Identifying the Abiotic Factors that Determine the Inland Range Limits of a Mesic-Adapted Lizard Species

For most species, the factors that determine geographical range limits are unknown. In mesic-adapted species, populations occurring near the edge of the species' distribution provide ideal study systems in which to investigate what limits distributional ranges. We aimed to identify the abiotic constraints that preclude an east-Australian mesic adapted lizard (Lampropholis delicata) from occupying arid environments. We performed lizard surveys at sites spanning an elevation/aridity gradient (380-1070 m), and measured the prevalence of habitat features (logs, rocks, leaf litter, bare ground, solar radiation) in addition to hourly temperatures in a variety of microhabitats available to lizards. Species distribution modelling (SDM) was used to identify the macroclimatic variables limiting the species' distribution. At its inland range limit, L. delicata is associated with mesic high-elevation forests with complex microhabitat structures, which gradually decline in availability towards lower (and more arid) elevations where the species is absent. Moreover, L. delicata is absent from sites with a shallow leaf litter layer, in which daily temperatures exceed the species' thermal preference range, which we determined in a laboratory thermal gradient. In regards to macroclimate, SDM revealed that temperature seasonality is the primary variable predicting the species' distribution, suggesting that L. delicata avoids inland areas owing to their high annual thermal variability. By combining multiple lines of evidence, this research highlights that habitat and microclimate suitability-not solely macroclimate suitability-are important range-limiting factors for mesic ectotherms, and should be incorporated in studies addressing range-limiting hypotheses.

Linking physiology and climate to infer species distributions in Australian skinks

Climate has a key impact on animal physiology, which in turn can have a profound influence on geographic distributions. Yet, the mechanisms linking climate, physiology and distribution are not fully resolved. Using an integrative framework, we tested the predictions of the climatic variability hypothesis (CVH), which states that species with broader distributions have broader physiological tolerance than range-restricted species, in a group of Lampropholis skinks (8 species, 196 individuals) along a latitudinal gradient in eastern Australia. We investigated several physiological aspects including metabolism, water balance, thermal physiology, thermoregulatory behaviour and ecological performance. Additionally, to test whether organismal information (e.g. behaviour and physiology) can enhance distribution models, hence providing evidence that physiology and climate interact to shape range sizes, we tested whether species distribution models incorporating physiology better predict the range sizes than models using solely climatic layers. In agreement with the CVH, our results confirm that widespread species can tolerate and perform better at broader temperature ranges than range-restricted species. We also found differences in field body temperatures, but not thermal preference, between widespread and range-restricted species. However, metabolism and water balance did not correlate with range size. Biophysical modelling revealed that the incorporation of physiological and behavioural data improves predictions of Lampropholis distributions compared with models based solely on macroclimatic inputs, but mainly for range-restricted species. By integrating several aspects of the physiology and niche modelling of a group of ectothermic animals, our study provides evidence that physiology correlates with species distributions. Physiological responses to climate are central in establishing geographic ranges of skinks, and the incorporation of processes occurring at local scales (e.g. behaviour) can improve species distribution models.

Long-term effects of incubation temperature on growth and thermal physiology in a small ectotherm

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, Lampropholis delicata, 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'.

Oligosoma aureocola sp. nov. (Reptilia: Scincidae) from the northern Southland high country of Aotearoa/New Zealand

A species of diurnal skink from the Mataura Range and Mid Dome in central northern Southland, Aotearoa/New Zealand is described as Oligosoma aureocola sp. nov. It is a small species, coloured mid- to dark brown with smooth longitudinal stripes, and lives along rocky alpine ridges, low-stature shrublands, and tussock grasslands. This skink is a conspicuous species, easily sighted basking and foraging in talus or alpine plants such as golden spear grass (Aciphylla aurea).

Does thermal biology differ between two colour pattern morphs of a widespread Australian lizard?

Alternative phenotypes allow individuals to pursue different adaptive pathways in response to the same selective challenge. Colour polymorphic species with geographically varying morph frequencies may reflect multiple adaptations to spatial variables such as temperature and climate. We examined whether thermal biology differed between colour morphs of an Australian lizard, the delicate skink, Lampropholis delicata. The delicate skink has two colour pattern morphs, with frequencies varying across latitude and sex: plain (darker, more common at temperate latitudes, more common in males) or striped (lighter, more common at lower latitudes, more common in females). We tested heating and cooling rate, sprint speed, thermal preference, field body temperature and metabolic rate in both morphs and sexes to determine any link between colour and morph frequency distribution. Plain individuals heated more quickly, but other thermal traits showed little variation among morphs. Lampropholis delicata colour influences rates of heat exchange, but the relationship does not appear to be adaptive, suggesting that behavioural thermoregulation homogenises body temperature in the field. While we find no substantial evidence of thermal differences between the two colour morphs, morph-specific behaviour may buffer against differences in heat exchange. Latitudinal variation in species colour may be driven by selection pressures other than temperature.

