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Ecology: Stop Madagascar's toad invasion now

May 2014
Nature 509(7502):563

DOI:10.1038/509563a

Source
PubMed

Authors:

Jonathan Kolby

James Cook University

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Content may be subject to copyright.

Correspondence

Stop Madagascar’s

toad invasion now

Asian common toads

(Duttaphrynus melanostictus)

have begun to invade

Madagascar, threatening the

biodiversity of its unique fauna.

Time is short, so we are issuing

an urgent call to the conservation

community and to governments

to prevent an ecological disaster.

The first reported sighting of

D.melanostictus on Madagascar

was on 26March in Toamasina.

We collected six adult toads from

a swamp in the humid eastern

region, six kilometres from

Madagascar’s largest seaport.

More were spotted nearby,

suggesting that they arrived from

Asia inside shipping containers,

as they have elsewhere (see

F.Kraus Alien Reptiles and

Amphibians; Springer, 2009).

The region provides ideal

resources and climate for the

toad’s spread into the island’s

interior, and D.melanostictus

can range up to an elevation of

1,800metres. Surveys are now

being directed by the biodiversity

organization Madagasikara

Voakajy to identify the extent

of invasion and develop a

programme of eradication.

The species poses a significant

risk to native fauna, given its

life-history characteristics, the

evolutionar y naivety of the

native fauna to toad toxins, and

the damage caused in Australia

and elsewhere by its relative, the

cane toad (Rhinella marina).

Without swift eradication of

D.melanostictus, the ecological

consequences of an invasion

include poisoning and decline

of vulnerable native predators

(birds, mammals, reptiles), the

spread of amphibian diseases,

and the secondary effects of

food-web disruption. Potential

impacts on humans include

loss of domestic animals,

contamination of drinking water

and transmission of parasites in

areas with poor sanitation.

Jonathan E. Kolby* James

Cook University, Townsville,

Queensland, Australia.

jonathan.kolby@my.jcu.edu.au

*On behalf of 11 co-signatories (see

go.nature.com/4ataw3 for full list).

US patient network

safeguards data

Concerns about privacy have led

the US National Patient-Centered

Clinical Research Network

(PCORnet; see go.nature.com/

d9eaee and Nature 508, 432;

2014) to adopt a slightly different

approach from the UK National

Health Service’s care.data

programme (see Nature 507, 7;

2014), which has similar goals.

Launched by the Patient-

Centered Outcomes Research

Institute, PCORnet aims to

improve patient outcomes by

connecting patients, clinicians,

researchers and health systems.

PCORnet will not use a

centralized database to pool

information from multiple

networks. Rather, it will leave

identifiable patient data

behind the firewalls of the

29participating networks, and

distribute programming code

that allows the same analysis

to be run within each network.

In most cases, only aggregated

results are transferred for

pooling and reporting, which

avoids privacy or security risks.

Each PCORnet partner

network must engage all its

stakeholders in governance.

The authority to make final

policy decisions on privacy and

security and to participate in

multi-network studies is vested

locally. All research uses of data

will be approved and overseen by

institutional review boards.

In some cases, individual

informed consent will be

deemed necessary. In low-risk

research, such as observational

studies that do not alter

treatment choices, networks

can favour other forms of

communication with patients,

especially if obtaining individual

consent would render the study

unfeasible. Such decisions will

also be made locally, and with

patient participation.

These measures aim to

ensure that PCORnet’s ‘big data’

approach will answer patients’

questions about their care while

safeguarding the privacy of their

personal health information.

Joe V. Selby Patie nt-Centered

Outcomes Research Institute,

WashingtonDC, USA.

jvselby@pcori.org

Tackle pollution

from solar panels

There is a downside to China

having become the largest

producer and consumer of

solar energy (J. A. Mathews

and H.Tan Nature 508, 319;

2014). The rapidly expanding

manufacture of solar

photovoltaic products is risking

serious environmental pollution.

