Range-wide ecological niche comparisons of parasite, hosts and dispersers in a vector-borne plant parasite system

Aim: To test whether the distribution of the mistletoe Phoradendron californicum is mediated by host distributions (host niche hypothesis, HNH), or by factors such as the mistletoe’s autecology (parasite niche hypothesis, PNH) or that of its vectors (vector niche hypothesis, VNH). Our null hypothesis is that the ecological niche of the mistletoe will not be distinct from that of its hosts or vectors; alternatively, mistletoe infections might appear in hosts only in regions where host distributions overlap suitable conditions for the parasite. Location: Sonoran and Mojave deserts, western North America. Methods: We used ecological niche modelling approaches to summarize suitable environmental conditions for hosts infected and uninfected with mistletoes, as well as for avian dispersers during winter and throughout the year. We compared ecological niches among pairs of species using background similarity tests in relation to the climatic conditions available and accessible to each species....研究目的：旨在检验加州槲寄生（Phoradendron californicum）的分布格局究竟是由寄主分布介导（寄主生态位假说，Host Niche Hypothesis, HNH），还是由槲寄生自身的种群生态学特征（寄生物生态位假说，Parasite Niche Hypothesis, PNH）或是其传播媒介的生态位特征（媒介生态位假说，Vector Niche Hypothesis, VNH）所驱动。本研究的零假设为：该槲寄生的生态位不会与其寄主或传播媒介的生态位存在显著差异；与之相对的备择假设则为，槲寄生的侵染仅会出现在寄主分布与该寄生物所需适宜条件重叠的区域。 研究区域：北美西部的索诺兰沙漠（Sonoran Desert）与莫哈韦沙漠（Mojave Desert）。 研究方法：我们采用生态位建模（ecological niche modelling）方法，分别总结受槲寄生侵染与未受侵染的寄主，以及冬季和全年的鸟类传播者的适宜生存环境条件。针对各物种可获取、可利用的气候条件，我们通过背景相似性检验对物种类群间的生态位进行了比较……