Phylogenomics and biogeography of arid-adapted Chlamydogobius goby fishes

The progressive aridification of the Australian continent from ∼ 20 million years ago posed severe challenges for the persistence of its resident biota. A key question involves the role of refugial habitats - specifically, their ability to mediate the effects of habitat loss and fragmentation, and their potential to shape opportunities for allopatric speciation. With freshwater species, for example, the patchiness, or absence, of water will constrain distributions. However, aridity may not necessarily isolate populations if disjunct refugia experience frequent hydrological connections. To investigate this potential dichotomy, we explored the evolutionary history of the Chlamydogobius gobies (Gobiiformes: Gobiidae), an arid-adapted genus of six small, benthic fish species that exploit all types of waterbodies (i.e. desert springs, waterholes and bore-fed wetlands, coastal estuarine creeks and mangroves) across parts of central and northern Australia. We used Anchored Phylogenomics to generate a highly resolved phylogeny of the group from sequence data for 260 nuclear loci. Buttressed by companion allozyme and mtDNA datasets, our molecular findings infer the diversification of Chlamydogobius in arid Australia, and provide a phylogenetic structure that cannot be simply explained by invoking allopatric speciation events reflecting current geographic proximity. Our findings are generally consistent with the existing morphological delimitation of species, with one exception: at the shallowest nodes of phylogenetic reconstruction, the molecular data do not fully support the current dichotomous delineation of C. japalpa from C. eremius in Kati Thanda-Lake Eyre-associated waterbodies. Together these findings illustrate the ability of structural (hydrological) connections to generate patterns of connectivity and isolation for an ecologically moderate disperser in response to ongoing habitat aridification. Finally, we explore the implications of these results for the immediate management of threatened (C. gloveri) and critically endangered (C. micropterus, C. squamigenus) congeners.

Global Protected Areas as refuges for amphibians and reptiles under climate change

Protected Areas (PAs) are the cornerstone of biodiversity conservation. Here, we collated distributional data for >14,000 (~70% of) species of amphibians and reptiles (herpetofauna) to perform a global assessment of the conservation effectiveness of PAs using species distribution models. Our analyses reveal that >91% of herpetofauna species are currently distributed in PAs, and that this proportion will remain unaltered under future climate change. Indeed, loss of species' distributional ranges will be lower inside PAs than outside them. Therefore, the proportion of effectively protected species is predicted to increase. However, over 7.8% of species currently occur outside PAs, and large spatial conservation gaps remain, mainly across tropical and subtropical moist broadleaf forests, and across non-high-income countries. We also predict that more than 300 amphibian and 500 reptile species may go extinct under climate change over the course of the ongoing century. Our study highlights the importance of PAs in providing herpetofauna with refuge from climate change, and suggests ways to optimize PAs to better conserve biodiversity worldwide.

Acclimation of thermal physiology to new basking regimes in a widespread Australian skink

Changes in thermal environments are a challenge for many ectotherms, as they would have to acclimate their physiology to new thermal environments to maintain high-levels of performance. Time spent basking is key for many ectothermic animals to keep their body temperature within optimal thermal ranges. However, little is known about the impact of changes in basking time on the thermal physiology of ectothermic animals. We investigated how different basking regimes (low intensity vs high intensity) affected key thermal physiological traits of a widespread Australian skink (Lampropholis delicata). We quantified thermal performance curves and thermal preferences of skinks subjected to low and high intensity basking regimes over a 12-week period. We found that skinks acclimated their thermal performance breadth in both basking regimes, with the skinks from the low-intensity basking regime showing narrower performance breadths. Although maximum velocity and optimum temperatures increased after the acclimation period, these traits did not differ between basking regimes. Similarly, no variation was detected for thermal preference. These results provide insight into mechanisms that allow these skinks to successfully overcome environmental constraints in the field. Acclimation of thermal performance curves seems to be key for widespread species to colonise new environments, and can buffer ectothermic animals in novel climatic scenarios.

Univariate and multivariate plasticity in response to incubation temperature in an Australian lizard

Environments, particularly developmental environments, can generate a considerable amount of phenotypic variation through phenotypic plasticity. Plasticity in response to incubation temperature is well characterised in egg-laying reptiles. However, traits do not always vary independently of one another, and studies encompassing a broad range of traits spanning multiple categories are relatively rare but crucial to better understand whole-organism responses to environmental change, particularly if covariation among traits may constrain plasticity. In this study, we investigated multivariate plasticity in response to incubation across three temperatures in the delicate skink, Lampropholis delicata, and whether this was affected by covariation among traits. At approximately 1 month of age, a suite of growth, locomotor performance, thermal physiology and behavioural traits were measured. Plasticity in the multivariate phenotype of delicate skinks was distinct for different incubation temperatures. Cool temperatures drove shifts in growth, locomotor performance and thermal physiology, while hot temperatures primarily caused changes in locomotor performance and behaviour. These differences are likely due to variation in thermal reaction norms, as there was little evidence that covariation among traits or phenotypic integration influenced plasticity, and there was no effect of incubation temperature on the direction or strength of covariation. While there were broad themes in terms of which trait categories were affected by different incubation treatments, traits appeared to be affected independently by developmental temperature. Comparing reaction norms of a greater range of traits and temperatures will enable better insight into these patterns among trait categories, as well as the impacts of environmental change.

Effects of developmental environment on animal personality in a tropical skink

Abstract

Developmental environments play a significant role in shaping animal phenotype, including behavior. Within a species, individuals often differ in behavior in a consistent and repeatable way (i.e., demonstrate animal personality). This consistency in behavior can be affected by differences in conditions experienced early in life. It is, however, unclear whether effects of developmental environments on animal personality are driven by changes in within- or between-individual variation. To investigate this, we measured activity, exploration, sociability, and boldness in adult male southern rainforest sunskinks, Lampropholis similis, incubated at either 23 °C or 26 °C, and compared behavioral phenotypes between these incubation treatments. We also compared the behavior of these incubation groups to a cohort of wild-caught skinks to determine whether rearing in captivity also affected the personality of the lizards. Skinks that had been incubated at a higher temperature were more explorative and demonstrated personality in a larger suite of traits compared to lizards incubated at a lower temperature or caught in the wild. These differences among developmental environment were primarily driven by within-individual variation, which tended to be higher among the high incubation treatment. We also found no evidence for a behavioral syndrome in either captive- or wild-reared skinks. Our results suggest the potential for greater behavioral plasticity in skinks incubated at a higher temperature, which may enable them to cope with environmental change, such as climate warming, in the short term. Overall, we show that effects of developmental environment are complex and play a pivotal role in shaping animal personality.

