Hybridization: Fowler's toads and American toads are both found throughout eastern North America with their ranges overlapping throughout much of it. Despite this, hybridization between these species only occurs in small isolated pockets, an anomaly known as "mosaic hybridization". In Canada, only one area exists where the two species have been documented hybridizing though the reason for this is of yet unknown. These hybrids exhibit intermediate traits from both parent species which can include the light colouration, smooth hind legs and reduced paratoid gland of the Fowler's toad, and the spotted underbelly, warty back and darker markings of the American toad although this changes between individuals. Hybrids also tend to have a mixed physiology in terms of internal anatomy as well, the most obvious being their vocal cords which produce calls intermediate between the American and Fowler's toad. These traits cannot always be used to identify a hybrid however with DNA testing being the most effective method of differentiating. Identification becomes difficult as these hybrids are able to back cross with their parent species producing F2 hybrids that have traits more like that of one particular species. This can create problems in regards to protecting the provincially Endangered Fowler's toad as it reduces the genetic integrity of populations.
|
Sources:
Green, David M. "Mating Call Characteristics of Hybrid Toads (Bufo americanus x B. fowleri) at Long Point, Ontario." Research Gate, Canadian Journal of Zoology, Feb. 2011, www.researchgate.net/publication/237993716_Mating_call_characteristics_of_hybrid_toads_Bufo_americanus_B_fowleri_at_Long_Point_Ontario. Accessed 29 July 2022. Green, David M., and Christine Parent. "Variable and Asymmetric Introgression in a Hybrid Zone in the Toads, Bufo americanus and Bufo fowleri." Bio One, Copeia, 1 Feb. 2003, bioone.org/journals/copeia/volume-2003/issue-1/0045-8511_2003_003_0034_VAAIIA_2.0.CO_2/Variable-and-Asymmetric-Introgression-in-a-Hybrid-Zone-in-the/10.1643/0045-8511(2003)003[0034:VAAIIA]2.0.. Accessed 29 July 2022. Volpe, E. Peter. "Physiological Evidence for Natural Hybridization of Bufo americanus and Bufo fowleri." Jstor, Society for the Study of Evolution, Dec. 1952, www.jstor.org/stable/2405702. Accessed 29 July 2022. |