According to Greenpeace and

the Chinese Renewable Energy

Industries Association, some

two-thirds of the country’s solar-

manufacturing firms are failing

to meet national standards

for environmental protection

and energy consumption. The

production of polysilicon and

silicon wafers for solar panels

creates dangerous by-products,

in particular silicon tetrachloride

and hydrofluoric acid, which

are being discharged into the

environment after inadequate

waste treatment (see go.nature.

com/mhtayz; in Chinese).

For example, in 2011, fluoride

concentrations in the Mujiaqiao

River near a solar-panel factory in

Haining City, eastern China, were

more than ten times higher than

permitted, killing fish and raising

concerns about human health.

Another source of pollution

is the careless disposal of

used solar-panel equipment,

which includes battery waste

containing lead, cadmium,

antimony and sulphuric acid

(see H.Wang and J.Nima

Qinghai Soc. Sci. 5, 58–60; 2007).

Improved waste treatment,

environmental monitoring

and education are essential to

avoid the undesirable impacts

of these otherwise valuable

technological advances.

Hong Yang University of Oslo,

Norw ay.

Xianjin Huang Nanjing

University, China.

Julian R. Thompson University

College London, UK.

hongyanghy@gmail.com

Industries depend

on biodiversity too

Andrew Moss and colleagues

lament that raising the public’s

awareness of biodiversity

will not necessarily change

behaviour (Nature 508, 186;

2014). A fresh perspective

might: the public needs to

recognize that biodiversity

is crucial to a variety of core

industries and not just the

province of conservationists.

Biodiversity is not only about

vertebrates and flowering

plants, as is popularly believed:

invertebrates and microbes

account for at least 90% of all

species. The genetic, metabolic,

physiological and chemical

diversity of these species

underpins primary industries

such as agriculture, grazing,

forestry and fisheries.

Many biodiversity elements

help to provide crops, timber,

seafood and other necessities

through ecosystem services.

For example, microbes

naturally regulate nitrogen and

phosphorus in agricultural soils,

and wild pollinators increase

crop yields. It is therefore ironic

that these primary industries

so often constitute a threat to

biodiversity conservation efforts.

Promoting a popular vision

of biodiversity that embraces all

kinds of species could lead to

conservation being taken more

seriously by the public, and by

those economic sectors that act

as though biodiversity is not

important to them.

Andrew J. Beattie Macquarie

University, Sydney, New South

Wales, Australia.

Paul R. Ehrlich Stanford

University, California, USA.

andrew.beattie@mq.edu.au

29 MAY 2014 | VOL 509 | NATURE | 563

Exploring the invasion dynamics and impacts of the invasive Asian common toad in Madagascar