Significance statement

Experiences during development are expected to influence how animals develop, including their behavior. We tested early environment effects on behavior in adult southern rainforest sunskinks by comparing lizards incubated at different temperatures as well as comparing those reared in the wild with those reared in captive environments. We found that lizards incubated at the higher temperature were more exploratory. Furthermore, both incubation temperature and captivity/wild-rearing had pronounced effects on the consistency of behavior—in different directions for different traits—demonstrating developmental environments have strong effects on animal personality. Such changes in behavioral traits likely have flow-on effects for the animal’s fitness and biotic interactions.

Social context mediates the expression of a personality trait in a gregarious lizard

The social environment is a key factor that influences behavioural traits across a wide array of species. Yet, when investigating individual differences in behaviour, studies tend to measure animals in isolation from other conspecifics—even in social species. Surprisingly, whether behavioural traits measured in isolation are predictive of individual-level behaviour when in social groups is still poorly understood. Here, we repeatedly measured risk-taking behaviour (i.e. boldness; 741 total trials) in both the presence and absence of conspecifics in a social lizard, the delicate skink (Lampropholis delicata). Further, we manipulated food availability during group trials to test whether the effect of the social environment on risk-taking behaviour was mediated by competition over resources. Using 105 lizards collected from three independent populations, we found that individual risk-taking behaviour was repeatable when measured in either social isolation or within groups both with and without food resources available. However, lizards that were bolder during individual trials were not also bolder when in groups, regardless of resource availability. This was largely driven by individual differences in social behavioural plasticity, whereby individual skinks responded differently to the presence of conspecifics. Together, this resulted in a rank order change of individual behavioural types across the social conditions. Our results highlight the importance of the social environment in mediating animal personality traits across varying levels of resource availability. Further, these findings suggest that behavioural traits when measured in isolation, may not reflect individual variation in behaviour when measured in more ecologically realistic social groups.

Intraspecific hybridisation of an invasive lizard on Lord Howe Island

Human-mediated dispersal of animals often acts to bring populations that have been separated for substantial periods of evolutionary time (e.g. millions of years) in their native range into contact in their introduced range. Whether these taxa successfully interbreed in the introduced range provides information on the strength of reproductive isolation amongst them. The invasive delicate skink (Lampropholis delicata) has been accidentally introduced to Lord Howe Island from four genetically divergent (>2 million years) regions of the species’ native range in eastern Australia. We used mitochondrial DNA and microsatellite data to investigate whether the individuals from four of the native-range source regions are interbreeding on Lord Howe Island. Our analyses indicate that intraspecific hybridisation among individuals from all four native-range source regions is occurring. Although there is little evidence for hybrids in the northern end of Lord Howe Island (proportion of hybrids: 0–0.02; n = 31), there is a high proportion of hybrids in the central (0.33–0.69; n = 59) and southern regions (0.38–0.75; n = 8) of the island. Given the strong evidence for interbreeding among all four native-range source regions examined, and the relatively minor morphological, life-history and phenotypic variation among them, we suggest that the delicate skink should continue to be treated as a single, widespread, but variable species.

Evolution of diel activity patterns in skinks (Squamata: Scincidae), the world's second-largest family of terrestrial vertebrates

Many animals have strict diel activity patterns, with unique adaptations for either diurnal or nocturnal activity. Diel activity is phylogenetically conserved, yet evolutionary shifts in diel activity occur and lead to important changes in an organism's morphology, physiology, and behavior. We use phylogenetic comparative methods to examine the evolutionary history of diel activity in skinks, one of the largest families of terrestrial vertebrates. We examine how diel patterns are associated with microhabitat, ambient temperatures, and morphology. We found support for a nondiurnal ancestral skink. Strict diurnality in crown group skinks only evolved during the Paleogene. Nocturnal habits are associated with fossorial activity, limb reduction and loss, and warm temperatures. Our results shed light on the evolution of diel activity patterns in a large radiation of terrestrial ectotherms and reveal how both intrinsic biotic and extrinsic abiotic factors can shape the evolution of animal activity patterns.

Automated assessment reveals that the extinction risk of reptiles is widely underestimated across space and phylogeny

The Red List of Threatened Species, published by the International Union for Conservation of Nature (IUCN), is a crucial tool for conservation decision-making. However, despite substantial effort, numerous species remain unassessed or have insufficient data available to be assigned a Red List extinction risk category. Moreover, the Red Listing process is subject to various sources of uncertainty and bias. The development of robust automated assessment methods could serve as an efficient and highly useful tool to accelerate the assessment process and offer provisional assessments. Here, we aimed to (1) present a machine learning–based automated extinction risk assessment method that can be used on less known species; (2) offer provisional assessments for all reptiles—the only major tetrapod group without a comprehensive Red List assessment; and (3) evaluate potential effects of human decision biases on the outcome of assessments. We use the method presented here to assess 4,369 reptile species that are currently unassessed or classified as Data Deficient by the IUCN. The models used in our predictions were 90% accurate in classifying species as threatened/nonthreatened, and 84% accurate in predicting specific extinction risk categories. Unassessed and Data Deficient reptiles were considerably more likely to be threatened than assessed species, adding to mounting evidence that these species warrant more conservation attention. The overall proportion of threatened species greatly increased when we included our provisional assessments. Assessor identities strongly affected prediction outcomes, suggesting that assessor effects need to be carefully considered in extinction risk assessments. Regions and taxa we identified as likely to be more threatened should be given increased attention in new assessments and conservation planning. Lastly, the method we present here can be easily implemented to help bridge the assessment gap for other less known taxa.

