一项研究报告说，与海蟾蜍种群在同一块土地上定居下来相比，当它们入侵一块土地的时候，它们的种群有不同的分散和移动的模式。Tom Lindström及其同事分析了关于入侵性海蟾蜍到达澳大利亚热带地区的一个研究地点并在之后8年的时间里定居下来的一个广泛的无线电追踪数据集。这组科研人员发现作为入侵先锋的蟾蜍和入侵后的几年在同一地点的蟾蜍之间的运动模式的差别。这组科研人员的模型区分了海蟾蜍运动的两个阶段，它们分别是转弯角度尖锐、步长较短的安营扎寨阶段和一个一直朝着一个方向长距离运动的分散阶段。先导蟾蜍把他们的时间的更大一部分用在了分散模式上，并且当它们处于分散模式的时候，它们显示出了比入侵后到来的蟾蜍更长的每日位移和更高的方向性。这些变化的一个结果是，在入侵前沿的海蟾蜍的总年位移是同一地点数年后跟踪的海蟾蜍总年位移的2倍以上。这组作者说，这些结果提示仅仅追踪定居下来的种群的研究可能低估了生物在新的土地上的散播。（生物谷 Bioon.com）
生物谷推荐的英文摘要
PNAS doi: 10.1073/pnas.1303157110
Rapid shifts in dispersal behavior on an expanding range edge
Tom Lindströma,1,2, Gregory P. Browna, Scott A. Sissonb, Benjamin L. Phillipsc, and Richard Shinea
Dispersal biology at an invasion front differs from that of populations within the range core, because novel evolutionary and ecological processes come into play in the nonequilibrium conditions at expanding range edges. In a world where species’ range limits are changing rapidly, we need to understand how individuals disperse at an invasion front. We analyzed an extensive dataset from radio-tracking invasive cane toads (Rhinella marina) over the first 8 y since they arrived at a site in tropical Australia. Movement patterns of toads in the invasion vanguard differed from those of individuals in the same area postcolonization. Our model discriminated encamped versus dispersive phases within each toad’s movements and demonstrated that pioneer toads spent longer periods in dispersive mode and displayed longer, more directed movements while they were in dispersive mode. These analyses predict that overall displacement per year is more than twice as far for toads at the invasion front compared with those tracked a few years later at the same site. Studies on established populations (or even those a few years postestablishment) thus may massively underestimate dispersal rates at the leading edge of an expanding population. This, in turn, will cause us to underpredict the rates at which invasive organisms move into new territory and at which native taxa can expand into newly available habitat under climate change.
