Aim
Physiological responses to climate can be used to quantify the environmental limits that a species can tolerate and are, therefore, key to biogeographical studies. Several ecophysiological ...responses to climatic factors may shape the distribution of species, but our knowledge is mostly centred in thermal ecophysiology. We applied an integrative approach to investigate how ecophysiological responses of a small ectotherm are modulated by climatic variation across an elevational gradient.
Location
Victoria, Australia.
Taxon
Lampropholis guichenoti (Scincidae, Squamata).
Methods
We examined metabolic rate, evaporative water loss, thermal physiology and locomotor performance, of four populations of the skink Lampropholis guichenoti across an elevational gradient in Australia (17–1546 m). We applied biophysical modelling to test how behaviour impacts the survival and activity of these skinks.
Results
Populations from the lowlands had lower metabolic rates and evaporative water loss, lower thermal preferences, higher optimal temperatures and increased locomotor performance compared populations from high elevations. Biophysical models revealed that behaviour allows skinks from high elevation to maintain their body temperatures above freezing and is key to determining activity patterns.
Main conclusions
Our holistic study shows that a combination of physiological and behavioural responses allows ectotherms to survive in different climatic environments. The interplay between physiology and behaviour can help to explain how climate sets limits for the geographical range of ectotherms.
ABSTRACT
Animal behaviour is remarkably sensitive to disruption by chemical pollution, with widespread implications for ecological and evolutionary processes in contaminated wildlife populations. ...However, conventional approaches applied to study the impacts of chemical pollutants on wildlife behaviour seldom address the complexity of natural environments in which contamination occurs. The aim of this review is to guide the rapidly developing field of behavioural ecotoxicology towards increased environmental realism, ecological complexity, and mechanistic understanding. We identify research areas in ecology that to date have been largely overlooked within behavioural ecotoxicology but which promise to yield valuable insights, including within‐ and among‐individual variation, social networks and collective behaviour, and multi‐stressor interactions. Further, we feature methodological and technological innovations that enable the collection of data on pollutant‐induced behavioural changes at an unprecedented resolution and scale in the laboratory and the field. In an era of rapid environmental change, there is an urgent need to advance our understanding of the real‐world impacts of chemical pollution on wildlife behaviour. This review therefore provides a roadmap of the major outstanding questions in behavioural ecotoxicology and highlights the need for increased cross‐talk with other disciplines in order to find the answers.
Pharmaceutical pollution is a major driver of global change, with the capacity to alter key behavioural and physiological traits in exposed animals. Antidepressants are among the most commonly ...detected pharmaceuticals in the environment. Despite well-documented pharmacological effects of antidepressants on sleep in humans and other vertebrates, very little is known about their ecologically relevant impacts as pollutants on non-target wildlife. Accordingly, we investigated the effects of acute 3-day exposure of eastern mosquitofish (Gambusia holbrooki) to field-realistic levels (nominal concentrations: 30 and 300 ng/L) of the widespread psychoactive pollutant, fluoxetine, on diurnal activity patterns and restfulness, as indicators of disruptions to sleep. We show that exposure to fluoxetine disrupted diel activity patterns, which was driven by augmentation of daytime inactivity. Specifically, unexposed control fish were markedly diurnal, swimming farther during the day and exhibiting longer periods and more bouts of inactivity at night. However, in fluoxetine-exposed fish, this natural diel rhythm was eroded, with no differences in activity or restfulness observed between the day and night. As a misalignment in the circadian rhythm has been shown to adversely affect fecundity and lifespan in animals, our findings reveal a potentially serious threat to the survival and reproductive success of pollutant-exposed wildlife.
Display omitted
•Pharmaceutical compounds are entering the environment at an unprecedented rate.•The pharmaceutical pollutant fluoxetine disrupts circadian rhythms of wild fish.•Disruptions to diel activity patterns was driven by increased daytime inactivity.•Misalignments in circadian rhythms have been shown to adversely affect lifespan.
•Flow-through respirometry revealed a high and narrow thermoneutral zone (33–42 °C).•Evaporative water loss increased sharply above 33 °C.•Despite panting above 40 °C, nestlings were unable to fully ...dissipate metabolic heat.•Nestlings are at high risk of dehydration with limited ability for cooling.