A global reptile assessment highlights shared conservation needs of tetrapods

Comprehensive assessments of species’ extinction risks have documented the extinction crisis¹ and underpinned strategies for reducing those risks². Global assessments reveal that, among tetrapods, 40.7% of amphibians, 25.4% of mammals and 13.6% of birds are threatened with extinction³. Because global assessments have been lacking, reptiles have been omitted from conservation-prioritization analyses that encompass other tetrapods^4–7. Reptiles are unusually diverse in arid regions, suggesting that they may have different conservation needs⁶. Here we provide a comprehensive extinction-risk assessment of reptiles and show that at least 1,829 out of 10,196 species (21.1%) are threatened—confirming a previous extrapolation⁸ and representing 15.6 billion years of phylogenetic diversity. Reptiles are threatened by the same major factors that threaten other tetrapods—agriculture, logging, urban development and invasive species—although the threat posed by climate change remains uncertain. Reptiles inhabiting forests, where these threats are strongest, are more threatened than those in arid habitats, contrary to our prediction. Birds, mammals and amphibians are unexpectedly good surrogates for the conservation of reptiles, although threatened reptiles with the smallest ranges tend to be isolated from other threatened tetrapods. Although some reptiles—including most species of crocodiles and turtles—require urgent, targeted action to prevent extinctions, efforts to protect other tetrapods, such as habitat preservation and control of trade and invasive species, will probably also benefit many reptiles.

An extinction-risk assessment of reptiles shows that at least 21.1% of species are threatened by factors such as agriculture, logging, urban development and invasive species, and that efforts to protect birds, mammals and amphibians probably also benefit many reptiles.

Conserved ecophysiology despite disparate microclimatic conditions in a gecko

Microscale differences in the habitats organisms occupy can influence selection regimes and promote intraspecific variation of traits. Temperature-dependent traits can be locally adapted to climatic conditions or be highly conserved and insensitive to directional selection under all but the most extreme regimes, and thus be similar across populations. The opposing slopes of Nahal Oren canyon in the Carmel Mountains, Israel, are strikingly different: the south-facing slope receives intensive solar radiation, is hot and supports mostly annual vegetation, whereas the north-facing slope is ~10°C cooler, more humid, and supports Mediterranean woodland. We examined whether these differences manifest in the thermal physiology of a common gecko species Ptyodactylus guttatus in controlled laboratory conditions. We predicted that geckos from the hotter south-facing slope would prefer higher temperatures, have faster gut passage times, lower metabolic and evaporative water loss rates, and start diel activity earlier compared with north-facing slope conspecifics. Contrary to these predictions, there were no differences between any of the ecophysiological traits in geckos from the opposing slopes. Nevertheless, our data showed that individuals from the north-facing slope were generally more active in earlier hours of the afternoon compared with south-facing individuals. We suggest that P. guttatus individuals disperse between the slopes and either gene-flow or behavioral plasticity deter local adaptation, resulting in similar physiological traits. Perhaps a stronger contrast in climatic conditions and a stronger barrier are needed to result in interpopulation divergence in temperature-dependent traits.

Testing a global standard for quantifying species recovery and assessing conservation impact

Recognizing the imperative to evaluate species recovery and conservation impact, in 2012 the International Union for Conservation of Nature (IUCN) called for development of a "Green List of Species" (now the IUCN Green Status of Species). A draft Green Status framework for assessing species' progress toward recovery, published in 2018, proposed 2 separate but interlinked components: a standardized method (i.e., measurement against benchmarks of species' viability, functionality, and preimpact distribution) to determine current species recovery status (herein species recovery score) and application of that method to estimate past and potential future impacts of conservation based on 4 metrics (conservation legacy, conservation dependence, conservation gain, and recovery potential). We tested the framework with 181 species representing diverse taxa, life histories, biomes, and IUCN Red List categories (extinction risk). Based on the observed distribution of species' recovery scores, we propose the following species recovery categories: fully recovered, slightly depleted, moderately depleted, largely depleted, critically depleted, extinct in the wild, and indeterminate. Fifty-nine percent of tested species were considered largely or critically depleted. Although there was a negative relationship between extinction risk and species recovery score, variation was considerable. Some species in lower risk categories were assessed as farther from recovery than those at higher risk. This emphasizes that species recovery is conceptually different from extinction risk and reinforces the utility of the IUCN Green Status of Species to more fully understand species conservation status. Although extinction risk did not predict conservation legacy, conservation dependence, or conservation gain, it was positively correlated with recovery potential. Only 1.7% of tested species were categorized as zero across all 4 of these conservation impact metrics, indicating that conservation has, or will, play a role in improving or maintaining species status for the vast majority of these species. Based on our results, we devised an updated assessment framework that introduces the option of using a dynamic baseline to assess future impacts of conservation over the short term to avoid misleading results which were generated in a small number of cases, and redefines short term as 10 years to better align with conservation planning. These changes are reflected in the IUCN Green Status of Species Standard.

