Showing papers by "David G. Chapple published in 2017"

Thermal physiology: A new dimension of the pace-of-life syndrome.

Abstract: 1.Current syndrome research focuses primarily on behavior with few incorporating components of physiology. One such syndrome is the Pace-of-Life Syndrome (POLS) which describes covariation between behaviour, metabolism immunity, hormonal response, and life history traits. Despite the strong effect temperature has on behavior, thermal physiology has yet to be considered within this syndrome framework. 2.We proposed the POLS to be extended to include a new dimension, the cold-hot axis. Under this premise, it is predicted that thermal physiology and behavior would covary whereby individual positioning along the thermal continuum would coincide with that of the behavioral continuum. 3.This hypothesis was tested by measuring thermal traits of delicate skinks (Lampropholis delicata) and linking it to their behavior. Principal components analysis and structural equation modelling were used to determine if traits were structured within the Pace-of-Life Syndrome (POLS) and to characterize the direction of their interactions. 4.Model results supported the inclusion of the cold-hot axis into the POLS and indicated that thermal physiology was the driver of this relationship, in that thermal traits either constrained or promoted activity, exploration, boldness, and social behavior. 5.This study highlights the need to integrate thermal physiology within a syndrome framework. This article is protected by copyright. All rights reserved.

Repeatability and correlation of physiological traits: Do ectotherms have a "thermal type"?

Abstract: Across a range of taxa, individuals within a species differ in suites of correlated traits. These trait complexes, known as syndromes, can have dramatic evolutionary consequences as they do not evolve independently but rather as a unit. Current research focuses primarily on syndromes relating to aspects of behavior and life history. What is less clear is whether physiological traits also form a syndrome. We measured 10 thermal traits in the delicate skink, Lampropholis delicata, to test this idea. Repeatability was calculated and their across-context correlations evaluated. Our results were in alignment with our predictions in that individual thermal traits varied consistently and were structured into a physiological syndrome, which we are referring to as the thermal behavior syndrome (TBS). Within this syndrome, lizards exhibited a "thermal type" with each being ranked along a cold-hot continuum. Hot types had faster sprint speeds and higher preferred body temperatures, whereas the opposite was true for cold types. We conclude that physiological traits may evolve as a single unit driven by the need to maintain optimal temperatures that enable fitness-related behaviors to be maximized.

Does personality influence learning? A case study in an invasive lizard

Abstract: Learning is a change in state resulting from new experiences enabling behavioural responses to be adjusted in alignment with external cues. Individuals differ in the speed and accuracy at which they learn. Personality has been postulated as being a major influence on learning ability in terms of attention and encounter rates of environmental cues. This link forms the basis of the cognitive style hypothesis (CSH), predicting that an individual's cognitive style will occur along a fast-slow behavioural gradient. Fast types are characterised as being active, neophilic, and bold individuals who sample their environment rapidly, yet superficially, enabling learning to occur at a higher speed, but at the cost of accuracy. Slow types have the opposite suite of personality traits resulting in them being more accurate flexible learners. Greater level of learning flexibility is thought to help promote invasions success. Here, we test the predictions of the CSH in an invasive lizard (Lampropholis delicata) to determine if personality dictates learning performance in a two-phase associative task. Results indicated that the delicate skink was capable of learning an associative task but only provided partial support for the CSH. Personality was found to influence learning accuracy, however, the direction of that relationship was opposite to that predicted. Instead, fast lizards made fewer mistakes when learning to associate a colour to a goal. These findings highlight the need to further investigate the CSH across taxa and consider its potential as an underlying mechanism of the invasion process.

Habitat saturation promotes delayed dispersal in a social reptile

Abstract: When and where offspring disperse has important implications for the evolutionary emergence and maintenance of group living. In noncooperative breeders, direct benefits of delayed dispersal are relatively limited, suggesting that decisions regarding whether or not to remain in the parental territory are largely driven by the availability of suitable habitat in which to settle. Although there is ample evidence of correlations between habitat saturation and delayed dispersal, experimental tests are rare, particularly for species with facultative group formation. We manipulated the density of conspecifics in enclosed populations of a family living reptile to experimentally evaluate the influence of habitat saturation on the tendency to delay dispersal. Habitat saturation did not influence whether or not offspring explored their surroundings. However, when conspecific density was high, more offspring delayed dispersal and those that did settle in high-density enclosures had reduced survival. These patterns appear to be due to increased dispersal costs imposed by conspecific aggression; offspring that explored high-density enclosures had reduced body condition and a greater risk of mortality. We discuss these results in the context of the evolutionary origins of family living.

