Sexual selection on performance traits in an Australian lizard with alternative reproductive tactics

Sexual selection shapes the adaptive landscape in complex ways that lead to trait integration. Much of our understanding of selection comes from studies of morphological traits. However, few studies attempt to quantify the form and direction of selection on performance even though it is predicted to be a more direct target of selection in nature. We measured sexual selection on performance traits (bite force, sprint speed and endurance) in an Australian lizard, the Eastern water skink (Eulamprus quoyii). We first staged 123 contests between size-matched males to investigate whether performance traits were important in determining contest outcome. In a second experiment, we established six breeding populations in large replicate semi-natural enclosures to estimate whether performance traits predicted reproductive success. Our results show that none of the performance measures were important in predicting contest outcome and were not generally strong predictors of reproductive success. However, our analyses suggest a complex fitness landscape driven by males adopting different alternative reproductive tactics (ARTs). We provide a rare test of the role performance plays in sexual selection and highlight the need to test common assumptions regarding the link between maximal performance and fitness. Our results suggest that performance traits may not necessarily be direct targets of sexual selection, but rather indirect targets through their integration with morphological and/or behavioural traits, highlighting a need for more explicit tests of the predicted links between performance and fitness.DN was supported by a grant from the Natural Sciences and Engineering Research Council (NSERC) of Canada, an ARC Discovery Early Career Research Award (DECRA) (DE150101774) and UNSW Vice Chancellors Fellowship. This work was also partially funded by an internal grant from Macquarie University to MJW. All procedures were approved by the Animal Ethics Committee at Macquarie University (ARA 2014/036) and the National Parks and Wildlife service of NSW (licence # SL100328)

Evidence for social learning in a family living lizard

This work was funded by the Australian Research Council (DP130102998 to MW and RB). DWAN was supported by an ARC DECRA (DE150101774) and UNSW VC Fellowship. JR was supported by the Natural Sciences and Engineering Research Council of Canada, and Macquarie University.Social learning is widespread among family living species, particularly mammals and birds with relatively high levels of social complexity and overt social interaction. However, the occurrence of social learning has never been documented in lizards with kin-based sociality, which have less obvious social interactions. We tested for social learning in Australian tree skinks (Egernia striolata), a species that commonly lives in family groups in the wild, using a two-step foraging task. Lizards were randomly allocated to either a social learning treatment or a control group and presented first with an instrumental task requiring the displacement of a lid, followed by an association task, consisting of two dishes with different colored lids. Prior to each task, lizards in the social learning treatment observed a trained demonstrator extract a food reward while the control also viewed a conspecific, but in the absence of the foraging task. The social learning treatment and control group solved the instrumental task at similar rates, but in the association task lizards in the social learning treatment made fewer errors and reached our learning criterion sooner. To the best of our knowledge, we present the first evidence for social learning in a lizard with kin-based sociality.Publisher PDFPeer reviewe

Predictors of social dominance and its role in social information use

Thesis by publication.Bibliography: pages 71-72.Introduction -- Chapter 1. Context dependent effects of prior contest experience on contest outcome in water skinks -- Chapter 2. Dominance relationships and social information use in a lizaed Conclusion and future directions.Social dominance is often determined through contest competition (physical combat). There are many factors that can influence the outcome of a contest, however very little is known about how prior contest experience can result in winner-loser effects. An individual’s dominance status can have profound effects on its fitness and behaviour but the effects of dominance on the ability to learn from others remain poorly understood. I use male Eastern Water skinks (Eulamprus quoyii) to understand 1) how prior contest experience influences contest outcome and test whether this depended on assessment stage and 2) the role dominance plays on social information use. I begin by exploring how contest experience influences behavioural traits under different levels of escalation. I show that prior winners were more likely to initiate contests and by doing so, initiators were much more likely to win in non-escalated contests. I then tested the effects of an observer’s dominance status of social information use in two association tasks. Contrary to my predictions, social dominance did not drive differences in social information use. Interestingly, lizards that viewed a demonstrator did not learn faster than the control group. My results, in light of a previous study on this species, seem to suggest that individuals may ignore social information from a demonstrator that may be similar in age or size. To the best of my knowledge, this study is the first to explore the effects on prior contest experience on behaviours in a context-dependent manner and to examine the effects of the outcome of these contests (i.e. dominance status) on social learning in a lizard.Mode of access: World wide web1 online resource (97 pages) 1 colour illustratio

