Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, Florida, United States of America.
U.S. Geological Survey, Wetland and Aquatic Research Center, Gainesville, Florida, United States of America.
PLoS One. 2019 Apr 10;14(4):e0213943. doi: 10.1371/journal.pone.0213943. eCollection 2019.
The Burmese python (Python bivittatus) is now established as a breeding population throughout south Florida, USA. However, the extent of the invasion, and the ecological impacts of this novel apex predator on animal communities are incompletely known, in large part because Burmese pythons (hereafter "pythons") are extremely cryptic and there has been no efficient way to detect them. Pythons are recently confirmed nest predators of long-legged wading bird breeding colonies (orders Ciconiiformes and Pelecaniformes). Pythons can consume large quantities of prey and may not be recognized as predators by wading birds, therefore they could be a particular threat to colonies. To quantify python occupancy rates at tree islands where wading birds breed, we utilized environmental DNA (eDNA) analysis-a genetic tool which detects shed DNA in water samples and provides high detection probabilities. We fitted multi-scale Bayesian occupancy models to test the prediction that pythons occupy islands with wading bird colonies at higher rates compared to representative control islands containing no breeding birds. Our results suggest that pythons are widely distributed across the central Everglades in proximity to active wading bird colonies. In support of our prediction that pythons are attracted to colonies, site-level python eDNA occupancy rates were higher at wading bird colonies (ψ = 0.88, 95% credible interval [0.59-1.00]) than at the control islands (ψ = 0.42 [0.16-0.80]) in April through June (n = 15 colony-control pairs). We found our water temperature proxy (time of day) to be informative of detection probability, in accordance with other studies demonstrating an effect of temperature on eDNA degradation in occupied samples. Individual sample concentrations ranged from 0.26 to 38.29 copies/μL and we generally detected higher concentrations of python eDNA in colony sites. Continued monitoring of wading bird colonies is warranted to determine the effect pythons are having on populations and investigate putative management activities.
缅甸蟒蛇（Python bivittatus）现已在美国佛罗里达州南部建立了繁殖种群。然而，由于这种新型顶级捕食者对动物群落的入侵程度和生态影响还不完全清楚，在很大程度上是因为缅甸蟒蛇（以下简称“蟒蛇”）非常隐匿，而且还没有有效的方法来检测它们。蟒蛇最近被证实是长腿涉禽繁殖群体（鹳形目和鹈形目）的巢穴捕食者。蟒蛇可以消耗大量的猎物，而且可能不会被涉禽视为捕食者，因此它们可能对群体构成特别威胁。为了量化树岛上涉禽繁殖时蟒蛇的占有情况，我们利用环境 DNA（eDNA）分析——一种检测水样中脱落 DNA 的遗传工具，并提供了高检测概率。我们拟合了多尺度贝叶斯占有模型，以检验蟒蛇在有涉禽繁殖的岛屿上的占有率高于没有繁殖鸟类的代表性对照岛屿的预测。我们的结果表明，蟒蛇在大沼泽地中部广泛分布，靠近活跃的涉禽繁殖地。我们的预测得到了支持，即在 4 月至 6 月期间（n = 15 个繁殖地-对照对），涉禽繁殖地的蟒蛇 eDNA 占有率（ψ=0.88，95%置信区间[0.59-1.00]）高于对照岛屿（ψ=0.42[0.16-0.80]），这表明蟒蛇被吸引到繁殖地。我们发现我们的水温代理（一天中的时间）对检测概率具有信息性，这与其他研究表明温度对占用样本中 eDNA 降解的影响一致。个别样本浓度范围为 0.26 到 38.29 拷贝/μL，我们通常在繁殖地检测到更高浓度的蟒蛇 eDNA。需要继续监测涉禽繁殖地，以确定蟒蛇对种群的影响，并调查潜在的管理活动。
