Stavert J R, Gaskett A C, Scott D J, Beggs J R
School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand,
Oecologia. 2014 Sep;176(1):259-71. doi: 10.1007/s00442-014-3001-z. Epub 2014 Jun 29.
Globally, dung beetles (Scarabaeidae: Scarabaeinae) are linked to many critical ecosystem processes involving the consumption and breakdown of mammal dung. Endemic New Zealand dung beetles (Canthonini) are an anomaly, occurring at high abundance and low diversity on an island archipelago historically lacking terrestrial mammals, except bats, and instead dominated by birds. Have New Zealand's dung beetles evolved to specialise on bird dung or carrion, or have they become broad generalist feeders? We test dietary preferences by analysing nitrogen isotope ratios of wild dung beetles and by performing feeding behaviour observations of captive specimens. We also use nitrogen and carbon stable isotopes to determine if the dung beetle Saphobius edwardsi will consume marine-derived carrion. Nitrogen isotope ratios indicated trophic generalism in Saphobius dung beetles and this was supported by behavioural observations where a broad range of food resources were utilised. Alternative food resource use was further illustrated experimentally by nitrogen and carbon stable isotope signatures of S. edwardsi, where individuals provided with decomposed squid had δ(15)N and δ(13)C values that had shifted toward values associated with marine diet. Our findings suggest that, in the absence of native mammal dung resources, New Zealand dung beetles have evolved a generalist diet of dung and carrion. This may include marine-derived resources, as provided by the seabird colonies present in New Zealand forests before the arrival of humans. This has probably enabled New Zealand dung beetles to persist in indigenous ecosystems despite the decline of native birds and the introduction of many mammal species.
在全球范围内，蜣螂（金龟科：蜉金龟亚科）与许多关键的生态系统过程相关，这些过程涉及哺乳动物粪便的消耗和分解。新西兰特有的蜣螂（斑金龟族）是个异类，在一个历史上除蝙蝠外缺乏陆生哺乳动物、而以鸟类为主导的群岛上大量存在且多样性较低。新西兰的蜣螂是进化为专门以鸟粪或腐肉为食，还是成为了广泛的杂食性觅食者呢？我们通过分析野生蜣螂的氮同位素比率以及对圈养标本进行摄食行为观察来测试其饮食偏好。我们还使用氮和碳稳定同位素来确定蜣螂爱德华氏斑金龟是否会食用海洋来源的腐肉。氮同位素比率表明爱德华氏斑金龟具有营养杂食性，行为观察也支持了这一点，即它们利用了广泛的食物资源。爱德华氏斑金龟的氮和碳稳定同位素特征通过实验进一步说明了其对替代食物资源的利用，给个体提供分解后的鱿鱼时，它们的δ(15)N和δ(13)C值向与海洋饮食相关的值偏移。我们的研究结果表明，在缺乏本土哺乳动物粪便资源的情况下，新西兰的蜣螂进化出了以粪便和腐肉为主的杂食性饮食。这可能包括海洋来源的资源，就像人类到来之前新西兰森林中存在的海鸟群落所提供的那样。这可能使新西兰的蜣螂能够在本土生态系统中持续存在，尽管本土鸟类数量减少且引入了许多哺乳动物物种。
