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

Abstract

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.

Impact of the Mid-Pleistocene Revolution and Anthropogenic Factors on the Dispersion of Asian Black-Spined Toads (Duttaphrynus melanostictus)

“…To base our analyses on an extensive and balanced sampling, we also acquired 345 matching sequences for the mtDNA tRNAGly ND3 fragment and 116 sequences for the nuDNA SOX9 fragment from Genbank. These sequences generally arise from the major taxonomy studies conducted by Wogan et al (2016) [ 54 ] and Vences et al (2017) [ 55 ].…”

Toxic toad invasion of Wallacea: A biodiversity hotspot characterized by extraordinary endemism

“…Invasions of poisonous species can cause rapid population declines among native fauna because predators are naïve and often vulnerable to these toxins. The recent invasion of Madagascar by the poisonous Asian common toad, Duttaphrynus melanostictus , has sparked international attention (Kolby, ) as well as research and conservation efforts to predict the climate suitability of Madagascar for the invasive toads (Pearson, ; Vences et al., ), pinpoint the origin of the invasive lineage (Vences et al., ; Wogan, Stuart, Iskandar, & McGuire, ), determining the toads’ distribution, and educating local communities (Andreone, ). While the invasion in Madagascar has received much attention, an invasion of this same toad species on the islands of Wallacea in eastern Indonesia is ongoing but virtually unrecognized.…”

Distribution and conservation status of the Caucasian parsley frog, Pelodytes caucasicus (Amphibia: Anura)

“…AUC values above 0.75 are considered useful and above 0.90 very good (Swets, 1988;Elith, 2002). To properly parameterise the model, we evaluated the performance of various combinations of ten regularisation multipliers (from 0.5 to 5.0, in increments of 0.5; see details in Vences et al, 2017). The best-fit model was parameterised with a regularisation multiplier of 1.0 (30 replicates).…”

“…Recently, numerous studies were made by using this method (Tarkhnishvili et al, 2008;Garcia-Porta et al, 2012;Dufresnes et al, 2016). The obtained models of species distribution could be useful for study of many aspects of ecology and conservation, predicting of new localities for rare and threatened species, and invasive species spread (Bombi et al, 2009;Lyet et al, 2013;Vences et al, 2017). This approach appears a good and reliable tool for past and future climatic scenario studies, too (Brito et al, 2011;Tarkhnishvili et al, 2012;Litvinchuk et al, 2013;Duan et al, 2016;Iannella et al, 2017;Wetterings & Vetter, 2018).…”