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首页> 外文期刊>Oecologia >Dragonfly predators influence biomass and density of pond snails
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Dragonfly predators influence biomass and density of pond snails

机译：蜻蜓捕食者影响池塘蜗牛的生物量和密度

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摘要

Studies in lakes show that fish and crayfish predators play an important role in determining the abundance of freshwater snails. In contrast, there are few studies of snails and their predators in shallow ponds and marshes. Ponds often lack fish and crayfish but have abundant insect populations. Here we present the results of field surveys, laboratory foraging trials, and an outdoor mesocosm experiment, testing the hypothesis that insects are important predators of pulmonate snails. In laboratory foraging trials, conducted with ten species of insects, most insect taxa consumed snails, and larval dragonflies were especially effective predators. The field surveys showed that dragonflies constitute the majority of the insect biomass in fishless ponds. More focused foraging trials evaluated the ability of the dragonflies Anax junius and Pantala hymenaea to prey upon different sizes and species of pulmonate snails (Helisoma trivolvis, Physa acuta, and Stagnicola elodes). Anax junius consumed all three species up to the maximum size tested. Pantala hymenaea consumed snails with a shell height of 3 mm and smaller, but did not kill larger snails. P. acuta were more vulnerable to predators than were H. trivolvis or S. elodes. In the mesocosm experiment, conducted with predator treatments of A. junius, P. hymenaea, and the hemipteran Belostoma flumineum, insect predators had a pronounced negative effect on snail biomass and density. A. junius and B. flumineum reduced biomass and density to a similar degree, and both reduced biomass more than did P. hymenaea. Predators did not have a strong effect on species composition. A model suggested that A. junius and P. hymenaea have the largest effects on snail biomass in the field. Given that both pulmonate snails and dragonfly nymphs are widespread and abundant in marshes and ponds, snail assemblages in these water bodies are likely regulated in large part by odonate predation.
机译：湖泊中的研究表明，鱼类和小龙虾的捕食者在确定淡水蜗牛的数量方面起着重要作用。相反，在浅水池塘和沼泽中对蜗牛及其捕食者的研究很少。池塘通常缺少鱼类和小龙虾，但昆虫种群丰富。在这里，我们介绍了实地调查，实验室觅食试验和室外中观试验的结果，这些试验证明了昆虫是肺蜗牛的重要天敌的假说。在对十种昆虫进行的实验室觅食试验中，大多数昆虫类群食用蜗牛，而幼虫蜻蜓尤其有效。实地调查表明，蜻蜓是无鱼池塘中昆虫生物量的主要组成部分。更集中的觅食试验评估了蜻蜓Anax junius和Pantala hymenaea捕食不同大小和种类的肺蜗牛（Helisoma trivolvis，Physa acuta和Stagnicola elodes）的能力。 Anaax junius消耗了这三个物种，直至测试的最大尺寸。潘塔拉膜虫（Pantala hymenaea）食用了壳高为3毫米或更小的蜗牛，但并未杀死更大的蜗牛。 P. acuta比H. trivolvis或S. elodes更容易受到掠食者的侵害。在介观试验中，捕食者对A. junius，P。hymenaea和半翅目Belostoma flumineum进行捕食，捕食性捕食者对蜗牛的生物量和密度产生了明显的负面影响。 A. junius和B. flumineum将生物量和密度降低到相似的程度，并且生物量都比膜状假单胞菌降低了更多。捕食者对物种组成没有强烈影响。一个模型表明，A。junius和P. hymenaea对田间蜗牛生物量的影响最大。考虑到在沼泽地和池塘中，肺蜗牛和蜻蜓若虫都广泛分布和丰富，这些水体中的蜗牛组合很可能受卵子捕食作用的调节。

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