Avoiding the misuse of BLUP in behavioral ecology

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Having recognized that variation around the population-level “Golden Mean” of labile traits contains biologically meaningful information, behavioural ecologists have focused increasingly on exploring the causes and consequences of individual variation in behaviour. These are exciting new directions for the field, assisted in no small part by the adoption of mixed-effects modelling techniques that enable the partitioning of among- and within-individual behavioural variation. It has become commonplace to extract predictions of individual random effects from such models for use in subsequent analyses (for example, between a personality trait and other individual traits such as cognition, physiology, or fitness-related measures). However, these predictions are made with large amounts of error that is not carried forward, rendering further tests susceptible to spurious P values from these individual-level point estimates. We briefly summarize the problems with such statistical methods that are used regularly by behavioural ecologists, and highlight the robust solutions that exist within the mixed model framework, providing tutorials to aid in their implementation.This work was supported by a Biotechnology and Biological Sciences Research Council grant (BB/L022656/1

Mating opportunities and energetic constraints drive variation in age-dependent sexual signalling

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Online Version of Record published before inclusion in an issue: 11 October 2016When males repeatedly produce energetically expensive sexual signals, trade-offs between current and future investment can cause plasticity in age-dependent signalling. Such variation is often interpreted as alternate adaptive strategies: live fast and die young vs. slow and steady. An alternative (yet rarely tested) explanation is that condition-dependent constraints on allocation cause variation in signalling with age (‘late bloomers’ do not have early investment options). Testing this hypothesis is challenging because resource acquisition and allocation are difficult to measure, and energetic reserves both affect and are affected by reproductive effort. We simultaneously manipulated acquisition (through dietary nutrition) and access to potential mates (as a proxy for manipulating sexual trait allocation) in male decorated crickets (Gryllodes sigillatus), while measuring age- and signalling effort-mediated changes in energy storage components. Increased diet quality caused increased signalling effort and energy storage, while access to females increased both the likelihood of and time spent signalling. Males with lower resource budgets signalled less, but still suffered energetic storage loss and viability costs. Our results suggest that energetic constraints, rather than strategic resource accumulation, reduced signalling levels in males with lower resource acquisition ability. Our findings imply a non-adaptive explanation for age-dependent variation in sexual signalling, and an important role for energetic constraints in maintaining the honesty of costly behavioural displays.T.M.H. and L.F.B. were supported by the University of Stirling. J.H. was funded by a University Royal Society Fellowship. J.R. was funded by a NERC studentship (awarded to J.H)

Heightened perception of competition hastens courtship

AbstractWhen animals use costly labile display or signal traits to display to the opposite sex, they face complex decisions regarding the degree and timing of their investment in separate instances of trait expression. Such decisions may be informed by not only the focal individual’s condition (or pool of available resources) but also aspects of the social environment, such as perceptions of same-sex competition or the quality of available mates. However, the relative importance of these factors to investment decisions remains unclear. Here, we use manipulations of condition (through dietary nutrition), recent social environment (exposure to a silenced male, nonsilenced male, female, or isolation), and female mating history (single or multiple male) to test how quickly male decorated crickets (Gryllodes sigillatus) decide to begin courting an available female. We find that males that were previously housed with nonsilenced males started courting the female earlier than other males. Females only mounted males after courtship began. Our results suggest a strong effect of the perception of competition on the decision to invest resources in sexual signaling behavior and that females might exert directional selection on its timing.</jats:p

Contributions of genetic and non‐genetic sources to variation in cooperative behaviour in a cooperative mammal

This is the author accepted manuscript. the final version is available from Wiley via the DOI in this recordData archiving: Data and code for reproducing the main analyses are available through the Dryad Digital Repository database (https://doi.org/10.5061/dryad.cfxpnvx68). The data and code for the meta-analysis of heritability estimates of selected traits in wild mammals are available in Files S3–S5.The evolution of cooperative behavior is a major area of research among evolutionary biologists and behavioral ecologists, yet there are few estimates of its heritability or its evolutionary potential, and long-term studies of identifiable individuals are required to disentangle genetic and nongenetic components of cooperative behavior. Here, we use long-term data on over 1800 individually recognizable wild meerkats (Suricata suricatta) collected over 30 years and a multigenerational genetic pedigree to partition phenotypic variation in three cooperative behaviors (babysitting, pup feeding, and sentinel behavior) into individual, additive genetic, and other sources, and to assess their repeatability and heritability. In addition to strong effects of sex, age, and dominance status, we found significant repeatability in individual contributions to all three types of cooperative behavior both within and across breeding seasons. Like most other studies of the heritability of social behavior, we found that the heritability of cooperative behavior was low. However, our analysis suggests that a substantial component of the repeatable individual differences in cooperative behavior that we observed was a consequence of additive genetic variation. Our results consequently indicate that cooperative behavior can respond to selection, and suggest scope for further exploration of the genetic basis of social behaviorEuropean Union Horizon 2020Human Frontier Science ProgramUniversity of Zurich.Swiss National Science FoundationMammal Research Institute at the University of Pretoria, South Afric

