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

Sovie, Adia; McCleery, Robert A.; Fletcher, Robert J.; Hart, Kristen M.

doi:10.1007/s10530-016-1221-3

Cited by 25 publications

(23 citation statements)

References 46 publications

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“…Burmese pythons are generalist predators with a diet primarily composed of mammals and birds (Snow et al, 2007;Reed & Rodda, 2009). Recent studies demonstrated that Burmese pythons are likely responsible for recent declines in native populations of marsh rabbits in the GEE (McCleery et al, 2015;Sovie et al, 2016), while correlative approaches suggest that this may also be the case for other sympatric mammal species (Dorcas et al, 2012). We predicted that negative effects of pythons on mammal distributions likely outweigh the influence of vegetation communities and hydrology.…”

Section: Introductionmentioning

confidence: 80%

“…The python R-D model was parameterized using 15 years of presence-only data, but makes a number of assumptions (random walk process, homogeneous landscape, a single point of invasion, logistic population growth and constant detection) which may limit its utility for fine-scale inferences. Previous studies on the impacts of pythons on mammals in the GEE have relied on related indices representing the relative impacts of pythons, including distance to the assumed invasion epicentre (Dorcas et al, 2012;Sovie et al, 2016) and opportunistic presence-only python data (collected primarily along roads) (Dorcas et al, 2012). Given these assumptions and lack of standardized empirical data on python abundance and/or occupancy, this estimate of python density may be best interpreted as a spatially explicit measure of the 'time since establishment' or 'residence time' of pythons in southern Florida.…”

Section: Burmese Pythonsmentioning

confidence: 99%

“…as apex predators) can exert major impacts on local biota (e.g. Recent studies demonstrated that Burmese pythons are likely responsible for recent declines in native populations of marsh rabbits in the GEE (McCleery et al, 2015;Sovie et al, 2016), while correlative approaches suggest that this may also be the case for other sympatric mammal species (Dorcas et al, 2012). Native to Southeast Asia, a Burmese python population has been established in portions of the GEE for at least 20 years.…”

Section: Introductionmentioning

confidence: 99%

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Urbanization may limit impacts of an invasive predator on native mammal diversity

Reichert

Sovie

Udell

et al. 2017

Diversity and Distributions

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Aim Our understanding of the effects of invasive species on faunal diversity is limited in part because invasions often occur in modified landscapes where other drivers of community diversity can exacerbate or reduce the net impacts of an invader. Furthermore, rigorous assessments of the effects of invasive species on native communities that account for variation in sampling, species-specific detection and occurrence of rare species are lacking. Invasive Burmese pythons (Python molurus bivittatus) may be causing declines in medium-to large-sized mammals throughout the Greater Everglades Ecosystem (GEE); however, other factors such as urbanization, habitat changes and drastic alteration in water flow may also be influential in structuring mammal communities. The aim of this study was to gain an understanding of how mammal communities simultaneously facing invasive predators and intensively humanaltered landscapes are influenced by these drivers and their interactions.Location Florida, USA.Methods We used data from trail cameras and scat searches with a hierarchical community model that accounts for undetected species to determine the relative influence of introduced Burmese pythons, urbanization, local hydrology, habitat types and interactive effects between pythons and urbanization on mammal species occurrence, site-level species richness, and turnover.Results Python density had significant negative effects on all species except coyotes. Despite these negative effects, occurrence of some generalist species increased significantly near urban areas. At the community level, pythons had the greatest impact on species richness, while turnover was greatest along the urbanization gradient where communities were increasingly similar as distance to urbanization decreased.Main conclusions We found evidence for an antagonistic interaction between pythons and urbanization where the impacts of pythons were reduced near urban development. Python-induced changes to mammal communities may be mediated near urban development, but elsewhere in the GEE, pythons are likely causing a fundamental restructuring of the food web, declines in ecosystem function, and creating complex and unpredictable cascading effects.

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Section: Introductionmentioning

confidence: 80%

Section: Burmese Pythonsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Urbanization may limit impacts of an invasive predator on native mammal diversity

Reichert

Sovie

Udell

et al. 2017

Diversity and Distributions

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“…Second, while animal care is still a top priority, the risk of potentially needing to euthanize an invasive Burmese python due to health concerns is more acceptable than the risk of potentially needing to euthanize a native species of conservation concern. Third, their striking impacts to the mammal community in ENP make them a top research and management priority [38][39][40].…”

