Science2014-06-16 2:27 PM

支离破碎的森林会给疾病敞开门户吗? Ecological and evolutionary effects of fragmentation on infectious disease dynamics

论文摘要 

一项为期12年的实地研究的结果提示,高度相连的植物种群比孤立种群更能抵抗真菌性病原体。由Jussi Jousimo及其同事所报告的发现似乎违反直觉,因为传统观念认为紧密簇集的种群会让病原体的定殖变得更为容易而不是变得更难。但是在对波罗的海奥兰群岛的茅尖状车前草这种野草的4000个不同种群对抗真菌性病原体——白粉菌——进行了10多年的观察之后,这些研究人员得出结论:高度连结的植物片块会进行更多的基因交互,并因此会比其孤立的对等植物更具抵抗力。他们的研究显示,连结良好的植物一般较难感染白粉菌,且能更有效地杀死白粉菌。此前,在动植物中的大多数类似的研究一直侧重于理解传染性疾病的爆发,但这种新的方法展示了研究疾病在野外持久存在的价值。据研究人员披露,但是需要进行分析地理空间的宿主-寄生物感染的研究以确定在这些零碎的种群中,生境破碎——这是目前广泛存在的情况——是否会增加疾病暴发的几率。他们的工作可作为一种自然疾病在野外持续存在的模型,并具有在生态学、疾病、生物学、环境保护及农业上的潜在用途。由Meghan Duffy等撰写的一篇《观点栏目》文章对该研究及其意义进行了更为详细的解释.

Abstract 

Ecological theory predicts that disease incidence increases with increasing density of host networks, yet evolutionary theory suggests that host resistance increases accordingly. To test the combined effects of ecological and evolutionary forces on host-pathogen systems, we analyzed the spatiotemporal dynamics of a plant (Plantago lanceolata)–fungal pathogen (Podosphaera plantaginis)relationship for 12 years in over 4000 host populations. Disease prevalence at the metapopulation level was low, with high annual pathogen extinction rates balanced by frequent (re-)colonizations. Highly connected host populations experienced less pathogen colonization and higher pathogen extinction rates than expected; a laboratory assay confirmed that this phenomenon was caused by higher levels of disease resistance in highly connected host populations.

Editor's Summary

Many connections are not always bad for health

Contrary to expectations, highly connected populations can experience less impact from infectious disease than isolated groups. What happens to pathogens in natural populations has been poorly studied, because they rarely cause devastating disease outbreaks. Thanks to a long-term study of an inconspicuous fungal-plant disease system, we have now gained some surprising insights. During a 12-year study, Jousimo et al. discovered that clustered and linked host-plant patches showed lower levels of fungal damage and higher fungal extinction rates than more distant patches (see the Perspective by Duffy). This phenomenon is explained by high gene flow and rapid evolution of host resistance within the connected patches. Populations of the modest weed Plantago, growing on the Åland Islands in the Baltic, were less than 10% infected by the Podosphaera mildew fungus in any given year, but infection turnover was high. These findings have broad implications for ecology, disease biology, conservation, and agriculture.

Science, this issue p. 1289; see also p. 1229

( http://www.sciencemag.org/content/344/6189/1289 and
  http://www.sciencemag.org/content/344/6189/1229 )

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