Abstract
When non-native species enter a new ecosystem, they often transport their natural parasites from their native range. These parasites may have the ability to spillover into native species and cause substantial ecological harm. Therefore, developing a baseline checklist for both non-native and closely related native species is essential. The cane toad (Rhinella horribilis) is a common invasive species in Florida's urban ecosystems that first became established in the Miami-Dade area but has since rapidly expanded its range. Most parasites infecting cane toads in Florida remain undocumented. The southern toad (Anaxyrus terrestris) is native to Florida and may be threatened by cane toads and other invasive species. In this thesis, we are developing a checklist of the parasites infecting the respiratory and digestive systems of cane toads from central, Southwest, and Southeast Florida. Additionally, we assess regional patterns in parasite infection of cane toads throughout the state. Finally, we aim to document the parasites infecting southern toads within the invasion front of cane toads to begin evaluating the potential for parasite spillover. To achieve these goals, we received cane toads from local contractors and homeowners across three regions. Southern toads were collected from two regions within the range of cane toads and subsequently euthanized. For both species, a necropsy was conducted on each toad by removing the lung tissue and digestive tract. Each organ was isolated, placed into a water-filled Petri dish, opened, and examined for parasites. Recovered parasites were extracted and sorted via external morphological characteristics. In cane toads, we recovered 11 parasite species, including 3 in the lungs, 6 in the gastrointestinal tract, 1 within the abdominal cavity, and 1 on the skin. Parasite diversity varied by region, with Southeast Florida toads harboring the highest diversity (9 species) and central Florida toads harboring the lowest (4 species). The prevalence of the lungworm Rhabdias pseudosphaerocephala was 72% in Southeast Florida but declined significantly to 9% in central Florida, with a similar trend in mean intensity. In southern toads, we recovered 11 parasite species including 7 species in the gastrointestinal tract and 4 in the lungs. Larger southern toads exhibited higher infection intensities of the trematode Mesocoelium sp. than smaller individuals. Both hosts shared five parasite species, indicating overlap in their parasite communities. The lower species richness and decreased prevalence of the lungworm in central Florida hosts could be due to the rapid migration of cane toads and the shorter time this population has been established. Higher infection intensity in larger southern toads may result from increased time spent near water during the breeding season. This increased proximity to water elevates exposure to the snail, intermediate hosts of Mesocoelium sp. The overlap of several species of parasites between the two hosts raises concerns of spillover from cane toads to southern toads. Future work should identify and determine the origins of the parasites shared by both hosts to better evaluate the risk of spillover of parasites from cane toads into southern toads.