An invasive species imposes selection on life‐history traits of a native frog

As well as their direct ecological impacts on native taxa, invasive species can impose selection on phenotypic attributes (morphology, physiology, behaviour, etc.) of the native fauna. In anurans, body size at metamorphosis is a critical life‐history trait: for most challenges faced by post‐metamorphic anurans, larger size at metamorphosis probably enhances survival. However, our studies on Australian frogs (Limnodynastes convexiusculus) show that this pattern can be reversed by the arrival of an invasive species. When metamorph frogs first encounter invasive cane toads (Bufo marinus), they try to eat the toxic invader and, if they are able to do so, are likely to die from poisoning. Because frogs are gape‐limited predators, small metamorphs cannot ingest a toad and thus survive long enough to disperse away from the natal pond (and thus from potentially deadly toads). These data show that larger size at metamorphosis can reduce rather than increase anuran survival rates, because larger metamorphs are more easily able to ingest (and thus be poisoned by) metamorph cane toads. Our results suggest that patterns of selection on life‐history traits of native taxa (such as size and age at metamorphosis, seasonal timing of breeding and duration of pondside aggregation prior to dispersal) can be modified by the arrival of an invasive species. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 329–336.     

Evaluation of the toxicity of eggs,hatchlings and tadpoles of the introduced toad Bufo marinus (Anura: Bufonidae) to native Australian aquatic predators

Abstract The early life history stages of anurans in the Family Bufonidae often possess chemicals that are noxious or toxic to predators. Predators with no evolutionary history of exposure to bufomds may be particularly susceptible to these toxins. We conducted a series of laboratory experiments to investigate the toxic effects of eggs, hatchlings and tadpoles of the introduced toad, Bufo marinus (Linnaeus), on native Australian aquatic predators. There was considerable interspecific and intraspecific variation in these effects. Bufo marinus were highly toxic to some predator species, but were readily consumed by other species without apparent ill effect. Interspecific variation in toxic effects was not related to predator feeding mode or the number of B. marinus ingested by predators, and there was no clear pattern of distribution of vulnerability among species within higher taxa. Intraspecific variation in responses to toxins may result from individual variation in the resistance of predators to B. marinus toxins, or from individual variation in toxicity among B. marinus. Some native species adversely affected by B. marinus appeared unable to detect and avoid B. marinus toxins. This may result from a general inability to assess the toxicity of food items or from a lack of evolutionary exposure to B. marinus toxins.     

Impacts of climate change and urban development on the spotted marsh frog (Limnodynastes tasmaniensis)

Climate change and urbanization are among the most serious threats to amphibians, although little is known about their combined effects. We used a predictive spatial habitat suitability model to explore the potential impacts of climate change and urban development on the spotted marsh frog (Limnodynastes tasmaniensis) on the urban‐fringe of Melbourne, Australia. The CSIRO climate‐change predictions for the region indicate likely temperature increases of 3°C, and annual rainfall reductions of around 200 mm by the year 2070. Much of the study area overlaps a region that has been identified as one of the city's growth corridors. We used Bayesian logistic regression modelling to estimate current and future habitat suitability of pond sites in the Merri Creek catchment, exploring a range of best‐ to worst‐case scenarios through the use of hydrological and urbanization models. Our predictions for 2070, even under a moderate climate‐change scenario, suggest that the majority of ponds in the study area will be dry throughout much of the year. This has obvious implications for L. tasmaniensis, which is an aquatic breeding species. However, in the short term, urbanization is likely to have a more significant effect on the distribution of L. tasmaniensis in the Merri Creek catchment, particularly if development moves beyond the current urban growth boundary. The combined effects of climate change and urbanization could have a profound impact on the species, potentially causing it to disappear from within the study area. We provide recommendations for including such predictive models in urban planning and restoration activities to prepare for future conservation challenges.     

