TWINSPAN

TWINSPAN was developed for, and is still mostly used by, botanists. However, the method can be used by other disciplines, although in fields such as archeology the concept of a pseudospecies may be difficult to present. This method can be used with presence-absence, % cover and quantitative data. The ability to effectively handle % cover makes the method particularly attractive to botanists. The Two-Way INdicator SPecies ANalysis procedure (Hill et al. 1975) also produces dendrograms of the relationship between species and samples, but uses the Reciprocal Averaging ordination method to order the species and samples. Thus the method is something of a hybrid between classificatory and ordination methods. It is particularly attractive in studies where the objective is to classify communities so that field workers can quickly assign an area to a community type, and is much favoured by botanists. This is because it identifies indicator species characteristic of each group identified.

TWINSPAN is a useful technique when you are seeking to identify species that can be used to characterise particular communities. It is, however, not always an easy method to understand. A particular oddity of the method is the concept of 'pseudospecies'. Each species is divided into a number of pseudospecies which represent the different abundance levels at which it was found.