Data from: Living on the edge: parasite prevalence changes dramatically across a range edge in an invasive gecko

Species interactions can determine range limits, and parasitism is the most intimate of such interactions. Intriguingly, the very conditions on range edges likely change host-parasite dynamics in non-trivial ways. Range edges are often associated with clines in host density, and with environmental transitions, both of which may affect parasite transmission. On advancing range edges, founder events and fitness/dispersal costs of parasitism may also cause parasites to be lost on range edges. Here we examine the prevalence of three species of parasite across the range edge of an invasive gecko, Hemidactylus frenatus, in north-eastern Australia. The gecko's range edge spans the urban-woodland interface at the edge of urban areas. Across this edge, gecko abundance shows a steep decline, being lower in the woodland. Two parasite species (a mite, and a pentastome) are co-evolved with H. frenatus, and these species become less prevalent as the geckos become less abundant. A third species of parasite (another pentastome) is native to Australia and has no co-evolutionary history with H. frenatus. This species became more prevalent as the geckos become less abundant. These dramatic shifts in parasitism (occurring over 3.5km) confirm that host-parasite dynamics can vary substantially across the range edge of this gecko host.

物种相互作用可决定物种的分布范围边界，而寄生关系是这类相互作用中最为紧密的形式。值得关注的是，分布边界处的环境条件极有可能以不容忽视的方式改变宿主-寄生动态（host-parasite dynamics）。分布边界通常伴随宿主密度的渐变群与环境过渡区，二者均可能影响寄生虫的传播过程。在扩张中的分布边界上，奠基者效应（founder events）以及寄生所带来的适合度代价与扩散代价，同样可能导致寄生虫在分布边界处丢失。本研究针对澳大利亚东北部入侵物种疣尾蜥虎（Hemidactylus frenatus）的分布边界，调查了三种寄生虫的感染流行率。该蜥虎的分布边界横跨城市区域边缘的城市-林地交错带。跨越该交错带时，蜥虎的种群丰度急剧下降，林地内的丰度显著更低。其中两种寄生虫（一种螨类与一种舌形虫）与疣尾蜥虎存在协同进化关系，其流行率随蜥虎丰度下降而降低。第三种寄生虫（另一种舌形虫）为澳大利亚本土物种，与疣尾蜥虎无协同进化历史。该物种的流行率则随蜥虎丰度下降而升高。上述寄生虫流行率的剧烈变化（发生在3.5公里的范围内）证实，宿主-寄生动态可在该蜥虎宿主的分布边界处发生大幅波动。