Showing papers by "David G. Chapple published in 2018"

Integrating thermal physiology within a syndrome: Locomotion, personality and habitat selection in an ectotherm

Abstract: 1. Physiology and temperature can both have a profound influence on behaviour and metabolism. Despite this, thermal physiology has rarely been considered within the animal personality framework, but could be an inherent mechanism maintaining consistent individual differences in behaviour, particularly in species that need to thermoregulate (i.e. ectotherms). 2. Here, we present evidence for a thermal-behavioural syndrome and detail how it is linked to variation in habitat selection in an Australian lizard, the delicate skink, Lampropholis delicata. 3. We predicted that individuals would occur along a cold-hot continuum – analogues to the slow-fast continuum proposed by the pace-of-life hypothesis - whereby an individual’s placement along a thermal physiological axis will correspond with their placement along a personality axis. We first tested the thermal-behavioural syndrome by measuring the thermal preferences and optimal performance temperature of individual skinks and linking it to their activity, exploratory, social and boldness behaviours. 4. In line with our predictions, we found that individuals with a ‘hot’ thermal type performed optimally at higher temperatures, had faster sprint speeds and were more active, explorative and bold relative to ‘cold’ thermal types. 5. We then monitored each individual’s habitat selection within an artificial environment containing three microhabitats differing in their thermal characteristics. 6. We found that an individual’s thermal type mediated their use of habitat, in which ‘hot’ individuals utilised a hotter microhabitat more regularly than both ‘cold’ and ‘intermediate’ thermal types, suggesting that the thermal-behavioural syndrome could drive ecological niche partitioning in this species. 7. We envisage that the thermal-behavioural syndrome concept is likely to extend to other study systems, particularly to ectothermic organisms that rely heavily on behavioural thermoregulation to maintain optimal body temperature.

Behavioural variation and plasticity along an invasive ant introduction pathway.

Abstract: Once established in new areas, introduced species may exhibit changes in their biology due to phenotypic plasticity, novel selection pressures and genetic drift Moreover, the introduction process itself has been hypothesised to act as a selective filter for traits that promote invasiveness We tested the hypothesis that behaviours thought to promote invasiveness-such as increased foraging activity and aggression-are selected for during invasion by comparing traits among native and introduced populations of the widespread Argentine ant (Linepithema humile) We studied Argentine ant populations in the native range in Argentina and in three invaded regions along an introduction pathway: California, Australia and New Zealand In each region, we set up 32 experimental colonies to measure foraging activity and interspecific aggression in a subset of the study regions These colonies were subject to experimental manipulation of carbohydrate availability and octopamine, a biogenic amine known to modulate behaviour in insects, to measure variation in behavioural plasticity We found variation in foraging activity among populations, but this variation was not consistent with selection on behaviour in relation to the invasion process We found that colonies with limited access to carbohydrates exhibited unchanged exploratory behaviour, but higher exploitation activity and lower aggression Colonies given octopamine consistently increased foraging behaviour (both exploration and exploitation), as well as aggression when also sugar-deprived There was no difference in the degree of behavioural response to our experimental treatments along the introduction pathway We did not find support for selection of behavioural traits associated with invasiveness along the Argentine ant's introduction pathway or clear evidence for an association between the introduction process and variation in behavioural plasticity These results indicate that mechanisms promote behavioural variation in a similar fashion both in native and introduced ranges Our results challenge the assumption that introduced populations always perform better in key behavioural traits hypothesised to be associated with invasion success

Evaluating cognition and thermal physiology as components of the pace-of-life syndrome