Sex-specific shifts in morphology and colour pattern polymorphism during range expansion of an invasive lizard

Abstract: Aim Human-assisted range expansion of animals to new environments can lead to phenotypic shifts over ecological time-scales. We investigated whether phenotypic changes are sex-specific using an invasive lizard (Lampropholis delicata). Location Pacific region (Hawaiian Islands, Lord Howe Island, New Zealand, eastern Australia). Methods Using our knowledge of the introduction history of L. delicata, we examined museum specimens of individuals collected across the native and introduced range to determine whether shifts in morphology or colour pattern polymorphism had occurred during its range expansion, and if so, whether they differed between the sexes. Results Sexual dimorphism in both size and shape was documented within the native range of the delicate skink. However, during range expansion, phenotypic shifts were observed in shape, but not size. In two of the three invasive populations, these phenotypic shifts were sex-specific. In the Hawaiian Islands, changes in shape were driven by males, whereas in New Zealand it was due to shifts in females. Similarly, changes in the frequency of a colour pattern polymorphism, a mid-lateral stripe shown to have sex-specific impacts on fitness (positive in females, negative in males), occurred following colonization of the Hawaiian Islands and Lord Howe Island. In Hawaii, the incidence of the polymorphism increased over time in females, and decreased in males. Main conclusions Phenotypic shifts during the range expansion of invasive species may be sex-specific, and are potentially related to the degree of realized niche shift that has occurred between the source and introduced range.

Rapid divergence of animal personality and syndrome structure across an arid-aquatic habitat matrix.

Abstract: Intraspecific trait variation, including animal personalities and behavioural syndromes, affects how individual animals and populations interact with their environment. Within-species behavioural variation is widespread across animal taxa, which has substantial and unexplored implications for the ecological and evolutionary processes of animals. Accordingly, we sought to investigate individual behavioural characteristics in several populations of a desert-dwelling fish, the Australian desert goby (Chlamydogobius eremius). We reared first generation offspring in a common garden to compare non-ontogenic divergence in behavioural phenotypes between genetically interconnected populations from contrasting habitats (isolated groundwater springs versus hydrologically variable river waterholes). Despite the genetic connectedness of populations, fish had divergent bold-exploratory traits associated with their source habitat. This demonstrates divergence in risk-taking traits as a rapid phenotypic response to ecological pressures in arid aquatic habitats: neophilia may be suppressed by increased predation pressure and elevated by high intraspecific competition. Correlations between personality traits also differed between spring and river fish. River populations showed correlations between dispersal and novel environment behaviours, revealing an adaptive behavioural syndrome (related to dispersal and exploration) that was not found in spring populations. This illustrates the adaptive significance of heritable behavioural variation within and between populations, and their importance to animals persisting across contrasting habitats.

A complex history of introgression and vicariance in a threatened montane skink (Pseudemoia cryodroma) across an Australian sky island system

Abstract: Species endemic to sky island systems are isolated to mountain peaks and high elevation plateaux both geographically and ecologically, making them particularly vulnerable to the effects of climate change. Pressures associated with climate change have already been linked to local extinctions of montane species, emphasizing the importance of understanding the genetic diversity and population connectivity within sky islands systems for the conservation management of remaining populations. Our study focuses on the endangered alpine skink Pseudemoia cryodroma, which is endemic to the Victorian Alps in south-eastern Australia, and has a disjunct distribution in montane habitats above 1100 m a.s.l. Using mitochondrial DNA (mtDNA) and microsatellite loci, we investigated species delimitation, genetic connectivity and population genetic structure across the geographic range of this species. We found discordance between genetic markers, indicating historical mtDNA introgression at one of the study sites between P. cryodroma and the closely related, syntopic P. entrecasteauxii. Molecular diversity was positively associated with site elevation and extent of suitable habitat, with inbreeding detected in three of the five populations. These results demonstrate the complex interaction between geography and habitat in shaping the population structure and genetic diversity of P. cryodroma, and highlight the importance of minimising future habitat loss and fragmentation for the long-term persistence of this species.

