Native Frogs Research Articles

Dietary preference of Alien Invasive Anurans (Rhinella marina, Hoplobatrachus rugulosus, and Kaloula pulchra) in Butuan City, Northeastern Mindanao, Philippines

Invasive anuran species (IAS) threaten the native anuran species as they compete for food sources. The diet of the three IAS, Rhinella marina, Kaloula pulchra, and Hoplobatrachus rugulosus, were collected from different localities in Butuan City. The gut collected from 91 individuals of IAS, i.e., R. marina (n=80), H. rugulosus (n=10), and K. pulchra (n=1) were examined for food items using a dissecting microscope. The R. marina had the most recorded prey items, consisting of plant materials, pebbles, insects, and reptile-like species, while K. pulchra prefers small and slow-moving insects. Hoplobatrachus rugulosus, which also preferred insects on their diet, exhibited frog predation. Among the food categories, plant materials (56%) had the highest percentage, followed by invertebrates (47%), other organic and inorganic materials (12%), and vertebrates (1%). Formicidae, Coleoptera, and Odonata have the highest percentage among the invertebrate prey types. The assessed amphibians feed on locally available prey, generally insects, and suggest potential competition for food resources with native anuran populations.

Trophic niche differentiation between invasive and native frog species in urban wetlands of Kunming, China

Non-native species often proliferate and become invasive in urban ecosystems. Knowing the interactions between the overlapping trophic niches of invasive and native species is imperative, and answering this question of how they succeed in these ecosystems is an area of active research. Here, frogs were collected from eight sites in the suburbs of Kunming, including 74 non-native American bullfrogs (Lithobates catesbeianus), 115 native Yunnan pond frogs (Nidirana pleuraden, YPF) and 26 non-native black-spotted pond frogs (Pelophylax nigromaculatus, BPF). The diversity indices and niche widths of the sampled frogs’ stomach contents were determined, and δ13C and δ15N isotopes in their muscle tissue measured for a subset of samples. At sites where multiple species occurred, the prey Shannon-Wiener diversity index and niche width of the bullfrog were higher than those of BPF yet lower than those of YPF. The prey diversity and niche width of YPF decreased significantly at the level of individual populations. The overlap between the trophic niches of bullfrog and sympatric frogs ranged from 0.3 to 0.37 based on their stomach contents, while that between the YPF and BPF was 0.68. These results demonstrate that bullfrog and YPF eat some items in common, for which competition is likely, but this is not as pronounced as between YPF and BPF. Plotting values of δ13C (x-axis) against δ15N (y-axis) isotopes, the standard ellipse areas at the LaoY site, where all three species co-occurred, were 23.75, 12.9, and 11.95 for bullfrog, YPF, and BPF, respectively. The maximal standard ellipse area of YPF across the sites without bullfrog invasion was 4.74. These results showed that bullfrog’s prey diversity did not exceed that of YPF in the co-distributed environments, yet its isotopic niche was nonetheless larger. Stomach contents can only convey short-term dietary composition whereas carbon isotopes can reveal relatively long-term nutritional trends, so we conclude the trophic niche width is larger for Bullfrog than YPF. Their degree of overlap is large, which suggests both species have similar ecological functions and experience intense interspecific competition.

06. Diet of the recently introduced white-lipped frog Leptodactylus fragilis from a suburban ecosystem in western Cuba

ABSTRACT - Diet and trophic interactions are essential for understanding aspects of the natural history of a species and evaluating its role within the ecosystem. A successful coloniser often has the ability to exploit a wide variety of prey during its establishment and may generate negative impacts due to competition with the local fauna. During both the dry and rainy seasons of 2019, in a suburban ecosystem in western Cuba, we analysed the diet of the recently introduced white-lipped frog Leptodactylus fragilis. Captured frogs were measured and stomach-flushed and released 24 h after analysis at the site of capture. Ninety-one L. fragilis were captured, 73 of them (80.2 %) had prey in the stomach. The most consumed prey were beetles, followed by spiders, and crickets. No difference was observed in prey consumption between seasons. This frog may change its foraging strategy according to the habitat it occupies. In this study, we observed high values of food niche breadth, which may imply a greater competition of L. fragilis for food resources with the native syntopic anurans in Cuba. Studies on temporal and spatial dynamics are needed to understand the possible competitive interaction with native amphibians in this area.

