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Considerable research has focused on microbes on amphibian skin, as they act as the first line of defense against invading pathogens. This effort has generated substantial data on patterns across species, space, time, and ontogeny, alongside a growing list of beneficial antifungal symbionts. Though there is evidence of stability in amphibian skin microbial communities, there is also an indication that regular skin shedding reduces cultivable bacteria, with regrowth and recolonization in the period between sheds. This suggests that skin communities are in constant flux, and we lack an understanding of how the membership and structure of those communities are affected by shedding events. In this study, we conducted experiments on cane toads (Rhinella marina) to investigate the influence of shedding on skin microbiomes. We first used quantitative PCR to verify a positive correlation between bacterial loads and time in the days after shedding. We then resampled individuals over time to describe changes in community composition in the 38 h after shedding using amplicon sequencing. Similar to trends of bacterial loads, we found increases in alpha diversity over time after shedding, suggesting that shedding reduces bacterial diversity as it knocks down bacterial loads. During the 38‐h period, community structure became similar to pre‐shed communities in some individuals, but there was no consistent pattern in structural changes among individuals. In light of the amphibian chytridiomycosis pandemic, understanding how physiological events such as skin shedding affect beneficial bacteria and communities on amphibians would provide important insight into amphibian ecology. [ABSTRACT FROM AUTHOR]

By imposing novel selection pressures on both participants, biological invasions can modify evolutionary 'arms races' between hosts and parasites. A spatially replicated cross-infection experiment reveals strong spatial divergence in the ability of lungworms (Rhabdias pseudosphaerocephala) to infect invasive cane toads (Rhinella marina) in Australia. In areas colonized for longer than 20 years, toads are more resistant to infection by local strains of parasites than by allopatric strains. The situation reverses at the invasion front, where super-infective parasites have evolved. Invasion-induced shifts in genetic diversity and selective pressures may explain why hosts gain advantage over parasites in long-colonized areas, whereas parasites gain advantage at the invasion front. [ABSTRACT FROM AUTHOR]

Variation in food resources can result in dramatic fluctuations in the body condition of animals dependent on those resources. Decreases in body mass can disrupt patterns of energy allocation and impose stress, thereby altering immune function. In this study, we investigated links between changes in body mass of captive cane toads (Rhinella marina), their circulating white blood cell populations, and their performance in immune assays. Captive toads that lost weight over a three-month period had increased levels of monocytes and heterophils and reduced levels of eosinophils. Basophil and lymphocyte levels were unrelated to changes in mass. Because individuals that lost mass had higher heterophil levels but stable lymphocyte levels, the ratio of these cell types was also higher, partially consistent with a stress response. Phagocytic ability of whole blood was higher in toads that lost mass, owing to increased circulating levels of phagocytic cells. Other measures of immune performance were unrelated to mass change. These results highlight the challenges faced by invasive species as they expand their range into novel environments which may impose substantial seasonal changes in food availability that were not present in the native range. Individuals facing energy restrictions may shift their immune function towards more economical and general avenues of combating pathogens. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'. [ABSTRACT FROM AUTHOR]

Objective: To assess the potential clinical efficacy of a novel model of energy psychology intervention, Advanced Integrative Therapy (AIT), this pilot study assessed clinician perceptions of AIT through a cross-sectional survey. Methods: A 17-item web-based questionnaire was administered to AIT therapists in November of 2021. The survey included clinician demographics and the clinician-observed response to AIT treatment based upon changes in reported Subjective Units of Distress (SUD), the associated emotion, and somatic sensation (when present). Results: A total of 76 complete responses were analyzed. The sample respondents were predominantly female (81.6%) and non-Hispanic white (68%). Over 80% of the respondents reported using AIT with their clients within the past six months and a significant proportion of participants self-assessed their AIT skills as of proficient or expert level. As reported by the therapists, 77% of the sessions described were used to clear patterns of negative events rather than a single event. Over 75% of events were identified as being either since childhood or otherwise chronic in nature. The average pre-AIT intervention SUD score was reported as 8.3±2.7 out of 10, which in 92% of cases, dropped to either 0 or 1 following a single session of AIT. Conclusions: Although this pilot study was limited to clinician responses in assessment of the ability of AIT to reduce the negative emotions related to past traumatic events, the initial observations were supportive of the potential clinical utility of this energy psychology technique. The findings suggest that additional client-based assessments and randomized clinical trials with known therapies as a control are warranted to continue the systematic observation of AIT. [ABSTRACT FROM AUTHOR]

Life-history traits such as rates of growth, survival and reproduction can vary though time within a single population, or through space among populations, due to abiotically-driven changes in resource availability. In terrestrial reptiles, parameters such as temperature and rainfall generate variation in life-histories—but other parameters likely are more important in marine systems. We studied three populations of sea snakes (Emydocephalus annulatus) in adjacent bays in the IndoPacific archipelago of New Caledonia. The extreme philopatry of individual snakes allows us to unambiguously allocate each animal to one of the three populations. Although water temperatures and rainfall do not differ over this small scale, one site experiences more intense winds, restricting opportunities for foraging. Our 18-year mark-recapture dataset (> 1,200 snakes, > 2,400 captures) reveals significant divergence among populations in life-history traits. Survival rates and population densities were similar among sites, but snakes at the most wind-exposed site (Anse Vata) exhibited lower body condition, slower growth, less frequent production of litters, and smaller litters. Weather-driven variation in feeding rates thus may affect life-history traits of marine snakes as well as their terrestrial counterparts, but driven by different parameters (e.g., wind exposure rather than variation in temperatures or rainfall). [ABSTRACT FROM AUTHOR]

Life-history traits such as rates of growth, survival and reproduction can vary though time within a single population, or through space among populations, due to abiotically-driven changes in resource availability. In terrestrial reptiles, parameters such as temperature and rainfall generate variation in life-histories—but other parameters likely are more important in marine systems. We studied three populations of sea snakes (Emydocephalus annulatus) in adjacent bays in the IndoPacific archipelago of New Caledonia. The extreme philopatry of individual snakes allows us to unambiguously allocate each animal to one of the three populations. Although water temperatures and rainfall do not differ over this small scale, one site experiences more intense winds, restricting opportunities for foraging. Our 18-year mark-recapture dataset (> 1,200 snakes, > 2,400 captures) reveals significant divergence among populations in life-history traits. Survival rates and population densities were similar among sites, but snakes at the most wind-exposed site (Anse Vata) exhibited lower body condition, slower growth, less frequent production of litters, and smaller litters. Weather-driven variation in feeding rates thus may affect life-history traits of marine snakes as well as their terrestrial counterparts, but driven by different parameters (e.g., wind exposure rather than variation in temperatures or rainfall). [ABSTRACT FROM AUTHOR]

