Invading Asian Toads

Biological invasions are an ongoing part of the Anthropocene. New invasions are

Asian Common Toad. Photo by Bryan L. Stuart

continually happening as we transport species around the globe. A toad (Duttaphrynus melanostictus) that I work on in its native range in mainland Southeast Asia (Wogan et al. 2016), has recently turned up near the port town of Toamasina in eastern Madagascar. It has been steadily increasing its range in Madagascar, and now seems to be a well established population. Madagascar is home to a highly endemic fauna. The toads present two major threats to the fauna- first, since the toads are highly toxic, they can incapacitate and kill naive predators that attempt to eat them. Second, they could serve as disease vectors that could carry the chytrid fungus (Bd). Although there are no reports of the toads carrying chytrid within their native range, they have not been tested extensively, so it may be possible that some populations do carry chytrid. Working with a team of amphibian biologists that focus on Madagascar in an effort lead by Miguel Vences, we are working on tracing the origins of the invasive lineage in Madagascar through fine-scaled sampling from the Indochina clade identified in Wogan et al. (2016). This work will help narrow down the geographic origin of the invasive toads, and perhaps provide clues about the port through which they moved  (Vences et al. 2017).

Interestingly, we also know that this same species has been island hopping and invading the non-Sundaic islands in Indonesia. Although the toads that are invading this area come from a the Sundaic “Insular” lineage (Wogan et al 2016), they present similar threats to the highly endemic island faunas as they invade. I am working with a team of Indonesia focused researchers to document the invasion in this part of the world (Reilly et al in prep). The invasion has been going on for decades, but has received relatively little attention.


Related publications

Wogan et al. 2016. Highly structured phylogeographic patterns in a wide-spread human commensal anuran species Duttaphrynus melanostictus in Asia. Biology Letters v. 12 (1) 20150807.  DOI: 10.1098/rsbl.2015.0807

Vences et al. Tracing a toad invasion: Lack of mitochondrial DNA variation, haplotype origins, and potential distribution of introduced Duttaphrynus melanostictus in Madagascar. Amphibia-Reptilia v. 38: 197-207

Reilly et al. Toxic toad invasion of Wallacea: a biodiversity hotspot characterized by extraordinary endemism. (in prep)