Rates of dispersal of cane toads during their global invasion

Invasions often accelerate through time, as dispersal-enhancing traits accumulate at the expanding range edge. How does the dispersal behaviour of individual organisms shift to increase rates of population spread? We collate data from 44 radio-tracking studies (in total, of 650 animals) of cane toads (Rhinella marina) to quantify distances moved per day, and the frequency of displacement in their native range (French Guiana) and two invaded areas (Hawai’i and Australia). Here we show that toads in their native-range, Hawai’i and eastern Australia are relatively sedentary, while toads dispersing across tropical Australia increased their daily distances travelled from 20 to 200 m per day. That increase reflects an increasing propensity to change diurnal retreat sites every day, as well as to move further during each nocturnal displacement. Daily changes in retreat site evolved earlier than did changes in distances moved per night, indicating a breakdown in philopatry before other movement...生物入侵进程通常随时间推移而加速，这是由于在扩张的分布边缘（expanding range edge）处，增强扩散的性状（dispersal-enhancing traits）逐渐积累。那么，单个生物体的扩散行为会发生何种演化，以提升种群扩散速率？我们整合了44项无线电追踪（radio-tracking）研究的数据（总计涵盖650只个体），针对蔗蟾（Rhinella marina）开展分析，量化其在原生分布区（法属圭亚那）以及两个入侵区域（夏威夷与澳大利亚）中的每日移动距离与位移发生频率。本研究结果显示：蔗蟾在原生分布区、夏威夷及澳大利亚东部的活动相对定栖；而在热带澳大利亚扩散的蔗蟾，其每日移动距离从20米提升至200米。这一变化反映出，蔗蟾每日更换日间休憩位点（diurnal retreat sites）的倾向不断增强，且每次夜间移动（nocturnal displacement）的距离也逐步增加。相较于夜间移动距离的变化，日间休憩位点的每日更换出现得更早，这表明恋巢性（philopatry）的瓦解先于其他移动行为的演化……