Matthew D. Hall - Research & Publications

The importance of listening: juvenile allocation shifts in response to acoustic cues of the social environment

Matt H. — Mon, 30 May 2011 11:36:43 +0000

The social environment has a strong effect on the strength and direction of sexual selection. Juveniles, however, often have social cues that signal the current competitive environment which may provide cues of future competitive challenges. Here we demonstrate that juvenile crickets (Teleogryllus commodus) use the calls of surrounding adult males as a cue of the quality and density of rivals/mates they are likely to encounter. We reared hatchling crickets in six acoustic environments that varied in the density and quality of calls and demonstrate that individuals modified their development rate, phenotype and behaviour at maturity. Males matured more rapidly at a smaller size and called more when reared in a low competition environment. In contrast, males delayed maturity to grow larger when faced with an increased density of high-quality males. Females matured more rapidly when reared in a high density of high-quality males and allocated proportionately more resources towards egg production. A second experiment limiting nutrient availability demonstrates sex-specific allocation shifts in the last stadium when cues are most reliable. Our results demonstrate that the social environment significantly affects allocation strategies and phenotypes, highlighting the importance of juvenile experience and competitive context when examining fitness and selection.

Authors: Michael M. Kasumovic, Matthew D. Hall, Heather Try & Robert C. Brooks

Link: http://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2011.02267.x/abstract

Filed under: Papers Tagged: Cricket, Plasticity, Quality, Sexual Selection, Social, Teleogryllus

Inbreeding and courtship calling in the cricket Teleogryllus commodus

Matt H. — Thu, 18 Nov 2010 12:05:47 +0000

Male field crickets produce two acoustic signals for mating: advertisement calls and courtship calls. While the importance of advertisement calling in mate attraction is well understood, the function of courtship calling is less clear. Here, we tested if the courtship call of male crickets Teleogryllus commodus signals aspects of male quality by comparing the calls of inbred and outbred males. We examined the effect of one generation of full sibling mating on fine-scale call structure, along with several life history traits. Inbreeding reduced nymph survival but had no significant effect on weight or development time. Inbreeding resulted in a small but significant change in two of the six call parameters measured. We then tested if inbreeding affects call trait combinations that are important to females by using the results of a previous selection analysis to compare the multivariate attractiveness of the calls of inbred and outbred males. There was no difference. We conclude that the courtship call of T. commodus is not a reliable signal of aspects of male quality that are affected by inbreeding (which generally reduces fitness-enhancing traits). It might, however, signal components of male fitness that are not affected by changes in heterozygosity.

Authors: Jean M. Drayton, Richard M. C. Miller, Matthew D. Hall & Michael D. Jennions

Link: http://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2010.02135.x/full

Filed under: Papers Tagged: Attractiveness, Courtship Call, Inbreeding, Quality, Sexual Selection, Teleogryllus

The adaptive value of functional and life-history traits across fertility treatments in an annual plant

Matt H. — Thu, 18 Nov 2010 10:44:33 +0000

Background and Aims: Plant functional traits are assumed to be adaptive. As selection acts on individuals and not on traits, interpreting the adaptive value of a trait not may be straightforward. For example, productive leaves are associated with fertile environments. However, it is not clear if productive leaves confer an advantage in these habitats, or if they are an advantage as part of a suite of coordinated traits.

Methods Genotypes of Arabidopsis thaliana were grown in high and low nutrient treatments and low, neutral and high pH treatments. Nutrient availability is reduced in acidic or basic soils relative to neutral pH soils. pH treatments were used to alter the availability of resources rather than the amount of resources.

Key Results: Leaf function (specific leaf area, SLA) and life history (size at reproduction, age at reproduction) were variable across genotypes and were plastic. High nutrient availability induced higher SLA and larger size at reproduction. Genotypes that reproduced at large size in high nutrient conditions at neutral pH had the greatest fruit production. SLA was only indirectly related to fruit production through a causal relationship with rosette size; in high nutrient conditions, plants with high SLA were large at reproduction and had higher fruit production. In high nutrient and high pH treatments, plants were large at reproduction, but large size at reproduction was associated with low fecundity. This suggests that large size is adaptive under high nutrient availability.