Potential health effects of contaminant mixtures from point and nonpoint sources on fish and frogs in the New Jersey Pinelands

Aquatic ecosystems convey complex contaminant mixtures from anthropogenic pollution on a global scale. Point (e.g., municipal wastewater) and nonpoint sources (e.g., stormwater runoff) are both drivers of contaminant mixtures in aquatic habitats. The objectives of this study were to identify the contaminant mixtures present in surface waters impacted by both point and nonpoint sources, to determine if aquatic biota (amphibian and fish) health effects (testicular oocytes and parasites) occurred at these sites, and to understand if differences in biological and chemical measures existed between point (on-stream) and nonpoint sources (off-stream). To accomplish this, water chemistry, fishes, and frogs were collected from 21 sites in the New Jersey Pinelands, United States. Off-stream sites consisted of 3 reference and 10 degraded wetlands. On-stream sites consisted of two reference lakes and six degraded streams/lakes (four sites above and two sites below wastewater outfalls). Surface water was collected four times at each site and analyzed for 133 organic and inorganic contaminants. One native and five non-native fish species were collected from streams/lakes and native green frogs from wetlands (ponds and stormwater basins). Limited differences in contaminant concentrations were observed in reference and degraded wetlands but for streams/lakes, results indicated that landscape alteration, (upland agricultural and developed land) was the primary driver of contaminant concentrations rather than municipal wastewater. Incidence of estrogenic endocrine disruption (intersex) was species dependent with the highest prevalence observed in largemouth bass and black crappie and the lowest prevalence observed in green frogs and tessellated darters. Parasite prevalence was site and species dependent. Prevalence of eye parasites increased with increasing concentrations of industrial, mycotoxin, and cumulative inorganic contaminants. These findings are critical to support the conservation, protection, and management of a wide range of aquatic species in the Pinelands and elsewhere as habitat loss, alteration, and fragmentation increase with increasing development.

Risk assessment for the native anurans from an alien invasive species, American bullfrogs (Lithobates catesbeianus), in South Korea

The invasive species are of global concern, and the Invasive American Bullfrog (IAB; Lithobates catesbeianus) is one of the worst invasive amphibian species worldwide. Like other countries, South Korea is also facing challenges from IAB. Although many studies indicated impacts of IAB on native anurans in Korea, the actual risk at the specific level is yet to evaluate. Considering the putative invasiveness of IAB, it is hypothesized that any species with the possibility of physical contact or habitat sharing with them, will have a potential risk. Thus, we estimated and observed their home range, preferred habitats, morphology, behavior, and ecology. Then, comparing with existing knowledge, we assessed risks to the native anurans. We found a home range of 3474.2 ± 5872.5 m2 and identified three types of habitats for IAB. The analyses showed at least 84% of native anurans (frogs and toads) were at moderate to extreme risks, which included all frogs but only 33% of toads. Finally, we recommended immediate actions to conserve the native anurans based on our results. As this study is the first initiative to assess the specific risk level from the invasiveness of L. catesbeianus, it will help the managers to set conservation priorities and strategies.

Non‐native stinging ant interactions with native anurans

AbstractNative predators may ignore or avoid non‐native prey because they do not recognize the novel organisms as food, or the invasive prey may bring antipredatory defences against which the native predators have not co‐evolved a sufficient attack. Non‐native ants successfully invade novel habitats worldwide and, in eastern North America, several invasive ant species bring venomous stings in quantities that far exceed that of native ant species. Ants make up a considerable portion of anuran diets, and we investigated how several native anurans reacted to the invasion of the non‐native European fire ant (Myrmica rubra). Myrmica rubra has a venomous sting, and it occurs in aggressive swarms that can deliver multiple stings. Despite these defences, based on field observations, we expected that leopard frogs (Lithobates pipiens) might consume the abundant ants. We also predicted that habitat niche differences from the moisture‐dependent ants would limit consumption by the more terrestrial American toads (Anaxyrus americanus) and more aquatic green frogs (Lithobates clamitans). Our results suggested that none of the anuran species make use of the M. rubra swarms. The anurans, particularly A. americanus, consumed ample native ants in the field, but not M. rubra ants. In the laboratory, A. americanus ate several M. rubra ants, and L. pipiens a few, but experienced anuran individuals collected from M. rubra‐invaded habitat were less likely to eat the ants in laboratory. Hence, at best, M. rubra invasion appears to supplant rather than supplement anuran food resources.

Hybrid swarm as a result of hybridization between two alien and two native water frog species (genus Pelophylax) in Central Croatia: Crna Mlaka fishpond acting as a species melting pot?