Abstract: The pace-of-life syndrome (POLS) suggests that behavioral traits are correlated and integrate within a fast–slow physiological continuum. At the fast extreme, individuals having higher metabolic rates are more active, exploratory, and bold with the opposite suite of traits characterizing those at the slow physiological extreme. A recent framework suggests that behavioral types may also differ consistently in their cognitive style. Accordingly, we propose that cognition could be further incorporated into the POLS framework comprised of behavioral and thermal physiological traits. Under this premise, fast behavioral types having high thermal traits are predicted to acquire a novel task faster but at the cost of accuracy while slow behavioral types with low thermal traits would be more attentive, responding to cues at a slower rate leading to higher accuracy and flexibility. This was tested by measuring physiological and behavioral traits in delicate skinks (Lampropholis delicata) and testing their learning ability. Correlations were detected between cognition and behavior but not thermal physiology. Contrary to our predictions, individual positioning along these axes opposed our predicted directions along the fast–slow continuum. Fast lizards preferring lower body temperatures expressed higher activity, exploration, sociality, and boldness levels, and learned the discrimination learning task at a slower rate but made the most errors. Additionally, modelling results indicated that neither thermal physiology, behavior, or their interaction influenced cognitive performance. Although the small number of animals completing the final stages of the learning assays limits the strength of these findings. Thus, we propose that future research involving a greater sample size and number of trials be conducted so as to enhance our understanding into how the integration of cognitive style, behavior, and physiology may influence individual fitness within natural populations.

Calling phenology of a diverse amphibian assemblage in response to meteorological conditions.

Abstract: The strong association between amphibian activity, breeding and recruitment with local environmental conditions raises concerns regarding how changes in climate may affect the persistence of species populations into the future. Additionally, in a highly diverse assemblage of anurans, competition for breeding sites affects the time and duration of activity, as species compete for limited resources such as water. Meteorological conditions are strong drivers of amphibian activity, so we assessed whether temperature, rainfall, atmospheric pressure and humidity were associated with the calling phenology of an assemblage of anurans in South East Queensland, Australia. We performed calling surveys and collected digital recordings at 45 ponds in an area known for high anuran diversity. We performed detection analyses to investigate the influence of 10 meteorological variables in detection of calling activity in 19 amphibian species. Our results suggest four breeding strategies in the assemblage: explosive summer breeders, prolonged breeders, opportunistic breeders and a winter breeder. Classifying these species into associations provides a framework for understanding how species respond to environmental conditions. Explosive breeders (i.e. species demonstrating short and highly synchronised breeding periods) were particularly responsive to temperature. Our findings help elucidate the breeding phenology of frogs and provide valuable information on their mating systems in native Australian forests. This study highlights the difficulties of surveying even common anurans. We highlight the importance of predictability and stability in climate and the vulnerability of species for which reproduction appears to require highly specific environmental cues.

Inherent behavioural traits enable a widespread lizard to cope with urban life

Abstract: The global human population is increasing at a staggering rate, and more than half of that population resides in urban areas. As urbanization spreads across the landscape, animals are often confronted with a vast number of unfamiliar stimuli. Existing evidence from studies of birds and mammals suggests that increased boldness, arising either through behavioural plasticity or an intrinsic risk-taking ability, can provide a fitness advantage in urban environments. What is less clear, is if these same patterns are prevalent in other taxa. Accordingly, we measured the expression of boldness in two contexts, novelty and anti-predatory behaviour, in a successful urban lizard, the delicate skink (Lampropholis delicata). Lizards from genetically related urban and non-urban populations were exposed to a novel object, scent and noise as well as a simulated predator attack. Contrary to much of the current research, we found no behavioural variation between urban and non-urban populations, as all lizards exhibited similarly high levels of risk-taking behaviour in their antipredator response as well as neophobia towards the novel object, scent and noise. Our results suggest that the delicate skink is able to cope with the challenges of urban conditions through its inherent traits. As urbanization becomes more widespread, we need to better understand which animals are able to cope with altered environmental conditions and how that is achieved. This will be critical if we are to fully grasp the impacts of anthropogenic change on faunal communities globally.

