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Invasive pythons, not anthropogenic stressors, explain the distribution of a keystone species

Abstract

Untangling the causes of native species loss in human-modified systems is difficult and often controversial. Evaluating the impact of non-native species in these systems is particularly challenging, as additional human perturbations often precede or accompany introductions. One example is the ongoing debate over whether mammal declines within Everglades National Park (ENP) were caused by either the establishment of non-native Burmese pythons (Python molurus bivittatus) or the effects of other anthropogenic stressors. We examined the influence of both pythons and a host of alternative stressors—altered hydrology and habitat characteristics, mercury contamination and development—on the distribution of the marsh rabbit (Sylvilagus palustris), a once common mammal in ENP. Distance from the epicenter of the python invasion best explained marsh rabbit occurrence in suitable habitat patches, whereas none of the alternative stressors considered could explain marsh rabbit distribution. Estimates of the probability of marsh rabbit occurrence ranged from 0 at the python invasion epicenter to nearly 1.0 150 km from the invasion epicenter. These results support the hypothesis that invasive pythons shape the distribution of marsh rabbits in southern Florida. The loss of marsh rabbits and similar species will likely alter trophic interactions and ecosystem function within the Everglades, an internationally important hotspot of biodiversity. Further, our results suggest that non-native species can have profound impacts on mainland biodiversity.

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Acknowledgments

This research was funded by the U.S. Geological Survey Priority Ecosystem Studies Program, the University of Florida Institute of Food and Agricultural Science and the Everglades Foundation. Special thanks to Everglades National Park, Florida Panther National Wildlife Refuge, Crocodile Lake National Wildlife Refuge, Biscayne National Park, Loxahatchee National Wildlife Refuge, Big Cypress National Preserve, Collier-Seminole State Park, Fakahatchee Strand Preserve State Park and the Florida Fish and Wildlife Conservation Commission for their assistance on this project. The project was carried out under research permit EVER-2012-SCI-0038, BICY-00110 and FWC_LSSC-12-00039. The authors acknowledge the Everglades Depth Estimation Network (EDEN) project and the U.S. Geological Survey for providing the water flow data for the purpose of this research/report. Special thanks to all field assistants and volunteers. The authors also thank two anonymous reviewers whose comments greatly benefited the paper’s clarity, organization and message. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

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Correspondence to Adia R. Sovie.

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Sovie, A.R., McCleery, R.A., Fletcher, R.J. et al. Invasive pythons, not anthropogenic stressors, explain the distribution of a keystone species. Biol Invasions 18, 3309–3318 (2016). https://doi.org/10.1007/s10530-016-1221-3

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  • DOI: https://doi.org/10.1007/s10530-016-1221-3

Keywords

  • North America
  • Mammals
  • Distribution modeling
  • Python molurus bivittatus
  • Sylvilagus palustris