Hybrid swarm as a result of hybridization between two alien and two native water frog species (genus Pelophylax) in Central Croatia: Crna Mlaka fishpond acting as a species melting pot?

Australian Frog Atlas: species’ distribution maps informed by the FrogID dataset

We use data from the citizen science project FrogID, comprised of expert-validated, spatially accurate occurrence records of frog species across Australia, to map the known distributions of Australia’s frogs. We combined over half a million occurrence records of 209 species from the FrogID dataset with expert-checked occurrence data from the national biodiversity data aggregate (Atlas of Living Australia) and published literature, to create distribution maps for all 247 native frog species known from Australia and the introduced cane toad (Rhinella marina). These maps represent the most up-to-date, accurate and detailed set of Australian frog species maps available, and reveal species richness patterns across the continent. They are an Open Access resource for researchers, conservation practitioners and land managers, with the aim of better understanding and conserving Australia’s frogs. This is version one of the Australian Frog Atlas, which we expect to update on an approximately annual basis. The Australian Frog Atlas maps—as shapefiles and in KML format—are published online as an Open Access supplemental dataset (see Cutajar et al., 2021).

Sex-based differences in the use of post-fire habitats by invasive cane toads (Rhinella marina)

Wildfires can modify habitat attributes, and those changes may differentially affect males versus females within a species if there is pre-existing niche divergence between the sexes. We used radio-tracking and dissections to study invasive cane toads (Rhinella marina), and performed transect counts on native frogs and cane toads 12 months after extensive fires in forests of eastern Australia. Both toads and native frogs were encountered more frequently in burned sites than in unburned sites. Most microhabitat features were similar between burned versus unburned areas, but fire had differential impacts on the ecology of male versus female toads. In burned areas females were less numerous but were larger, in better body condition, and had consumed more prey (especially, coleopterans and myriapods). The impact of fire on attributes of retreat-sites (e.g., temperature, density of vegetation cover) also differed between the sexes. More generally, intraspecific divergence in ecological traits within a species (as a function of body size as well as sex) may translate into substantial divergences in the impacts of habitat change.

Freshwater floodplain habitats buffer native food webs from negative effects of nonnative centrarchids and bullfrogs

Species introductions are common in freshwater environments and have the potential to transform community and ecosystem structure. Predatory centrarchid fishes and American Bullfrogs (Lithobates catesbeianus Shaw, 1802 previously Rana catesbeiana) are both widespread aquatic invaders implicated in native amphibian declines. In lowland ecosystems, co-occurrence between native and nonnative amphibian and fish taxa is common; however, the mechanisms that facilitate their co-occurrence are poorly studied. Stable isotope analysis offers a tool to examine trophic interactions among native and nonnative taxa, including predation, competition, and shifting food resource availability, which may provide mechanistic insight into the drivers of co-occurrence. In this study, we used stable isotopes (δ13C and δ15N) to determine how the trophic structure of native fishes and amphibians differs between waterbodies with and without nonnative centrarchid fishes and bullfrogs across a floodplain in southwestern Washington, USA. We hypothesized that native species alter their feeding strategies to reduce niche overlap with nonnative taxa. In the presence of nonnative taxa, Three-spine Stickleback (Gasterosteus aculeatus Linnaeus, 1758), all native larval salamander species (Ambystoma gracile Baird, 1859 and Ambystoma macrodactylum Baird, 1850), and 1 of 2 native larval frog species (Rana aurora Baird and Girard, 1852) exhibited shifts in food resources or trophic position. Despite trophic differences, only 1 species (A. macrodactylum) had a smaller niche size in the presence of nonnatives. The observed trophic shifts reflect changes in habitat or food resources, which may reduce competition or predation and promote co-occurrence between nonnative and native taxa. Our results suggest that the co-occurrence of native and nonnative amphibians and fishes in lowland floodplain habitats may be facilitated by a broad range of food resources and complex habitat structure.

Genomic basis for an informed conservation management of Pelophylax water frogs in Luxembourg.