A multi-site method to capture turnover in rare to common interactions in bipartite species networks

Ecological network structure is maintained by a generalist core of common species. However, rare species contribute substantially to both the species and functional diversity of networks. Capturing changes in species composition and interactions, measured as turnover, is central to understanding the contribution of rare and common species and their interactions. Due to a large contribution of rare interactions, the pairwise metrics used to quantify interaction turnover are, however, sensitive to compositional change in the interactions of, often rare, peripheral specialists rather than common generalists in the network. Here we expand on pairwise interaction turnover using a multi-site metric that enables quantifying turnover in rare to common interactions (in terms of occurrence of interactions). The metric further separates this turnover into interaction turnover due to species turnover and interaction rewiring. We demonstrate the application and value of this method using a host-parasitoid system sampled along gradients of environmental modification. In the study system, both the type and amount of habitat needed to maintain interaction composition depended on the properties of the interactions considered, that is, from rare to common. The analyses further revealed the potential of host switching to prevent or delay species loss, and thereby buffer the system from perturbation. Multi-site interaction turnover provides a comprehensive measure of network change that can, for example, detect ecological thresholds to habitat loss for rare to common interactions. Accurate description of turnover in common, in addition to rare, species and their interactions is particularly relevant for understanding how network structure and function can be maintained.

How do the physiological traits of a lizard change during its invasion of an oceanic island?

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.

A new species of Oligosoma (Squamata: Scincidae) from the northern North Island, New Zealand

New Zealand is home to a diverse cool temperate assemblage of skinks, with 60+ identified taxa (genus Oligosoma Girard), of which only 50 have been formally described. Here we describe a new species (Oligosoma kakerakau sp. nov.) from Bream Head Scenic Reserve, near Whangrei Heads, Northland. This species is considered to be conspecific with a single specimen (Oligosoma Whirinaki) previously reported (in 2003) from Whirinaki Te Pua-a-Tne Conservation Park ~370 km further south. Oligosoma kakerakau sp. nov. can be distinguished from all other members of the genus by a combination of a distinctive teardrop marking below the eye, a distinctive mid-lateral stripe, and the colouration and pattern on its ventral surface. Our phylogenetic analyses indicate that Oligosoma kakerakau sp. nov. is most closely related to O. zelandicum (Gray), and more distantly to O. striatum (Buller) and O. homalonotum (Boulenger). Sea level changes during the Pliocene, such as the formation of the Manawat Strait, may have contributed to the divergence between Oligosoma kakerakau sp. nov. and O. zelandicum. We discuss the distribution, ecology and conservation of Oligosoma kakerakau sp. nov., and outline future research and conservation priorities for the species.

Population differences in the effect of context on personality in an invasive lizard

Within populations, individuals often differ consistently in their average level of behavior (i.e., animal personality), as well as their response to environmental change (i.e., behavioral plasticity). Thus, changes in environmental conditions might be expected to mediate the structure of animal personality traits. However, it is currently not well understood how personality traits change in response to environmental conditions, and whether this effect is consistent across multiple populations within the same species. Accordingly, we investigated variation in personality traits across two ecological contexts in the invasive delicate skink (Lampropholis delicata). Specifically, lizards from three different populations were repeatedly measured for individual activity in group behavioral assays under differing levels of food availability. We found that environmental context had a clear effect on the structure of lizard personality, where activity rates were not repeatable in the absence of food, but were repeatable in the presence of food resources. The difference in repeatability of activity rates across contexts appeared to be largely driven by an increase in among-individual variance when tested in the presence of food resources. However, this was only true for one of the populations tested, with food context having no effect on the expression of personality traits in the other two populations. Our results highlight the important role of environmental context in mediating the structure of animal personality traits and suggest that this effect may vary among populations.

A national-scale dataset for threats impacting Australia's imperiled flora and fauna

Australia is in the midst of an extinction crisis, having already lost 10% of terrestrial mammal fauna since European settlement and with hundreds of other species at high risk of extinction. The decline of the nation's biota is a result of an array of threatening processes; however, a comprehensive taxon-specific understanding of threats and their relative impacts remains undocumented nationally. Using expert consultation, we compile the first complete, validated, and consistent taxon-specific threat and impact dataset for all nationally listed threatened taxa in Australia. We confined our analysis to 1,795 terrestrial and aquatic taxa listed as threatened (Vulnerable, Endangered, or Critically Endangered) under Australian Commonwealth law. We engaged taxonomic experts to generate taxon-specific threat and threat impact information to consistently apply the IUCN Threat Classification Scheme and Threat Impact Scoring System, as well as eight broad-level threats and 51 subcategory threats, for all 1,795 threatened terrestrial and aquatic threatened taxa. This compilation produced 4,877 unique taxon-threat-impact combinations with the most frequently listed threats being Habitat loss, fragmentation, and degradation (n = 1,210 taxa), and Invasive species and disease (n = 966 taxa). Yet when only high-impact threats or medium-impact threats are considered, Invasive species and disease become the most prevalent threats. This dataset provides critical information for conservation action planning, national legislation and policy, and prioritizing investments in threatened species management and recovery.

