MessagerOlden2019_Phenotypic_variability_of_rusty_crayfish_JDR

Scripts, data, and directory structure used to sssess phenotypic changes in rusty crayfish Faxonius rusticus (previously Orconectes rusticus) across their invasion gradient in the John Day River (JDR, Oregon, U.SA.), a major tributary of the Columbia River.<br>Updated code, data, and documentation at: https://github.com/messamat/InvasionEdge_rustycrayfish<br><br>Abstract: 1. Species around the globe are undergoing phenotypic shifts at ecologically relevant timescales as they invade new ecosystems and respond to changing environments. Disentangling the contribution of environmental gradients from the process of range expansion in shaping these changes, and identifying the specific traits undergoing selection, are both critical to anticipate the secondary spread and impact of invasive species. 2. Here, we investigate phenotypic changes in rusty crayfish (<i>Faxonius rusticus</i>), a nuisance invasive species, through an extensive survey of their invasion gradient in multiple tributaries of the John Day River (JDR, Oregon, U.SA.), a major tributary of the Columbia River. 3. Rusty crayfish in the JDR have developed better physiological condition (intrinsic growth and/or reproductive potential measured as RNA/DNA ratio) but less competitive morphology (lighter body and smaller claws) as they spread upstream and downstream from their location of initial introduction. In addition, rusty crayfish in invasion front populations are at a lower trophic level than conspecifics closer to core areas. 4. By accounting for variations in temperature, primary productivity, and prey (macroinvertebrates) biomass throughout the invasion extent of rusty crayfish, our findings suggest that low conspecific densities at the invasion edge and spatial sorting primarily drive these phenotypic changes. The trends observed here are thus likely to intensify over time as rusty crayfish continues to rapidly spread throughout the JDR and reach the mainstem Columbia River. 5. Our study shows that phenotypic shifts can manifest rapidly over environmental gradients experienced during the range expansion of aquatic invasive species. Patterns in both morphological and functional traits documented in the JDR demonstrate the importance of both environmental factors and dispersal processes in shaping these responses in riverine networks.

本数据集包含用于评估锈色螯虾（*Faxonius rusticus*，曾用名*Orconectes rusticus*）沿入侵梯度的表型变化的脚本、数据与目录结构，该入侵梯度位于美国俄勒冈州约翰·戴河（John Day River, JDR）——哥伦比亚河的主要支流之一。
更新后的代码、数据与文档可通过以下链接获取：https://github.com/messamat/InvasionEdge_rustycrayfish

摘要：
1. 全球范围内的物种在入侵新生态系统并响应环境变化的过程中，正以具有生态学意义的时间尺度发生表型转变。厘清环境梯度与物种范围扩张过程对这类表型变化的相对贡献，并鉴定受选择的具体性状，是预测入侵物种二次扩散与生态影响的关键前提。
2. 本研究针对锈色螯虾——一种有害入侵物种，通过对哥伦比亚河主要支流约翰·戴河（JDR，美国俄勒冈州）多条支流的入侵梯度开展广泛调查，探究其表型变化。
3. 随着从初始引入点向上游及下游扩散，约翰·戴河中的锈色螯虾逐渐演化出更优的生理状态（以RNA/DNA比值衡量的内在生长和/或繁殖潜力），但竞争相关形态却出现退化（体色更浅、螯足更小）。此外，入侵前沿种群的锈色螯虾营养层级较核心区域的同类更低。
4. 在控制锈色螯虾入侵范围内的水温、初级生产力以及猎物（大型无脊椎动物）生物量等变量后，本研究结果表明，入侵边缘较低的同类种群密度与空间分选效应是驱动这些表型变化的主要动因。随着锈色螯虾继续快速扩散至整个约翰·戴河并抵达哥伦比亚河干流，本研究观测到的表型趋势预计将随时间进一步加剧。
5. 本研究证实，水生入侵物种在范围扩张过程中所经历的环境梯度下，表型转变可以快速发生。在约翰·戴河中记录到的形态与功能性状模式表明，环境因子与扩散过程在塑造河流网络中的这类响应时均发挥着关键作用。