Thesis

Jun 2022

Fulvio Licata

Invasive alien species (IAS) are a major driver of global change, having severe impacts on ecosystems and societies. Insular biotas and biodiversity hotspots can be particularly vulnerable to biological invasions, especially within countries with a low capacity to counter IAS. Amphibian invasions can have important impacts on recipient environments, including competition, predation, and transmission of diseases, among others, however, only a few species have been extensively studied. Investigating the invasion dynamics and impacts of understudied invasive amphibians in biodiverse developing countries can be relevant to improving our understanding and management of amphibian invasions worldwide. The Asian common toad Duttaphrynus melanostictus is native to southeast Asia, is highly fecund, toxic, and could represent a vector for amphibian diseases. In 2014, an invasive population of this species has been reported in Madagascar, raising concerns about the potential impacts it could have on its megadiverse ecosystems. In this study, I explore the invasion dynamics and impacts of the Asian common toad in Madagascar through a set of studies that examine: (1) the distribution and rate of spread, (2) the factors regulating toad abundances, (3) morphology, (4) spatial ecology, (5) the occurrence and magnitude of toxic effect on native predators, (6) and the potential socioeconomic impacts on local populations. Initially, I assessed the invasive range and the rate of spread of the invasion using distributional records. Furthermore, I evaluated the environmental factors determining toad abundances in six localities across urban and rural areas across the invasive range. I demonstrated that the invasive range increased fivefold over three years, showing an acceleration of the invasion. Toads’ abundances were heterogeneous, but densities were highest in the presence of organic waste. These results confirmed the high invasive potential of this species, suggesting that proper waste control and disposal programs could help reduce toad abundance. I tested whether the accelerating range expansion could be caused by spatial sorting of dispersal-relevant traits, conducting a morphological analysis of adult toads captured in several localities along the invasion gradient. I found no evidence of spatial sorting in the traits analyzed. On the contrary, I found that morphological variation was largely dependent on the sex and body size of individuals. Furthermore, toads’ size did not vary across the invasive range, which could indicate that both adults and juveniles contribute to the range expansion of the species. This hypothesis was also supported by field observations of juveniles outnumbering adults at the invasion front. This work provides the first insights into the invasion dynamics of this species in Madagascar, highlighting important differences with the Cane toad invasion of Australia. To understand the factors determining the spreading dynamics, I conducted a radio-tracking study of adult toads in three localities along the invasion gradient, testing the occurrence of spatial sorting of behavioral traits, and investigating intrinsic and extrinsic determinants of spatial behavior. Toads showed sedentary behavior, and their movements were dictated by weather conditions. Spatial sorting of dispersal behavior was not detected, and the frequency distribution of movements was not exponentially bounded, supporting an invasion scenario dominated by short-distance leading-edge dispersal, with invasion speed expected to increase over time. Toad poisoning of native predators was the most dreaded impact of the Asian toad invasion to Madagascar due to the predicted high vulnerability of native predators to its toxins. The magnitude of these impacts likely depends on the ability of toads to colonize forest habitats, where frog-eating predators are especially abundant. After confirming toads’ capability of invading forests, I documented lethal toad poisoning in the native cat-eyed snake Madagascarophis colubrinus. Monthly estimates of snakes’ mortality due to toad poisoning showed that, if constant through time, this impact could halve the predator population within one year. Besides highlighting the potentially disruptive impact of toads on a native snake, this study also urges future research to focus on the potential repercussions of the toad-induced decline of predators on human health due to indirect facilitation of human-commensal rodent pests. Lastly, using public survey data, coupled with a multi-analytical approach, I showed that: (1) locals reliably identify the species, (2) the invasion followed a linear range expansion of approx. 2 km/year, although man-mediated dispersal was found to facilitate the long-distance spread of the species, (3) negative public perception is highest in rural areas (due to high perceived impacts on ecosystems), and in recently invaded localities, suggesting density- or time-dependent effects; loss of domestic apiaries, poisoning of poultry, and decline of snakes were the impacts that caused the greatest societal concerns. With this study, I describe the complex human-toad interactions in different environmental contexts and at different stages of the invasion. I highlighted the extreme versatility of public survey data to address fundamental requirements for invasion science and management applications, which can be especially useful in hard-to-monitor regions of the world with a low in-country capacity to counter IAS. This thesis provides important baseline information for the management of the invasive Asian toad both in Madagascar and elsewhere, highlighting the importance of investigating fundamental aspects of IAS biology to understand the mechanisms underlying invasion dynamics and impacts. In summary, I showed that the range expansion is linear and relatively slow, although man-mediated dispersal facilitates the long-distance spread of the species, stressing the importance of implementing biosecurity measures, as well as developing early detection and rapid response systems. Toad invasion of forest habitats and lethal poisoning of a frog-eating predator can potentially determine local extinctions of some native species, with potential trophic cascades across ecosystems, and possible implications also for human health. In addition, a combination of potential impacts on local communities, if confirmed, can deepen systemic socioeconomic vulnerabilities in Madagascar.More broadly, this work provides important insights into the challenges associated with the management of highly problematic invasive species in developing countries, offering methodological suggestions for the study of the invasion dynamics and impacts which are transferable to other study systems.

