Within the last month, a new species of vertebrate has been added to The Bahamas. It’s not a beautiful, obscure reef fish, but rather a large, brown toad called the Cane toad, Rhinella marina (story here). So how did it get here? For now, we don’t know, but I thought I might hazard a guess…plants.
The international trade in ornamental and landscaping plants (including sod) is extensive. While I can’t be sure as to the origin of the recent introduction of toads to New Providence or any of the other Bahamas introductions over the last several decades there is some evidence that the transportation of plants can often bring with it stowaways. A quick look at a list of the introduced species in The Bahamas reveals at least eight species that would very likely have found their way into The Bahamas tucked into the crowns of palms or around the roots (one pan-tropical exotic is even known colloquially as the “Flower-pot Snake”!).
Now the only problem with this hypothesis is that there just are no data per se. Rather we are left with anecdotal observations of animals found in potted plants, or the fact that quarantine areas in destination countries are often the epicenter of introductions. Gad Perry, a herpetologist from Texas Tech University has been doing research in the Caribbean for decades and during that time seems to have dedicated quite a bit of effort to providing evidence for a ‘Plant Vector Theory of Animal Introduction’. One of these papers was just recently discussed in Anole Annals which is what precipitated this short post. In this paper Gad and coauthors report their findings after searching a shipment of plants en route to the Virgin Islands. While their findings are not overwhelming they do find several species of stow-aways amongst the roots and leaves of the plants on board, thereby proving an otherwise hypothetical situation is more than simply plausible. Past efforts of by Dr. Perry and many others have also found evidence that a wide range of vertebrates have been transported around the Caribbean region in potted plants as well (Powell et al. 2011).
So while other vectors of introduction are possible, such as excaped pets or transportation in building materials, the most likely agent seems to be internatinal trade in ornamental and landscaping plants. Below are eight species that have been introduced to The Bahamas, all of which are likely spread via ornamental plants.
Knight Anoles (Anolis equestris)
Green Anoles (Anoles carolinensis)
Narrowmouth Toads (Gasterophryne carolinensis)
Corn Snakes (Pantherophis guttata)
Southeastern Five-lined Skink (Pleistodon inexpectatus)
Flower-pot Snake (Ramphotyphlops braminus)
Brown snake (Storeria dekayi)
Squirrel Treefrog (Hyla squirella)
For further reading, here a few papers to check out:
Krysko, K., N.A. Albury, and D.W. Steadman. 2012. Confirmation of the Southeastern Five-lined Skink, Pleistodon inexpectatus Taylor 1932 (Scincidae), on Grand Bahama Island, Commonwealth of The Bahamas. IRCF Reptiles and Amphibians 19: 126-127. (.pdf)
Knapp, C.R., J.B. Iverson, S.D. Buckner, and S.V. Cant. 2011. Conservation of amphibians and reptiles in The Bahamas. pp. 53-87. In: A. Hailey, B.S. Wilson, and J.A. Horrocks (eds.), Conservation of Caribbean Island Herpetofaunas. Volume 2: Regional Accounts of the West Indies. Brill, Leiden, The Netherlands. (.pdf)
Powell, R., R.W. Henderson, M.C. Farmer, M. Breuil, A.C. Echternacht, G. van Buurt, C.M. Romagosa, and G. Perry. 2011. Introduced amphibians and reptiles in the Greater Caribbean: Patterns and conservation implications, pp. 63–143. In: A. Hailey, B.S. Wilson, and J.A. Horrocks (eds.), Conservation of Caribbean Island Herpetofaunas. Volume 1: Conservation Biology and the Wider Caribbean. Brill, Leiden, The Netherlands.
Giery, S.T. 2013. First records of the corn snake (Pantherophis guttata) from Abaco Island, The
Bahamas, and notes their current distribution in the greater Caribbean region. IRCF Reptiles & Amphibians, Conservation and Natural History. 20(1): 36-39. (.pdf)
Perry, G., R. Powell, and H. Watson. 2006. Keeping invasive species off Guana Island, British Virgin Islands. 13(4):273-277. (.pdf)