Evolutionary theory suggests that polymorphic traits can be maintained within a single population only under specific conditions, such as negative frequency-dependent selection or heterozygote advantage. Non-venomous turtle-headed sea snakes (Emydocephalus annulatus) living in shallow bays near Noumea in New Caledonia exhibit three colour morphs: black, black-and-white banded, and an intermediate (grey-banded) morph that darkens with age. We recorded morph frequencies during 18 consecutive years of surveys, and found that the numbers of recruits (neonates plus immigrants) belonging to each morph increased in years when that morph was unusually rare in the population, and decreased when that morph was unusually common. Thus, morph frequencies are maintained by negative frequency-dependent selection. We interpret the situation as Batesian mimicry of highly venomous sea snakes (Aipysurus, Hydrophis, Laticauda) that occur in the same bays, and range in colour from black-and-white banded to grey-banded. Consistent with the idea that mimicry may protect snakes from attack by large fish and sea eagles, behavioural studies have shown that smaller fish species in these bays flee from banded snakes but attack black individuals. As predicted by theory, mimetic (banded) morphs are less common than the cryptically-coloured melanic morph. [ABSTRACT FROM AUTHOR]

For sea snakes as for many types of animals, long-term studies on population biology are rare and hence, we do not understand the degree to which annual variation in population sizes is driven by density-dependent regulation versus by stochastic abiotic factors. We monitored three populations of turtle-headed sea snakes (Emydocephalus annulatus) in New Caledonia over an 18-year period. Annual recruitment (% change in numbers) showed negative density-dependence: that is, recruitment increased when population densities were low, and decreased when densities were high. Windy weather during winter increased survival of neonates, perhaps by shielding them from predation; but those same weather conditions reduced body condition and the reproductive output of adult snakes. The role for density-dependence in annual dynamics of these populations is consistent with the slow, K-selected life-history attributes of the species; and the influence of weather conditions on reproductive output suggests that females adjust their allocation to reproduction based on food availability during vitellogenesis. [ABSTRACT FROM AUTHOR]

Understanding how animal populations respond to environmental factors is critical because large-scale environmental processes (e.g., habitat fragmentation, climate change) are impacting ecosystems at unprecedented rates. On an overgrazed floodplain in north-western Australia, a native rodent (Pale Field Rat, Rattus tunneyi) constructs its burrows primarily beneath an invasive tree (Chinee Apple, Ziziphus mauritiana) rather than native trees. The dense thorny foliage of the Chinee Apple may allow high rat densities either because of abiotic effects (shade, in a very hot environment) or biotic processes (protection from trampling and soil compaction by feral horses, and/or predation). To distinguish between these hypotheses, we manipulated Chinee Apple foliage to modify biotic factors (access to horses and predators) but not shade levels. We surveyed the rat population with Elliott traps under treatment and control trees and in the open woodland, in two seasons (the breeding season—January, and the nesting season—May). In the breeding season, we ran giving-up density experiments (GUD) with food trays, to assess the perceived risk of predation by rats across our three treatments. Selective trimming of foliage did not affect thermal regimes underneath the trees but did allow ingress of horses and we observed two collapsed burrows as a consequence (although long term impacts of horses were not measured). The perceived predation risk also increased (GUD values at food trays increased) and was highest in the open woodland. Our manipulation resulted in a shift in rat sex ratios (indicating female preference for breeding under control but not foliage-trimmed trees) and influenced rat behaviour (giving-up densities increased; large dominant males inhabited the control but not treatment trees). Our data suggest that the primary benefit of the Chinee Apple tree to native rodents lies in physical protection from predators and (potentially) feral horses, rather than in providing cooler microhabitat. [ABSTRACT FROM AUTHOR]

Anthropogenic activities often create distinctive but discontinuously distributed habitat patches with abundant food but high risk of predation. Such sites can be most effectively utilized by individuals with specific behaviors and morphologies. Thus, a widespread species that contains a diversity of sizes and behavioral types may be pre‐adapted to exploiting such hotspots. In eastern Australia, the giant (to >2 m) lizard Varanus varius (lace monitor) utilizes both disturbed (campground) and undisturbed (bushland) habitats. Our surveys of 27 sites show that lizards found in campgrounds tended to be larger and bolder than those in adjacent bushland. This divergence became even more marked after the arrival of a toxic invasive species (the cane toad, Rhinella marina) caused high mortality in larger and bolder lizards. Some of the behavioral divergences between campground and bushland lizards may be secondary consequences of differences in body size, but other habitat‐associated divergences in behavior are due to habituation and/or nonrandom mortality. [ABSTRACT FROM AUTHOR]

If optimal investment in anti-predator defences depends on predation risk, invading new regions (and thus, encountering different predators) may favour shifts in that investment. Cane toads offer an ideal system to test this prediction: expensive anti-predator toxins are stored mainly in parotoid glands whose dimensions are easy to measure, and toad invasions have changed the suites of predators they encounter. Although plasticity may influence parotoid morphology, comparisons between parents and progeny revealed that gland dimensions were highly heritable. That heritability supports the plausibility of an evolved basis to variation in gland dimensions. Measurements of 3779 adult toads show that females have larger glands than males, invasive populations have larger glands than in the native-range, and that parotoid sexual size dimorphism varies strongly among invaded areas. Geographic variation in parotoid morphology may be driven by predation risk to both adult toads and offspring (provisioned with toxins by their mother), with toxins allocated to eggs exacerbating the risk of cannibalism but reducing the risk of interspecific predation. Investment into chemical defences has evolved rapidly during the cane toad's international diaspora, consistent with the hypothesis that organisms flexibly adjust resource allocation to anti-predator tactics in response to novel challenges. [ABSTRACT FROM AUTHOR]

The water‐permeable skin of amphibians renders them highly sensitive to climatic conditions, and interspecific correlations between environmental moisture levels and rates of water exchange across the skin suggest that natural selection adapts hydroregulatory mechanisms to local challenges. How quickly can such mechanisms shift when a species encounters novel moisture regimes? Cutaneous resistance to water loss and gain in wild‐caught cane toads (Rhinella marina) from Brazil, USA (Hawai'i) and Australia exhibited strong geographic variation. Cutaneous resistance was low in native‐range (Brazilian) toads and in Hawai'ian populations (where toads were introduced in 1932) but significantly higher in toads from eastern Australia (where toads were introduced in 1935). Toads from recently invaded areas in western Australia exhibited cutaneous resistance to water loss similar to the native‐range populations, possibly because toads are restricted to moist sites within this highly arid landscape. Rates of rehydration exhibited significant but less extreme geographic variation, being higher in the native range than in invaded regions. Thus, in less than a century, cane toads invading areas that impose different climatic challenges have diverged in the capacity for hydroregulation. [ABSTRACT FROM AUTHOR]

