Dahl Jonas
Department of Ecology, Limnology, Ecology Building, S-223 62 Lund, Sweden e-mail:
Oecologia. 1998 Nov;117(1-2):217-226. doi: 10.1007/s004420050651.
I assessed the impact of both vertebrate and invertebrate predators on a lotic benthic community in a 1-month-long experiment, using enclosures containing cobble/gravel bottoms, with large-mesh netting that allowed invertebrates to drift freely. Brown trout (Salmo trutta) and leeches (Erpobdella octoculata) were used as predators and four treatments were tested: a predator-free control, leeches only, trout only, and leeches and trout together. A density of 26.7 leeches/m (20 leeches/enclosure) and 1.3 trout/m (one trout per enclosure) was stocked into the enclosures. The total biomass of invertebrate prey was significantly lower in the trout and trout plus leech treatments than in the leech and control treatments, which were due to strong negative effects of trout on Gammarus. On the individual prey taxon level, both trout and leeches affected the abundance of Asellus , Baetis and Ephemerella, whereas the abundance of Gammarus was only affected by trout, and the abundance of Orthocladiinae and Limnephilidae was only affected by leeches. In the treatment with trout and leeches together, the abundance of Ephemerella and Baetis was higher than when trout or leeches were alone, which was probably due to predator interactions. Leeches and trout had no effects on prey immigration but did affect per capita emigration rates. Both trout and leeches indirectly increased periphyton biomass in enclosures, probably due to their strong effects on grazers. Both trout and leeches were size-selective predators, with trout selecting large prey, and leeches selecting small prey. Size-selective predation by trout and leeches affected the size structure of five commonly consumed prey taxa. Trout produced prey populations of small sizes owing to consumption of large prey as well as increased emigration out of enclosures by these large prey. Leech predation produced prey assemblages of larger size owing to consumption and increased emigration of small prey. These results suggest that in lotic habits, predatory invertebrates can be as strong interactors as vertebrate predators.
在一项为期1个月的实验中，我评估了脊椎动物和无脊椎动物捕食者对流水底栖生物群落的影响，实验使用了装有卵石/砾石底部的围隔，围隔采用大网眼网，允许无脊椎动物自由漂移。褐鳟（Salmo trutta）和水蛭（Erpobdella octoculata）被用作捕食者，并测试了四种处理方式：无捕食者对照、仅水蛭、仅鳟鱼以及水蛭和鳟鱼一起。在围隔中投放了每米26.7条水蛭（每个围隔20条水蛭）和每米1.3条鳟鱼（每个围隔1条鳟鱼）的密度。在鳟鱼处理组以及鳟鱼加水蛭处理组中，无脊椎动物猎物的总生物量显著低于水蛭处理组和对照组，这是由于鳟鱼对钩虾有强烈的负面影响。在个体猎物分类单元水平上，鳟鱼和水蛭都影响了阿氏摇蚊、小蜉蝣和短脉蜉蝣的丰度，而钩虾的丰度仅受鳟鱼影响，直突摇蚊科和沼石蛾科的丰度仅受水蛭影响。在鳟鱼和水蛭一起的处理组中，短脉蜉蝣和小蜉蝣的丰度高于单独有鳟鱼或水蛭的情况，这可能是由于捕食者之间的相互作用。水蛭和鳟鱼对猎物的迁入没有影响，但确实影响了人均迁出率。鳟鱼和水蛭都间接增加了围隔中周丛生物的生物量，这可能是由于它们对食草动物有强烈影响。鳟鱼和水蛭都是大小选择性捕食者，鳟鱼选择大型猎物，水蛭选择小型猎物。鳟鱼和水蛭的大小选择性捕食影响了五种常见被食猎物分类单元的大小结构。由于大型猎物被消耗以及这些大型猎物从围隔中迁出增加，鳟鱼导致了小型猎物种群的出现。由于小型猎物被消耗以及迁出增加，水蛭捕食产生了更大尺寸的猎物组合。这些结果表明，在流水生境中，捕食性无脊椎动物可以与脊椎动物捕食者一样，成为强大的相互作用者。