Genetic identification methods have become increasingly important for species that are difficult to identify in the field. A case in point is Pelophylax water frogs. While their morphological determination is highly complex, they include species protected under EU law and some that are classified as invasive. Additionally, genetic data can provide insights into their complex breeding systems, which may or may not involve the reproductive dependency of one species on another. Here, we generate baseline data for water frog monitoring in Luxembourg. We applied a countrywide sampling approach and used SNPs generated by ddRAD sequencing to identify individuals and infer the breeding systems present in the country. We found Pelophylax lessonae and P. kl. esculentus throughout Luxembourg, mostly living in syntopy. In general, a reproductive dependency of P. kl. esculentus on P. lessonae (L‐E system) was revealed. Besides this general system, we detected triploid P. kl. esculentus in six ponds. This indicates a modified L‐E system with reproductive dependency of the triploids on the diploid P. kl. esculentus. The invasive P. cf. bedriagae was detected in three ponds in southern Luxembourg, with evidence for hybridization with native water frogs. In addition to the ddRAD data, we tested a simple genetic method for future monitoring based on the MND1 marker. It showed in almost all cases, an identical species identification as the ddRAD data and was successfully applied to DNA extracts from mouth swabs. Combining this method with our baseline data will enable informed choices for the protection of native water frog species in Luxembourg.

Choosy cannibals: Targeted consumption of conspecific hatchlings by larval cane toads is triggered by species-specific defensive toxins.

In many species, cannibalism is uncommon and involves nonselective consumption of conspecifics as well as heterospecifics. However, within their invasive Australian range, cane toad larvae (Rhinella marina) specifically target and voraciously consume the eggs and hatchlings of conspecifics, often extirpating entire clutches. In contrast, toad larvae rarely consume the eggs and hatchlings of native frogs. Here, we use laboratory studies to demonstrate that this selective consumption is triggered by species‐specific chemical cues: maternally‐invested bufadienolide toxins that otherwise defend cane toad eggs and hatchlings against predators. We find that these cues stimulate feeding behaviors in toad tadpoles, such that the addition of bufadienolide toxins to the water column increases predation on eggs, not only of conspecifics, but also of native anuran species that are otherwise usually ignored. In contrast, we find that cannibalism rates on conspecific hatchlings are high and unaffected by the addition of bufadienolide cues. The maternally‐invested toxins present in conspecific eggs may therefore be more easily detected post‐hatching, at which point tadpole feeding behaviors are induced whether or not additional toxin cues are present. As bufadienolide cues have previously been found to attract toad tadpoles to vulnerable hatchlings, our present findings demonstrate that the same toxin cues that attract cannibalistic tadpoles also induce them to feed, thereby facilitating cannibalism through multiple behavioral effects. Because native fauna do not produce bufadienolide toxins, the species specificity of these chemical cues in the Australian landscape may have facilitated the evolution of targeted (species‐specific) cannibalism in invasive cane toad populations. Thus, these bufadienolide toxins confer cost (increased vulnerability to cannibalism in early life‐stages) as well as benefit (reduced vulnerability to predation by other taxa).

Competition between the tadpoles of Japanese toads versus frogs

Competition within and among species can play a key role in structuring the assemblages of anuran tadpoles. Previous studies have reported that tadpoles of the invasive cane toad (Rhinella marina) are more strongly disadvantaged by the presence of native frog tadpoles than by the same number of conspecific toad tadpoles. That effect might arise from a lack of coevolution of the invasive toad with its competitors; and/or from a generalized superiority of frog tadpoles over toad tadpoles. To clarify those possibilities, we conducted experimental trials using the larvae of a native rather than invasive toad (Bufo japonicus formosus in Japan) exposed to larvae of native anurans (the sympatric frogs Rana japonica and Rana ornativentris and the parapatric toad Bufo japonicus japonicus). In intraspecific competition trials, higher densities of B. j. formosus prolonged the larval period and reduced size at metamorphosis, but did not affect survival. In interspecific competition trials, the effects of the other anuran species on B. j. formosus were similar to the effects of the same number of conspecific larvae. This similarity in impact of interspecific versus intraspecific competition argues against any overall competitive superiority of frog larvae over toad larvae. Instead, the vulnerability of larval cane toads to frog tadpoles may result from a lack of coevolutionary history.

Presence of invasive American bullfrogs may reduce infectious disease in a native frog species.