Pervasive admixture and the spread of a large-lipped form in a cichlid fish radiation

Adaptive radiations have proven important for understanding the mechanisms and processes underlying biological diversity. The convergence of form and function, as well as admixture and adaptive introgression, are common in adaptive radiations. However, distinguishing between these two scenarios remains a challenge for evolutionary research. The Midas cichlid species complex (Amphilophus spp.) is a prime example of adaptive radiation, with phenotypic diversification occurring at various stages of genetic differentiation. One species, A. labiatus, has large fleshy lips, is associated with rocky lake substrates, and occurs patchily within Lakes Nicaragua and Managua. By contrast, the similar, but thin-lipped, congener, A. citrinellus, is more common and widespread. We investigated the evolutionary history of the large-lipped form, specifically regarding whether the trait has evolved independently in both lakes from ancestral thin-lipped populations, or via dispersal and/or admixture events. We collected samples from distinct locations in both lakes, and assessed differences in morphology and ecology. Using RAD-seq, we genotyped thousands of SNPs to measure population structure and divergence, demographic history, and admixture. We found significant between-species differences in ecology and morphology, local intraspecific differences in body shape and trophic traits, but only limited intraspecific variation in lip shape. Despite clear ecological differences, our genomic approach uncovered pervasive admixture between the species and low genomic differentiation, with species within lakes being genetically more similar than species between lakes. Taken together, our results suggest a single origin of large-lips, followed by pervasive admixture and adaptive introgression, with morphology being driven by local ecological opportunities, despite ongoing gene-flow.

Specialist versus Generalist at the Intraspecific Level: Functional Morphology and Substrate Preference of Mediodactylus kotschyi Geckos

Populations of the same species occupying different microhabitats can either exhibit generalized traits across them or display intraspecific variability, adapting to each microhabitat in order to maximize performance. Intraspecific variability contributes to the generation of diversity, following selection and adaptation, and understanding such variability is important for comprehending how individuals choose their microhabitats. Compared with interspecific variability, however, intraspecific variability in functional morphology and its relationship with microhabitat preference and use have been relatively little studied. Here we examined whether populations of the gecko Mediodactylus kotschyi that differ in the substrates they occupy display habitat-specific behaviors and differing morphologies associated with functional adaptation to their microhabitats. We collected 207 geckos from under or on rocks or on trees from seven populations in Greece. On large islands individuals occupy both substrates; whereas small islets are devoid of trees and the geckos are restricted to rocks, while on the mainland they are only found on trees. We determined gecko substrate preferences in the laboratory, together with their clinging abilities to the different substrates. We measured their limbs, digits, and claws and assessed how these measurements relate to clinging ability. Geckos from all populations preferred the tree made available to them, but this preference was not statistically significant. Geckos from both large and small islands clung better to the tree than to the rock in the laboratory, while those from the mainland clung similarly to both substrates. Geckos collected from trees had longer manual digits and hind limbs. Geckos collected from large and small islands had taller (longer on the dorso-ventral axis; henceforth "deeper") claws. Longer digits and deeper but shorter claws were associated with a better ability to cling to rocks. Our findings suggest that while M. kotschyi is potentially preferentially arboreal, due to the great variation and plasticity it possesses, it can successfully also exploit the habitats available on the smallest, treeless islets in the Aegean Sea. Our study suggests that the dichotomous use of generalist versus specialist in describing species' habitat use is oversimplified, and we suggest the use of a generalist-specialist gradient instead.

A return-on-investment approach for prioritization of rigorous taxonomic research needed to inform responses to the biodiversity crisis

Global biodiversity loss is a profound consequence of human activity. Disturbingly, biodiversity loss is greater than realized because of the unknown number of undocumented species. Conservation fundamentally relies on taxonomic recognition of species, but only a fraction of biodiversity is described. Here, we provide a new quantitative approach for prioritizing rigorous taxonomic research for conservation. We implement this approach in a highly diverse vertebrate group-Australian lizards and snakes. Of 870 species assessed, we identified 282 (32.4%) with taxonomic uncertainty, of which 17.6% likely comprise undescribed species of conservation concern. We identify 24 species in need of immediate taxonomic attention to facilitate conservation. Using a broadly applicable return-on-investment framework, we demonstrate the importance of prioritizing the fundamental work of identifying species before they are lost.

Using multiple sources during reintroduction of a locally extinct population benefits survival and reproduction of an endangered freshwater fish

Through using different sources, population reintroductions can create genetically diverse populations at low risk of harmful inbreeding and well equipped for adaptation to future environments. Genetic variation from one source can mask locally nonoptimal alleles from another, thereby enhancing adaptive potential and population persistence. We assessed the outcomes in survival, growth and reproduction of using two differentiated sources (genetically diverse Yarra and moderately diverse Dartmouth) for translocations and stocking to reintroduce the endangered Australian freshwater Macquarie perch Macquaria australasica into the Ovens River. For stocking, same- and different-population parents ("cross-types") were used during hatchery production. Genetic samples and data on individual fish were collected over three years of monitoring the Ovens. We genetically assigned Ovens fish to their broodstock parents and tested whether cross-type and genetic dissimilarity between parents are associated with offspring survival, and whether cross-type and parental dissimilarity or individual genetic diversity are associated with somatic growth rates of stocked fish. We genetically identified translocated fish and assessed local recruit ancestry. Of 296 Ovens fish, 31.1% were inferred to be stocked, 1.3% translocated and 67.6% locally born. Cross-type strongly predicted survival of stocked offspring: those with two Yarra parents had the highest survival, followed by offspring with two-population, then Dartmouth, ancestry. Of the Ovens recruits, 59.5% had Yarra, 33.5% two-population and 7.0% Dartmouth ancestry, despite 67% of stocked and 98% of translocated fish originating from Dartmouth. Offspring with two Yarra parents grew faster than offspring of Dartmouth or two-population ancestry. Although Dartmouth fish appear to be less fit in the Ovens compared to Yarra fish, possibly due to deleterious variation or genetic or plastic maladaptation, they contribute to the reintroduced population through local interbreeding with Yarra fish and relatively high survival of stocked offspring of two-population ancestry. Thus, combining compatible stocks is likely to benefit restoration of other wildlife populations.

