Söderström O, Nilsson A N
Department of Animal Ecology, University of Umeå, S-901 87, Umeå, Sweden.
Oecologia. 1987 Nov;74(1):39-46. doi: 10.1007/BF00377343.
The possible effect of predation on the habitat selection of nymphs of the two mayfly species Parameletus chelifer Bengtsson and P. minor (Bengtsson) was investigated for different habitats of a North Swedish boreal river. In spring, these two species migrate to river margins and subsequently, in different proportions, to adjacent seasonal ponds. Feeding rates on mayfly nymphs and mosquito larvae by some dytiscid beetles and larvae, a corixid waterbug and a caddisfly larva were studied in the laboratory. In the seasonal pond, the consumption rate of invertebrate predators on Parameletus nymphs was below that expected from their relative abundance, and mosquito larvae were preferred. At the river margin, where mosquito larvae were absent, Parameletus nymphs were consumed in agreement with their relative abundance. The absolute abundance of macroinvertebrate predators was similar at the river margin and in the pond. Fish predators visited the seasonal pond only during a short time of flood, while at the river margin their presence was continuous. In the seasonal pond, minnow and roach consumed nymphs of both P. chelifer and P. minor in a lower proportion than expected. At the river margin, nymphs of P. chelifer were consumed by minnow and ten-spined stickleback in a higher proportion than expected. Nymphs of P. minor were consumed according to expectance. Imagines of P. minor emerged early, and nymphs were equally abundant in the river and in the seasonal pond. In contrast, almost all nymphs of P. chelifer migrated to the seasonal pond. The later emergence of P. chelifer would probably result in a very high mortality from predation if it remained at the river margin.
研究了捕食作用对瑞典北部一条寒带河流不同栖息地中两种蜉蝣（Parameletus chelifer Bengtsson和P. minor (Bengtsson)）若虫栖息地选择的可能影响。春季，这两种蜉蝣会迁移至河边，随后按不同比例迁移至相邻的季节性池塘。在实验室中研究了一些龙虱科甲虫及其幼虫、一种划蝽和一种毛翅目幼虫对蜉蝣若虫和蚊幼虫的捕食率。在季节性池塘中，无脊椎动物捕食者对Parameletus若虫的消耗率低于根据其相对丰度预期的水平，且它们更喜欢捕食蚊幼虫。在河边，由于没有蚊幼虫，Parameletus若虫的被捕食情况与其相对丰度相符。河边和池塘中大型无脊椎动物捕食者的绝对丰度相似。鱼类捕食者仅在洪水期间的短时间内会光顾季节性池塘，而在河边它们则持续存在。在季节性池塘中，麦穗鱼和拟鲤对P. chelifer和P. minor若虫的捕食比例低于预期。在河边，麦穗鱼和三刺鱼对P. chelifer若虫的捕食比例高于预期。P. minor若虫的被捕食情况符合预期。P. minor的成虫出现较早，其若虫在河流和季节性池塘中的数量相当。相比之下，几乎所有P. chelifer的若虫都迁移到了季节性池塘。如果P. chelifer的若虫留在河边，其较晚出现可能会导致因捕食而产生非常高的死亡率。