Amphibians breeding in aquatic environments may encounter a myriad of threats during their life cycle. One species known to prey on native amphibians in aquatic habitats is the invasive North American bullfrog Lithobates catesbeianus, which, besides being a voracious predator and competitor, often acts as a pathogen carrier and disease superspreader because it tolerates high infection loads of the frog-killing fungus Batrachochytrium dendrobatidis (Bd). Here, we hypothesized that the presence of the bullfrogs in microcosms should either (1) decrease Bd disease severity in native frog species by discouraging them from using the aquatic environment, or (2) increase the mortality of the native species. We tested these 2 mutually exclusive hypotheses by co-housing the snouted treefrog Scinax x-signatus (native to our study area) with L. catesbeianus in the laboratory, exposing them to Bd, and using qPCR analysis to quantify the resulting Bd infection loads in the native frogs. Our experiment had the following replicated treatments: (1) native-only treatment (3 individuals of S. x-signatus), (2) native-predominant treatment (2 S. x-signatus + 1 L. catesbeianus), and (3) exotic-predominant treatment (1 S. x-signatus + 2 L. catesbeianus). We found that Bd infection loads in the native S. x-signatus were highest in the native-only treatment, and lowest in the exotic-predominant treatment, indicating that bullfrogs may discourage native frogs from occupying the aquatic habitat, thus reducing encounter rates between native frogs and the waterborne pathogen. This effect could be driven by the bullfrogs' predatory behavior and their high philopatry to aquatic habitats. Our results highlight that predation risk adds to the complexity of host-species interactions in Bd epidemiology.

Seasonal drought and its effects on frog population dynamics and amphibian disease in intermittent streams

AbstractChytridiomycosis, caused by the pathogenic fungusBatrachochytrium dendrobatidis(Bd), has contributed to amphibian declines globally, but drivers of outbreaks vary locally. Here, we explore the role of drought in population and host‐disease dynamics of the endangered stream‐breeding foothill yellow‐legged frog (Rana boylii). In central California (USA) where severity of seasonal drought is increasing, we observed the non‐native, Bd‐tolerant and lentic‐adapted North American bullfrog (Lithobates catesbeianus) extend into streams when flood disturbance was minimal. Analysis of skin swabs revealed that prevalence and load of Bd infection among bullfrogs was low. Yet, among the native frogs, prevalence and load intensified as the seasonal drought progressed and surface flow became intermittent. When temperatures decreased in autumn and frogs concentrated at a reduced number of water points, we found dozens of dead foothill yellow‐legged frogs (2018–2019). Necropsies suggested chytridiomycosis as the likely cause of death. Despite recent lethal outbreaks, foothill yellow‐legged frog population abundance appeared resilient based on comparison to prior decades when no die‐offs were observed. Wet–dry mapping of the stream channel and retrospective analysis of hydrologic records revealed that the native frogs spawn away from perennial pools, a behaviour that may allow them to avoid bullfrogs and predatory fish. In an ecological trade‐off, tadpoles face the risk of the stream drying before metamorphosis. Fluctuations in population size thus corresponded to extremes of inter‐annual variation in streamflow that limit recruitment rather than disease outbreaks. We conclude that hydrologic constraints, which climate change may exacerbate, appear to override the stressors of non‐indigenous species and chytridiomycosis.

Invasive predators induce plastic and adaptive responses during embryo development in a threatened frog

Invasive predators can strongly affect native populations. If alien predator pressure is strong enough, it can induce anti-predator responses, including phenotypic plasticity of exposed individuals and local adaptations of impacted populations. Furthermore, maternal investment is an additional pathway that could provide resources and improve performance in the presence of alien predators. We investigated the potential responses to an alien predator crayfish (Procambarus clarkii) in a threatened frog (Rana latastei) by combining field observations with laboratory measurements of embryo development rate, to assess the importance of parental investment, origin and exposure to the crayfish cues. We detected a strong variation in parental investment amongst frog populations, but this variation was not related to the invasion status of the site of origin, suggesting that mothers did not modulate parental investment in relation to the presence of alien predators. However, cues of the invasive crayfish elicited plastic responses in clutches and tadpoles development: embryos developed faster when exposed to the predator. Furthermore, embryos from invaded sites reached Gosner’s development stage 25 faster than those from non-invaded sites. This ontogenetic shift can be interpreted as a local adaptation to the alien predator and suggests that frogs are able to recognise the predatory risk. If these plastic responses and local adaptation are effective escape strategies against the invasive predator, they may improve the persistence of native frog populations.