A farewell to arms and legs: a review of limb reduction in squamates

Elongated snake-like bodies associated with limb reduction have evolved multiple times throughout vertebrate history. Limb-reduced squamates (lizards and snakes) account for the vast majority of these morphological transformations, and thus have great potential for revealing macroevolutionary transitions and modes of body-shape transformation. Here we present a comprehensive review on limb reduction, in which we examine and discuss research on these dramatic morphological transitions. Historically, there have been several approaches to the study of squamate limb reduction: (i) definitions of general anatomical principles of snake-like body shapes, expressed as varying relationships between body parts and morphometric measurements; (ii) framing of limb reduction from an evolutionary perspective using morphological comparisons; (iii) defining developmental mechanisms involved in the ontogeny of limb-reduced forms, and their genetic basis; (iv) reconstructions of the evolutionary history of limb-reduced lineages using phylogenetic comparative methods; (v) studies of functional and biomechanical aspects of limb-reduced body shapes; and (vi) studies of ecological and biogeographical correlates of limb reduction. For each of these approaches, we highlight their importance in advancing our understanding, as well as their weaknesses and limitations. Lastly, we provide suggestions to stimulate further studies, in which we underscore the necessity of widening the scope of analyses, and of bringing together different perspectives in order to understand better these morphological transitions and their evolution. In particular, we emphasise the importance of investigating and comparing the internal morphology of limb-reduced lizards in contrast to external morphology, which will be the first step in gaining a deeper insight into body-shape variation.

Reptiles as food: predation of Australian reptiles by introduced red foxes compounds and complements predation by cats

ContextInvasive species are a major cause of biodiversity loss across much of the world, and a key threat to Australia’s diverse reptile fauna. There has been no previous comprehensive analysis of the potential impact of the introduced European red fox, Vulpes vulpes, on Australian reptiles. AimsWe seek to provide an inventory of all Australian reptile species known to be consumed by the fox, and identify characteristics of squamate species associated with such predation. We also compare these tallies and characteristics with reptile species known to be consumed by the domestic cat, Felis catus, to examine whether predation by these two introduced species is compounded (i.e. affecting much the same set of species) or complementary (affecting different groups of species). Methods We collated records of Australian reptiles consumed by foxes in Australia, with most records deriving from fox dietary studies (tallying >35000 samples). We modelled presence or absence of fox predation records against a set of biological and other traits, and population trends, for squamate species. Key resultsIn total, 108 reptile species (~11% of Australia’s terrestrial reptile fauna) have been recorded as consumed by foxes, fewer than that reported for cats (263 species). Eighty-six species have been reported to be eaten by both predators. More Australian turtle species have been reported as consumed by foxes than by cats, including many that suffer high levels of predation on egg clutches. Twenty threatened reptile species have been reported as consumed by foxes, and 15 by cats. Squamate species consumed by foxes are more likely to be undergoing population decline than those not known to be consumed by foxes. The likelihood of predation by foxes increased with squamate species’ adult body mass, in contrast to the relationship for predation by cats, which peaked at ~217g. Foxes, but not cats, were also less likely to consume venomous snakes. ConclusionsThe two introduced, and now widespread, predators have both compounding and complementary impacts on the Australian reptile fauna. ImplicationsEnhanced and integrated management of the two introduced predators is likely to provide substantial conservation benefits to much of the Australian reptile fauna.

The functions of CAP superfamily proteins in mammalian fertility and disease

BACKGROUND

Members of the cysteine-rich secretory proteins (CRISPS), antigen 5 (Ag5) and pathogenesis-related 1 (Pr-1) (CAP) superfamily of proteins are found across the bacterial, fungal, plant and animal kingdoms. Although many CAP superfamily proteins remain poorly characterized, over the past decade evidence has accumulated, which provides insights into the functional roles of these proteins in various processes, including fertilization, immune defence and subversion, pathogen virulence, venom toxicology and cancer biology.

OBJECTIVE AND RATIONALE

The aim of this article is to summarize the current state of knowledge on CAP superfamily proteins in mammalian fertility, organismal homeostasis and disease pathogenesis.

SEARCH METHODS

The scientific literature search was undertaken via PubMed database on all articles published prior to November 2019. Search terms were based on following keywords: 'CAP superfamily', 'CRISP', 'Cysteine-rich secretory proteins', 'Antigen 5', 'Pathogenesis-related 1', 'male fertility', 'CAP and CTL domain containing', 'CRISPLD1', 'CRISPLD2', 'bacterial SCP', 'ion channel regulator', 'CatSper', 'PI15', 'PI16', 'CLEC', 'PRY proteins', 'ASP proteins', 'spermatogenesis', 'epididymal maturation', 'capacitation' and 'snake CRISP'. In addition to that, reference lists of primary and review article were reviewed for additional relevant publications.

OUTCOMES

In this review, we discuss the breadth of knowledge on CAP superfamily proteins with regards to their protein structure, biological functions and emerging significance in reproduction, health and disease. We discuss the evolution of CAP superfamily proteins from their otherwise unembellished prokaryotic predecessors into the multi-domain and neofunctionalized members found in eukaryotic organisms today. At least in part because of the rapid evolution of these proteins, many inconsistencies in nomenclature exist within the literature. As such, and in part through the use of a maximum likelihood phylogenetic analysis of the vertebrate CRISP subfamily, we have attempted to clarify this confusion, thus allowing for a comparison of orthologous protein function between species. This framework also allows the prediction of functional relevance between species based on sequence and structural conservation.

WIDER IMPLICATIONS

This review generates a picture of critical roles for CAP proteins in ion channel regulation, sterol and lipid binding and protease inhibition, and as ligands involved in the induction of multiple cellular processes.

