Tracing a toad invasion: lack of mitochondrial DNA variation, haplotype origins, and potential distribution of introduced Duttaphrynus melanostictus in Madagascar

The black-spined toad, Duttaphrynus melanostictus, is widespread in South and South-East (SE) Asia, although recent molecular analyses have revealed that it represents a species complex (here called the D. melanostictus complex). Invasive populations of this toad have been detected in Madagascar since, at least, 2014. We here trace the origin of this introduction based on mitochondrial DNA sequences of 340 samples. All 102 specimens from Madagascar have identical sequences pointing to a single introduction event. Their haplotype corresponds to a lineage occurring in Cambodia, China, Laos, Thailand, Vietnam, and some locations of eastern Myanmar and northern Malaysia, here named the SE Asian lineage. Within this lineage, specimens from one location in Cambodia and three locations in Vietnam have the same haplotype as found in Madagascar. This includes Ho Chi Minh City, which has a major seaport and might have been the source for the introduction. Species distribution models suggest that the current range of the Madagascan invasive population is within the bioclimatic space occupied by the SE Asian lineage in its native range. The potential invasion zone in Madagascar is narrower than suggested by models from localities representing the full range of the D. melanostictus complex. Thus, an accurate taxonomy is essential for such inferences, but it remains uncertain if the toad might be able to spread beyond the potential suitable range because (1) knowledge on species-delimitation of the complex is insufficient, and (2) the native range in SE Asia might be influenced by historical biogeography or competition

Madagascar’s extraordinary biodiversity: Evolution, distribution, and use

Madagascar's biota is hyperdiverse and includes exceptional levels of endemicity. We review the current state of knowledge on Madagascar's past and current terrestrial and freshwater biodiversity by compiling and presenting comprehensive data on species diversity, endemism, and rates of species description and human uses, in addition to presenting an updated and simplified map of vegetation types. We report a substantial increase of records and species new to science in recent years; however, the diversity and evolution of many groups remain practically unknown (e.g., fungi and most invertebrates). Digitization efforts are increasing the resolution of species richness patterns and we highlight the crucial role of field- and collections-based research for advancing biodiversity knowledge and identifying gaps in our understanding, particularly as species richness corresponds closely to collection effort. Phylogenetic diversity patterns mirror that of species richness and endemism in most of the analyzed groups. We highlight humid forests as centers of diversity and endemism because of their role as refugia and centers of recent and rapid radiations. However, the distinct endemism of other areas, such as the grassland-woodland mosaic of the Central Highlands and the spiny forest of the southwest, is also biologically important despite lower species richness. The documented uses of Malagasy biodiversity are manifold, with much potential for the uncovering of new useful traits for food, medicine, and climate mitigation. The data presented here showcase Madagascar as a unique living laboratory for our understanding of evolution and the complex interactions between people and nature. The gathering and analysis of biodiversity data must continue and accelerate if we are to fully understand and safeguard this unique subset of Earth's biodiversity

Madagascar’s extraordinary biodiversity: Threats and opportunities

Madagascar's unique biota is heavily affected by human activity and is under intense threat. Here, we review the current state of knowledge on the conservation status of Madagascar's terrestrial and freshwater biodiversity by presenting data and analyses on documented and predicted species-level conservation statuses, the most prevalent and relevant threats, ex situ collections and programs, and the coverage and comprehensiveness of protected areas. The existing terrestrial protected area network in Madagascar covers 10.4% of its land area and includes at least part of the range of the majority of described native species of vertebrates with known distributions (97.1% of freshwater fishes, amphibians, reptiles, birds, and mammals combined) and plants (67.7%). The overall figures are higher for threatened species (97.7% of threatened vertebrates and 79.6% of threatened plants occurring within at least one protected area). International Union for Conservation of Nature (IUCN) Red List assessments and Bayesian neural network analyses for plants identify overexploitation of biological resources and unsustainable agriculture as themost prominent threats to biodiversity. We highlight five opportunities for action at multiple levels to ensure that conservation and ecological restoration objectives, programs, and activities take account of complex underlying and interacting factors and produce tangible benefits for the biodiversity and people of Madagascar

Abundance, distribution and spread of the invasive Asian toad Duttaphrynus melanostictus in eastern Madagascar

The Asian toad, Duttaphrynus melanostictus, was accidentally introduced to Toamasina (eastern Madagascar) around 2010, and since then has spread at a substantial rate across a larger area. This study documents the expansion of the invasive range of this species, calculates the invasion spread rate, and provides estimates of toad abundance and habitat preferences. Updates of the distribution range revealed a fivefold increase of the invaded area over 3 years, and a doubling of the rate of spread, showing a shift of the invasion towards the North-West, most probably because of the absence of ecological barriers. We used N-mixture models to estimate toad abundance on the basis of repeated count data of six areas in Toamasina and its surrounding countryside. Toad distribution shows heterogeneous density across the distribution range, with an average abundance of 184 toads ha 121 (95% CI 132\u2013263). The toad\u2019s abundance was highest in sites with the presence of organic waste, and was negatively related to the density of road networks in the proximity of study sites. The rapid expansion of the Asian toad in the Toamasina region suggests that this toad is an increasing threat for Madagascar. We propose immediate management actions that could limit the spread of alien toads in this megadiverse country