Conclusions: Interpreting the adaptive value of functional traits will sometimes only be possible when these traits are considered as a suite of correlated and coordinated traits. Leaf functional traits may be important in defining adaptive strategies in A. thaliana but only through how they affect plant life history. Finally, manipulating soil pH can be a valuable tool in assessing adaptive plasticity on nutrient gradients.

Authors: Stephen P. Bonser, Brenton Ladd, Keyne Monro, Matthew D. Hall and Michael A. Forster.

Link: http://aob.oxfordjournals.org/content/early/2010/09/29/aob.mcq195.abstract

Filed under: Papers Tagged: Adaptive Plasticity, Arabidopsis, Functional Traits, Nutrients, Path Analysis, Plants

Performance is no proxy for genetic quality: trade-offs between locomotion, attractiveness, and life history in crickets

Matt H. — Fri, 07 May 2010 15:53:01 +0000

The genetic relationships among traits contributing to overall fitness are an important subject of inquiry because such relationships influence how suites of traits respond to selection. Within the field of sexual selection, these relationships are also of interest for assessing whether any given trait can be used as a proxy for total fitness. A growing number of studies have demonstrated close links between whole-organism performance traits and determinants of individual fitness; however, an understanding of the genetic relationships between performance and important aspects of genetic quality is currently lacking. We present the results of a quantitative genetic study in which we estimate covariation between a locomotor performance trait (maximal jumping ability), calling effort, sexual attractiveness, and life-history traits in male Teleogryllus commodus crickets. We show that the major axis of genetic variation (g_max) is characterized by a contrast between jump performance and life-history traits associated with mating success. Moreover, two additional axes of significant multivariate genetic variation exist, each characterized by strong contrasts among traits. These results argue against the existence of a single axis representing genetic quality, favoring instead the idea that resource allocation strategies shape multiple dimensions of genetic quality through trade-offs among key life-history traits, including performance.

Authors: Simon P. Lailvaux, Matthew D. Hall, and Robert C. Brooks

Link: http://www.esajournals.org/doi/abs/10.1890/09-0963.1

Filed under: Papers Tagged: Attractiveness, Genetic Quality, Life-history, Lifespan, Performance, Quantitative genetics, Reproduction, Sexual Selection

Sex in a material world: why the study of sexual reproduction and sex-specific traits should become more nutritionally-explicit

Matt H. — Wed, 21 Apr 2010 13:51:48 +0000

Recent advances in nutritional ecology, particularly arising from Ecological Stoichiometry and the Geometric Framework for nutrition, have resulted in greater theoretical coherence and increasingly incisive empirical methodologies that in combination allow for the consideration of nutrient-related processes at many levels of biological complexity. However, these advances have not been consistently integrated into the study of sexual differences in reproductive investment, despite contemporary emphasis on the material costs associated with sexually selected traits (e.g. condition-dependence of exaggerated ornaments). Nutritional ecology suggests that material costs related to sex-specific reproductive traits should be linked to quantifiable underlying differences in the relationship between individuals of each sex and their foods. Here, we argue that applying nutritionally-explicit thought to the study of sexual reproduction should both deepen current understanding of sex-specific phenomena and broaden the tractable frontiers of sexual selection research. In support of this general argument, we examine the causes and consequences of sex-specific nutritional differences, from food selection and nutrient processing to sex-specific reproductive traits. At each level of biological organization, we highlight how a nutritionally-explicit perspective may provide new insights and help to identify new directions. Based on predictions derived at the individual level, we then consider how sex-specific nutrient limitation might influence population growth, and thus potentially broader patterns of life history evolution, using a simple population dynamics model. We conclude by highlighting new avenues of research that may be more accessible from this integrative perspective.

Authors: Nathan I. Morehouse, Takefumi Nakazawa, Christina M. Booher, Punidan D. Jeyasingh and Matthew D. Hall.

