Pyramids

The pyramids technique is an extension of   the hierarchical clustering framework. Whereas traditional hierarchical   methods such as Unweighted Pair Group with Arithmetic Means (UPGAM) represent   a nested set of nonoverlapping clades, pyramids represent a set of clades   that can overlap without necessarily being nested. The input data is a   (Robinsonian) distance matrix (Box 1). The pyramid is obtained by using   agglomerative algorithms. By allowing overlapping clusters, pyramids can be   used to represent reticulate events, although these events are only allowed   to be placed among terminal nodes that are sister taxa.

金字塔

金字塔拓扑结构是层次聚类框架的扩展。传统的层次方法，如不加权算术平均组对方法（UPGAM）表示一组嵌套的非重叠族，而金字塔表示一组可以重叠而不必嵌套的族。输入数据为（Robinsonian）距离矩阵（框注1）。金字塔是用凝聚算法得到的。通过允许重叠的集群，金字塔可以用来表示网状事件，尽管这些事件只允许放置在作为姊妹分类群的终端节点之间。