Determining boundaries between abundance biozones using minimal equipment

Abstract

The areal extent of a biological community is usually determined using statistical techniques that only give reliable results where samples contain similar and high numbers of specimens. This paper presents a simple, inexpensive method for determining the geographical limits of biological communities applicable where adjacent samples contain widely differing numbers of specimens. The method is a development of SHE Analysis, which discerns boundaries between adjacent abundance biozones (ABs), an AB being an area with a distinct community structure. As originally conceived, SHEbi (SHE Analysis for the identification of Biozones) commences with species' absolute abundances and works best with large samples of equal sizes. If the variance in N (per sample) is high, SHEbi may place AB boundaries in unexpected locations. A modification, based on proportional abundances, is developed here using species' proportional abundances (pi = ni/N) for each sample where ni is the number of specimens in the ith species in the sample. For intertidal foraminifera from the Caroni Swamp, Trinidad, where N, the number of specimens, fluctuates widely between samples, the modification (SHEbip) gives ecologically more sensible results than does traditional SHEbi. © 2010 BrentWilson et al.