PDF(Pubmed)
Abstract：
Factors behind intraspecific variation in sensitivity to pathogens remain poorly understood. We investigated how geographical origin in two North European amphibians affects tolerance to infection by the chytrid fungus Batrachochytrium dendrobatidis (Bd), a generalist pathogen which has caused amphibian population declines worldwide. We exposed newly metamorphosed individuals of moor frog Rana arvalis and common toad Bufo bufo from two latitudinal regions to two different BdGPL strains. We measured survival and growth as infections may cause sub-lethal effects in fitness components even in the absence of mortality. Infection loads were higher in B. bufo than in R. arvalis, and smaller individuals had generally higher infection loads. B. bufo had high mortality in response to Bd infection, whereas there was little mortality in R. arvalis. Bd-mediated mortality was size-dependent and high-latitude individuals were smaller leading to high mortality in the northern B. bufo. Bd exposure led to sub-lethal effects in terms of reduced growth suggesting that individuals surviving the infection may have reduced fitness mediated by smaller body size. In both host species, the Swedish Bd strain caused stronger sublethal effects than the British strain. We suggest that high-latitude populations can be more vulnerable to chytrids than those from lower latitudes and discuss the possible mechanisms how body size and host geographical origin contribute to the present results.
摘要：
对病原体敏感性种内变异背后的因素仍然知之甚少。我们调查了两种北欧两栖动物的地理起源如何影响食糜真菌Batrachochytriumdendrobatidis（Bd）对感染的耐受性，一种导致全球两栖动物数量下降的通才病原体。我们将来自两个纬度区域的Moor青蛙Ranaarvalis和普通蟾蜍Bufobufo的新变态个体暴露于两种不同的BdGPL菌株。我们测量了存活和生长，因为即使在没有死亡的情况下，感染也可能在健身成分中引起亚致死性影响。B.bufo的感染负荷高于R.arvalis，和较小的个体通常有较高的感染负荷。B.bufo对Bd感染有很高的死亡率，而Arvalis的死亡率很少。Bd介导的死亡率取决于大小，高纬度个体较小，导致北部B.bufo的高死亡率。Bd暴露导致生长减少方面的亚致死效应，这表明在感染中幸存的个体可能因体型较小而降低了适应性。在两个寄主物种中，瑞典Bd菌株比英国菌株造成更强的亚致死效应。我们建议高纬度人群比低纬度人群更容易受到Chytrid的影响，并讨论了体型和寄主地理起源如何影响本结果的可能机制。
