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.