Experimental manipulation suggests effect of polyandry but not mate familiarity on within-pair aggression in the social skink, Liopholis whitii

Abstract: Long-term monogamy is a key characteristic of family living across animals. The evolutionary maintenance of long-term monogamy has been suggested to be facilitated by increased reproductive coordination as a result of mate familiarity, leading to increased reproductive success. However, such effects can be compromised if females mate outside the pair bond (e.g. female polyandry), introducing conflicts of interest between the male and female. Here, we experimentally test the effects of both mate familiarity and female polyandry on agonistic behaviour and reproduction in a family living lizard, Liopholis whitii. We found that mate familiarity did not decrease the level of aggression between pairs whereas reducing female polyandry did. However, we did not find an effect of either mate familiarity or female polyandry on female reproductive output. These results suggest that male behavioural responses to female polyandry may influence pair stability in Liopholis whitii, providing support for the growing appreciation of the multiple ways in which female polyandry can influence the stability of family living.

Gall wasp biocontrol of invasive Acacia longifolia: implications of strong bottom-up effects

Abstract: The population dynamics of insect herbivore biocontrol agents is central to the successful control of invasive weeds. Although the importance of agent population dynamics is recognized, it is rarely considered in assessments of the biocontrol potential of herbivore agents. Herbivore insect population dynamics are influenced by a combination of top-down effects from natural enemies, bottom-up effects from plant resource availability (resource quality and quantity), and potential interactions between these effects. To better understand the tri-trophic interactions that are likely to determine biocontrol success in a host plant–gall wasp–parasitoid system, the relative importance of top-down and bottom-up effects for the survival of a herbivore biocontrol agent (Trichilogaster acaciaelongifoliae), on two Acacia host plants in their native range, was estimated using path analysis. On both host plants, there was a strong positive relationship between gall mass per chamber and gall wasp survival and a strong negative relationship between gall mass per chamber and gall parasitism, with parasitoids being less common in large than small galls. There was, however, no significant correlation between parasitism and gall wasp survival and, therefore, no evidence for top-down effects in this system. Strong bottom-up effects of host plant resources on both gall wasp survival and gall parasitism have implications for the spatio-temporal variability of biocontrol success. Such variation should be considered in pre-release assessments and post-release monitoring of gall wasps used as herbivore biocontrol agents.

Connectivity and habitat type shape divergent dispersal behavior in a desert-dwelling fish

Abstract: Dispersal has important fitness consequences for individuals, populations, and species. Despite growing theoretical insights into the evolution of dispersal, its behavioral underpinnings remain empirically understudied, limiting our understanding of the extent and impact of responses to landscape-level heterogeneity of environments, and increasing the risk of inferring species-level responses from biased population sampling. We asked if predictable ecological variation among naturally fragmented arid waterbodies is correlated with disparate dispersal responses of populations of the desert goby Chlamydogobius eremius, which naturally inhabits two habitat “types” (permanent springs, ephemeral rivers), and different levels of hydrological connectivity (high and low) that potentially convey different costs and benefits of dispersal. To test for possible behavioral divergence between such populations, we experimentally compared the movement behaviors (correlates of emigration and exploration) of wild-caught fish. We used two biologically relevant spatial scales to test movement relevant to different stages of the dispersal process. Behavior differed at both spatial scales, suggesting that alternative dispersal strategies enable desert gobies to exploit diverse habitat patches. However, while emigration was best predicted by the connectivity (flood risk) of fish habitats, exploration was linked to their habitat type (spring versus river). Our findings demonstrate that despite a complex picture of ecological variation, key landscape factors have an overarching effect on among-population variation in dispersal traits. Implications include the maintenance of within-species variation, potentially divergent evolutionary trajectories of naturally or anthropogenically isolated populations, and the direction of future experimental studies on the ecology and evolution of dispersal behavior.

