Bethke Raymond W, Nudds Thomas D
Department of Zoology, University of Guelph, N1G 2W1, Guelph, Ontario, Canada.
Oecologia. 1993 Mar;93(2):242-250. doi: 10.1007/BF00317677.
Tramer (1969) proposed that communities regulated by competition in benign, predictable environments were characterized by (i) damped variation in evenness relative to variation in richness over time, and (ii) high evenness relative to communities regulated by variation in the abundance and diversity of resources in rigorous, unpredictable environments. To test whether patterns of variation in diversity could reflect the mechanisms proposed to regulate community structure, temporal and spatial changes in the diversity, richness and evenness of breeding duck communities were examined along a gradient of variability in wetland conditions using thirty-three years of duck census and climate data from the Canadian prairie and boreal forest regions. Temporal variation in evenness was independent of wetland habitat variability. Changes in richness were more parsimoniously explained by the appearance of ducks displaced (by drought) from rigorous, variable, wetland habitats into relatively benign ones, than by competition in benign areas. Evenness was not significantly higher for duck guilds in more constant wetland habitats, as predicted. Variation in richness, evenness and diversity, predicted by Tramer, do not provide a basis for distinguishing the factors that regulate duck community structure.
特拉默（1969年）提出，在良性、可预测环境中受竞争调节的群落具有以下特征：（i）相对于丰富度随时间的变化，均匀度的变化呈衰减趋势；（ii）相对于在严酷、不可预测环境中受资源丰度和多样性变化调节的群落，其均匀度较高。为了检验多样性的变化模式是否能反映调节群落结构的机制，利用来自加拿大大草原和北方森林地区的33年鸭类普查和气候数据，沿着湿地条件变化梯度，研究了繁殖鸭群落多样性（diversity）、丰富度（richness）和均匀度（evenness）的时空变化。均匀度的时间变化与湿地栖息地的变化无关。丰富度的变化更能简单地解释为，鸭子（因干旱）从严酷、多变的湿地栖息地转移到相对良性的栖息地，而不是良性区域的竞争。如预期的那样，在更稳定的湿地栖息地中，鸭类群落的均匀度并没有显著更高。特拉默预测的丰富度、均匀度和多样性的变化，并没有为区分调节鸭群落结构的因素提供依据。