Dominance and social information use in a lizard

Cognition data used for analyses presented in the manuscript: "Dominance and social information use in a lizard"<div><br></div><div>"male.id" = Identification number of a lizard</div><div><br></div><div>"dom" = Two level factor indicating dominance status of </div><div>lizard. Dominant = 1, subordinate = 0</div><div><br></div><div>"treatment" = Two level factor indicating which treatment group lizard is in. 1 = social, control = 0</div><div><br></div><div>"status" = Character variable indicating dominance status and treatment group of lizard. DS = dominant social, DC = dominant control, SS = subordinate social, SC = subordinate control<br></div><div><br></div><div>"svl" = Snout-vent-length of a lizard in millimeters</div><div><br></div><div>"mass" = Mass of a lizard in grams</div><div><br></div><div>"sc.svl" = <i>Z</i>-transformed snout-vent-length of a lizard</div><div><br></div><div>"sc.mass" = <i>Z</i>-transformed mass of a lizard </div><div><br></div><div>"task" = Two level factor indicating task given to lizard. 1 = association task, 0 = reversal</div><div><br></div><div>"trial" = Number of the trial a lizard received a task</div><div><br></div><div>"correct" = Two level factor indicating whether lizard made a correct choice or not. 1 = correct , 0 = incorrect</div><div><br></div><div>"blue.lat" = Latency in seconds of a lizard displacing the dish covered by a blue lid</div><div><br></div><div>"white.lat" = Latency in seconds of a lizard displacing the dish covered by a white lid</div><div><br></div><div>"correct.choice.only" = Two level factor indicating whether lizard only displaced the lid from the correct dish or not. 1 = correct dish only, 0 = both dish</div><div><br></div><div>"lt" = Two level factor indicating when lizard reached the learning criterion on each trial. 1 = has not reached criterion , 0 = reached criterion</div><div><br></div><div>"learnt" = Two level factor indicating whether lizard reached criterion and therefore learnt the task. 1 = learnt , 0 = did not learn</div><div><br></div

Individual variation in thermal plasticity and its impact on mass-scaling

An empirical study that will assess the repeatability of metabolic reaction norms in male L.delicata lizards and how metabolic scaling relationships differ within- and among-individual

The Role of Developmental Temperature on Phenotypic Development and Evolution

Animals live in an ever-changing world, but environmental perturbations are occurring at an alarming rate - threatening biodiversity and population persistence. Developmental plasticity may be an effective solution for animals to cope with environmental variation. However, it is unclear how developmental environments affect consistent phenotypic variability and shape individual responses to environmental variation later in life. Understanding these impacts of developmental environments will be important for populations living in fluctuating environments.I employed experimental and comparative approaches to investigate the impacts of incubation temperatures on phenotypic development in an Australian lizard (Lampropholis delicata). Using ‘pace-of-life’ theory as a framework, I investigated how variation in metabolic rate can result in concordant changes in life history. I used a variety of statistical tools to quantify consistent phenotypic variation of energy metabolism and growth. While development temperatures did not affect metabolic rate and its thermal plasticity, lizards reared in hot temperatures exhibited less consistent individual differences in their metabolic rate. This may be problematic in the context for global warming. However, individuals also consistently varied in their acute thermal plasticity and these consistent individual differences were robust to changes in developmental temperatures. This suggests that populations may harbour the ability to evolve suitable responses to a warming climate. Despite there being no developmental changes in metabolism, we found differences in hatching mass that persisted through to the onset of sexual maturity. Growth, and its heritability, were not affected by developmental environments. Instead, maternal effects may play an important role governing variation in growth.While metabolic rate has been purported to be a causal mechanism for variation in life history strategies, I did not find strong support for this hypothesis. Across 500 species of terrestrial ectotherms, I demonstrated that environmental factors that dictate how animals acquire and allocate resources to reproduction are major drivers to life history variation. The environment is comprised of many facets that interact to give rise to the myriad of variation we observe in nature. My thesis highlights the need to shift away from unifying theories and focus on untangling the complexities of the environment in which animals inhabit. that interact to give rise to the myriad of variation we observe in nature. My thesis highlights the need to shift away from unifying theories and focus on untangling the complexities of the environment in which animals inhabit

