The Cuban tree frog (Osteopilus septentrionalis): Distribution, diet, and reproduction of an invasive species in the British Virgin Islands
Owen, Jennifer L.
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Invasive species have the ability to inflict monetary and ecological damage on the systems they invade. Because of this, invasives and the characteristics that facilitate their invasion have received much attention including the compilation of set of key characteristics that make a species a successful colonizer. The Cuban tree frog (CTF) (Osteopilus septentrionalis) is an invasive species that has spread through Florida and the Caribbean. Because of its success as an invader, the CTF has been utilized as a model for examining successful invaders and invasions. To gain further insight into the CTF as a successful colonizing species, three of the putative characteristics of successful colonizing ability are investigated here through research on the invasive Cuban tree frog populations in the British Virgin Islands (BVI). The CTF is native to Cuba, the Bahamas, and the Cayman Islands. As a successful invasive species, the Cuban tree frog has increased its distribution and is now recorded as an invasive in Florida, Hawaii, Puerto Rico, Anguilla, Bonaire, the U.S. Virgin Islands, and most recently the British Virgin islands (BVI). In Chapter II, I examine one proposed characteristic of a successful colonizing species, the vagility of the CTF. This is accomplished by first establishing that CTFs are indeed populating the BVI, and then, tracking their spread throughout the islands. Since 1990, the CTF has been collected on five islands within the BVI, several of which I document for the first time. Four of the islands currently sustain breeding populations which were the basis for the studies that follow. I conducted an examination of the methodology of studying dietary composition. It is common in studies of the diet of reptiles and amphibians to solely rely on items found in the stomach. Chapter III addresses the potential biases entailed in this approach. Prey items found in the stomach and intestine were compared and found to be significantly different. I recommend the use of both methods to gain a complete view of a population’s diet and to gain a more complete view of what effect it may have on its prey. Chapter IV addresses another putative characteristic of successful colonizers, a generalist or broad diet. When the invasive CTF population in Florida was examined by Walter Meshaka, their diet was found to be quite broad, consisting of many orders of invertebrates as well as vertebrates. I assessed dietary breadth of the CTF in the BVI by analyzing stomach and intestinal contents of 428 frogs. Additionally, I examined the dietary plasticity of the CTF by comparing the diet of the CTF between islands within the BVI and between the BVI and Florida. Both traits, generalist diet and plasticity of diet, are demonstrated by the CTF. Chapter V focuses on another proposed characteristic of successful colonizers, high fecundity. I monitored reproductive ability and potential output in the BVI compared then to data collected by Meshaka in Florida. Both year-round reproductive ability and potential high reproductive output are present in the CTF population of the BVI, which also showed an increased body size, and increased clutch production compared to the Florida CTF population. On the whole, data collected on the CTF in the BVI support the validity of the proposed characteristics of successful colonizing species. This may help the ongoing increase in the CTFs range throughout the BVI, the Caribbean, and other novel habitats. Future research should be turned towards management and control methods for this pest species.