(^) The ordination procedure provided Peterson and Vayssieres with an efficient means
for presenting the community gradient, thanks to the reduced dimensionality of the
ordination plots. It allowed ready demonstration of its main cause (Plate 14.2). There
is more information in Plate 14.1: while all the station clusters from a zone in the
estuary fall above the same sector of nMDS axis 1, they separate strongly on axis 2.
Another ordination plot coupled with community composition pie diagrams (Plate
14.3) shows convincingly that some of that variability was likely an effect of the C.
amurensis invasion.
Community Analysis – a Functional Guild
Approach
(^) There are completely different approaches to community analysis that require
extensive biological expertise and, thus, are much less common despite the insights
they generate. Under the punning^1 title, “A Diet of Worms”, Fauchald and Jumars
(1979) gave an example of how the extreme detail available (and that may become
available) in our knowledge of the biology of species and higher taxa of animals can
be applied in community analysis. Most ecologists become expert in the biology of
some group of organisms, and they apply that biology to enlarge the understanding of
how those organisms interact with their habitats. Fauchald and Jumars are both
interested in polychaetes. An advantage of polychaetes for such studies (Jumars &
Fauchald 1977) is that, in addition to numerical and biomass dominance, they
originated in the Precambrian, so their radiation into families is very ancient. Thus,
the absence of an extant polychaete life mode in any given habitat is unlikely to be