Froese and Pauly argue that our model is contradicted by the observation that fish reproduce before their growth rate decreases. Kearney and Jusup show that our model incompletely describes growth ...and reproduction for some species. Here we discuss the costs of reproduction, the relationship between reproduction and growth, and propose tests of models based on optimality and constraint.
The effect of temperature on the evolution of metabolism has been the subject of debate for a century; however, no consistent patterns have emerged from comparisons of metabolic rate within and among ...species living at different temperatures. We used experimental evolution to determine how metabolism evolves in populations of Drosophila melanogaster exposed to one of three selective treatments: a constant 16°C, a constant 25°C, or temporal fluctuations between 16 and 25°C. We tested August Krogh’s controversial hypothesis that colder environments select for a faster metabolism. Given that colder environments also experience greater seasonality, we also tested the hypothesis that temporal variation in temperature may be the factor that selects for a faster metabolism. We measured the metabolic rate of flies from each selective treatment at 16, 20.5, and 25°C. Although metabolism was faster at higher temperatures, flies from the selective treatments had similar metabolic rates at each measurement temperature. Based on variation among genotypes within populations, heritable variation in metabolism was likely sufficient for adaptation to occur. We conclude that colder or seasonal environments do not necessarily select for a faster metabolism. Rather, other factors besides temperature likely contribute to patterns of metabolic rate over thermal clines in nature.
Physiology is crucial for the survival of invasive species in new environments. Yet, new climatic conditions and the limited genetic variation found within many invasive populations may influence ...physiological responses to new environmental conditions. Here, we studied the case of the delicate skinks (
Lampropholis delicata
) invading Lord Howe Island (LHI), Australia. On LHI, the climate is different from the mainland source of the skinks, and independent introduction events generated invasive populations with distinct genetic backgrounds. To understand how climate and genetic background may shape physiological responses along biological invasions, we compared the physiological traits of a source and two invasive (single-haplotype and multi-haplotype) populations of the delicate skink. For each population, we quantified physiological traits related to metabolism, sprint speed, and thermal physiology. We found that, for most physiological traits analysed, population history did not influence the ecophysiology of delicate skinks. However, invasive populations showed higher maximum speed than the source population, which indicates that locomotor performance might be a trait under selection during biological invasions. As well, the invasive population with a single haplotype was less cold-tolerant than the multi-haplotype and source populations. Our results suggest that limited genetic variability and climate may influence physiological responses of invasive organisms in novel environments. Incorporating the interplay between genetic and physiological responses into models predicting species invasions can result in more accurate understanding of the potential habitats those species can occupy.
Thermal conditions in the developmental environment can substantially affect an individual's phenotype, particularly in egg-laying ectotherms. However, whether these effects persist into adulthood is ...rarely examined. To investigate this, we incubated delicate skink,
, eggs at either cool (22°C), mild (26°C) or hot (30°C) temperatures. After hatching, we measured growth, thermal performance curves of locomotor activity, and thermal sensitivity of resting metabolic rate of offspring as juveniles (4-6 weeks of age), sub-adults (approx. 200 days of age), and adults (approx. 2 years of age), and then measured developmental temperature impacts on male fertility. Incubation temperature had a lasting effect on growth and locomotor performance, with cool and hot incubation temperatures resulting in faster growth and larger maximum size, and hot incubation temperatures reducing locomotor performance at all timepoints. Effects on resting metabolic rate were only present in sub-adults, with a higher metabolic rate at high and average body mass and negative metabolic scaling exponent in cool-incubated lizards. Additionally, cool and hot incubation treatments resulted in shorter sperm midpieces and heads. Incubation temperature did not affect testis mass or sperm count. Overall, our results demonstrate that incubation temperature can have lasting effects on later life stages, highlighting the importance of maternal nest-site selection, but that some effects are age dependent. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'.
A search for neutral heavy leptons (NHLs) has been performed using an instrumented decay channel at the NuTeV (E-815) experiment at Fermilab. The data were examined for NHLs decaying into muonic ...final states ({mu}{mu}{nu} , {mu}e{nu} , {mu}{pi} , and {mu}{rho} ); no evidence has been found for NHLs in the 0.25-2.0 GeV mass range. This analysis places limits on the mixing of NHLs with standard light neutrinos at a level up to an order of magnitude more restrictive than previous search limits in this mass range. (c) 1999 The American Physical Society.
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