Brown Gregory P, Shine Richard, Rollins Lee A
School of Natural Sciences, Macquarie University, Sydney, NSW 2109, Australia.
Evolution & Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
R Soc Open Sci. 2025 Jan 15;12(1):240669. doi: 10.1098/rsos.240669. eCollection 2025 Jan.
Biological invasions can disrupt the close and longstanding coevolved relationships between host and parasites. At the same time, the shifting selective forces acting on demography during invasion can result in rapid evolution of traits in both host and parasite. Hosts at the invasion front may reduce investment into costly immune defences and redistribute those resources to other fitness-enhancing traits. Parasites at the invasion front may have reduced pathogenicity because traits that negatively impact host dispersal are left behind in the expanding range. The host's immune system is its primary arsenal in the coevolutionary 'arms race' with parasites. To assess the effects of invasion history on immune responses to parasite infection, we conducted a cross-infection experiment which paired common-garden reared cane toads and lungworm parasites originating from various sites in their invaded range across northern Australia. Infected toads had larger spleens and higher concentrations of eosinophils than did uninfected toads. Infected toads also exhibited lower bacteria-killing ability, perhaps reflecting a trade-off of resources towards defences that are more specifically anthelminthic. The impact of infection intensity on multiple immune measures differed among toads and parasites from different parts of the invasion trajectory, supporting the hypothesis that invasion has disrupted patterns of local adaptation.
生物入侵会破坏宿主与寄生虫之间长期共同进化形成的紧密关系。与此同时，入侵过程中作用于种群统计学的不断变化的选择压力，可能导致宿主和寄生虫的性状快速进化。处于入侵前沿的宿主可能会减少对代价高昂的免疫防御的投入，并将这些资源重新分配到其他有助于提高适应性的性状上。处于入侵前沿的寄生虫致病性可能会降低，因为那些对宿主扩散产生负面影响的性状在不断扩大的分布范围内被淘汰了。宿主的免疫系统是其在与寄生虫的协同进化 “军备竞赛” 中的主要武器。为了评估入侵历史对寄生虫感染免疫反应的影响，我们进行了一项交叉感染实验，将在共同环境中饲养的甘蔗蟾蜍与源自澳大利亚北部其入侵范围内不同地点的肺吸虫寄生虫进行配对。受感染的蟾蜍比未受感染的蟾蜍脾脏更大，嗜酸性粒细胞浓度更高。受感染的蟾蜍细菌杀灭能力也较低，这可能反映了资源在向更具特异性抗蠕虫防御方面的权衡。感染强度对多种免疫指标产生的影响在来自入侵轨迹不同部位的蟾蜍和寄生虫之间存在差异，这支持了入侵扰乱了局部适应模式这一假设。
