Department of Wildlife, Fish & Conservation Biology, University of California Davis, Davis, California, United States of America; Graduate Group in Ecology, University of California Davis, Davis, California, United States of America.
Department of Wildlife, Fish & Conservation Biology, University of California Davis, Davis, California, United States of America.
PLoS One. 2014 Jun 25;9(6):e100277. doi: 10.1371/journal.pone.0100277. eCollection 2014.
Species distribution models (SDMs) are increasingly used to project the potential distribution of introduced species outside their native range. Such studies rarely explicitly evaluate potential conflicts with native species should the range of introduced species expand. Two snake species native to eastern North America, Nerodia fasciata and Nerodia sipedon, have been introduced to California where they represent a new stressor to declining native amphibians, fish, and reptiles. To project the potential distributions of these non-native watersnakes in western North America, we built ensemble SDMs using MaxEnt, Boosted Regression Trees, and Random Forests and habitat and climatic variables. We then compared the overlap between the projected distribution of invasive watersnakes and the distributions of imperiled native amphibians, fish, and reptiles that can serve as prey or competitors for the invaders, to estimate the risk to native species posed by non-native watersnakes. Large areas of western North America were projected to be climatically suitable for both species of Nerodia according to our ensemble SDMs, including much of central California. The potential distributions of both N. fasciata and N. sipedon overlap extensively with the federally threatened Giant Gartersnake, Thamnophis gigas, which inhabits a similar ecological niche. N. fasciata also poses risk to the federally threatened California Tiger Salamander, Ambystoma californiense, whereas N. sipedon poses risk to some amphibians of conservation concern, including the Foothill Yellow-legged Frog, Rana boylii. We conclude that non-native watersnakes in California can likely inhabit ranges of several native species of conservation concern that are expected to suffer as prey or competing species for these invaders. Action should be taken now to eradicate or control these invasions before detrimental impacts on native species are widespread. Our methods can be applied broadly to quantify the risk posed by incipient invasions to native biodiversity.
物种分布模型（SDMs）越来越多地被用于预测引入物种在其原生范围以外的潜在分布。然而，此类研究很少明确评估引入物种的范围扩大时与本地物种可能产生的冲突。两种原产于北美洲东部的蛇类，Nerodia fasciata 和 Nerodia sipedon，已被引入加利福尼亚州，成为当地正在减少的本地两栖动物、鱼类和爬行动物的新威胁。为了预测这些非本地水蛇在北美西部的潜在分布，我们使用 MaxEnt、Boosted Regression Trees 和 Random Forests 以及栖息地和气候变量构建了集合 SDM。然后，我们比较了入侵水蛇的预测分布与受威胁的本地两栖动物、鱼类和爬行动物的分布之间的重叠程度，这些本地物种可以作为入侵物种的猎物或竞争者，以估计非本地水蛇对本地物种构成的风险。根据我们的集合 SDM，西部北美洲的大片地区被预测为两种 Nerodia 物种的气候适宜区，包括加利福尼亚州中部的大部分地区。N. fasciata 和 N. sipedon 的潜在分布与受联邦威胁的巨型束带蛇（Thamnophis gigas）广泛重叠，后者栖息在类似的生态位上。N. fasciata 还对受联邦威胁的加利福尼亚虎蛙（Ambystoma californiense）构成威胁，而 N. sipedon 对一些受保护关注的两栖动物构成威胁，包括山麓黄腿蛙（Rana boylii）。我们的结论是，加利福尼亚州的非本地水蛇可能栖息在几个受保护关注的本地物种的范围内，这些物种可能因作为猎物或竞争者而受到这些入侵物种的影响。现在应该采取行动，在这些入侵对本地物种造成广泛的不利影响之前，消灭或控制这些入侵。我们的方法可以广泛应用于量化初发入侵对本地生物多样性构成的风险。
