PLOS ONE2013-12-02 6:00 AM

Is Chytridiomycosis Driving Darwin’s Frogs to Extinction? 是壶菌病导致达尔文的青蛙灭绝了吗?

Abstract Darwin’s frogs (Rhinoderma darwinii and R. rufum) are two species of mouth brooding frogs from Chile and Argentina that have experienced marked population declines. Rhinoderma rufum has not been found in the wild since 1980. We investigated historical and current evidence of Batrachochytrium dendrobatidis (Bd) infection in Rhinoderma spp. to determine whether chytridiomycosis is implicated in the population declines of these species. Archived and live specimens of Rhinoderma spp., sympatric amphibians and amphibians at sites where Rhinoderma sp. had recently gone extinct were examined for Bd infection using quantitative real-time PCR. Six (0.9%) of 662 archived anurans tested positive for Bd (4/289 R. darwinii; 1/266 R. rufum and 1/107 other anurans), all of which had been collected between 1970 and 1978. An overall Bd-infection prevalence of 12.5% was obtained from 797 swabs taken from 369 extant individuals of R. darwinii and 428 individuals representing 18 other species of anurans found at sites with current and recent presence of the two Rhinoderma species. In extant R. darwinii, Bd-infection prevalence (1.9%) was significantly lower than that found in other anurans (7.3%). The prevalence of infection (30%) in other amphibian species was significantly higher in sites where either Rhinoderma spp. had become extinct or was experiencing severe population declines than in sites where there had been no apparent decline (3.0%; x2 = 106.407, P<0.001). This is the first report of widespread Bd presence in Chile and our results are consistent with Rhinoderma spp. declines being due to Bd infection, although additional field and laboratory investigations are required to investigate this further. 论文摘要 达尔文蛙属是用嘴育雏的蛙类,它包含两种不同的达尔文蛙,一种是来自智利的智利达尔文蛙,另一种是来自阿根廷的达尔文蛙。现今这一蛙属面临着数量急剧下降的困境。智利达尔文蛙直到1980年才在野外被发现。我们调查了以前和现今有关达尔文蛙属蛙壶菌感染的证据来探寻到底蛙壶菌病是否与达尔文蛙属数量剧降有关。我们采集了达尔文蛙属存档标本和活标本,同域两栖类动物以及那些达尔文蛙属最近灭绝地域处的其他两栖类动物,然后使用定量实时PCR检测对它们进行了检验。我们在662只存档无尾两栖类动物中的6只(比例约占0.9%)检测到了蛙壶菌病的阳性反应(其中达尔文蛙阳性比例占4/289,智利达尔文蛙比例占1/266,其他无尾两栖类占1/107),所有这些样本均采集于1970年至1978年间。我们采集了797只蛙类及两栖类动物的分泌物,通过计算得到了总体的蛙壶菌病感染的患病率为12.5%。采集的这797只两栖类动物中的369只个体来自现存的达尔文蛙类,另外的428只个体则是从近期经常发现两种达尔文蛙类的相同地域中采集到的18种其他无尾两栖类物种。经过比较我们发现,现存的达尔文蛙类中蛙壶菌病感染患病率(患病比例为1.9%)显著低于发现的其他无尾两栖类物种(患病比例为7.3%)。那些达尔文蛙属已遭灭绝或正处于数量剧降困境的同域内其他两栖类物种的感染患病率(30%)显著高于其他达尔文蛙属数量稳定地域内的两栖类物种(3.0%;x2=106.407,P<0.001)。这是有关智利国内广泛存在的蛙壶菌病感染的首次研究报告,我们得到的研究结果与达尔文蛙属物种数量减退归咎于蛙壶菌病感染这一假设吻合。但我们仍需对额外的领域进行进一步探究且进行更深入的实验调查。

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