Invasive Ecology of the America Bullfrog (Rana Catesbeiana) in Hawai`i
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Cutia, Heidi Beswick
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Marine Science
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The American Bullfrog, Rana catesbeiana, is considered one of the most successful and damaging invasive amphibians, having spread by various means from the eastern US, currently established in Europe, Asia, South America and Oceania. Through various ecological interactions including competition, predation, and possible transmission of pathogens, this amphibian is extremely damaging to the aquatic ecosystems it invades. Numerous studies have documented devastating ecological impacts of bullfrogs in non-native ranges that include the western US, but very little information on this topic is available in the Hawaiian Islands, despite having been established for over 120 years. This project investigated aspects of bullfrog invasion ecology in Hawaii, including morphological divergence from mainland populations in terms of total body size, head width, and leg length, characters which substantially affect bullfrog interactions with native Hawaiian ecosystems. Hawaii bullfrog specimens differed significantly from most mainland groups for all morphological traits, exhibiting larger bodies, narrower heads, and shorter legs than observed in the native range. I also characterized bullfrog diet at two Oahu coastal wetlands, Kualoa Ranch and James Campbell National Wildlife Refuge. Finally, I assessed genetic diversity, inferred source populations, and evaluated the occurrence of the genetic invasion paradox in Hawaii bullfrog populations. This information will inform prioritization of management action and utilization of personnel and resources in an effective manner. Invasive ecology on islands like Oahu can also serve as a useful model for bullfrog-invaded ecosystems worldwide.
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Hawaii Pacific University