Life History Traits and Longevity of the Invasive Asian Common Toad Duttaphrynus melanostictus (Schneider, 1799) in Madagascar

Article

Full-text available

Jun 2023

We analyzed the body length, age structure, and age at sexual maturity of the invasive Asian common toad Duttaphrynus melanostictus from different sites in Toamasina, east Madagascar. We used skeletochronology as a proxy for age estimation, while gonads were histologically analyzed to determine the age of sexual maturity. The analysis of pooled age data from three sites investigated in 2016 showed that both sexes were larger, although not older, than those of native populations. For the individuals from Madagascar, the males were significantly smaller and younger (mean SD, SVL: 71.4 1.6 mm; age: 1.8 0.7 years) than the females (SVL: 78.42 1.9 mm; age: 2.7 1.3 years), when the data were pooled, but when the data were analyzed separately for each of the three sites, similar results were obtained only for one site. The oldest recorded male and female were 3 and 6 years old, respectively. Gonadal histology showed that the males and females reach sexual maturity after the first and second years of age, respectively. Further studies are needed to understand if the larger size and faster growth rates observed in the invasive population of D. melanostictus in Madagascar are a consequence of more favorable environmental conditions with respect to the native range (e.g., the availability of larger trophic niches, a lack of competitors, and lower predatory pressure), and we suggest to extend the monitoring of these life history traits to understand how they might influence the invasion.

Ecological Consequences of a Millennium of Introduced Dogs on Madagascar

Article

Full-text available

Jun 2021

Introduced predators currently threaten endemic animals on Madagascar through predation, facilitation of human-led hunts, competition, and disease transmission, but the antiquity and past consequences of these introductions are poorly known. We use directly radiocarbon dated bones of introduced dogs (Canis familiaris) to test whether dogs could have aided human-led hunts of the island’s extinct megafauna. We compare carbon and nitrogen isotope data from the bone collagen of dogs and endemic “fosa” (Cryptoprocta spp.) in central and southwestern Madagascar to test for competition between introduced and endemic predators. The distinct isotopic niches of dogs and fosa suggest that any past antagonistic relationship between these predators did not follow from predation or competition for shared prey. Radiocarbon dates confirm that dogs have been present on Madagascar for over a millennium and suggest that they at least briefly co-occurred with the island’s extinct megafauna, which included giant lemurs, elephant birds, and pygmy hippopotamuses. Today, dogs share a mutualism with pastoralists who also occasionally hunt endemic vertebrates, and similar behavior is reflected in deposits at several Malagasy paleontological sites that contain dog and livestock bones along with butchered bones of extinct megafauna and extant lemurs. Dogs on Madagascar have had a wide range of diets during the past millennium, but relatively high stable carbon isotope values suggest few individuals relied primarily on forest bushmeat. Our newly generated data suggest that dogs were part of a suite of animal introductions beginning over a millennium ago that coincided with widespread landscape transformation and megafaunal extinction.

Challenges and Solutions in Solar Photovoltaic TechnologyLife Cycle

Article

Jun 2023

Solar energy offers a clean and abundant alternative to the challenges associated with fossil fuels such as greenhouse gas emissions and resource depletion. The review focuses on the environmental impacts of solar photovoltaic technology throughout its life cycle, from manufacturing to disposal, and highlights potential hazards associated with using and producing photovoltaic technology, including releasing toxic gases and other trace elements into the environment. The paper concludes by summarizing various recycling techniques that can be employed to address these challenges and to take full advantage of solar photovoltaic technology without causing harm to the environment.

