Golden David M, Crist Thomas O
Department of Zoology, Miami University, Oxford, OH 45056, USA e-mail:
Oecologia. 1999 Mar;118(3):371-380. doi: 10.1007/s004420050738.
We examined the effects of habitat fragmentation on the species distributions, guild membership, and community structure of old-field insects using a fine-scale experimental approach. A continuous 1-ha goldenrod field was fragmented into four treatments that varied in both patch size and degree of isolation. Each treatment was replicated four times and arranged in a Latin square design. Canopy insects in fragmented patches were sampled with sweep nets during early and late summer 1995. The species richness of insects was significantly lower in fragmented than in unfragmented treatments during July, but was similar among treatments in September. Overall community abundance showed no treatment effect during either month. We also found significant row and column effects, suggesting there was spatial heterogeneity in species richness and abundance apart from treatment effects. Differences in species richness during July were primarily due to the loss of rare species in highly fragmented plots. Overall abundance was less responsive to community change because deletions of rare species in fragmented areas were not detected in abundance analyses. Four feeding guilds showed different responses to fragmentation: the species richness of sucking herbivores and the abundance of parasitoids were significantly reduced by fragmentation but predators and chewing herbivores were largely unaffected. Analyses of a subset of individual species within guilds suggest that the greater effects of fragmentation on sucking herbivores and parasitoids may be due to the degree of habitat specificity of guild members. The effects of small-scale habitat fragmentation were therefore detectable at the level of community, guild, and individual species. Changes in species richness, guild structure and species distributions were likely due to differential effects of habitat alteration on individual movements and patch selection rather than dispersal or demographic change. Nonetheless, the selective loss of rare species, differential guild effects and changes in species occupancy that we found in this small-scale experiment are also factors that are likely to operate in fragmented habitats over broader spatial scales.
我们采用精细尺度的实验方法，研究了栖息地破碎化对弃耕地昆虫物种分布、功能群归属和群落结构的影响。一块连续的1公顷的秋麒麟草田被分割成四种处理方式，这些处理方式在斑块大小和隔离程度上各不相同。每种处理方式重复四次，并采用拉丁方设计进行排列。1995年夏初和夏末，用扫网对破碎斑块中的冠层昆虫进行采样。7月时，破碎处理中昆虫的物种丰富度显著低于未破碎处理，但9月时各处理间相似。在这两个月中，总体群落丰度均未显示出处理效应。我们还发现了显著的行和列效应，这表明除了处理效应外，物种丰富度和丰度存在空间异质性。7月物种丰富度的差异主要是由于高度破碎地块中稀有物种的丧失。总体丰度对群落变化的反应较小，因为在丰度分析中未检测到破碎区域中稀有物种的减少。四个取食功能群对破碎化表现出不同的反应：吸食性草食动物的物种丰富度和寄生蜂的丰度因破碎化而显著降低，但捕食者和咀嚼性草食动物基本未受影响。对功能群内单个物种子集的分析表明，破碎化对吸食性草食动物和寄生蜂的影响更大，可能是由于功能群成员的栖息地特异性程度所致。因此，在群落、功能群和单个物种水平上都能检测到小规模栖息地破碎化的影响。物种丰富度、功能群结构和物种分布的变化可能是由于栖息地改变对个体移动和斑块选择的不同影响，而不是扩散或种群统计学变化。尽管如此，我们在这个小规模实验中发现的稀有物种的选择性丧失、不同的功能群效应和物种占有率的变化，也是可能在更广泛空间尺度的破碎栖息地中起作用的因素。
