Genetic and environmental drivers of colour and pattern in the Australian jacky dragon (Amphibolurus muricatus)

The underlying drivers of variation in the colouration (colour and pattern) of animals can be genetic, non-genetic, or more likely, a combination of both. Understanding the role of heritable genetic elements, as well as non-genetic factors such as age, habitat or temperature, in shaping colouration can provide insight into the evolution and function of these traits, as well as the speed of response to changing environments. This project examined the genetic and non-genetic drivers of continuous variation in colouration in a lizard, the jacky dragon (Amphibolurus muricatus). We leveraged a large captive experiment that manipulated parental and offspring thermal environment to simultaneously estimate the genetic and non-genetic drivers of variation in colouration. We found that the overall brightness, the elongation of the longitudinal stripes on the dorsum and the contrast between light and dark patches of the pattern were all heritable. Colouration varied according to the age of the hatchling; however, the thermal environment of neither the parents nor offspring contributed significantly to colouration. It appears that developmental plasticity and maternal effects associated with temperature are not important drivers of variation in our measures of colouration

Phylogenetics of the skyhoppers (Kosciuscola) of the Australian Alps : evolutionary and conservation implications

The true biodiversity of Australia's alpine and subalpine endemics is unknown. Genetic studies to date have focused on sub-regions and restricted taxa, but even so, indicate deep divergences across small geographic scales and therefore that the bulk of biodiversity remains to be discovered. We aimed to study the phylogeography of the Australian Alps by focusing on the skyhoppers (Kosciuscola), a genus of five species of flightless grasshoppers whose combined distributions both span the region and are almost exclusively contained within it. Our sampling covered 650 km on the mainland and several sites in Tasmania with total of 260 specimens used to reconstruct a robust phylogeny of Koscisucola. Phylogenies were based on single nucleotide polymorphism data generated from double-digested restriction-associated DNA sequencing. Skyhoppers diverged around 2 million years ago and have since undergone complex diversification seemingly driven by climatic oscillations throughout the Pleistocene. We recovered not 5 but 14 clades indicating the presence of many unknown species. Our results support conspicuous geographic features as genetic breaks; e.g. the Murray Valley, and inconspicuous ones; e.g. between the Bogong High Plains and Mt Hotham. Climate change is progressing quickly in the region and its impact, particularly on snow, could have severe consequences for the skyhoppers' overwinter survival. The true diversity of skyhoppers highlights that biodiversity loss in the Alps as a result of climate change is likely to be far greater than what can be estimated based on current species numbers and that management including small geographical scales is key

Predicting species and community responses to global change using structured expert judgement : an Australian mountain ecosystems case study

Conservation managers are under increasing pressure to make decisions about the allocation of finite resources to protect biodiversity under a changing climate. However, the impacts of climate and global change drivers on species are outpacing our capacity to collect the empirical data necessary to inform these decisions. This is particularly the case in the Australian Alps which has already undergone recent changes in climate and experienced more frequent large-scale bushfires. In lieu of empirical data, we used a structured expert elicitation method (the IDEA protocol) to estimate the abundance and distribution of nine vegetation groups and 89 Australian alpine and subalpine species by the year 2050. Experts predicted that most alpine vegetation communities would decline in extent by 2050; only woodlands and heathlands are predicted to increase in extent. Predicted species-level responses for alpine plants and animals were highly variable and uncertain. In general, alpine plants spanned the range of possible responses, with some expected to increase, decrease or not change in cover. By contrast, almost all animal species are predicted to decline or not change in abundance or elevation range; more species with water-centric life-cycles are expected to decline in abundance than other species. While long-term ecological data will always be the gold-standard in informing the future of biodiversity, the method and outcomes outlined here provide a pragmatic and coherent basis upon which to start informing conservation policy and management in the face of rapid change and paucity of data

Turn the temperature to turquoise : cues for colour change in the male chameleon grasshopper (Kosciuscola tristis) (Orthoptera: Acrididae)

Rapid, reversible colour change is unusual in animals, but is a feature of male chameleon grasshoppers (Kosciuscola tristis). Understanding what triggers this colour change is paramount to developing hypotheses explaining its evolutionary significance. In a series of manipulative experiments the author quantified the effects of temperature, and time of day, as well as internal body temperature, on the colour of male K. tristis. The results suggest that male chameleon grasshoppers change colour primarily in response to temperature and that the rate of colour change varies considerably, with the change from black to turquoise occurring up to 10 times faster than the reverse. Body temperature changed quickly (within 10 min) in response to changes in ambient temperature, but colour change did not match this speed and thus colour is decoupled from internal temperature. This indicates that male colour change is driven primarily by ambient temperature but that their colour does not necessarily reflect current internal temperature. I propose several functional hypotheses for male colour change in K. tristis

Towards a tractable working hypothesis for deimatic displays

Upon being agitated, the mountain katydid, Acripeza reticulata, performs a remarkable defensive display that includes a defensive posture, a display of conspicuous coloration and the release of distasteful, possibly toxic, exudate. From our initial investigations this display appears to be best described as a deimatic display. Deimatic displays are conspicuous behaviours that a prey animal performs when it perceives the threat of an imminent attack by a predator. It can cause a predator to stop, slow or pause its attack, allowing the potential prey to escape ( Edmunds, 1974). In Umbers and Mappes (2015) and Umbers, Lehtonen, and Mappes (2015) we recommended that the definition be extended to include both displays performed early, for example before predators make physical contact, and displays that take place late in the predation sequence, for example after physical attacks by the predator ( Endler, 1991 and Umbers and Mappes, 2015). This forum article provides a valuable opportunity to reflect on the classic definition of deimatic displays, how the definition has been used and how it can be refined