Dogs occupying grassy habitat near protected areas in eastern Madagascar rely on foods from forests

Article

Full-text available

Sep 2022

Societal Impact Statement Identifying where introduced animals fit in a food web relative to each other and to endemic species is key for biodiversity conservation planning. Using a multiproxy study of dog feces from eastern Madagascar, we infer that even dogs that spend time in derived grasslands typically eat forest‐derived foods. Regardless of the time that dogs spend in cleared forest, their impacts are likely concentrated on forest‐dwelling prey. If dogs in forests mostly consume threatened endemic animals (and not other introduced animals such as rats), then the exclusion of dogs from protected forests should be a priority. Summary Introduced predators on islands can help control invasive species yet can also contribute to the extirpation and extinction of endemic taxa. The spread of dogs on Madagascar by ~1000 years ago coincided with the introduction of livestock and spread of grazer‐adapted grasslands, and we help evaluate the extent to which modern dogs are part of novel grassland food webs. To infer dog diet, we identified food remains, where possible, and conducted stable isotope ratio analysis for n = 100 modern dog feces collected in derived grassland at varying distances from protected forest edges around Analamazoatra and Andasibe‐Mantadia National Park in eastern Madagascar. Animal remains in feces and the observed range of fecal δ ¹⁵ N values are consistent with dog meals at multiple trophic levels. However, the observed distribution of fecal δ ¹³ C values suggest that few dogs in the study area consumed food derived from open C 4 grasslands. Existing data suggest that dogs rely primarily on C 3 consumers inhabiting forest biomes (forest‐dwelling animals) for their prey, which may include endemics such as tenrecs, Malagasy rodents, and lemurs and introduced rodents such as rats. These findings indicate that dogs are not confined to the anthropogenic niche defined by grazer‐adapted grasslands, but rather use and impact animal food resources associated with protected forests. Higher resolution study of dog diet and mobility can further clarify the potential for dogs to exploit endemic prey, compete with endemic predators, and spread disease across ecotones.

Toad invasion of Malagasy forests triggers severe mortality of a predatory snake

Article

Full-text available

Apr 2022
BIOL INVASIONS

The Asian common toad Duttaphrynus melanostictus has been introduced to the eastern province of Toamasina in Madagascar, where it is feared to be having devastating effects on native communities by poisoning frog-eating predators. So far it is unclear whether the toad can invade forest habitats, and empirical evidence of its impact on native predators is lacking. We used radio tracking to investigate the spatial behaviour of adult toads in a small parcel of lowland humid forest and we quantify the disruptive effects of toad poisoning on a native frog-eating snake, the Malagasy cat-eyed snake (Madagascarophis colubrinus). We used N-mixture models to estimate the population size of cat-eyed snakes, and used the mortality events recorded in the same area to obtain an estimate of monthly mortality rate of snakes due to toad poisoning. Our results point to a drastic mortality rate of snakes that, if constant through the year, could halve the predator population, with the potential risk of local extirpation. We expect cat-eyed snake populations across rural and suburban areas of Toamasina to be severely affected by the toad invasion, and suggest that future research should investigate the effects of indirect facilitation of human-commensal rodents and the potential repercussions on human health and well-being.

Assessing the uncertainty arising from standard land-cover mapping procedures when modelling species distributions

Article

Full-text available

Jan 2022
DIVERS DISTRIB

Aim Habitat loss and degradation is one of the main threats to biodiversity worldwide. Ecological modelling community has been increasingly incorporating habitat changes in the species distribution models (SDMs). However, the effect that the uncertainty arising from the standard procedures of land‐use/land‐cover (LULC) mapping can have on SDMs has been overlooked. Remote sensing offers a great source of information to assess the habitat changes at different spatiotemporal scales. However, despite the great variety of satellite imagery preprocessing and supervised classification procedures currently available, their effects on SDMs remain largely unknown. Location Baixa Limia–Serra do Xurés Natural Park, NW Spain. Methods We developed SDMs for 27 bird species with 4 modelling algorithms using 12 sets of the LULC predictors derived from the combination of 3 image preprocessing levels and 4 supervised classification algorithms. Results The preprocessing level, classification method and modelling algorithm had a significant impact on the SDM performance and on the spatial and temporal predictions, with the considerable variation between species. Even if the effects of satellite image processing and classification procedures on the performance and transferability of SDMs were lower than that of the modelling algorithms themselves, the spatial and temporal predictions of SDMs were overall strongly affected by these LULC mapping procedures, sometimes overriding the effect of modelling algorithms. Main conclusions We argue that the uncertainty arising from the standard LULC mapping procedures when predicting species distribution dynamics should receive the same level of attention as the variability due to the different types of climate simulations and models often used in the ecological research. We also highlight the need to report accuracy of the satellite‐based LULC maps for each LULC class since some of these classes can be of key importance for certain types of the ecological applications.