The structure of the skin may evolve rapidly during a biological invasion, for two reasons. First, novel abiotic challenges such as hydric conditions may modify selection of traits (such as skin thickness) that determine rates of evaporative water loss. Second, invaders might benefit from enhanced rates of dispersal, with locomotion possibly facilitated by thinner (and hence more flexible) skin. We quantified thickness of layers of the skin in cane toads (Rhinella marina) from the native range (Brazil), a stepping-stone population (Hawaii), and the invaded range in Australia. Overall, the skin is thinner in cane toads in Australia than in the native range, consistent with selection on mobility. However, layers that regulate water exchange (epidermal stratum corneum and dermal ground substance layer) are thicker in Australia, retarding water loss in hot dry conditions. Within Australia, epidermal thickness increased as the toads colonized more arid regions, but then decreased in the arid Kimberley region. That curvilinearity might reflect spatial sorting, whereby mobile (thin-skinned) individuals dominate the invasion front; or the toads' restriction to moist sites in this arid landscape may reduce the importance of water-conservation. Further work is needed to clarify the roles of adaptation versus phenotypic plasticity in generating the strong geographic variation in skin structure among populations of cane toads. [ABSTRACT FROM AUTHOR]

Within all wild populations, individuals vary in ways that affect their vulnerability to threatening processes. Understanding that variation may clarify mechanisms of population persistence and/or evolution. In Australia, Yellow-spotted Monitors (Varanus panoptes), decline by >90% when toxic Cane Toads (Rhinella marina) invade an area. Taste-aversion training (exposing animals to non-lethal toads) can buffer impacts; but does pre-existing behavioural variation also influence survival? An individual's fate can be predicted from its behaviour during aversion-training trials. Lizards presented with small toads either consumed them, rejected them, or fled. When Cane Toads invaded our study site, mortality was lower in lizards that 'consumed' (aversion-trained) than in those that 'fled' (untrained), but even lower in lizards that 'rejected' toads outright. Thus, animals reluctant to consume toads in trials survived despite never being aversion-trained. In this system, lizard vulnerability is driven by boldness, behavioural responses to novel prey types, and the opportunity to learn aversion. [ABSTRACT FROM AUTHOR]

Amphibians in hot climates may be able to avoid high temperatures by controlling their rates of heating. In northern Australia, invasive cane toads (Rhinella marina) experience hot dry conditions in newly-colonized (western) sites but milder conditions in longer-occupied (eastern) sites. Under standardized conditions, toads from western sites heated less rapidly than did conspecifics from an eastern site. The availability of free water slowed heating rates of eastern but not western toads. Thus, the colonization of climatically extreme sites has been accompanied by a rapid shift in the toads' ability to remain cool under hot conditions, even when free water is not available. [ABSTRACT FROM AUTHOR]

Tidal cycles are known to affect the ecology of many marine animals, but logistical obstacles have discouraged behavioural studies on sea snakes in the wild. Here, we analyse a large dataset (1,445 observations of 126 individuals) to explore tidally-driven shifts in the behaviour of free-ranging turtle-headed sea snakes (Emydocephalus annulatus, Hydrophiinae) in the Baie des Citrons, New Caledonia. Snakes tended to move into newly-inundated areas with the rising tide, and became more active (e.g. switched from inactivity to mate-searching and courting) as water levels rose. However, the relative use of alternative habitat types was largely unaffected by tidal phase. [ABSTRACT FROM AUTHOR]

In many populations of terrestrial snakes, the phenotype of an individual (e.g. body size, sex, colour) affects its habitat use. One cause for that link is gape limitation, which can result in larger snakes eating prey that are found in different habitats. A second factor involves thermoregulatory opportunities, whereby individuals select habitats based upon thermal conditions. These ideas predict minimal intraspecific variation in habitat use in a species that eats small prey and lives in a thermally uniform habitat, such as the sea snake Emydocephalus annulatus , which feeds on tiny fish eggs and lives in inshore coral reefs. To test that prediction, we gathered data on water depths and substrate attributes for 1475 sightings of 128 free-ranging E. annulatus in a bay near Noumea, New Caledonia. Habitat selection varied among individuals, but with a preference for coral-dominated substrates. The body size and reproductive state of a snake affected its detectability in deep water, but overall habitat use was not linked to snake body size, colour morph, sex or pregnancy. A lack of ontogenetic shifts in habitat use allows extreme philopatry in E. annulatus , thereby reducing gene flow among populations and, potentially, delaying recolonization after local extirpation events. [ABSTRACT FROM AUTHOR]

Objective: To examine psychotropic medication prescription practices in federal Canadian penitentiaries.Method: 468 files were drawn from a purposive sample of thirteen Canadian federal institutions representing the five regions, different security levels, and male and female designated facilities. Information on the names of all psychotropic medications prescribed, indications for use, dosage, frequency, and route of administration was retrieved. Designation of approved or off-label use of medications was determined by consulting: (1) the Health Canada (2016) Drug Product Database, (2) the Canadian Compendium of Pharmaceuticals and Specialties 2016, and (3) the American Hospital Formulary Service Drug Information 2016. Prescription rates were examined by gender, Indigenous ancestry, drug class, institutional infractions, and current offence.Results: 36.2% of prescriptions for psychotropic medication were coded as 'off-label'. Anxiolytic/hypnotics drugs were the psychotropic drugs most commonly used for off-label purposes. There were no differences in the prevalence of approved versus off-label prescriptions based on Indigenous ancestry or gender, and no pattern of elevated off-label prescription practices for offenders involved in institutional misconducts or those sentenced for the most serious crimes.Conclusions: The rates of prescribing 'off-label' psychotropic medication are not elevated relative to other correctional settings or to rates cited in Canadian surveys conducted in the community. [ABSTRACT FROM AUTHOR]

Measurements of > 3700 field-collected cane toads (Rhinella marina) show that head width relative to body length differs between the sexes and has become modified during the toad's translocation from French Guiana to Hawai'i and then Australia. Relative head width was highest in the native range, and declined progressively during the invasion. In long-colonized areas (French Guiana through to Queensland) male toads have wider heads than females, but this dimorphism decreases and eventually reverses at invasion fronts in both northern and southern Australia. To explore reasons for that variation, we conducted experiments on captive toads. A toad's head width affected its maximal ingestible prey size and prey-handling ability. Head width relative to body length was highly repeatable, consistent over ontogeny, and exhibited significant heritability (h2 = 0.20). Relative head widths differed between the sexes and populations-of-origin even if offspring were raised under standard conditions in captivity. Nonetheless, relative head width of a cane toad also is affected by prey availability. Captive toads raised on a diet of small prey items developed wider heads than did conspecifics raised on larger prey, partly compensating for the trophic limitations of smaller body size. Sexual and geographical divergences in relative head widths in cane toads are thus the combined result of rapid evolutionary divergence (in < 100 years) and an ability of individual toads to flexibly modify this important morphological feature depending upon local conditions. [ABSTRACT FROM AUTHOR]

Abstract: Acute activation of the immune system often initiates a suite of behavioural changes. These “sickness behaviours”—involving lethargy and decreased activity—may be particularly costly on invasion fronts, where evolutionary pressures on dispersal favour individuals that move large distances. We used a combination of field and laboratory studies to compare sickness behaviours of cane toads from populations differing in invasion history. To do this we stimulated immune system activation by injecting lipopolysaccharide (LPS) to mimic bacterial infection. We predicted that LPS would result in less severe sickness behaviour in toads from range‐edge populations because they had undergone selection for rapid and sustained dispersal (activities in conflict with lethargy and decreased activity). Contrary to our prediction, LPS injection caused a greater reduction in dispersal‐relevant traits in invasion‐front individuals than in conspecifics from the range‐core. Our data suggest that the rapid invasion of cane toads through tropical Australia has seen an evolutionary shift in the magnitude of sickness behaviour elicited by pathogen infection. The increased sickness behaviour among range‐edge toads suggests a shift away from pathogen tolerance (seen in range‐core populations) towards resistance to pathogen attack. But as a consequence, when pathogens do become successfully established, toads from invasion‐front populations may have less capacity to tolerate their ill‐effects. [ABSTRACT FROM AUTHOR]