A Molecular Phylogeny for the Frog Genus Limnodynastes (Anura: Myobatrachidae)

Members of the genus Limnodynastes are a prominent and widespread feature of the Australian frog fauna. Yet despite their potential to be informative about biogeographic history and mechanisms of speciation, the relationships among these taxa are not well known. We investigated phylogenetic relationships within the genus Limnodynastes via sequencing of mitochondrial (mt)DNA from current members of the genus Limnodynastes and the monotypic genus Megistolotis. a 450-bp fragment of the 16S rRNA gene and a 370-bp fragment of the protein-coding gene ND4 were used to infer a molecular phylogeny. We revise traditional species groupings and now recognize four species groups within Limnodynastes: the L. ornatus group (L. ornatus and L. spenceri), the L. peronii group (L. peronii, L. tasmaniensis, L. fletcheri, the L. depressus), the L. salmini group (L. salmini, L. convexiusculus, and L. lignarius), and the L. dorsalis group (L. dorsalis, L. terraereginae, L. dumerilii and L. interioris). The L. ornatus species group forms a highly distinctive clade that is a sister group to the other Limnodynastes groups. Pending broader phylogenetic studies it could be removed from the genus Limnodynastes. Our results concur with previous suggestions that Megistolotis lignarius is nested within Limnodynastes, and we therefore reclassify this species as Limnodynastes lignarius. Furthermore, specimens identified as L. depressus form a mtDNA lineage distinct from other species in the genus, confirming the validity of the species. Specimens of species from the L. dorsalis group (L. dorsalis, L. dumerilii, L. interioris, and L. terraereginae) are closely related such that L. dumerilii is paraphyletic with two other species. Finally, our study provides broad support for previous phylogenies based on microcomplement fixation.     

Heavy metal pollution negatively correlates with anuran species richness and distribution in south‐eastern Australia

Heavy metal pollution has likely played an important role in global biodiversity decline, but there remains a paucity of information concerning the effects of metals on amphibian diversity. This study assessed anuran species richness and distribution in relation to sediment metal content and water chemistry in wetlands located along the Merri Creek corridor in Victoria, south‐eastern Australia. Anurans were present in 60% (21/35) of study sites, with a total of six species detected: the eastern common froglet (Crinia signifera), the eastern sign‐bearing froglet (Crinia parinsignifera), the southern brown tree frog (Litoria ewingii), the growling grass frog (Litoria raniformis), the eastern banjo frog (Limnodynastes dumerilii) and the spotted marsh frog (Limnodynastes tasmaniensis). Mean species richness was 1.77 ± 0.32 per site, and species richness ranged from zero to six species per site. Across sites, species richness correlated negatively with sediment concentrations of six heavy metals: copper, nickel, lead, zinc, cadmium and mercury. Species richness also correlated negatively with wetland water electrical conductivity (a proxy for salinity) and concentrations of orthophosphate. Distributions of the three most commonly observed frog species (C. signifera, L. tasmaniensis and L. ewingii) were significantly negatively associated with the total level of metal contamination at individual sites. The study is the first to provide evidence for an association between metal contamination and anuran species richness and distribution in the southern hemisphere, adding to a small but growing body of evidence that heavy metal pollution has contributed to global amphibian decline.     

Weitere Untersuchungen über Chromosomenverhältnisse und DNS-Gehalt bei Anuren (Amphibia)

The karyotypes of the toad Bufo marinus L. (2n=22) and the frogs Limnodynastes tasmaniensis Gthr. (2n=24), Rana temporaria L., R. esculenta L. (both 2n=26) and R. arvalis Nills. (2n=24) were analysed in colchicine treated leukocyte and spermatogonial metaphases and/or embryonic and larval mitoses. The DNA content of Feulgen stained erythrocyte nuclei was measured microspectrophotometrically. Heteromorphic sex chromosomes are absent in all species. L. tasmaniensis has the lowest DNA content among these species. The south American toad B. marinus shows a karyotype similar to the other known toad species and contains the same amount of DNA as the European species B. calamita with the lowest DNA amount among the European toads. In southern German populations of R. temporaria besides animals with the “standard”-karyotype (2n=26) individuals with 1 or 2, in rare cases with 3 or 4 supernumerary chromosomes have been found. The supernumeraries are heterochromatic and smaller than the smallest chromosome of the “standard”-karyotype. If only 1 or 2 supernumerary chromosomes are present, they seem to show normal mendelian inheritance as a rule. The observation of a few tadpoles with intraindividual different numbers of supernumeraries points to the occurrence of unequal distribution of these chromosomes in individuals containing a higher number of supernumerary chromosomes. The karyotype of R. esculenta is very similar to the “standard”-karyotype of R. temporaria, but the chromosomes of R. esculenta are somewhat longer than those of R. temporaria. R. esculenta contains about 54% more DNA than R. temporaria in the erythrocyte nuclei, so that it must be assumed that all chromosomes of R. esculenta contain more DNA than their homologues in R. temporaria. R. arvalis possesses about 28% more DNA than R. temporaria. It is supposed that these interspecific differences in DNA content of the Rana species — as observed earlier in Bufo species — are not a consequence of differential polyteny but are caused during evolutionary processes by local increase in DNA in the chromosomes of R. esculenta and R. arvalis.     