Journal of entomology / A

Prey use many strategies to avoid being detected by their predators. However, once detected and identified as potentially palatable, prey must employ a second line of defence such as performing a deimatic (startle) display. During the predation sequence, composed of the stages encounter, detection, identification, approach, subjugation and consumption, such defences should be deployed as the predator approaches, but before prey are brought under the predator's control (i.e. before subjugation). We tested this assumption in the mountain katydid (or bush cricket), which is cryptic at rest, but when disturbed flashes spectacular abdominal colours by lifting its wings, and is chemically defended. We experimentally determined which visual, auditory and tactile stimuli trigger their deimatic display via six treatments. Contrary to expectations of the predation sequence katydids required tactile cues before performing their deimatic display, that is, it was performed only after attempted subjugation. Field experiments also showed that katydids perform their deimatic display after experiencing tactile stimuli. Mountain katydid natural history may explain this counterintuitive behaviour. Being slow and cryptic, katydids cannot effect a fast escape after performing their deimatic display but their tough cuticle and chemical defences make survival of initial subjugation attempts likely. Holding their deimatic display until after initial subjugation may prevent continued attack and avoid the potentially large cost of revealing themselves to predators that have not yet noticed them. Performance of deimatic display after subjugation may be more common than currently recognized and we encourage further investigation

Meta-analytic evidence for quantitative honesty in aposematic signals

The combined use of noxious chemical defences and conspicuous warning colours is a ubiquitous anti-predator strategy. That such signals advertise the presence of defences is inherent to their function, but their predicted potential for quantitative honesty - the positive scaling of signal salience with the strength of protection - is the subject of enduring debate. Here, we systematically synthesized the available evidence to test this prediction using meta-analysis. We found evidence for a positive correlation between warning colour expression and the extent of chemical defences across taxa. Notably, this relationship held at all scales; among individuals, populations and species, though substantial between-study heterogeneity remains unexplained. Consideration of the design of signals revealed that all visual features, from colour to contrast, were equally informative of the extent of prey defence. Our results affirm a central prediction of honesty-based models of signal function and narrow the scope of possible mechanisms shaping the evolution of aposematism. They suggest diverse pathways to the encoding and exchange of information, while highlighting the need for deeper knowledge of the ecology of chemical defences to enrich our understanding of this widespread anti-predator adaptation

The effects of perch height, time in residence and distance from opponent on aggressive display in male lizards

In antagonistic encounters individuals' displays reflect both the quality of the resource under dispute and their perception of the threat posed by their rival. All else being equal, as the value or threat to contested resources increases, so should an individual's level of aggression. Using a territorial species of Australian agamid lizard, the tawny dragon (Ctenophorus decresii), we tested three hypotheses about the relationship between territory quality and aggression. In three experiments we measured aggression whilst manipulating time in residence, perch height as a measure of territory quality and distance to an opponent's territory. Our measurement of aggression was a summary of behaviours used by tawny dragons in antagonistic displays (wrestling, hind-leg push-up display, chasing, raising of nuchal or vertebral crests, back arching, lateral compression, lowering dewlap, jerky walk and tail flick). Animals had significantly lower aggression scores when the opponent's territory was further away, but time in residence and perch height did not affect our measures of aggression. These experimental results provide good grounding for further tests of these hypotheses in field scenarios specifically manipulating distance between neighbours to determine what maintains the spatial distribution of tawny dragons in the wild

Male mate choice in the chameleon grasshopper (Kosciuscola tristis)

In many species, males can increase their fitness by mating with the highest quality females. Female quality can be indicated by cues, such as body size, age and mating status. In the alpine grasshopper Kosciuscola tristis, males can be found riding on subadult females early in the season, and as the season progresses, males engage in fights over ovipositing females. These observations suggest that males may be competing for females that are either unmated (early season) or sperm-depleted (late season). We thus hypothesised that male K. tristis may be choosy in relation to female mating status, and specifically, we predicted that males prefer females that are unmated. We conducted behavioural experiments in which males were given the choice of two females, one mated and one unmated. Contrary to our prediction, males did not mate preferentially with unmated females. However, copulation duration with unmated females was, on average, 24 times the length of copulation with mated females. While female K. tristis can reject mates, we did not observe any evidence of overt female choice during our trials. Females may gain additional benefits from mating multiply and may therefore not readily reject males. While our experiment cannot definitively disentangle female from male control over copulation duration, we suggest that males choose to invest more time in copula with unmated females, perhaps for paternity assurance, and that male mate assessment occurs during copulation rather than beforehand

Colour in insect thermoregulation : empirical and theoretical tests in the colour-changing grasshopper, Kosciuscola tristis

Body colours can result in different internal body temperatures, but evidence for the biological significance of colour-induced temperature differences is inconsistent. We investigated the relationship between body colour and temperature in a model insect species that rapidly changes colour. We used an empirical approach and constructed a heat budget model to quantify whether a colour change from black to turquoise has a role in thermoregulation for the chameleon grasshopper (Kosciuscola tristis). Our study shows that colour change in K. tristis provides relatively small temperature differences that vary greatly with wind speed (0.55 °C at ms-1 to 0.05 °C at 10 ms-1). The biological significance of this difference is unclear and we discuss the requirement for more studies that directly test hypotheses regarding the fitness effects of colour in manipulating body temperature