Abstract: Biological invasions can stimulate rapid shifts in organismal performance, via both plasticity and adaptation. We can distinguish between these two proximate mechanisms by rearing offspring from populations under identical conditions and measuring their locomotor abilities in standardized trials. We collected adult cane toads (Rhinella marina) from invasive populations that inhabit regions of Australia with different climatic conditions. We bred those toads and raised their offspring under common‐garden conditions before testing their locomotor performance. At high (but not low) temperatures, offspring of individuals from a hotter location (northwestern Australia) outperformed offspring of conspecifics from a cooler location (northeastern Australia). This disparity indicates that, within less than 100 years, thermal performance in cane toads has adapted to the novel abiotic challenges that cane toads have encountered during their invasion of tropical Australia. [ABSTRACT FROM AUTHOR]

We incubated the eggs of field‐caught keelback snakes (Tropidonophis mairii) on wet versus dry substrates to explore impacts of incubation conditions on white blood cell (WBC) concentrations and differential WBC counts of hatchlings. In a second, independent study young snakes were released into the field, allowing us to explore fitness correlates of WBC profiles. Dry incubation reduced embryonic survival and hatchling body size, thus decoupling egg size from hatchling size. Incubation conditions also altered WBC profiles. Lymphocyte and azurophil counts were related to hatchling body size but not to initial egg mass, whereas heterophil counts were related to both of these traits. The egg‐size effect on heterophil counts may reflect a maternal effect on offspring immune configuration. The ratio of heterophils to lymphocytes (an index of stress) was higher in hatchlings from eggs incubated on dry substrates. Snakes with higher counts of lymphocytes at hatching were more likely to be recaptured as adults (H:L; an index of survival), whereas snakes with higher basophil counts exhibited more rapid growth. In summary, our experiments show that incubation moisture levels influence the immune configuration of hatchling snakes, and that variation among individuals in WBC counts at hatching is a significant predictor of an individual's fitness after it is released into the wild. The demonstrated link between incubation conditions and offspring fitness is likely to impose strong selection on maternal nest‐site choice. The amount of moisture available to incubating snake eggs affects the types of circulating white blood cells in the resultant hatchlings. The proportions of different cell types are linked to fitness traits of hatchlings following their release into the wild. [ABSTRACT FROM AUTHOR]

Broad phylogenetic patterns in sexual size dimorphism ( SSD) are shaped by sex differences in net selection pressures (e.g. sexual selection, fecundity selection, survival selection), but environmental and ecological factors can also affect the expression of SSD., Discussions of proximate ecological influences on SSD have focused on niche divergence; for example, increase in a prey type used by only one sex can elevate growth rates of that sex but not the other. Food limitation also can generate spatial and temporal variation in SSD. Under restricted prey abundance, curtailed growth may mask SSD even if the optimal size is greater for one sex than the other. Because an increase in food availability elicits increased feeding and growth by the sex that benefits more from increased body size, variation in prey abundance can generate variation in SSD., We used mark-recapture methods to study growth rates relative to prey (frog) abundance in two species of sexually dimorphic colubrid snake species in tropical Australia., In slatey-grey snakes ( Stegonotus cucullatus), a species in which larger body size enhances reproductive output in both sexes (because larger males win combat bouts, and larger females produce more/heavier eggs), increased abundance of frogs caused equivalent increases in growth rates in both sexes and hence did not affect SSD. In keelbacks ( Tropidonophis mairii), a species in which larger size enhances reproductive output in females more than males (reflecting a lack of male-male combat), increased abundance of frogs elicited higher growth rates of females only. Thus, SSD in keelbacks was modified by prey abundance., Our results show that the magnitude of sex differences in adult body size can be influenced by proximate environmental factors and support the hypothesis of sex-specific targets for maximum feeding rates., A is available for this article. [ABSTRACT FROM AUTHOR]

Toe-clipping is a standard technique for marking reptiles and amphibians individually, but concerns have been raised about the impact of the practice on animal welfare, survival, and behavior. We used a long-term mark-recapture dataset to investigate the impact of toe removal on free-ranging adult Cane Toads ( Rhinella marina). Our analysis of 213 toads showed no impact of the number of toes removed on growth rates for mass or snout-urostyle length, nor any effect on body condition. Trials with sub-adult toads on a laboratory raceway revealed a short-term impact of toe-clipping on willingness to move (i.e., decreased immediately post-clipping), but no other significant impacts on locomotion. In summary, toe-clipping had minimal effects on Cane Toad locomotor ability, growth rate, or body condition. [ABSTRACT FROM AUTHOR]

In an ecosystem under simultaneous threat from multiple alien species, one invader may buffer the impact of another. Our surveys on a remote floodplain in the Kimberley region of north western Australia show that invasive chinee apple trees ( Ziziphus mauritiana) provide critical refuge habitat for native rodents (pale field rats, Rattus tunneyi). Feral horses ( Equus caballus) have trampled most of the remaining floodplain, but are excluded from the area around each chinee apple tree by thorny foliage. Although chinee apple trees constituted <10% of trees along our transects, they represented >50% of trees that harboured rat burrows. The mean number of burrows under each chinee apple tree was twice as high as under most other tree species, and we trapped more than seven times as many rats under chinee apple trees as under other types of trees. The extensive burrow systems under chinee apple trees contained female as well as male rats, whereas we only captured males around the smaller burrow systems under other tree species. Our data suggest that this invasive tree plays a critical role in the persistence of pale field rat populations in this degraded ecosystem, and that managers should maintain these trees (despite their alien origins) at least until feral horses have been removed. [ABSTRACT FROM AUTHOR]

Although primarily terrestrial, cane toads ( Rhinella marina) sometimes climb near-vertical surfaces (tree-trunks, cliffs, fences) during foraging or dispersal activities. We scored climbing ability (in laboratory trials) of 288 cane toads from four regions in Australia, plus two sites on the island of Hawai'i. We found strong divergence in climbing ability associated not only with sex and relative limb length, but also population of origin. Within each population, longer-limbed individuals (and hence, males rather than females) were better climbers, although the geographical divergence in climbing ability remained significant even when sex and limb length were included in multivariate regression models. The geographical difference in climbing ability (but not morphology) disappeared when the progeny were raised in captivity under identical conditions, without climbing opportunities. Although influenced by morphology, climbing ability in wild-caught cane toads appears to be driven primarily by local environmental conditions that facilitate and/or reward arboreal activity. [ABSTRACT FROM AUTHOR]