Link: http://www3.interscience.wiley.com/journal/123324943/abstract

Filed under: Papers Tagged: Diet, Ecological Stoichiometry, Geometric Framework, Reproduction, Sexual Selection

The assessment of insemination success in yellow dung flies using competitive PCR

Matt H. — Mon, 15 Feb 2010 10:42:00 +0000

In spite of considerable interest in postcopulatory sexual selection, separating the effects of sperm competition from cryptic female choice remains difficult because mechanisms underlying postcopulatory processes are poorly understood. One methodological challenge is to quantify insemination success for individual males within the sperm stores of multiply mated females to discover how insemination translates into eventual paternity. Any proposed method must be applicable in organisms without extensive DNA sequence information (which include the majority of model species for sexual selection). Here, we describe the development and application of microsatellite competitive-multiplex-PCR for quantifying relative contributions to a small number of sperm in storage. We studied how DNA template characteristics affect PCR amplification of known concentrations of mixed DNA and generated regressions for correcting observations of allelic signal strength based on such characteristics. We used these methods to examine patterns of sperm storage in twice-mated female yellow dung flies, Scathophaga stercoraria. We confirm previous findings supporting sperm displacement and demonstrate that average paternity for the last mate accords with the mean proportion of sperm stored. We further find consistent skew in storage across spermathecae, with more last male sperm stored in the singlet spermatheca on one side of the body than in the doublet on the opposite side. We also show that the time between copulations may be important for effectively sorting sperm. Finally, we demonstrate that male size may influence the opportunity for sperm choice, suggesting future work to disentangle the roles of male competition and cryptic female choice.

Authors: Luc F. Bussière, Marco Demont, Andrew J. Pemberton, Matthew D. Hall & Paul I. Ward.

Link: http://www3.interscience.wiley.com/journal/122533899/abstract

Filed under: Papers Tagged: Competitive PCR, Dung flies, Multiple Mating, Paternity, Sexual Selection, Sperm

Competitive PCR reveals the complexity of postcopulatory sexual selection in Teleogryllus commodus

Matt H. — Mon, 18 Jan 2010 13:42:26 +0000

The outcome of mate choice depends on complex interactions between males and females both before and after copulation. Although the competition between males for access to mates and premating choice by females are relatively well understood, the nature of interactions between cryptic female choice and male sperm competition within the female reproductive tract is less clear. Understanding the complexity of postcopulatory sexual selection requires an understanding of how anatomy, physiology and behaviour mediate sperm transfer and storage within multiply mated females. Here we use a newly developed molecular technique to directly quantify mixed sperm stores in multiple mating females of the black field cricket, Teleogryllus commodus. In this species, female postcopulatory choice is easily observed and manipulated as females delay the removal of the spermatophore in favour of preferred males. Using twice-mated females, we find that the proportion of sperm in the spermatheca attributed to the second male to mate with a female (S₂) increases linearly with the time of spermatophore attachment. Moreover, we show that the insemination success of a male increases with its attractiveness and decreases with the size of the female. The effect of male attractiveness in this context suggests a previously unknown episode of mate choice in this species that reinforces the sexual selection imposed by premating choice and conflicts with the outcome of postmating male harassment. Our results provide some of the clearest evidence yet for how sperm transfer and displacement in multiply mated females can lead directly to cryptic female choice, and that three distinct periods of sexual selection operate in black field crickets.

Authors: Matthew D. Hall, Luc F. Bussière, Marco Demont, Paul I. Ward & Robert C. Brooks.

Link: http://www3.interscience.wiley.com/journal/123236246/abstract

Posted in Papers Tagged: Competitive PCR, Cricket, Multiple Mating, Reproduction, Sexual Selection, Sperm, Teleogryllus

