Can dispersal mode predict corridor effects on plant parasites?

Habitat corridors, a common management strategy for increasing
connectivity in fragmented landscapes, have experimentally validated
positive influences on species movement and diversity. However,
long-standing concerns that corridors could negatively impact native
species by spreading antagonists, such as disease, remain largely
untested. Using a large-scale, replicated experiment, we evaluated
whether corridors increase the incidence of plant parasites. We found
that corridor impacts varied with parasite dispersal mode.
Connectivity provided by corridors increased incidence of biotically
dispersed parasites (galls on Solidago odora) but not of abiotically
dispersed parasites (foliar fungi on S. odora and three Lespedeza
spp.). Both biotically and abiotically dispersed parasites responded
to edge effects, but the direction of responses varied across species.
Although our results require additional tests for generality to other
species and landscapes, they suggest that, when establishing
conservation corridors, managers should focus on mitigating two
potential negative effects: the indirect effects of narrow corridors
in creating edges and direct effects of corridors in enhancing
connectivity of biotically dispersed parasites.

生境廊道（Habitat corridors）是提升破碎化景观（fragmented landscapes）连通性的常用管理策略，经实验证实其对物种移动与物种多样性具有积极作用。然而，长期以来存在一项担忧：廊道可能通过传播病害等拮抗生物（antagonists）对本土物种造成负面影响，但该问题迄今仍未得到充分验证。本研究依托大规模重复实验，评估了廊道是否会提升植物寄生物（plant parasites）的侵染发生率。研究发现，廊道的影响效应随寄生物的传播模式而异：廊道所提供的连通性提升了生物传播型寄生物的侵染率，具体表现为Solidago odora上的虫瘿（galls）侵染量增加，但对非生物传播型寄生物无显著影响，后者包括S. odora与三种胡枝子属Lespedeza spp.物种上的叶部真菌（foliar fungi）。两类传播模式的寄生物均对边缘效应（edge effects）存在响应，但其响应方向因物种而异。尽管本研究结果尚需针对其他物种与景观开展更多验证以确认其普适性，但研究结果提示，在设置保护廊道（conservation corridors）时，管理者应着重规避两类潜在负面影响：一是狭窄廊道引发边缘效应带来的间接影响，二是廊道增强生物传播型寄生物连通性带来的直接影响。