Native and introduced Argentine ant populations are characterised by distinct transcriptomic signatures associated with behaviour and immunity

Biological invasions can be influenced by trait variation in the invader, such as behavioural traits and ecological factors, such as variation in pathogen pressure. High-throughput nucleotide sequencing has increased our capacity to investigate the genomic basis of the functional changes associated with biological invasions. Here, we used RNA-sequencing in Argentina and California, Australia and New Zealand to investigate if native and introduced Argentine ant populations were characterised by distinct transcriptomic signatures. We focused our analysis on viral pressure and immunity, as well as genes associated with biogenic amines known to modulate key behaviour in social insects. Using a combination of differential expression analysis, gene co-expression network analysis and candidate gene approach, we show that native and introduced populations have distinct transcriptomic signatures. Genes associated with biogenic amines were overall up-regulated in the native range compared to introduced populations. Although we found no significant variation in overall viral loads amongst regions for viruses known to infect Argentine ants, viral diversity was lower in most of the introduced range which was interestingly associated with down-regulation of the RNAi immune pathway, primarily directed against viruses. Altogether, our data show that Argentine ant populations exhibit range-specific transcriptomic signatures, perhaps reflecting regional adaptations that may contribute to the ecological success of introduced populations.

Quantifying maladaptation during the evolution of sexual dimorphism

Females and males have distinct trait optima, resulting in selection for sexual dimorphism. However, most traits have strong cross-sex genetic correlations, which constrain evolutionary divergence between the sexes and lead to protracted periods of maladaptation during the evolution of sexual dimorphism. While such constraints are thought to be costly in terms of individual and population fitness, it remains unclear how severe such costs are likely to be. Building upon classical models for the 'cost of selection' in changing environments (sensu Haldane), we derived a theoretical expression for the analogous cost of evolving sexual dimorphism; this cost is a simple function of genetic (co)variances of female and male traits and sex differences in trait optima. We then conducted a comprehensive literature search, compiled quantitative genetic data from a diverse set of traits and populations, and used them to quantify costs of sexual dimorphism in the light of our model. For roughly 90% of traits, costs of sexual dimorphism appear to be modest, and comparable to the costs of fixing one or a few beneficial substitutions. For the remaining traits (approx. 10%), sexual dimorphism appears to carry a substantial cost-potentially orders of magnitude greater than costs of selection during adaptation to environmental changes.

Lost and Found: Taxonomic revision of the speckled skink (Oligosoma infrapunctatum; Reptilia; Scincidae) species complex from New Zealand reveals a potential cryptic extinction, resurrection of two species, and description of three new species

New Zealand has a diverse skink fauna, comprising 45 described native species, and at least 15 undescribed taxa, within the single genus Oligosoma Girard, 1857. One of the earliest described, and best known, species is the speckled skink, Oligosoma infrapunctatum (Boulenger 1887). Despite a relatively stable taxonomic history for nearly 114 years, recent molecular work has indicated that O. infrapunctatum represents a species complex, comprising numerous genetically divergent, range restricted taxa. We completed the first stage of a taxonomic revision of O. infrapunctatum, conducting a morphological re-evaluation of existing voucher material, and newly collected specimens, and generated a molecular phylogeny for the species complex. This allowed us to distinguish six species: O. infrapunctatum, two species resurrected from synonymy (O. newmani, O. robinsoni), and three new species (O. salmo sp. nov., O. albornense sp. nov. O. auroraensis sp. nov.). The name bearing type population of O. infrapunctatum has not been located again for at least 130 years: it remains to be rediscovered and may already be extinct. Two of the six species here are considered 'Nationally Critical' (O. albornense sp. nov., O. salmo sp. nov.) under the New Zealand Threat Classification System, the others are Nationally Vulnerable (O. auroraensis sp. nov.) and At Risk-Relict (O. newmani, O. robinsoni). Further taxonomic work will be required to determine the taxonomy of other speckled skink genetic lineages in the South Island, particularly O. aff. infrapunctatum "cobble", O. "Hokitika", O. "Southern North Island" and O. "Westport".

The effect of network size and sampling completeness in depauperate networks

The accurate estimation of interaction network structure is essential for understanding network stability and function. A growing number of studies evaluate under-sampling as the degree of sampling completeness (proportional richness observed). How the relationship between network structural metrics and sampling completeness varies across networks of different sizes remains unclear, but this relationship has implications for the within- and between-system comparability of network structure. Here, we test the combined effects of network size and sampling completeness on the structure of spatially distinct networks (i.e., subwebs) in a host-parasitoid model system to better understand the within-system variability in metric bias. Richness estimates were used to quantify a gradient of sampling completeness of species and interactions across randomly subsampled subwebs. The combined impacts of network size and sampling completeness on the estimated values of twelve unweighted and weighted network metrics were tested. The robustness of network metrics to under-sampling was strongly related to network size, and sampling completeness of interactions were generally a better predictor of metric bias than sampling completeness of species. Weighted metrics often performed better than unweighted metrics at low sampling completeness; however, this was mainly evident at large rather than small subweb size. These outcomes highlight the significance of under-sampling for the comparability of both unweighted and weighted network metrics when networks are small and vary in size. This has implications for within-system comparability of species-poor networks and, more generally, reveals problems with under-sampling ecological networks that may otherwise be difficult to detect in species-rich networks. To mitigate the impacts of under-sampling, more careful considerations of system-specific variation in metric bias are needed.

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

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. 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: (a) examine the covariation of physiology, environmental variables and colouration at a local scale; and (b) determine if these factors and their interplay explain broad clinal variation in morph frequency. 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. 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. 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.