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In general, species richness in wetlands corresponded to that predicted by the regional species-area curve, except perhaps for aquatic beds, which had fewer species than would be expected by their size. At this scale, zones with vegetation did not appear to be richer than zones without vegetation.
Similarly, the cluster analysis showed a strong similarity between wetland types in terms of species richness: the cluster comprising relatively shallow habitats and habitats on the edge of the floodplain (shallow water, wet meadows and swamps) shared on average 70% of species with the cluster of deeper habitats (open water, marshes and aquatic beds).
As in the case of sediments, most relationships for habitat selection were not significant. Only 16 species favoured areas of water without vegetation, while 28 avoided them. Conversely, marshes were selected by 20 species but avoided by only seven species. There was a very strong similarity in the species lists for these two habitats (nearly 90% of species in common), a statistic that masks the selection of very different habitats by certain species. Aquatic beds were favoured by six species but avoided by 25 species. Lastly, relatively shallow habitats (shallow water, wet meadows, swamps) were frequented by large number of species and avoided by few species.
An examination of the ecological traits of species that preferred the different wetland habitats shows that large species that are not associated much with vegetation in open water can be differentiated from smaller species with a great affinity for vegetation in a vegetated habitat. Fishes preferring aquatic beds differed from this pattern, often consisting of large species that prefer areas of vegetation.
Jacques Leclerc
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