Sugihara George, Bersier L-F, Schoenly Kenneth
Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0202, USA, , , , , , US.
Entomology and Plant Pathology Division, International Rice Research Institute, P.O. Box 933, 1099 Manila, Philippines, , , ,.
Oecologia. 1997 Oct;112(2):272-284. doi: 10.1007/s004420050310.
Historically, ecologists have been more interested in organisms feeding at the tops of food chains than in organisms feeding at or near the bottom. The problem of taxonomic and trophic inconsistency within and among described food webs is central to criticisms of contemporary food web research. To study the effects of taxonomic and trophic aggregation on food web properties, 38 published food webs, each containing a large fraction of investigator-defined biological species, were systematically aggregated by taxonomy and trophic (functional) group similarity. During each step of taxonomic and trophic aggregation, eight food web properties (MIN, MAX, mean chain lengths; the fractions of basal, intermediate and top species; the ratio of all links by the total number of species, L/S; and rigid circuits) were calculated and their departures from the original, unaggregated version were recorded. We found only two␣properties showing wide systematic departure from initial values after both taxonomic and trophic group aggregation: the fraction of basal species and L/S. One reason for the relative `constancy' of the six other properties was due in part to large numbers of trophically equivalent species (species with identical sets of prey and predators) found in these and other published webs. In the 38 webs, the average number of trophically equivalent species was 45% and ranged from a low of 13% in aquatic webs to a high of 71% in certain terrestrial systems (i.e., carrion webs). Six of the eight properties (MIN, MAX and mean chain lengths, the fractions of top and basal species, and the L/S ratio) were found to be more sensitive to taxonomic than to trophic aggregation. The relatively smaller variations observed in trophically lumped versions suggest that food web properties more aptly reflect functional, rather than taxonomic, attributes of real food webs. These findings parallel earlier trophic-based results, and bolster the conclusion that uneven lumping of taxonomic and trophic groups in published food web reports do not modify markedly the scaling behaviour of most of their descriptive properties.
从历史上看，生态学家对处于食物链顶端觅食的生物更感兴趣，而不是处于或接近食物链底部觅食的生物。已描述的食物网内部和之间的分类学和营养级不一致问题是当代食物网研究受到批评的核心。为了研究分类学和营养级聚合对食物网属性的影响，通过分类学和营养级（功能）组相似性，对38个已发表的食物网进行了系统聚合，每个食物网都包含很大一部分由研究者定义的生物物种。在分类学和营养级聚合的每个步骤中，计算了八个食物网属性（最小值、最大值、平均链长；基础物种、中间物种和顶级物种的比例；所有链接数与物种总数的比率，L/S；以及刚性回路），并记录它们与原始未聚合版本的差异。我们发现，在分类学和营养级组聚合之后，只有两个属性与初始值有广泛的系统差异：基础物种的比例和L/S。其他六个属性相对“恒定”的一个原因部分是由于在这些以及其他已发表的食物网中发现了大量营养级等效物种（具有相同猎物和捕食者集合的物种）。在这38个食物网中，营养级等效物种的平均数量为45%，范围从水生食物网中的低至13%到某些陆地系统（即腐肉食物网）中的高至71%。八个属性中的六个（最小值、最大值和平均链长、顶级和基础物种的比例以及L/S比率）被发现对分类学聚合比对营养级聚合更敏感。在营养级归并版本中观察到的相对较小的变化表明，食物网属性更恰当地反映了真实食物网的功能而非分类学属性。这些发现与早期基于营养级的结果相似，并支持了这样的结论：已发表的食物网报告中分类学和营养级组的不均匀归并不会显著改变其大多数描述性属性的缩放行为。
