Thomas J A, Bourn N A, Clarke R T, Stewart K E, Simcox D J, Pearman G S, Curtis R, Goodger B
Natural Environment Research Council Centre for Ecology and Hydrology, CEH Dorset, Winfrith Technology Centre, Dorset DT2 8ZD, UK.
Proc Biol Sci. 2001 Sep 7;268(1478):1791-6. doi: 10.1098/rspb.2001.1693.
Habitat quality and metapopulation effects are the main hypotheses that currently explain the disproportionate decline of insects in cultivated Holarctic landscapes. The former assumes a degradation in habitat quality for insects within surviving ecosystems, the latter that too few, small or isolated islands of ecosystem remain in landscapes for populations to persist. These hypotheses are often treated as alternatives, and this can lead to serious conflict in the interpretations of conservationists. We present the first empirical demonstration that habitat quality and site isolation are both important determinants of where populations persist in modern landscapes. We described the precise habitat requirements of Melitaea cinxia, Polyommatus bellargus and Thymelicus acteon, and quantified the variation in carrying capacity within each butterfly's niche. We then made detailed surveys to compare the distribution and density of every population of each species with the size, distance apart and quality of their specific habitats in all their potential habitat patches in three UK landscapes. In each case, within-site variation in habitat quality explained which patches supported a species' population two to three times better than site isolation. Site area and occupancy were not correlated in any species. Instead of representing alternative paradigms, habitat quality and spatial effects operate at different hierarchical levels within the same process: habitat quality is the missing third parameter in metapopulation dynamics, contributing more to species persistence, on the basis of these results, than site area or isolation. A reorientation in conservation priorities is recommended.
栖息地质量和集合种群效应是目前解释全北区农耕景观中昆虫不成比例减少的主要假说。前者假定现存生态系统中昆虫的栖息地质量下降，后者认为景观中生态系统的岛屿数量过少、面积过小或过于孤立，导致种群难以持续存在。这些假说常常被视为相互替代的观点，这可能会在保护主义者的解释中引发严重冲突。我们首次通过实证证明，栖息地质量和地点隔离都是现代景观中种群持续存在地点的重要决定因素。我们描述了荨麻蛱蝶、大蓝闪蝶和阿氏弄蝶的精确栖息地需求，并量化了每种蝴蝶生态位内承载能力的变化。然后，我们进行了详细调查，以比较在英国三个景观中所有潜在栖息地斑块内，每个物种的每个种群的分布和密度与其特定栖息地的大小、间距和质量。在每种情况下，栖息地质量的场内变化对哪些斑块能支持物种种群的解释能力，比地点隔离强两到三倍。任何物种的地点面积和占有率都没有相关性。栖息地质量和空间效应并非代表相互替代的范式，而是在同一过程中的不同层次上起作用：根据这些结果，栖息地质量是集合种群动态中缺失的第三个参数，对物种持续存在的贡献比地点面积或隔离更大。建议重新调整保护重点。