Cane toads a threat to West Indian wildlife: mortality of Jamaican boas attributable to toad ingestion

The notorious “cane toad” (Bufo marinus) is considered to be one of the 100 worst invasive species in the world. A native of South and Central America, Mexico, and the Rio Grande Valley of the United States, this large toad was intentionally introduced to islands in the Caribbean, and subsequently throughout the southern Pacific, as a biological control agent to combat sugar cane pests. Unfortunately, the primary result of those introductions has been deleterious impacts on native biotas, primarily through competition and predation. More recently, the cane toad has devastated populations of amphibian-eating predators in Australia, through the ingestion of this highly toxic anuran. Elsewhere, however, the impact of the toad on native predators has not been documented. Here we report the first evidence that the cane toad is impacting native predators in other geographic regions. Specifically, we document death due to cane toad poisoning in the endemic and threatened Jamaican boa (Epicrates subflavus). To our knowledge, this is the first report of cane toads causing mortality in naturally occurring predators outside of Australia. Like all members of the genus, B. marinus secretes a powerful bufogenin toxin, which is often fatal if ingested by naïve species that have not co-evolved with Bufo species. Our results should therefore serve as a warning that other endemic predator species in the West Indies and elsewhere may be at risk. Thus, efforts to control the population growth and spread of cane toads may be of even greater conservation concern than previously recognized.     

Genetic variation and population ecology of some southeast asian frogs of the genera Bufo and Rana

The relationship between population structure and amount of genetic variation within populations has been investigated in seven species of anurans from Southeast Asia. Two populations each of Bufo asper, B. parvus, B. melanostictus, Rana blythi, and R. erythraea and one population each of R. hosei and R. laticeps were studied; all except B. melanostictus and R. erythraea are forest species. Information on distributional characteristics such as general habitat, form of the adult range, the relationships of nonbreeding range to breeding site, the tendency to aggregate at the breeding site, and the size of the breeding aggregation was used to outline major aspects of the breeding structure of each species and predict relative amounts of genic variation. Genetic variation was estimated from measures of protein polymorphism as detected through gel electrophoresis. The assays used were liver EST, FUM, GDH, LAP, LDH, MDH, and total protein; muscle EST, GOT, MDH, and total protein; plasma EST and total protein. The pattern of variation of the populations of Bufo species agreed with predictions based on population structure, with B. asper the least polymorphic, B. melanostictus the most polymorphic, and B. parvus intermediate. Interspecific differences were not as great in Rana as in Bufo. Although R. erythraea was more variable than R. blythi in terms of mean number of morphs per zone (as predicted from distributional characteristics), R. blythi possessed polymorphism at more zones. R. hosei was the most polymorphic Rana studied, but distributional data are insufficient to explain why this was the case.     

Vulnerability of an Australian anuran tadpole assemblage to the toxic eggs of the invasive cane toad (Bufo marinus)

The invasion of cane toads (Bufo marinus) across tropical Australia has fatally poisoned many native predators; the most frequent victims may be tadpoles of native frogs, which die when they consume the toxic eggs of the toads. Field studies have documented high and species‐specific mortality of tadpoles following toad spawning. To clarify the determinants of tadpole vulnerability, we conducted 1593 laboratory trials in which single tadpoles were exposed to 10 toad eggs, either with or without an alternative food source (lettuce). At least some tadpoles within all 15 species tested consumed toad eggs. Interspecific variance in survival rates (from 0 to >70%) was driven by feeding responses not by physiological tolerance to toxins: almost all native tadpoles that consumed eggs died rapidly. Tadpole mortality was decreased by the presence of an alternative food source in four species, increased in two species, and not affected in seven species. In three of four taxa where we tested both small (early‐stage) and large (late‐stage) tadpoles, both mean survival rates and the effects of alternative food on survival shifted with tadpole body size. Trials with one species (Limnodynastes convexiusculus) showed no significant inter‐clutch variation in feeding responses or tolerance to toxins. Overall, our data show that cane toad eggs are highly toxic to native anuran tadpoles, but that whether or not a tadpole is killed by encountering toad eggs depends upon a complex interaction between the native anuran's species, its body size, and whether or not alternative food was present. In nature, larval vulnerability also depends upon the seasonal timing and location of spawning events, and habitat selection and foraging patterns of the tadpoles. Our results highlight the complexity of vulnerability determinants, and identify ecological factors (rather than physiology or feeding behaviour) as the primary determinants of cane toad impact on native tadpoles.     