Age-dependent variation in the terminal investment threshold in male crickets

This is the author accepted manuscript, made available online by the publisher 1st February 2018. Final version to be available from the publisher via the DOI in this record.The terminal investment hypothesis proposes that decreased expectation of future reproduction (e.g., arising from a threat to survival) should precipitate increased investment in current reproduction. The level at which a cue of decreased survival is sufficient to trigger terminal investment (i.e., the terminal investment threshold) may vary according to other factors that influence expectation for future reproduction. We test whether the terminal investment threshold varies with age in male crickets, using heat-killed bacteria to simulate an immune-inducing infection. We measured calling effort (a behavior essential for mating) and hemolymph antimicrobial activity in young and old males across a gradient of increasing infection cue intensity. There was a significant interaction between the infection cue and age in their effect on calling effort, confirming the existence of a dynamic terminal investment threshold: young males reduced effort at all infection levels, whereas old males increased effort at the highest levels relative to naïve individuals. A lack of a corresponding decrease in antibacterial activity suggests that altered reproductive effort is not traded against investment in this component of immunity. Collectively, these results support the existence of a dynamic terminal investment threshold, perhaps accounting for some of the conflicting evidence in support of terminal investment. This article is protected by copyright. All rights reserved.This research was funded, in part, by a grant from the National Science Foundation IOS 16-54028 (SKS, BMS, and JH), grants from the Beta Lambda Chapter of the Phi Sigma Biological Honor Society, Graduate Student Association of Illinois State University, Animal Behavior Society, and Orthopterists‘ Society to KRD, and an Illinois State University Summer Faculty Fellowship and Faculty Research Award to SKS

Cooperative interactions within the family enhance the capacity for evolutionary change in body size

Classical models of evolution seldom predict the rate at which populations evolve in the wild. One explanation is that the social environment affects how traits change in response to natural selection. Here, we determine how social interactions between parents and offspring, and among larvae, influence the response to experimental selection on adult size. Our experiments focus on burying beetles (Nicrophorus vespilloides), whose larvae develop within a carrion nest. Some broods exclusively self-feed on the carrion while others are also fed by their parents. We found populations responded to selection for larger adults but only when parents cared for their offspring. We also found populations responded to selection for smaller adults too, but only by removing parents and causing larval interactions to exert more influence on eventual adult size. Comparative analyses revealed a similar pattern: evolutionary increases in species size within the genus Nicrophorus are associated with the obligate provision of care. Synthesising our results with previous studies, we suggest that cooperative social environments enhance the response to selection whereas excessive conflict can prevent further directional selection

Vertically transmitted rhabdoviruses are found across three insect families and have dynamic interactions with their hosts.

A small number of free-living viruses have been found to be obligately vertically transmitted, but it remains uncertain how widespread vertically transmitted viruses are and how quickly they can spread through host populations. Recent metagenomic studies have found several insects to be infected with sigma viruses ($\textit{Rhabdoviridae}$). Here, we report that sigma viruses that infect Mediterranean fruit flies ($\textit{Ceratitis capitata}$), $\textit{Drosophila}$ immigrans, and speckled wood butterflies ($\textit{Pararge aegeria}$) are all vertically transmitted. We find patterns of vertical transmission that are consistent with those seen in $\textit{Drosophila}$ sigma viruses, with high rates of maternal transmission, and lower rates of paternal transmission. This mode of transmission allows them to spread rapidly in populations, and using viral sequence data we found the viruses in $\textit{D. immigrans}$ and $\textit{C. capitata}$ had both recently swept through host populations. The viruses were common in nature, with mean prevalences of 12% in $\textit{C. capitata}$, 38% in $\textit{D. immigrans}$ and 74% in $\textit{P. aegeria}$. We conclude that vertically transmitted rhabdoviruses may be widespread in a broad range of insect taxa, and that these viruses can have dynamic interactions with their hosts.B.L. is supported by a Sir Henry Dale Fellowship jointly funded by the Wellcome Trust and the Royal Society (grant no. 109356/Z/15/Z). B.L. and F.M.J. are supported by an NERC grant no. (NE/L004232/1 http://www.nerc.ac.uk/) and by an ERC grant (281668, DrosophilaInfection, http://erc.europa.eu/). P.T.L., T.C. and L.A.F. are supported by a BBSRC grant no. (BB/K000489/1)

Aggregating behaviour in invasive Caribbean lionfish is driven by habitat complexity

Caribbean lionfish (Pterois spp.) are considered the most heavily impacting invasive marine vertebrate ever recorded. However, current management is largely inadequate, relying on opportunistic culling by recreational SCUBA divers. Culling efficiency could be greatly improved by exploiting natural aggregations, but to date this behaviour has only been recorded anecdotally, and the drivers are unknown. We found aggregations to be common in situ, but detected no conspecific attraction through visual or olfactory cues in laboratory experiments. Aggregating individuals were on average larger, but showed no further differences in morphology or life history. However, using visual assessments and 3D modelling we show lionfish prefer broad-scale, but avoid fine-scale, habitat complexity. We therefore suggest that lionfish aggregations are coincidental based on individuals’ mutual attraction to similar reef structure to maximise hunting efficiency. Using this knowledge, artificial aggregation devices might be developed to concentrate lionfish densities and thus improve culling efficiency