poor condition bias mating towards males in good condition although it is currently unclear why these females are choosier in this species. Ours is the first study to demonstrate that nutritional condition during sexual maturation can influence mating behaviour, which may have implications for the rate and direction of sexual selection. • In burying beetles, females in poor nutritional condition prefer well-fed males. • Well-fed females show no such preference for well-fed males. • Females did not avoid males that were starved during sexual maturation. • Males starved during sexual maturation spent more time signalling for females. [ABSTRACT FROM AUTHOR]

Closely related species with overlapping geographic ranges encounter a significant challenge: they share many ecological traits and preferences but must partition resources to coexist. In Ontario, potentially eleven species of carrion beetles (Coleoptera: Silphidae) live together and require vertebrate carrion for reproduction. Their reliance on an ephemeral and uncommon resource that is unpredictable in space and time is thought to create intense intra- and interspecific competition. Evidence suggests that burying beetle species reduce competition by partitioning carrion for breeding across different habitats, temperatures, and seasons. Here, we test predictions of an alternative axis for partitioning carrion: vertical partitioning between the ground and forest canopy. We conducted a survey of carrion beetles from May to July 2016 at the Queen’s University Biological Station across 50 randomly generated points using baited lethal traps at zero and six metres. Ground traps yielded more species and individuals compared to those in the canopy, and the number of individuals and species caught increased through the season in both trap types. Ground and canopy traps were accurately distinguished by the presence or absence of three species: ground traps contained more Nicrophorus orbicollis and Necrophila americana, while canopy traps contained more Nicrophorus pustulatus. We trapped 253 N. pustulatus in the canopy, but only 60 on the ground. N. pustulatus is thought to be rare across its geographic range, but our results suggest it is uniquely common in canopy habitats, demonstrating a vertical partitioning of habitat and resources. Our results are consistent with N. pustulatus having diverged into canopy habitats as a strategy to coexist with closely related sympatric species when competing for similar resources. We still, however, do not know the traits that allow N. pustulatus to flourish in the canopy, exactly how N. pustulatus uses canopy resources for breeding, or the factors that restrict the expansion of other burying beetles into this habitat.