Integrating variability in detection probabilities when designing wildlife surveys: a case study of amphibians from south-eastern Australia

Occupancy-based monitoring programs rely on survey data to infer presence or absence of the target species. However, species may occupy a site and go undetected, leading to erroneous inference of absence (‘false absence’). If detectability is influenced by the time of year or weather conditions, survey protocols can be adjusted to minimize the chance of false absences. In this study, detection probabilities for three amphibian species from south-eastern Australia were modelled using a Bayesian approach. For aural surveys, we compared basic models, which only included effects of survey date, duration and time of day on detection, to models including additional effects of weather. Model selection using deviance information criterion (DIC) suggested that the basic model was the most parsimonious for Crinia signifera, while models including relative humidity and water temperature were most supported for Limnodynastes dumerilii and L. tasmaniensis respectively. When predictive performance was assessed by cross validation, DIC results were largely matched for C. signifera and L. dumerilii, while models of detection for L. tasmaniensis were indistinguishable, AUC scores suggesting inadequate performance. We show how results such as these can be used to design surveys, developing protocols for individual surveys and estimating the number of surveys required under those protocols to achieve a threshold cumulative probability of detection. Conservation managers can use these models to maximize the efficiency of surveys. This will improve the accuracy of occupancy data, and reduce the risk of misdirected conservation actions resulting from false absences.     

Competitive ability and the coexistence of anuran larvae in freshwater rock‐pools

• 1 I examined the competitive ability of larval common frogs (Rana temporaria) and common toads (Bufo bufo) in a laboratory experiment by manipulating the number and size of Rana and the number of Bufo.
• 2 Bufo was the most active tadpole type, whereas small Rana was more active than large Rana.
• 3 Especially at high food availability, the growth rate of large Rana at metamorphosis was reduced in the presence of small Rana, whereas that of small Rana was not affected by larger conspecifics.
• 4 Both size classes of Rana were negatively affected by the presence of Bufo. Size at metamorphosis of Bufo was greater when large Rana was present. These results suggest that activity level is important in determining competitive ability.
• 5 To study competition in the field, tadpoles of Bufo were introduced to small rock‐pools that did not support Bufo naturally, but were with or without Rana.
• 6 In the experimental pools, there were no interspecific effects on the growth rate of either species. However, the growth rate of Bufo was lower in the experimental pools than in pools inhabited naturally. Futher, survival of Bufo was low in small pools. Lower food availability or physical factors associated with small pools, rather than interspecific competition, may be the reason why Bufo avoids breeding in small rock‐pools.

     

Sublethal costs associated with the consumption of toxic prey by snakes

Costs of plant defences to herbivores have been extensively studied, but costs of chemical defences to carnivores are less well understood. We examine the costs to Australian keelback snakes (Tropidonophis mairii, Gray 1841) of consuming cane toads (Bufo[Rhinella]marinus Linnaeus 1758). Cane toads (an invasive species in Australia) are highly toxic. Although keelbacks can consume toads without dying (unlike most Australian snakes), we show that cane toads are poor quality prey for keelbacks. Toads are of low net nutritional value, take longer to consume than do native frogs and reduce the snake's locomotor performance for up to 6 h after ingestion of a meal. These latter effects may increase a snake's vulnerability to predation. Nutritional content of vertebrate prey is not the only factor driving the evolution of foraging behaviour; other more subtle costs, such as risk of predation, may be widespread.     

