Box Bryozoans and environments

The majority of bryozoans grow as mounds, sheets or runners parallel to the substrate, many grow erect colonies perpendicular to the seabed and some colonies are actually mobile. There have been a number of growth-mode type classifications, some associated with particular genera, constructional geometry or based on autecology. A more comprehensive way at looking at these complex colonies is to combine attachment modes, construction orientation and the geometry of the individual zooids (Hageman et al. 1997). Such a hierarchical growth-mode classification can be used to describe regional biotas and predict paleoenvironments on limited datasets. However, as in many ecological studies, the most common species or growth forms can swamp the overall ecological signal; some form of scaling is needed. We can ask a couple of questions: How important is D at locality 1 relative to other occurrences of D and how important is D relative to all the other localities? Firstly a simple data table is set up with growth forms along the y-axis and localities along the x-axis (see below). One method of standardizing the data is to: (i) divide the number of growth type D at locality 1 by the product of all the different growth types and the total at this one locality [10/(45 * 22)]; and (ii) this is then multipled by 1002 to scale values to roughly between 0 and 100. This equals 101; this growth is clearly important at this locality. The relative importance of each growth form at each locality can be plotted in a histogram.

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