Individual variation in thermal plasticity and its impact on mass-scaling

Physiological processes vary widely across individuals and can influence how individuals respond to environmental change. Repeatability in how metabolic rate changes across temperatures (i.e. metabolic thermal plasticity) can influence mass-scaling exponents in different thermal environments. Moreover, repeatable plastic responses are necessary for reaction norms to respond to selective forces which is important for populations living in fluctuating environments. Nonetheless, only a small number of studies have explicitly quantified repeatability in metabolic plasticity, and fewer have explored how it can impact mass-scaling. We repeatedly measured standard metabolic rate of n = 42 delicate skinks Lampropholis delicata at six temperatures over the course of four months (N = 4952). Using hierarchical statistical techniques, we accounted for multi-level variation and measurement error in our data in order to obtain more precise estimates of reaction norm repeatability and mass-scaling exponents at different acute temperatures. Our results show that individual differences in metabolic thermal plasticity were somewhat consistent over time (R = 0.25, 95% CI = 2.48 × 10 – 0.67), however estimates were associated with a large degree of error. After accounting for measurement error, which decreased steadily with temperature, we show that among individual variance remained consistent across all temperatures. Congruently, temperature specific repeatability of average metabolic rate was stable across temperatures. Cross-temperature correlations were positive but were not uniform across the reaction norm. After taking into account multiple sources of variation, our estimates for mass-scaling did not change with temperature and were in line with published values for snakes and lizards. This implies that repeatable plastic responses may promote thermal stability of scaling exponents. Our work contributes to understanding how energy expenditure scales with abiotic and biotic factors and the capacity for reaction norms to respond to selection. [observations] slope −

Sexual selection on whole-organism performance traits in an Australian lizard with alternative reproductive tactics

Understanding selection on performance (bite force, sprint speed, and endurance) and how it variation in selection on traits relate to ARTs and sexual dimorphis

Evidence for Social Learning in a Family Living Lizard

Social learning is widespread among family living species, particularly mammals and birds with relatively high levels of social complexity and overt social interaction. However, the occurrence of social learning has never been documented in lizards with kin-based sociality, which have less obvious social interactions. We tested for social learning in Australian tree skinks (Egernia striolata), a species that commonly lives in family groups in the wild, using a two-step foraging task. Lizards were randomly allocated to either a social learning treatment or a control group and presented first with an instrumental task requiring the displacement of a lid, followed by an association task, consisting of two dishes with different colored lids. Prior to each task, lizards in the social learning treatment observed a trained demonstrator extract a food reward while the control also viewed a conspecific, but in the absence of the foraging task. The social learning treatment and control group solved the instrumental task at similar rates, but in the association task lizards in the social learning treatment made fewer errors and reached our learning criterion sooner. To the best of our knowledge, we present the first evidence for social learning in a lizard with kin-based sociality

Divide and conquer? Size adjustment with allometry and intermediate outcomes

Abstract Many trait measurements are size-dependent, and while we often divide these traits by size before fitting statistical models to control for the effect of size, this approach does not account for allometry and the intermediate outcome problem. We describe these problems and outline potential solutions