Leibold Mathew, Tessier Alan J
Department of Zoology, Duke University, 27706, Durham, NC, USA.
W.K. Kellogg Biological Station and Department of Zoology, Michigan State University, 49060, Hickory Corners, MI, USA.
Oecologia. 1991 May;86(3):342-348. doi: 10.1007/BF00317599.
We investigate how body size of two coexisting Daphnia species varies among 7 lakes that represent a gradient of predation risk. The two species segregate vertically in stratified lakes; D. galeata mendotae is typically smaller and more eplimnetic than D. pulicaria. The extent of vertical habitat partitioning, however, varies seasonally within and among lakes in apparent response to predation intensity by epilimnetic planktivorous fishes. Daphnia pulicaria uses the epilimnion at low levels of fish predation but is restricted to the hypolimnion under high fish predation, whereas D. galaeta mendotae always utilizes the epilimnion. The species display contrasting patterns of genetic variation in neonate size and size at maturity. D. pulicaria is larger in lakes with higher fish and Chaoborus densities whereas D. galeata mendotae is smaller. This contrast in body size in lakes with high predation is associated with greater habitat segregation in those lakes. In lakes with low predation risk, the two species are similar in body size at birth and maturity.
我们研究了两种共存的水蚤物种的体型在7个代表捕食风险梯度的湖泊中的变化情况。这两个物种在分层湖泊中垂直分离；明多塔水蚤通常比蚤状水蚤体型更小，且更多地分布在上层水域。然而，垂直栖息地划分的程度在湖泊内部和不同湖泊之间会随季节变化，这显然是对上层浮游性鱼类捕食强度的一种响应。在鱼类捕食水平较低时，蚤状水蚤利用上层水域，但在鱼类捕食强度较高时则局限于下层水域，而明多塔水蚤总是利用上层水域。这两个物种在幼体大小和成熟时的大小上表现出不同的遗传变异模式。在鱼类和摇蚊密度较高的湖泊中，蚤状水蚤体型较大，而明多塔水蚤体型较小。在高捕食压力的湖泊中，这种体型差异与这些湖泊中更大的栖息地隔离有关。在捕食风险较低的湖泊中，这两个物种在出生时和成熟时的体型相似。
