Akatov V V, Perevozov A G
Zh Obshch Biol. 2011 Mar-Apr;72(2):111-26.
Dominance level is traditionally expressed as a ratio between the number of individuals belonging to the most abundant species and the total number of individuals in a biological community. It is known that local species richness is usually higher in biological communities with high dominance level than in communities with low one. Taking into account a complex nature of the dominance phenomenon, the underlying reasons (or mechanisms) may be diverse: 1. Dominance level may be determined by bioecological traits of the most abundant species as well as stochastic impacts. The more abundant is dominant species, the fewer amount of resources goes to concomitant species and, therefore, the lower is community species richness. 2. The part of community resources used by the dominant species may be not a special case but can be a reflection of general pattern of resources distribution among species under specific environmental conditions. Correspondingly, in communities with higher dominance level there might be more "strict" distribution of resources among concomitant species, which, in turn, might influence community species richness. 3. The relationship between dominance level and community species richness may be caused by their dependence on the third variable, namely regional species pool. In the present paper we tackle the problem using arboreal and insectivorous bird communities of the West Caucasus as a case study. The data were collected in different altitudinal belts on both macroslopes of the western part of the Main Caucasian Ridge. The number of tree species and individual trees was counted within homogenous patches of arboreal phytocenoses 300 m2 in area. Species richness and numbers of insectivorous birds were estimated in course of route surveys with a route length being about 5 km. An analysis of empirical data was carried out using univariate and multiple correlation-regression techniques. The results indicate that the relationship between dominance and local species richness is determined to a large extent (by 50-60%) by a dominant taking over greater or lesser amount of the resources (mechanism 1). The role of two other mechanisms (2 and 3) is not so prominent--together, they are responsible for 25-40% of the relationship power. Relative contribution of different mechanisms to the relationship under consideration depends on conformity of species abundance rank structure with the geometric series model. At those sites where this conformity is manifested, the relationship between dominance level and species richness is due mainly to mechanisms 1 and 2, i.e., is determined by local processes. At other sites, where the conformity of species abundance rank structure with the geometric series model is not so good, a certain role belongs to the size of regional species pool (mechanism 3).
优势度水平传统上表示为生物群落中最丰富物种的个体数量与生物群落中个体总数之间的比率。众所周知，优势度水平高的生物群落中当地物种丰富度通常高于优势度水平低的群落。考虑到优势度现象的复杂性，其潜在原因（或机制）可能多种多样：1. 优势度水平可能由最丰富物种的生物生态特征以及随机影响决定。优势物种越丰富，分配给伴生物种的资源量就越少，因此群落物种丰富度就越低。2. 优势物种利用的群落资源部分可能并非特殊情况，而是特定环境条件下物种间资源分配一般模式的反映。相应地，在优势度水平较高的群落中，伴生物种之间的资源分配可能更“严格”，这反过来可能影响群落物种丰富度。3. 优势度水平与群落物种丰富度之间的关系可能是由它们对第三个变量，即区域物种库的依赖引起的。在本文中，我们以西高加索地区的乔木和食虫鸟类群落为例来解决这个问题。数据收集于大高加索山脉西部主要山坡的不同海拔带。在面积为300平方米的乔木植物群落的同质斑块内统计树种和个体树木的数量。在路线长度约为5公里的路线调查过程中估计食虫鸟类的物种丰富度和数量。使用单变量和多元相关回归技术对实证数据进行分析。结果表明，优势度与当地物种丰富度之间的关系在很大程度上（50%-60%）是由优势物种占据或多或少的资源（机制1）决定的。其他两种机制（2和3）的作用不那么突出——它们共同作用占关系强度的25%-40%。不同机制对所考虑关系的相对贡献取决于物种丰度等级结构与几何级数模型的符合程度。在那些表现出这种符合的地点，优势度水平与物种丰富度之间的关系主要归因于机制1和2，即由当地过程决定。在其他地点，物种丰度等级结构与几何级数模型的符合程度不太好，区域物种库的大小（机制3）起到一定作用。