Multiple host use by the egg parasitoid Trissolcus basalis (Wollaston) in a soybean agricultural system: biological control and environmental implications

1 Species of bugs (Hemiptera: Pentatomidae and other families) that are parasitized by the egg parasitoid Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) in the soybean agricultural system on the Darling Downs in south-eastern Queensland, Australia, are reported. The degree to which eggs of each bug species are used by T. basalis is quantified, which allows assessment of the role of these alternative host species in the biological control of the green vegetable bug Nezara viridula (L.). 2 Egg masses of nine species of pentatomid bugs and one unidentified bug species were collected. Parasitism rates of egg masses of all species averaged 50–70% but were significantly lower for the more important pest species, including the green vegetable bug, than for some of the agriculturally less important species. 3 Trissolcus basalis emerged from nearly all species collected and was the major parasitoid to emerge from most species. A number of native species were parasitized heavily by T. basalis and parasitism of such species may enhance biological control of the green vegetable bug, but may also pose environmental concerns. Parasitism of predatory bugs by T. basalis may have a negative impact on the biological control of other pests, especially lepidopterous pests. 4 Although the impact of T. basalis on native and predatory host species was not directly quantified, these host species remain abundant and therefore do not appear to be affected adversely by such high rates of parasitism.     

Conservation genetics and species status of an endangered Australian dragon, <Emphasis Type="Italic">Tympanocryptis pinguicolla</Emphasis> (Reptilia: Agamidae)

We present a phylogenetic and morphological study of the grassland earless dragon, Tympanocryptis pinguicolla, an endangered habitat specialist that occurs in a few isolated populations in eastern Australia. Tympanocryptis pinguicolla occurred historically in Victoria in south-eastern Australia, but has not been seen since 1990, and current populations are known in New South Wales and Canberra in south-eastern Australia. Recently, new populations identified as T. pinguicolla were discovered on the Darling Downs, Queensland. Translocation of individuals between these populations has been suggested as a conservation management strategy to maintain genetic diversity. To address this issue, we undertook a phylogenetic study of all major populations of T. pinguicolla using a 1838 bp region of mitochondrial DNA, incorporating ND1, ND2, COI and eight tRNA genes. We incorporated specialized degraded-DNA techniques to amplify DNA from historical museum specimens, as no extant tissue was available for Victorian populations. Our results, which include morphological analysis, provide convincing evidence that populations currently identified as T.␣pinguicolla do not comprise a monophyletic species, as the populations from the Darling Downs are more closely related to T. tetraporophora than to T. pinguicolla. In addition, we find that there is a significant level of haplotype divergence between populations of T. pinguicolla, indicating that these lineages separated at least 1.5 mya. Our results suggest translocation may not be an appropriate management strategy and our findings that Darling Downs populations are not T.␣pinguicolla will significantly influence the conservation management of this species in Queensland.     

Frog breeding in rain-fed wetlands after a period of severe drought: implications for predicting the impacts of climate change

Globally, rain-fed wetlands provide critical habitat for a wide range of amphibian species, however, information on the use of rain-fed wetlands by Australian frog species is extremely limited. This study examined the distribution of frog breeding in rain-fed wetlands following the first significant rain event after a period of severe drought (2002–2009) in order to predict how frog communities may be affected in the future by changed climate. Tadpole communities along with vegetation and water quality variables were described in 35 rain-fed wetlands across the South West Slopes and Riverina bioregions of inland south-eastern Australia. In addition, weekly tadpole surveys were conducted in a subset of these wetlands to describe temporal patterns of occupancy. Despite the protracted dry period prior to this study 50% of the rain-fed wetlands surveyed contained tadpoles. However, frog communities were species poor with only five species recorded. The majority of wetlands were dominated be a single species, Limnodynastes tasmaniensis which is also common within permanent waterbodies such as farm dams and irrigation infrastructure in both bioregions. Tadpoles of two burrowing species L. interioris and Neobatrachus sudelli were restricted to a small number of wetlands mostly in the South West Slopes. The composition of tadpole communities changed over time, and Crinia parinsignifera was the only species that continued to breed over winter. The dominance of generalist species within rain-fed wetlands indicates that characteristics such as dispersal capability, flexibility in breeding times and the ability to utilise created habitats may be more important than burrowing ability and longevity when predicting vulnerability to climate change.     

Ecological impacts of invading species: Do parasites of the cane toad imperil Australian frogs?

Parasite transfer to native fauna is a potentially catastrophic impact of invasive species. Introduced cane toads in Australia frequently host the nematode lungworm Rhabdias pseudosphaerocephala, which reduces viability of metamorph toads. If native frogs are vulnerable to this South American parasite, cane toad invasion may affect native species via this route; but if the native taxa are not vulnerable, we may be able to exploit the parasites for managing toads. Our laboratory experiments show that infective larvae can penetrate the body of all seven species of Australian frogs (five hylids: Cyclorana longipes, Litoria caerulea, Litoria dahlii, Litoria nasuta, Litoria rothii, one myobatrachid: Opisthodon ornatus, and one limnodynastid: Limnodynastes convexiusculus) we tested, but most did not host the adult worms at the end of the trials, and none showed major impairment of growth, survival or locomotor performance. One native tree‐frog (L. caerulea) retained high infection levels with few ill effects, suggesting that we might be able to use this taxon as a reservoir species to build up local parasite densities for toad management. However, the interspecific variation in lungworm retention suggests that generalizations about parasite effects on native frogs will be elusive.     