Parasite spillover to native hosts from more tolerant, supershedding invasive hosts: Implications for management

AbstractIntroduced hosts are capable of introducing parasite species and altering the abundance of parasites that are already present in native hosts, but few studies have compared the tolerances of native and invasive hosts to introduced parasites or identified the traits of introduced hosts that make them supershedders of non‐native parasites.Here, we compare the effects of a nematodeAplectana hamatospiculathat is native to Cuba but appears to be introduced to Florida on the native Floridian treefrog,Hyla femoralis, and on the Cuban treefrog (CTF),Osteopilus septentrionalis. We were particularly interested in CTFs because their introduction to Florida has led to reported declines of native treefrogs.In the laboratory, infection withA. hamatospiculacaused a greater loss in body mass ofH. femoralisthan CTFs despiteH. femoralisshedding fewer total worms in their faeces than CTFs. Field collections of CTFs,H. femoralis, and another native Floridian treefrog,H.squirella(Squirrel treefrog) from Tampa, FL also showed that CTFs shed more larval worms in their faeces than both native frogs when controlling for body size. Hence, the non‐native CTF is a supershedder of this non‐native parasite that is spilling over to less tolerant native treefrogs.Any conservation intervention to reduce the effects of CTFs on native treefrogs would benefit from knowing the traits that contribute to the invasive host being a supershedder of this parasite. Hence, we conducted necropsies on 330 CTFs to determine how host sex and body size affect the abundance ofA. hamatospicula, and two other common parasites in this species (acuariid nematodes and trematode metacercariae).There was a significant linear increase inA. hamatospiculaand encysted acuariids with CTF body size, but there was no detectable relationship between host body size and the intensity of metacercariae. Female CTFs were bigger, lived longer and, on average, had moreA. hamatospiculathan male CTFs.Synthesis and applications. These results of the study suggest that there is parasite spillover from the invasive Cuban treefrog (CTF) to native treefrogs in Florida. Additionally, at least some of the adverse effects of CTFs on native treefrogs could be caused by the introduction and amplification of this introduced parasite, and female and larger CTFs seem to be amplifying these infections more than males and smaller CTFs, respectively, suggesting that management could benefit from targeting these individuals.

Native frogs (Rana pirica) do not respond adaptively to alien toads (Bufo japonicus formosus) 100 years after introduction

AbstractBiological invasions adversely affect the survival of many native species, but long‐term consequences of the novel pressures imposed by invaders on natives are less clear. If natives can adapt to the presence of the invader, the severity of impact will decline with time. On Hokkaido, Japan, alien toads (Bufo japonicus formosus) are highly toxic to native frog tadpoles (Rana pirica) that attempt to eat their hatchlings. Therefore, the arrival of toads potentially imposes selection pressure on native frogs in the context of behavioral response (feeding aversion) and physiological resistance to toad toxins. Here, we compared the consumption tendency and toxin resistance of R. pirica from several sites with different histories of toad invasion (0 to >100 years exposure). We found no evidence of adaptive response to invasive toads. The vast majority of R. pirica tadpoles from all sites readily consumed toad hatchlings and died, regardless of time since invasion or whether hatchlings were from sympatric versus allopatric toad populations. In contrast, tadpoles of a closely related species (Rana ornativentris), which co‐occurs naturally with B. j. formosus on Honshu, readily consumed toad hatchlings without ill effect. Our results indicate that the lethal toxic effect of the alien toads on native frogs on Hokkaido is maintained over long time periods without mitigation through adaptation.

Native anurans threatened by the alien tree Ligustrum lucidum in a seasonal subtropical forest

Native anurans threatened by the alien tree Ligustrum lucidum in a seasonal subtropical forest

Characterization of the microbiome of the invasive Asian toad in Madagascar across the expansion range and comparison with a native co-occurring species

Biological invasions are on the rise, with each invader carrying a plethora of associated microbes. These microbes play important, yet poorly understood, ecological roles that can include assisting the hosts in colonization and adaptation processes or as possible pathogens. Understanding how these communities differ in an invasion scenario may help to understand the host’s resilience and adaptability. The Asian common toad, Duttaphrynus melanostictus is an invasive amphibian, which has recently established in Madagascar and is expected to pose numerous threats to the native ecosystems. We characterized the skin and gut bacterial communities of D. melanostictus in Toamasina (Eastern Madagascar), and compared them to those of a co-occurring native frog species, Ptychadena mascareniensis, at three sites where the toad arrived in different years. Microbial composition did not vary among sites, showing that D. melanostictus keeps a stable community across its expansion but significant differences were observed between these two amphibians. Moreover, D. melanostictus had richer and more diverse communities and also harboured a high percentage of total unique taxa (skin: 80%; gut: 52%). These differences may reflect the combination of multiple host-associated factors including microhabitat selection, skin features and dietary preferences.