In midsummer 2002-2003, intense wildfires raged through the Brindabella Range of south-eastern Australia, including sites where we have studied the ecology of scincid lizards (especially Bassiana duperreyi) for decades. Data-loggers measured the thermal regimes experienced by eggs during these fires (revealing lethally high temperatures in nests under logs in the forest but minimal effect in nests under rocks in clearings). Eggs from forest-clearing nests hatched successfully. Reproductive output of lizards in one area was reduced in the years post-fire (perhaps because of inadequate food [insect] abundance to fuel female reproduction) but soon recovered. The fires reduced vegetation density and thus increased the availability of sun-exposed rocks that serve as potential nest sites. However, the magnitude and duration of these effects differed among sites. Five years after these intense fires, canopy openness (and thus, sunlight penetration to create thermally suitable nest sites) was indistinguishable from pre-fire conditions. Our data reveal strong spatial heterogeneity both in the immediate effects of fire on lizard reproduction and in longer-term post-fire changes in habitat quality. Surprisingly, these intense wildfires had only transitory and local effects on nest-site availability for the heliothermic lizards that we study, but impacts likely were more severe on sympatric taxa that depend upon moist cool microhabitats. [ABSTRACT FROM AUTHOR]

Abstract: Although widespread declines in anuran populations have attracted considerable concern, the stochastic demographics of these animals make it difficult to detect consistent trends against a background of spatial and temporal variation. To identify long‐term trends, we need datasets gathered over long time periods, especially from tropical areas where anuran biodiversity is highest. We conducted road surveys of four anurans in the Australian wet–dry tropics on 4637 nights over a 16‐year period. Our surveys spanned the arrival of invasive cane toads (Rhinella marina), allowing us to assess the invader's impact on native anuran populations. Our counts demonstrate abrupt and asynchronous shifts in abundance and species composition from one year to the next, not clearly linked to rainfall patterns. Typically, periods of decline in numbers of a species were limited to 1–2 years and were followed by 1‐ to 2‐year periods of increase. No taxa showed consistent declines over time, although trajectories for some species showed significant perturbations coincident with the arrival of toads. None of the four focal frog species was less common at the end of the study than at the beginning, and three of the species reached peak abundances after toad arrival. Survey counts of cane toads increased rapidly during the initial stage of invasion but have subsequently declined and fluctuated. Distinguishing consistent declines versus stochastic fluctuations in anuran populations requires extensive time‐series analysis, coupled with an understanding of the shifts expected under local climatic conditions. This is especially pertinent when assessing impacts of specific perturbations such as invasive species. [ABSTRACT FROM AUTHOR]

At an invasion front, energetic and physiological trade-offs may differ from those at the range-core as a result of selection for enhanced dispersal, combined with a low density of conspecifics (which reduces pathogen transmission and competition for food). We measured traits related to energy stores and immunity in wild cane toads ( Rhinella marina) across a 750-km transect from their invasion front in tropical Australia, back into sites colonized 21 years earlier. Several traits were found to vary with population age; some linearly and others in a curvilinear manner. The relative size of spleens and fat bodies was highest in the oldest and newest populations, where rates of lungworm infection were lowest. Toads from older populations produced more corticosterone in response to a standardized stressor, and had higher lymphocyte counts (but lower basophil counts). The amount of skin swelling elicited by phytohaemagglutinin injection did not vary geographically, although recruitment of leukocytes to the injected tissue was higher in toads from long-colonized areas. Because this was a field-based study, we cannot differentiate the effects of population age, toad density or pathogen pressure on our measures of stress and immune responses, nor can we distinguish whether the causation involves hard-wired adaptive processes or phenotypically plastic responses. Nonetheless, our data demonstrate substantial variation in immune systems among toads at varying distances from an invasion front, showing that a biological invasion imposes strong pressures on physiological systems of the invader. [ABSTRACT FROM AUTHOR]

Although generalized habitat use may contribute to the success of invasive taxa, even species that are typically described as habitat generalists exhibit non-random patterns of habitat use. We measured abiotic and biotic factors in 42 plots (each 100 × 10 m) along a 4.2-km long unpaved road in tropical Australia, at a site that had been invaded by cane toads ( R hinella marina Bufonidae) seven years previously. We also counted anurans at night in each of these plots on 103 nights during the tropical wet season, over a five-year period, beginning soon after the initial toad invasion. Spatial distributions differed significantly among adult male toads ( n = 1047), adult female toads ( n = 1222), juvenile toads ( n = 342) and native frogs ( C yclorana australis Hylidae, n = 234). Adult male toads were closely associated with water bodies used as calling and/or spawning sites, whereas adult female toads and native frogs were most commonly encountered in drier forested areas on sloping ground. Juvenile toads used the margins of the floodplain more than conspecific adults did, but the floodplain itself was rarely used. Understanding which components of the habitat are most important to specific age and sex classes within a population, or how invasive species differ from native species in this respect, can clarify issues such as the spatial and temporal location of ecological impact by an invader, and the most effective places for control of the invader with minimal collateral effects on the native biota. [ABSTRACT FROM AUTHOR]

We investigated patterns of prevalence and intensity of gastrointestinal nematode infections in a tropical natricine snake, the keelback ( T ropidonophis mairii). Ninety-eight per cent of keelbacks were infected with T anqua anomala ( Gnathostomidae), with infection intensities of up to 243 worms per snake. Infection with T . anomala caused severe inflammation of stomach mucosa and submucosa at the sites of parasite attachment and encystment. Nonetheless, we did not detect detrimental effects of nematode infection on measures of fitness among wild or captive snakes. Snakes with heavier nematode infections had higher body condition scores than less-infected individuals. Deworming captive snakes had no measurable effect on their growth rate, body condition or locomotor performance. In combination with an earlier study on blood-dwelling hepatozoons, our work suggests that keelbacks have a high tolerance to parasites. The 'fast-pace' life history and short lifespan of these snakes may make it beneficial for them to tolerate infection, rather than expend energy on resisting parasite attack. [ABSTRACT FROM AUTHOR]

The ability to disperse along a consistent compass heading strongly affects the rate and efficiency of an animal's displacement, and thus is under selection at the expanding edge of a biological invasion., We used radiotelemetry to assess whether the dispersal direction of cane toads ( Rhinella marina) changed as a function of time since invasion, by comparing (i) toads at a single site monitored annually for 10 years subsequent to toad arrival; (ii) toads collected from sites across the species' invaded range in Australia, and radiotracked at a common site; and (iii) the offspring of those transported toads that were reared in captivity under common-garden conditions., The first of these data sets showed non-random directionality, indicating strong spatial sorting operating on this trait: toads moved in a north-westerly direction for the first 6 years post-invasion, but in random directions thereafter. Despite the evidence for trait sorting, no consistent directionality was seen in toads relocated from populations with different invasion histories nor in their offspring. Why do we see no evolutionary shifts?, Dispersal directionality of the offspring was not correlated with that of their parents, arguing against a genetic basis to this behavioural trait. Thus, while an expanding invasion front creates an evolutionary pressure for animals to move in a specific direction, evolution of this trait has not occurred in this system because directionality is not heritable., The observed north-westerly movements of toads at the invasion front were due to simple density differentials: in the first few years, most toads arriving at our study site originated from earlier-colonized (and hence denser) populations to the south-east. [ABSTRACT FROM AUTHOR]

