Effects of an invasive top predator on Ecosystem structure and function in a Graminoid Marsh food web

In this era of global change, understanding the effects of human-mediated dispersal of organisms has become a priority for ecological and conservation research. Non-native species introductions can result in biological invasions that have substantial impacts on native population abundances, community interactions, and ecosystem processes. Over the past twenty years, the establishment and subsequent invasion of the Burmese python (Python molurus bivittatus) in the Greater Everglades ecosystem has become a topic of concern amongst land managers and conservation practitioners in southern Florida. The objective of this study is to assess community-wide impacts of the python on the native food web as well as the function of the Greater Everglades Ecosystem by attempting to answer two central questions: 1) What functional role does the python occupy within the native food web and 2) is there a shift in overall food web structure and/or function post-invasion? We used ecological network analysis and an extensive diet dataset to quantify the python’s trophic role relative to other residents in the food web as well as compare ecosystem characteristics between pre- and post-invaded network models. Our findings demonstrate that the python functions similarly to the largemouth bass, another torrid, highly invasive predator that exhibits strong top-down impacts within its aquatic habitats. The python also behaves as a dominant predator akin to the Florida panther, primarily affecting native mammal populations through top-down predation effects, displacing other top predators within the food web, and altering patterns of carbon flow along the food chain. Finally, at the system scale, although we see increasing trends in ecosystem activity and decreasing trends in ecosystem structure and organization, functional metrics remain relatively stable pre- and post- invasion indicating functional resilience. Our findings provide a holistic assessment of the Burmese python invasion on the native community and function of the greater Everglades graminoid marsh ecosystem.