Pisces Conservation Ltd., The Square, Pennington, Lymington, Hampshire, UK.
Proc Biol Sci. 2010 May 22;277(1687):1561-70. doi: 10.1098/rspb.2009.2189. Epub 2010 Jan 13.
Species abundance distributions (SADs) are widely used as a tool for summarizing ecological communities but may have different shapes, depending on the currency used to measure species importance. We develop a simple plotting method that links SADs in the alternative currencies of numerical abundance and biomass and is underpinned by testable predictions about how organisms occupy physical space. When log numerical abundance is plotted against log biomass, the species lie within an approximately triangular region. Simple energetic and sampling constraints explain the triangular form. The dispersion of species within this triangle is the key to understanding why SADs of numerical abundance and biomass can differ. Given regular or random species dispersion, we can predict the shape of the SAD for both currencies under a variety of sampling regimes. We argue that this dispersion pattern will lie between regular and random for the following reasons. First, regular dispersion patterns will result if communities are comprised groups of organisms that use different components of the physical space (e.g. open water, the sea bed surface or rock crevices in a marine fish assemblage), and if the abundance of species in each of these spatial guilds is linked to the way individuals of varying size use the habitat. Second, temporal variation in abundance and sampling error will tend to randomize this regular pattern. Data from two intensively studied marine ecosystems offer empirical support for these predictions. Our approach also has application in environmental monitoring and the recognition of anthropogenic disturbance, which may change the shape of the triangular region by, for example, the loss of large body size top predators that occur at low abundance.
物种丰度分布（SAD）被广泛用作总结生态群落的工具，但可能具有不同的形状，具体取决于用于衡量物种重要性的货币。我们开发了一种简单的绘图方法，将数值丰度和生物量的替代货币中的 SAD 联系起来，并基于关于生物体如何占据物理空间的可测试预测。当对数数值丰度与对数生物量作图时，物种位于一个近似三角形区域内。简单的能量和采样约束解释了三角形的形状。物种在这个三角形内的离散度是理解为什么数值丰度和生物量的 SAD 可以不同的关键。给定规则或随机的物种离散度，我们可以预测在各种采样制度下两种货币的 SAD 形状。我们认为这种离散模式将介于规则和随机之间，原因如下。首先，如果群落由使用物理空间不同组成部分的生物体组成（例如海洋鱼类群落中的开阔水域、海底表面或岩石裂缝），并且这些空间群体中物种的丰度与个体的大小使用栖息地的方式相关联，则会产生规则的离散模式。其次，丰度和采样误差的时间变化会使这种规则模式随机化。来自两个经过深入研究的海洋生态系统的数据为这些预测提供了经验支持。我们的方法在环境监测和人为干扰的识别中也有应用，人为干扰可能会通过例如失去在低丰度下发生的大型身体大小顶级捕食者来改变三角形区域的形状。
