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Species of the Week
Rhinella marina , Cane Toad Photo © Andrew Snyder

The introduction history of cane toads to Australia is well documented; however, their introduction history in North America is unclear. Mittan-Moreau et al. (2022) sequenced Rhinella spp. populations across five introduced and five native populations to identify possible sources for North American introductions and the evolutionary consequences of introduction. They found the introduced Rhinella species in Florida is more closely related to Rhinella horribilis than to Rhinella marina (the source of all other known cane toad introductions). All introduced populations of toads had slightly lower genetic diversity than native populations, and showed genetic signals of population bottlenecks (sudden, rapid declines in population size) in their recent history. Nonetheless, introduced Florida populations showed less severe population declines (>500, at the lowest point) than had been reported by an oft-cited 1955 newspaper article describing an accidental release of just 100 toads. Lastly, genetic variants that may be under selection in introduced populations are largely present in native populations, suggesting that adaptation in the new, introduced environment may be enabled by genetic diversity already present in native populations. This study highlights the utility of genetic sequencing in understanding species introduction history, and the role of pre-existing genetic diversity in population persistence and expansion.

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As of (Dec 3, 2022)


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Total Amphibian Species by Order

215 Caecilians 777 Salamanders 7,532 Frogs