Sexual conflict and the maintenance of multivariate genetic variation

Matt H. — Mon, 18 Jan 2010 13:36:26 +0000

Mate choice should erode additive genetic variation in sexual displays, yet these traits often harbour substantial genetic variation. Nevertheless, recent developments in quantitative genetics have suggested that multivariate genetic variation in the combinations of traits under selection may still be depleted. Accordingly, the erosion and maintenance of variation may only be detectable by studying whole suites of traits. One potential process favouring the maintenance of genetic variance in multiple trait combinations is the modification of sexual selection via sexually antagonistic interactions between males and females. Here we consider how interlocus sexual conflict can shape the genetic architecture of male sexual traits in the cricket, Teleogryllus commodus. In this species the ability of each sex to manipulate insemination success significantly alters the selection acting on male courtship call properties. Using a quantitative genetic breeding design we estimated the additive genetic variation in these traits and then predicted the change in variation due to previously documented patterns of sexual selection. Our results indicate that female choice should indeed deplete multivariate genetic variance, but that sexual conflict over insemination success may oppose this loss of variance. We suggest that changes in the direction of selection due to sexually antagonistic interactions will be an important and potentially widespread factor in maintaining multivariate genetic variation.

Authors: Matthew D. Hall, Simon P. Lailvaux, Mark W. Blows & Robert C. Brooks

Link: http://www3.interscience.wiley.com/journal/123226724/abstract

Posted in Papers Tagged: Cricket, Lek paradox, Quantitative genetics, Selection Analysis, Sexual Conflict, Teleogryllus

Interactions among performance capacities predict male combat outcomes in the field cricket

Matt H. — Tue, 27 Oct 2009 12:45:07 +0000

There is a growing appreciation that male fighting ability is influenced by multiple traits. In particular, studies of male combat have identified a variety of performance capacities that predict victory in conflicts between conspecifics in several animal species. However, while multiple aspects of male fighting ability are often examined with a single study, the interactions among traits are rarely considered.
We conducted fight trials between size-matched males in the black field crickets, Teleogryllus commodus, with the aim of testing how two whole-organism performance traits, jumping ability and bite force, together with weight at eclosion, interact to determine combat outcomes. We then examined the relationships between these traits and the outcome of a fight using: a univariate framework, where we examined the difference between winners and losers for each trait separately; and, a multivariate framework known as response surface analysis, where we examined how the interactions amongst traits predict the outcome of a fight.
We show that males that won fights tended to exert significantly more force when biting, but were neither better at jumping nor heavier at eclosion than their rivals. However, when we examined the effects of these three traits while statistically controlling for one another in a multiple regression, we showed that overall fighting ability depends not only on contributions of individual traits to contest resolution, but also on the interactions amongst traits and their relationship to the capabilities of the rival male. We found that the probability of winning was highest for the male with the greatest positive difference from his rival in the combination of bite force, jump power and weight at eclosion.
These findings highlight how studying multiple performance capabilities in isolation from each other may obscure the importance of some variables. Our multivariate analyses revealed that the interactions between multiple dimensions of performance are important in male combat. We discuss the broader implications of these findings, including the role of whole-organism performance in determining male quality.

Authors: Matthew D. Hall, Luke McLaren, Robert C. Brooks & Simon P. Lailvaux

Link: http://www3.interscience.wiley.com/journal/122510840/abstract

Posted in Papers Tagged: Combat, Cricket, Performance, Teleogryllus

Diet-dependent female evolution influences male lifespan in a nuptial feeding insect

Matt H. — Fri, 17 Apr 2009 06:01:36 +0000

Theory predicts that lifespan will depend on the dietary intake of an individual, the allocation of resources towards reproduction and the costs imposed by the opposite sex. Although females typically bear the majority of the cost of offspring production, nuptial feeding invertebrates provide an ideal opportunity to examine the extent to which reproductive interactions through gift provisioning impose a cost on males. Here we use experimental evolution in an Australian ground cricket to assess how diet influences male lifespan and how the costs of mating evolve for males. Our findings show that males had significantly shorter lifespans in populations that adapted to a low-quality diet and that this divergence is driven by evolutionary change in how females interact with males over reproduction. This suggests that the extent of sexual conflict over nuptial feeding may be under-realized by focusing solely on the consequences of reproductive interactions from the female’s perspective.

Authors: Matthew D. Hall, Luc F. Bussière & Robert Brooks

Link: http://www3.interscience.wiley.com/journal/122196937/abstract

Posted in Papers Tagged: Aging, Diet, Evolution, Experimental Evolution, Lifespan, Nuptial gifts, Pteronemobius, Sexual Conflict