Mathematical Geology, Vol. 14, No. 6, 1982
Use of the Bray-Curtis Similarity Measure in
Cluster Analysis of Foraminiferal Data j
Michael G. Michie 2
Transformation of data effectively limits the distortion by outlying values on the Bray-
Curtis similarity measure. It represents an effective method of using cluster analysis in
distinguishing biotopes of benthic foraminifera.
KEY WORDS: biotopes, Bray-Curtis, cluster analysis, foraminifera.
Several recent papers involving analysis of patterns in benthic populations, not-
ably of Australian origin (e.g., Stephenson and Williams, 1971, Stephenson,
Raphael, and Cook, 1976, Stephenson and Campbell, 1977) have made use of
the Bray-Curtis similarity measure. This measure is a city-block metric derived
from Bray and Curtis (1957). In its currently used form it is expressed as
is the similarity between two operational taxonomic units (OTUs) i
and j, each defined by a set of n attributes
In this study the OTUs
are the sampling stations from a small estuary, and the attributes are the benthic
foraminiferal species found at those stations. Some authors (Stephenson, Rafael,
and Cook, 1976, Stephenson and Campbell, 1977) transform each datum
to loglo(Xik + 1). This, and other possible transformations, are commonly used
when the frequency range of the species encountered is excessive, since the
Bray-Curtis measure is sensitive to outlying values (Williams, 1976). Although
Bray and Curtis (1957) used standardized normal data in their original paper
the present measure should be used with nonnegative data.
In a previous paper (Michie, 1978) the author discussed the use of the
lManuscript received 21 September 1981; revised 15 March 1982.
~Division of Natural Sciences, Northern Territory Museum of Arts and Sciences, PO Box
4646, Darwin NT 5794, Australia.
0020-5958 / 82 / 1200-0661 $03.00/0 © 1982 Plenum Publishing