Using public surveys to rapidly profile biological invasions in hard‐to‐monitor areas

Article

Full-text available

Nov 2022
ANIM CONSERV

Understanding the impact and dynamics of invasive alien species (IAS) is essential for tailoring appropriate management plans. This information can be difficult to obtain in the short term, and intrinsic difficulties of monitoring hard‐to‐reach areas may hamper prompt estimation of IAS distributions. Using the case of the invasive Asian common toad (Duttaphrynus melanostictus) in Madagascar, we show how public surveys coupled with a multi‐analytical approach can promptly provide accurate information on invasion dynamics and impacts. On the basis of key‐informant responses, we built polynomial regressions to investigate the spatiotemporal invasion patterns, false‐positive occupancy models to estimate species occupancy, and mixed‐effect models to evaluate the public perception and attitudes. The invasion followed a linear expansion of approx. 2 km year⁻¹, with human‐mediated dispersal facilitating the spread of the species. Toad occupancy decreased towards the invasion front and increased in the southern portion of its range. Negative perception decreased in urban areas, where people were less concerned by toad impacts on ecosystems, and in recently invaded localities, suggesting density‐ or time‐dependent effects. We also identified 12 potential impacts, with “loss of domestic apiaries”, “poisoning of poultry” and “decline of snakes” standing out for prevalence and potential severity. Our results bring important insights into the invasion dynamics and the human‐toad interactions in Madagascar, highlighting the versatility of public surveys to obtain essential information for invasion science and management, which can be especially useful in hard‐to‐monitor regions of the world with a low in‐country capacity to counter invasive species.

Review on the impacts of invasive alien vertebrates on biodiversity

Article

Full-text available

Sep 2022

Abstract: Alien species invasion is one of the major causes of global biodiversity loss. As the top predators of the food web, invasive alien vertebrates have dominant impacts on native species population, community structure and ecosystem functions. Based on intensive and systematic literature review, we summarize the direct (e.g., predation, competition, reproductive interference and gene pollution) and indirect (e.g., disease transmission and habitat modifications) impacts of invasive alien vertebrates on native biota across population, community, ecosystem, and biogeography levels. We particularly focus on the impacts of invasive alien species on island ecosystems, protected areas and the regions along the “Belt and Road Initiative”, which are located in biodiversity conservation hotspots and are extremely sensitive to biological invasions. We finally summarize recent research progress and the directions of future studies on invasive alien vertebrates and potential conservation and management strategies in China. 摘要：外来物种入侵是造成全球生物多样性下降的重要因素之一。入侵脊椎动物作为食物链的上游类群，对生物多样性的危害尤为显著，但长期以来缺少对脊椎动物入侵危害的系统阐述。本文从直接影响（捕食危害、种间竞争和繁殖干扰、种间杂交和基因污染等）和间接影响（疾病传播、栖息地环境改变等）两个方面，分别在种群、群落、生态系统和生物地理格局等不同水平上，阐述外来入侵鱼类、两栖爬行类、鸟类和兽类等脊椎动物类群对生物多样性的影响机制，并以典型生物多样性脆弱区（岛屿生态系统和自然保护地）以及 “一带一路”倡议沿线为例，探讨外来脊椎动物入侵对生物多样性保护的挑战；最后，概述我国入侵脊椎动物对生物多样性危害的研究现状，并结合生态安全的国家需求以及国际科学前沿，展望我国外来脊椎动物入侵危害研究的未来发展方向。

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

Article

Full-text available

Jun 2021

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.

ResearchGate has not been able to resolve any references for this publication.

Ecology: Stop Madagascar's toad invasion now

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