Consistent temporal variation in the diet of an endangered alpine lizard across two south-eastern Australian sky-islands

Abstract: A species’ diet and feeding strategy directly affect fitness and environmental interactions. Understanding spatial and temporal variation in diets can identify key resources, inform trophic relationships, and assist in managing threatened species. The nationally endangered Guthega skink, Liopholis guthega, is restricted to two isolated Australian alpine plateaux, the Bogong High Plains (BHP) in Victoria and Kosciuszko National Park (KNP) in New South Wales. We compared this species’ foraging ecology over the summer period between these ‘sky-islands’ separated by ~100 km of lowland valleys. Scat composition did not differ between the two lizard populations, despite differences in the invertebrate assemblages present. However, L. guthega diet varied temporally over summer at both locations. Invertebrates, predominantly Hymenoptera and Coleoptera, were the dominant food group in early summer (78% volume (V), 100% frequency occurrence (F)) and mid-summer (80% V, 100% F). A significant dietary shift occurred in late summer, when lizards consumed predominantly plant material (63% V, 95.5% F), consisting primarily of seasonally abundant berries from the snow beard heath, Acrothamnus montanus. In contrast to similar-sized Egerniinae species, it appears L. guthega is capable of opportunistically shifting its diet towards plant material in response to temporal variation in resource availability. Furthermore, the prevalence of intact seeds in scats indicates L. guthega may play a significant role in seed dispersal. Understanding these trophic interactions will assist conservation management of L. guthega, allowing conditions for an already established captive colony to mimic the temporally variable diets present in situ, as well as informing revegetation initiatives aimed at maintaining and expanding wild populations.

Avian predation intensity as a driver of clinal variation in colour morph frequency

Abstract: 1) Phenotypic variation provides the framework for natural selection to work upon , enabling adaptive evolution. One of the most discernible manifestations of phenotypic variability is colour variation. When this variation is discrete, genetically -based colour pattern morphs occur simultaneously within a population. 2) Why and how colour polymorphisms are maintained is an evolutionary puzzle. Several evolutionary drivers have been hypothesized as influencing clinal patterns of morph frequency, with spatial variation in climate and predation being considered especially important. Despite this, no study has examined both of their roles simultaneously. The aims of this study were to: 1) examine the covariation of physiology, environmental variables, and colouration at a local scale; and 2) determine if these factors and their interplay explain broad clinal variation in morph frequency. 3) We used the lizard Liopholis whitii as a model system, as this species displays a discrete, heritable polymorphism for colour pattern (plain -backed, patterned morphs) whose morph frequency varies latitudinally. We measured reflectance, field activity temperatures, and microhabitat structure to test for differences in crypsis, thermal biology, and microhabitat selection of patterned and plain -backed morphs within a single population where colour morphs occur sympatrically. We then used data from the literature to perform a broad -scale analysis to identify whether these factors also explained the latitudinal variation of morph frequency in this species. 4) At the local scale, plain -backed morphs were found to be less cryptic than patterned morphs while no other differences were detected in terms of thermal biology, dorsal reflectance, and microhabitat use. At a broader scale, predation was the most influential factor mediating morph frequency across latitudes. However, the observed pattern of morph frequency is opposite to what the modelling results suggest in that the incidence of the least cryptic morph is highest where predation pressure is most severe. Clinal variation in the level of background matching between morphs or the potential reproductive advantage by the plain -backed morph may, instead, be driving the observed morph frequency. 5) Together, these results provide key insights into the evolution of local adaptation as well as the ecological forces involved in driving the dynamics of colour polymorphism.

A new species of scincid lizard in the genus Oligosoma (Reptilia: Scincidae) from the mid-Canterbury high country, New Zealand.

Abstract: New Zealand has a diverse, endemic skink fauna, which is recognised as the most species rich skink assemblage of any cool temperate region on earth All native New Zealand skink species are assigned to a single genus, Oligosoma Girard A new species of Oligosoma is described from screes in montane tussock grassland in the mid-Canterbury high country, New Zealand, where it is currently known from four sites on two mountain ranges The new species ( Oligosoma hoparatea sp nov) can be distinguished from all congeners by a combination of mid-body scale row and lamellae counts, scale morphologies, and a bold striped pattern with smooth-edged, dark lateral bands It is part of the O longipes Patterson species complex, and occurs in sympatry with its closest relative, O aff longipes ‘southern’ The species is currently highly threatened, and is listed as Nationally Critical in New Zealand Predation by a suite of introduced mammals is assumed to be a major threat to its survival