This study measured the prevalence of current, severe symptoms of a mental health problem in an adult population of inmates in Ontario, Canada. The Resident Assessment Instrument–Mental Health was used to measure the prevalence of symptoms among a sample of 522 inmates. Propensity score weighting was used to adjust for nonrandom selection into the sample. Prevalence estimates were derived for the total inmate population, remand and sentenced, males and females, and Aboriginal and non-Aboriginal inmates. It is estimated that 41.1% of Ontario inmates will have at least one current, severe symptom of a mental health problem; of this group, 13.0%, will evidence two or more symptoms. The number of symptoms is strongly associated with presence of a psychiatric diagnosis and level of mental health care needs. Female (35.1%) and Aboriginal (18.7%) inmates are more likely to demonstrate two or more current, severe symptoms. Greater efforts must be made to bridge the gap between correctional and mental health care systems to ensure inmates in correctional facilities can access and receive appropriate mental health care services. [ABSTRACT FROM PUBLISHER]

Because an individual's investment into the immune system may modify its dispersal rate, immune function may evolve rapidly in an invader. We collected cane toads ( Rhinella marina) from sites spanning their 75-year invasion history in Australia, bred them, and raised their progeny in standard conditions. Evolved shifts in immune function should manifest as differences in immune responses among the progeny of parents collected in different locations. Parental location did not affect the offspring's cell-mediated immune response or stress response, but blood from the offspring of invasion-front toads had more neutrophils, and was more effective at phagocytosis and killing bacteria. These latter measures of immune function are negatively correlated with rate of dispersal in free-ranging toads. Our results suggest that the invasion of tropical Australia by cane toads has resulted in rapid genetically based compensatory shifts in the aspects of immune responses that are most compromised by the rigours of long-distance dispersal. [ABSTRACT FROM AUTHOR]

We used GPS-based radiotelemetry to quantify diel activity patterns and movements by two species of large scincid lizards in the Australian wet-dry tropics. From an average of 63 days tracking of 54 Northern Bluetongues ( Tiliqua scincoides intermedia) and 42 days tracking of 8 Centralian Bluetongues ( Tiliqua multifasciata), we obtained 53,801 and 8,139 data points, respectively, on lizard locations over a 13-month period. Lizard species, sex, and study site had relatively little effect on distances moved, at both daily and hourly levels. However, Northern Bluetongues moved further per day than did Centralian Bluetongues at a site where they were sympatric. Most movements were <20 m, with longer movements (dispersal between core areas within the wider home range) occurring primarily during midmorning and late afternoon. The only major effect of ambient temperatures on lizard activity patterns likely was that midday movements were precluded by the risk of overheating; at all other times of the day and night, temperatures remained within a range that enabled effective locomotion and foraging. Thus, thermal constraints of the timing and extent of movements are less important in this system than in the cool-temperate squamate species that have been the focus of most previous research on this topic. [ABSTRACT FROM AUTHOR]

Individual variation in behavioural traits (including responses to social cues) may influence the success of invasive populations. We studied the relationship between sociality and personality in invasive cane toads (Rhinella marina) from a recently established population in tropical Australia. In our field experiments, we manipulated social cues (the presence of a feeding conspecific) near a food source. We captured and compared toads that only approached feeding sites where another toad was already present, with conspecifics that approached unoccupied feeding sites. Subsequent laboratory trials showed correlated personality differences (behavioural syndromes) between these two groups of toads. For example, toads that approached already-occupied rather than unoccupied feeding sites in the field, took longer to emerge from a shelter-site in standardized trials, suggesting these individuals are ‘shy’ (whereas toads that approached unoccupied feeding stations tended to be ‘bold’). Manipulating hunger levels did not abolish this difference. In feeding trials, a bold toad typically outcompeted a shy toad under conditions of low prey availability, but the outcome was reversed when multiple prey items were present. Thus, both personality types may be favored under different circumstances. This invasive population of toads contains individuals that exhibit a range of personalities, hinting at the existence of a wide range of social dynamics in taxa traditionally considered to be asocial. [ABSTRACT FROM AUTHOR]

What level of immunocompetence should an animal maintain while undertaking long-distance dispersal? Immune function (surveillance and response) might be down-regulated during prolonged physical exertion due to energy depletion, and/or to avoid autoimmune reactions arising from damaged tissue. On the other hand, heightened immune vigilance might be favored if the organism encounters novel pathogens as it enters novel environments. We assessed the links between immune defense and long-distance movement in a population of invasive cane toads (Rhinella marina) in Australia. Toads were radio-tracked for seven days to measure their activity levels and were then captured and subjected to a suite of immune assays. Toads that moved further showed decreased bacteria-killing ability in their plasma and decreased phagocytic activity in their whole blood, but a heightened skin-swelling response to phytohemagglutinin. Baseline and post-stress corticosterone levels were unrelated to distance moved. Thus, long-distance movement in cane toads is associated with a dampened response in some systems and enhanced response in another. This pattern suggests that sustained activity is accompanied by trade-offs among immune components rather than an overall down or up-regulation. The finding that high mobility is accompanied by modification of the immune system has important implications for animal invasions. [ABSTRACT FROM AUTHOR]

Male body size can play an important role in the mating systems of anuran amphibians. We conducted laboratory- based trials with cane toads Rhinella (Bufo) marina from an invasive population in the wet-dry tropics of northern Australia, to clarify the effects of a male's body size on his reproductive success and behavior (mate choice). Males were stimulated with a synthetic hormone to induce reproductive readiness. Larger body size enhanced a male toad's ability to displace a smaller rival from amplexus, apparently because of physical strength: more force was required to dislodge a larger than a smaller amplectant male. A male's body size also affected his mate-choice criteria. Males of all body sizes were as likely to attempt amplexus with another male as with a female of the same size, and preferred larger rather than smaller sexual targets. However, this size preference was stronger in larger males and hence, amplexus was size-assortative. This pattern broke down when males were given access to already-amplectant male-female pairs: males of all body sizes readily attempted amplexus with the pair, with no size discrimination. An amplectant pair provides a larger visual stimulus, and prolonged amplexus provides a strong cue for sex identification (one of the individuals involved is almost certainly a female). Thus, a male cane toad's body size affects both his ability to defeat rivals in physical struggles over females, and the criteria he uses when selecting potential mates, but the impacts of that selectivity depend upon the context in which mating occurs. [ABSTRACT FROM AUTHOR]

