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Data on maximum body size, maximum egg size and maximum Gonad Index,
were plotted against depth of maximum abundance for all the species, and the
resulting graphs were investigated in order to find possible patterns or relations
between the reproductive features. The degree to which the variables were related was
tested by using the Spearman Rank
Correlation Coefficient (Rs) and the results discussed (Fowler et al., 2000). A nonparametric
test was preferred because the data were presented as actual observations,
observations converted to ranks and indices; furthermore a parametric test would
require the data to be normally distributed and to have homogeneous variances
(Fowler et al., 2000).
Although the relatively low number of data would suggest that the data set is
not suitable for a multivariate analysis, this analysis was performed with the PRIMER
(Plymouth Routines in Multivariate Ecological Research) Version 5 programme
(Clarke and Warwick, 2001) to investigate if a pattern could be observed.
Data on adult size, egg size and Gonad Index were analyzed together by the
Normalized Euclidean distance measure applied to all the asteroid species.
Hierarchical clustering with group-averaged linking and non-metric multidimensional
scaling using all resulting similarity matrices was performed (Clarke and
Warwick, 2001). The groupings identified by both cluster analysis and the MDS plots
were investigated using the available data on the species regarding reproductive
features determined in this study and depth related distribution in the NE Atlantic
established by Howell et al. 2002.
4.3- Results
The Spearman’s correlation coefficient showed that no correlation exists
between depth (over the entire range) and body size (as R) of the species (Rs= 0.056,
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