Section: Study Systemmentioning

confidence: 99%

Evaluating GPS biologging technology for studying spatial ecology of large constricting snakes

et al. 2018

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Background: GPS telemetry has revolutionized the study of animal spatial ecology in the last two decades. Until recently, it has mainly been deployed on large mammals and birds, but the technology is rapidly becoming miniaturized, and applications in diverse taxa are becoming possible. Large constricting snakes are top predators in their ecosystems, and accordingly they are often a management priority, whether their populations are threatened or invasive. Fine-scale GPS tracking datasets could greatly improve our ability to understand and manage these snakes, but the ability of this new technology to deliver high-quality data in this system is unproven. In order to evaluate GPS technology in large constrictors, we GPS-tagged 13 Burmese pythons (Python bivittatus) in Everglades National Park and deployed an additional 7 GPS tags on stationary platforms to evaluate habitat-driven biases in GPS locations. Both python and test platform GPS tags were programmed to attempt a GPS fix every 90 min.Results: While overall fix rates for the tagged pythons were low (18.1%), we were still able to obtain an average of 14.5 locations/animal/week, a large improvement over once-weekly VHF tracking. We found overall accuracy and precision to be very good (mean accuracy = 7.3 m, mean precision = 12.9 m), but a very few imprecise locations were still recorded (0.2% of locations with precision > 1.0 km). We found that dense vegetation did decrease fix rate, but we concluded that the low observed fix rate was also due to python microhabitat selection underground or underwater. Half of our recovered pythons were either missing their tag or the tag had malfunctioned, resulting in no data being recovered.Conclusions: GPS biologging technology is a promising tool for obtaining frequent, accurate, and precise locations of large constricting snakes. We recommend future studies couple GPS telemetry with frequent VHF locations in order to reduce bias and limit the impact of catastrophic failures on data collection, and we recommend improvements to GPS tag design to lessen the frequency of these failures.

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“…The cryptic nature of these snakes has limited detection and control efforts (Hunter et al., ; Reed et al., ), and the population has now expanded from Everglades National Park (ENP) into the eastern and western coasts of southern Florida and the Florida Keys (Dove, Snow, Rochford, & Mazzotti, ; Pittman et al., ; Snow, Brien, Cherkiss, Wilkins, & Mazzotti, ). Pythons are impacting the ecosystem through heavy predation on mesomammals, including imperiled species, resulting in extensive declines of formerly common species (Dorcas et al., ; McCleery et al., ; Reichert et al., ; Sovie, McCleery, Fletcher, & Hart, ).…”

Section: Introductionmentioning

confidence: 99%

Cytonuclear discordance in the Florida Everglades invasive Burmese python (Python bivittatus) population reveals possible hybridization with the Indian python (P. molurus)

Hunter

Johnson

Smith

et al. 2018

Ecology and Evolution

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The invasive Burmese python (Python bivittatus) has been reproducing in the Florida Everglades since the 1980s. These giant constrictor snakes have caused a precipitous decline in small mammal populations in southern Florida following escapes or releases from the commercial pet trade. To better understand the invasion pathway and genetic composition of the population, two mitochondrial (mtDNA) loci across 1,398 base pairs were sequenced on 426 snakes and 22 microsatellites were assessed on 389 snakes. Concatenated mtDNA sequences produced six haplotypes with an average nucleotide and haplotype diversity of π = 0.002 and h = 0.097, respectively. Samples collected in Florida from morphologically identified P. bivittatus snakes were similar to published cytochrome oxidase 1 and cytochrome b sequences from both P. bivittatus and Python molurus and were highly divergent (genetic distances of 5.4% and 4.3%, respectively). The average number of microsatellite alleles and expected heterozygosity were N A = 5.50 and H E = 0.60, respectively. Nuclear Bayesian assignment tests supported two genetically distinct groups and an admixed group, not geographically differentiated. The effective population size (N E = 315.1) was lower than expected for a population this large, but reflected the low genetic diversity overall. The patterns of genetic diversity between mtDNA and microsatellites were disparate, indicating nuclear introgression of separate mtDNA lineages corresponding to cytonuclear discordance. The introgression likely occurred prior to the invasion, but genetic information on the native range and commercial trade is needed for verification. Our finding that the Florida python population is comprised of distinct lineages suggests greater standing variation for adaptation and the potential for broader areas of suitable habitat in the invaded range.

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

Cited by 25 publications

References 46 publications

Urbanization may limit impacts of an invasive predator on native mammal diversity

Urbanization may limit impacts of an invasive predator on native mammal diversity

Evaluating GPS biologging technology for studying spatial ecology of large constricting snakes

Cytonuclear discordance in the Florida Everglades invasive Burmese python (Python bivittatus) population reveals possible hybridization with the Indian python (P. molurus)

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