The success of a biological invasion can depend upon other invasions; and in some cases, an earlier invader may fail to spread until facilitated by a second invader. Our study documents a case whereby an invasive parasite has remained patchily distributed for decades due to the fragmented nature of available hosts; but the recent arrival of a broadly distributed alternative invasive host species provides an opportunity for the parasite to expand its range considerably. At least 20 years ago, endoparasitic pentastomids ( Raillietiella frenata) were brought with their native host, the invasive Asian house gecko Hemidactylus frenatus, to the port city of Darwin in tropical Australia. These geckos rarely disperse away from human habitation, restricting the transmission of their parasites to urban environments - and thus, their pentastomids have remained patchily distributed and have only been recorded in scant localities, primarily surrounding Darwin. The recent range expansion of the invasive cane toad Rhinella marina into the Darwin area has provided an alternative host for this pentastomid. Our results show that the cane toad is a competent host for Ra. frenata- toads shed fully embryonated pentastomid eggs in their faeces - and that pentastomids are now common in cane toads near Darwin. Likely reflecting the tendency for the parasite's traditional definitive host (the Asian house gecko) and only known intermediate host (the cockroach) to reside around buildings, we found the prevalence of this parasite follows an urban distribution. Because cane toads are widely distributed through urban and rural habitat and can shed viable pentastomid eggs, the toad invasion is likely to facilitate the parasite's spread across the tropics, into areas (and additional susceptible hosts) that were previously inaccessible to it. [ABSTRACT FROM AUTHOR]

Dispersal biology at an invasion front differs from that of populations within the range core, because novel evolutionary and ecological processes come into play in the nonequilibrium conditions at expanding range edges. In a world where species' range limits are changing rapidly, we need to understand how individuals disperse at an invasion front. We analyzed an extensive dataset from radio-tracking invasive cane toads (Rhinella marina) over the first 8 y since they arrived at a site in tropical Australia. Movement patterns of toads in the invasion vanguard differed from those of individuals in the same area postcolonization. Our model discriminated encamped versus dispersive phases within each toad's movements and demonstrated that pioneer toads spent longer periods in dispersive mode and displayed longer, more directed movements while they were in dispersive mode. These analyses predict that overall displacement per year is more than twice as far for toads at the invasion front compared with those tracked a few years later at the same site. Studies on established populations (or even those a few years postestablishment) thus may massively underestimate dispersal rates at the leading edge of an expanding population. This, in turn, will cause us to underpredict the rates at which invasive organisms move into new territory and at which native taxa can expand into newly available habitat under climate change. [ABSTRACT FROM AUTHOR]

New technologies for quantifying animal locations enable us to document habitat-selection patterns of cryptic taxa in extraordinary detail. Northern bluetongues ( Tiliqua scincoides intermedia) and centralian bluetongues ( Tiliqua multifasciata) are large heavy-bodied scincid lizards that are broadly sympatric in the wet-dry tropics of north-western Australia. We used data from GPS-based radiotelemetry ( n = 49 lizards, tracked for 2-121 days, total n = 61 640 locations) to examine the size, internal structure and overlap of lizard home ranges. Despite substantial habitat differences at our two study sites (semi-arid and relatively pristine habitat at Keep River National Park, Northern Territory, vs. highly disturbed and fragmented flood plain habitat in an agricultural area near Kununurra, Western Australia), home ranges were similar between the two areas, and between the two species. Our radio-tracked lizards continued to disperse into previously unused areas throughout the duration of the study, so that the total areas used by lizards continued to increase. Based on the minimum convex polygon method, total home ranges averaged 4 ha (range 2-12 ha), but only about two-thirds of each home range was used intensively. Each home range had multiple core areas, and overlap of core as well as peripheral areas (especially with same-sex conspecifics) was high at the disturbed ( Western Australia) site where lizard densities were high. The concentration of lizard activity within small core areas, often used by multiple individuals, suggests that these heavily used sites are critical to lizard conservation. However, the lizards' infrequent long-distance displacements also make them vulnerable to changes in the wider landscape mosaic. Because GPS-based radiotelemetry can quantify habitat use at finer spatial and temporal scales than earlier technologies, it can provide a robust base for management of at-risk fauna. [ABSTRACT FROM AUTHOR]

In biological invasions, rates of range expansion tend to accelerate through time. What kind of benefits to more rapidly dispersing organisms might impose natural selection for faster rates of dispersal, and hence the evolution of range-edge acceleration? We can answer that question by comparing fitness-relevant ecological traits of individuals at the invasion front compared with conspecifics in the same area a few years post-invasion., In tropical Australia, the rate of invasion by cane toads ( Rhinella marina) has increased substantially over recent decades, due to shifts in heritable traits. Our data on field-collected cane toads at a recently invaded site in the Australian wet-dry tropics span a 5-year period beginning with toad arrival., Compared with conspecifics that we monitored in the same sites post-invasion, toads in the invasion vanguard exhibited higher feeding rates, larger energy stores, better body condition and faster growth., Three processes may have contributed to this pattern: (i) higher prey availability at the front (perhaps due to reduced competition from conspecifics); (ii) the lack of viability-reducing parasites and pathogens in invasion-front toads; and (iii) distinctive (active, fast-growing) phenotypes of the invasion-front toads., Nutritional benefits to individuals in the invasion vanguard (whether because of higher prey availability, or lower pathogen levels) thus may have conferred a selective advantage to accelerated dispersal in this system. [ABSTRACT FROM AUTHOR]

Disentangling the effects of prey limitation (bottom-up) and predation (top-down) processes on natural populations is difficult, but the perturbations introduced by an invasive species can provide pseudo-experimental evidence on this issue., In tropical Australia, keelbacks ( Tropidonophis mairii) and slatey-grey snakes ( Stegonotus cucullatus) experience little direct cost or benefit from the arrival of toxic invasive cane toads ( Rhinella marina), because they rarely eat toads and if they do, are relatively resistant to the toads' toxins. Nonetheless, these snakes could be affected indirectly by toad-induced decreases in the availability of prey (native frogs) and/or by fatal poisoning of the snakes' predators (large varanid lizards). The former (bottom-up) effect predicts decreases in snake body condition, feeding and growth rates after toads arrive, whereas the latter (top-down) effect predicts increases in survival., Our mark-recapture studies on these snakes in tropical Australia (for 7 years before and 7 years after toad arrival) reveal bottom-up effects both on an anurophagous dietary specialist (keelbacks) and a generalist feeder (slatey-grey snakes)., Top-down effects of toad arrival were seen in keelbacks but not in slatey-grey snakes, perhaps reflecting the latter's larger body size., Indirect effects coinciding with the timing of toad invasion thus were mediated through changes in food supply for both native species and in rates of predation for one species. [ABSTRACT FROM AUTHOR]

Ecology Letters (2012) 15: 329-337 Abstract Parasites of invading species undergoing range advance may be exposed to powerful new selective forces. Low host density in range-edge populations hampers parasite transmission, requiring the parasite to survive longer periods in the external environment before encountering a potential host. These conditions should favour evolutionary shifts in offspring size to maximise parasite transmission. We conducted a common-garden experiment to compare life history traits among seven populations of the nematode lungworm ( Rhabdias pseudosphaerocephala) spanning from the parasite population core to the expanding range-edge in invasive cane toads ( Rhinella marina) in tropical Australia. Compared to conspecifics from the population core, nematodes from the range-edge exhibited larger eggs, larger free-living adults and larger infective larvae, and reduced age at maturity in parasitic adults. These results support a priori predictions regarding adaptive changes in offspring size as a function of invasion history, and suggest that parasite life history traits can evolve rapidly in response to the selective forces exerted by a biological invasion. [ABSTRACT FROM AUTHOR]