Does range-restricted evolutionary history predict extinction risk? A case study in lizards

Abstract: Aim Conservation is often prioritized by identifying regional clusters of threatened or endemic species. Another approach is to assess the evolutionary distinctiveness of groups of taxa using phylodiversity measures. However, quantification of evolutionary history has traditionally not accounted for its uneven geographical distribution due to the variation in species ranges. We assess the efficacy of phylogenetic endemism (PE) to predict high extinction risk in comparison to estimates of species range restriction (weighted endemism, WE) and phylogenetic diversity (PD). PE measures the relative range restriction of evolutionary history (lineages), while WE concentrates on the tips of the tree of life, treating all such branches as being of equal length. Location/Methods Using New Zealand's endemic skinks and geckos, we mapped the geographical variation in their extinction risk, PE, WE and PD and measured the extent to which extinction risk exhibited phylogenetic clustering for each group. Correlations between geographical concentrations of high skink and gecko extinction risk with PE, WE and PD were calculated. Results PE was predictive of spatial clusters of high extinction risk for geckos (r2 = 0.34, P < 0.001) while WE was markedly less so (r2 = 0.19, P < 0.001). The reverse applied to skinks, with WE most predictive of high risk (r2 = 0.26, P < 0.001). The phylogenetic signal of extinction risk was significantly conserved for geckos, but was weaker and non-significant for skinks. PE and WE were not predictive of low risk. PD was not predictive of risk. Main conclusions PE and related measures may be predictive of extinction risk when risk is phylogenetically conserved. Mapping the geographical variation in PE could be a useful first assessment of extinction risk for many groups because phylogenies are increasingly available, while full risk status categories are not. These findings might apply to other groups and locations and warrant further investigation.

Nest-site selection and the factors influencing hatching success and offspring phenotype in a nocturnal skink

Abstract: Nest-site selection in ectothermic animals influences hatching success and offspring phenotype, and it is predicted that females should choose nesting sites that maximise their reproductive fitness, ultimately through the reproductive success of their offspring. We completed nest-site choice experiments on a nocturnal lizard, the egg-laying skink ( Oligosoma suteri ), to determine whether eggs (and subsequent hatchlings) from cooler nests do better at cooler incubation temperatures, and conversely if those laid in warmer nests perform better at warmer incubation temperatures. We provided a simple nest-choice experiment, with oviposition-retreat sites available in either a hot or a cool sector of the enclosure; in the wild females nest under objects. Female O. suteri laid eggs both during the day and night, and nested more in the hot than cool sector. Eggs from each clutch were split across three egg incubation temperatures (18°C, 22°C, 26°C) to decouple the impact of initial nest-site choice from the subsequent incubation temperature regime. Whether eggs were initially laid in the hot or cool sector was not related to hatching success, offspring phenotype or offspring locomotor performance. We conclude that offspring phenotype and performance is primarily influenced by the temperature during incubation, rather than the initial thermal environment of the nest location. Thus, female O. suteri may select warmer nesting sites to ensure higher incubation temperature and enhanced offspring fitness.

Can the Incorporation of Quick Response Codes and Smartphones Improve Field-based Science Education?

Abstract: Innovative approaches to field-based biology classes are needed to overcome logistic and financial constraints to running them. Quick Response (QR) technology, which links users to online content by scanning barcodes with their smartphones, provides an inexpensive, customisable way to support field-based learning. This paper reports on the trial of mobile learning, using hand-held devices and online material, in an undergraduate biology class. Students conducted a wildlife survey with reference to an online identification guide, accessed by scanning QR codes on site. Students expressed mixed opinions about the use of QR technology in field-based classes. Technical problems with scanning QR codes, weak wifi coverage and apprehension towards new technologies appeared to influence their attitudes towards mobile learning. However, they felt that they benefited from online resources and endorsed QR codes for learning. To improve student engagement with QR technology, staff should provide students with adequate training, test QR scanning software before use, and emphasise cellular coverage.