Native Australian frogs avoid the scent of invasive cane toads

Invasive species can affect the ecosystems they colonize by modifying the behaviour of native taxa; for example, avoidance of chemical cues from the invader may modify habitat use (shelter site selection) by native species. In laboratory trials, we show that metamorphs of most (but not all) native frog species on a tropical Australian floodplain avoid the scent of invasive cane toads (Bufo marinus Linnaeus 1758). Cane toads also avoid conspecific scent. This response might reduce vulnerability of metamorph frogs and toads to larger predatory toads. However, similar avoidance of one type of pungency control (garlic), and the presence of this avoidance behaviour in frogs at the toad invasion front (and hence, with no prior exposure to toads), suggest that this may not be an evolved toad‐specific response. Instead, our data support the simpler hypothesis that the metamorph anurans tend to avoid shelter sites that contain strong and unfamiliar scents. Temporal and spatial differences in activity of frogs versus toads, plus the abundance of suitable retreat sites during the wet season (the primary time of frog activity), suggest that avoiding toad scent will have only a minor impact on the behaviour of native frogs. However, this behavioural impact may be important when environmental conditions bring toads and frogs into closer contact.     

Freezing tolerance/intolerance and cryoprotectant synthesis in terrestrially overwintering anurans in the Great Plains,USA

Mechanistic bases for freezing tolerance in anurans have been well-studied only in wood frogs, Rana sylvatica, so comprehensive explanations for the mechanisms and evolution of freezing tolerance in anurans are lacking. We measured crystallization temperatures, freezing tolerance/intolerance, and tissue glucose and glycogen phosphorylase activities in frozen and unfrozen winter-acclimated Pseudacris triseriata, Bufo cognatus and B. woodhousei. Freezing occurred at higher subzero temperatures on wet substrate than on dry substrate in all species, indicating susceptibility to inoculative freezing. P. triseriata was freeze-tolerant, but survival was dependent on the level of supercooling prior to freezing. All Bufo were freezing intolerant, regardless of crystallization temperature. Glucose was significantly elevated by freezing in both liver (35-fold) and leg muscle (22-fold) in winter P. triseriata, but only liver glucose was significantly elevated in B. cognatus. However, freezing did not alter glycogen phosphorylase activity in either species. Liver phosphorylase activity was significantly higher in P. triseriata than in B. cognatus, suggesting that capacity for mobilizing glucose from liver glycogen is associated with freezing tolerance. Summer measurements of liver phosphorylase activity, however, did not differ between species. Thus, P. triseriata, but not B. cognatus, exhibited winter increment of liver phosphorylase activity that is correlated with the development of freezing tolerance.Abbreviation T _b body temperature - T _c crystallization temperature - T _r rebound temperature - T _eq equilibrium temperature     

Factors regulating the invasive success of an alien frog: a comparison of the ecology of the native and alien populations

We examined niche occupancy of Discoglossus pictus, an anuran recently established in Europe, comparing the niches of native (North Africa) and alien populations (south-western Europe) at two spatial scales to determine whether adaptive divergence had occurred between these two populations. Additionally, we determine whether the alien species showed a wider larvae niche and higher phenotypic variability compared with co-occurring anurans. We characterized the breeding habitats and the climatic space occupied by native and alien groups of populations of D. pictus and examined morphological traits of D. pictus and sympatric anuran larvae. Our results revealed no divergence in breeding habitat use between native and alien populations. A shift was observed between the realized niches occupied by the native and alien populations, but this shift might only reflect cryptic niche conservatism. The range of reproductive habitats selected by D. pictus was not wider than those of most native species. In the invaded range, D. pictus showed morphological overlap with some native species and broader phenotypic variability, but the adaptive advantages of this latter attribute were uncertain. Our results suggest that the invasive capacity of this species depends on favourable abiotic conditions rather than on its adaptive advantages over native anurans.