Hjelm J, Persson L, Christensen B
Department of Ecology and Environmental Science, Umeå University, SE-901 87, Sweden e-mail:
Oecologia. 2000 Feb;122(2):190-199. doi: 10.1007/PL00008846.
Despite the common occurrence of ontogenetic niche shifts, their consequences for morphological adaptations have been little studied. To address this question, we studied morphological adaptations related to ontogenetic niche shifts in Eurasian perch (Perca fluviatilis) in eight lakes that varied in density of benthic resources and planktivorous fish biomass. Perch start to feed on pelagic zooplankton, then shift to benthic resources at intermediate sizes, and finally, when large enough, mainly feed on fish. These three functional niches over ontogeny are expected to set constraints on the morphology and size-specific growth of perch. The growth of perch was negatively related to planktivorous fish biomass in the zooplanktivorous niche, but positively related to planktivorous fish biomass in the piscivorous niche. The number of gill rakers of perch was negatively related to the biomass of planktivorous fish, providing evidence for the occurrence of character displacement as a consequence of competition in the zooplanktivorous niche. Perch in lakes with low densities of predator-sensitive macroinvertebrates had greater body height measurements and a larger mouth early during ontogeny. This pattern is suggested to be a result of a selection for increased efficiency in the benthic niche when the availability of benthic resources is low. Perch in lakes with a high biomass of planktivorous fishes had fusiform body morphology, a thicker tail and a larger mouth then the average piscivorous perch. The different responses of perch morphology to variation in the availability of benthic resources compared to variation in planktivore biomass are suggested to be partly because the availability of the former resource to a larger extent is set by abiotic conditions (humic content). We suggest that the key factors affecting size-specific growth and body morphology of perch in the system studied are the availability of resources in the benthivorous and piscivorous niches. We also provide evidence for morphological trade-offs, especially between the benthivorous and the piscivorous ontogenetic niches.
尽管个体发育生态位转移很常见，但它们对形态适应的影响却鲜有研究。为了解决这个问题，我们研究了欧亚鲈鱼（Perca fluviatilis）在八个湖泊中与个体发育生态位转移相关的形态适应，这些湖泊的底栖资源密度和浮游食性鱼类生物量各不相同。鲈鱼开始以浮游动物为食，然后在中等体型时转向底栖资源，最后，当足够大时，主要以鱼类为食。这三个个体发育阶段的功能生态位预计会对鲈鱼的形态和特定大小的生长产生限制。在浮游动物食性生态位中，鲈鱼的生长与浮游食性鱼类生物量呈负相关，但在食鱼生态位中与浮游食性鱼类生物量呈正相关。鲈鱼的鳃耙数量与浮游食性鱼类的生物量呈负相关，这为浮游动物食性生态位竞争导致性状替代的发生提供了证据。在捕食者敏感的大型无脊椎动物密度较低的湖泊中，鲈鱼在个体发育早期身体高度测量值更大，嘴巴也更大。这种模式被认为是在底栖资源可用性较低时，为提高底栖生态位效率而进行选择的结果。与浮游食性鱼类生物量变化相比，鲈鱼形态对底栖资源可用性变化的不同反应部分是因为前者资源的可用性在更大程度上由非生物条件（腐殖质含量）决定。我们认为，在所研究的系统中，影响鲈鱼特定大小生长和身体形态的关键因素是底栖食性和食鱼生态位中的资源可用性。我们还提供了形态权衡的证据，特别是在底栖食性和食鱼个体发育生态位之间。