The ecological impacts of an invasive species may be reduced by prior invasions if selective pressures imposed by earlier events preadapt the native biota to deal with the newer arrival. In northwestern Australia, invasion of the cane toad (Rhinella marina) kills many native predators if they ingest the highly toxic toads. Remarkably, the toads' defensive toxins (bufadienolides) are chemically similar to those of another invasive species: an ornamental plant from Madagascar, Bryophyllum spp. (Crassulaceae, mother-ofmillions). Omnivorous lizards (bluetongue skinks, Tiliqua scincoides) are imperiled by the invasion of toads in northwestern Australia, but conspecifics from other areas of the continent (those where exotic plants were introduced and including areas where toads have yet to invade) are less affected because they exhibit higher physiological tolerance of toad toxins (and also of plant toxins). The willingness of captive bluetongues to consume both toads and these plants and the high correlation in the lizards' sensitivity to toad toxins versus plant toxins suggest that exotic plants may have imposed strong selection on the lizards' physiological tolerance of bufadienolides. As a result, populations of lizards from areas previously exposed to these alien plants may be preadapted to deal with the toxins of the more recent anuran invader. [ABSTRACT FROM AUTHOR]

Summary 1. Measuring the costs imposed by specific environmental challenges is difficult, because organisms adapt in ways that reduce those costs. Invasive species provide an opportunity to quantify environmental impacts before organisms can make adaptive changes. 2. The native range of cane toads ( Rhinella marina) lies within the wet neotropics; although part of this range experiences seasonal drought, many of the places recently invaded by this large anuran species are much more arid. 3. Five years' fieldwork from a seasonally arid site in the Australian wet-dry tropics shows strong seasonal shifts in the toads' (i) population structure, reflecting seasonality in breeding and recruitment; (ii) adult morphology (secondary sexual characteristics in males); (iii) growth rates; (iv) energy balance; (v) spatial ecology (philopatry, dispersal rates) and (vi) adult mortality rates. 4. Some of these patterns accord with intuition: for example, wet-season conditions resulted in higher rates of growth, reproduction and movement, better body condition and more pronounced secondary sexual characteristics. However, seasonal patterns for other traits were non-intuitive: for example, neither hematocrit levels (reflecting hydration state) nor corticosterone levels (reflecting stress) showed significant seasonal variation, and mortality rates were higher in the wet season than the dry season. 5. The toads' ability to flexibly adjust their behaviour and ecology to local hydric conditions has allowed them to thrive even under climatic conditions that preclude activity, feeding and reproduction for most of the year. [ABSTRACT FROM AUTHOR]

In classical evolutionary theory, traits evolve because they facilitate organismal survival and/or reproduction. We discuss a different type of evolutionary mechanism that relies upon differential dispersal. Traits that enhance rates of dispersal inevitably accumulate at expanding range edges, and assortative mating between fast-dispersing individuals at the invasion front results in an evolutionary increase in dispersal rates in successive generations. This cumulative process (which we dub "spatial sorting") generates novel phenotypes that are adept at rapid dispersal, irrespective of how the underlying genes affect an organism's survival or its reproductive success. Although the concept is not original with us, its revolutionary implications for evolutionary theory have been overlooked. A range of biological phenomena (e.g., acceleration of invasion fronts, insular flightlessness, preadaptation) may have evolved via spatial sorting as well as (or rather than) by natural selection, and this evolutionary mechanism warrants further study. [ABSTRACT FROM AUTHOR]

Many parasites affect the viability of their hosts, but detailed studies combining empirical data from both the field and the laboratory are limited. Consequently, the nature and magnitude of such effects are poorly known for many important host-parasite systems, including macroparasites of amphibians. We examined the effects of lungworm ( Rhabdias pseudosphaerocephala) infections in cane toads ( Bufo marinus) within their invasive Australian range. The host-specificity of this parasite suggests that it might serve as a biological control agent for toads in Australia, if infection proves to reduce toad viability. Mark-recapture studies in the field (near Darwin, Northern Territory) revealed lowered growth rates in infected adult toads when compared to uninfected toads, and a laboratory experiment confirmed causality: experimental infection with R. pseudosphaerocephala reduce toad growth rates. In combination with previous work on the current host-parasite system, it is now evident that nematode lungworms reduce the viability of both newly metamorphosed and adult cane toads, and do so in the field as well as in the laboratory. Rhabdias pseudosphaerocephala may be a valuable component of a biological control strategy for cane toads in Australia. [ABSTRACT FROM AUTHOR]

Predicting which species will be affected by an invasive taxon is critical to developing conservation priorities, but this is a difficult task. A previous study on the impact of invasive cane toads (Bufo marinus) on Australian snakes attempted to predict vulnerability a priori based on the assumptions that any snake species that eats frogs, and is vulnerable to toad toxins, may be at risk from the toad invasion. We used time-series analyses to evaluate the accuracy of that prediction, based on >3600 standardized nocturnal surveys over a 138- month period on 12 species of snakes and lizards on a floodplain in the Australian wet-dry tropics, bracketing the arrival of cane toads at this site. Contrary to prediction, encounter rates with most species were unaffected by toad arrival, and some taxa predicted to be vulnerable to toads increased rather than declined (e.g., death adder Acanthophis praelongus; Children's python Antaresia childreni). Indirect positive effects of toad invasion (perhaps mediated by toad-induced mortality of predatory varanid lizards) and stochastic weather events outweighed effects of toad invasion for most snake species. Our study casts doubt on the ability of a priori desktop studies, or short-term field surveys, to predict or document the ecological impact of invasive species. [ABSTRACT FROM AUTHOR]

Most evolutionary theory does not deal with populations expanding or contracting in space. Invasive species, climate change, epidemics, and the breakdown of dispersal barriers, however, all create populations in this kind of spatial disequilibrium. Importantly, spatial disequilibrium can have important ecological and evolutionary outcomes. During continuous range expansion, for example, populations on the expanding front experience novel evolutionary pressures because frontal populations are assorted by dispersal ability and have a lower density of conspecifics than do core populations. These conditions favor the evolution of traits that increase rates of dispersal and reproduction. Additionally, lowered density on the expanding front eventually frees populations on the expanding edge from specialist, coevolved enemies, permitting higher investment into traits associated with dispersal and reproduction rather than defense against pathogens. As a result, the process of range expansion drives rapid life-history evolution, and this seems to occur despite ongoing serial founder events that have complex effects on genetic diversity at the expanding front. Traits evolving on the expanding edge are smeared across the landscape as the front moves through, leaving an ephemeral signature of range expansion in the life-history traits of a species across its newly colonized range. Recent studies suggest that such nonequilibrium processes during recent population history may have contributed to many patterns usually ascribed to evolutionary forces acting in populations at spatial equilibrium. [ABSTRACT FROM AUTHOR]