The role of habitat and dispersal in shaping the biodiversity of riverine insect assemblages
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Date
2013
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University of New Brunswick
Abstract
Given limited resources, biomonitoring progrrum are touted as a source of biodiversity
information for conservation planning in riverine ecosystes. However, the degree to
which patterns revealed by biomonitoring are reflected in unsampled mesohabitats and
undersampled taxonomic groups has not been fully addressed. Differences in dispersal
capacity among taxonomic groups, in particular, may result in divergent patterns of
biodiversity at landscape and regional scales. I sought to address the suitability of
biological monitoring data in freshwater biodiversity assessment, and to test the
prediction that the degree of spatial structuring in aquatic insect assemblages is inversely
related to their dispersal capacity. My thesis comprises four articles. The first addresses
whether macroinvertebrate biodiversity patterns in riffles, the target mesohabitat of
Canada's national aquatic biomonitoring program, are reflective of those in riverine
wetlands. The second addresses whether biodiversity in a group of insects that is
abundant in biomonitoring samples (Trichoptera) reflects that of an underrepresented
group (Odonata). The third tests the above prediction by comparing the degree of spatial
structuring in the weakly dispersing Trichoptera and the stronger dispersing Odonata. The
final article investigates regional and national aquatic insect biodiversity patterns utilizing
the national biomonitoring dataset, and seeks to evaluate the influence of scale on the
observation of spatial structuring aquatic insect assemblages. Several key findings
emerged from this work: 1) Patterns of invertebrate taxon richness and beta diversity in
riftles poorly reflect those in riverine wetlands. 2) Odonata and Trichoptera biodiversity
were not always congruent, however, differences in abundance among groups may
account for weak correlations. 3) Both Odonata and Trichoptera assemblages
demonstrate relatively weak spatial structuring at a landscape (ie. 5th order catchment)
scale. The weak explanatory ability of spatial variables was also apparent at a regional
scale, as just one of the Water Survey of Canada sub drainages within the Pacific
drainage demonstrated a significant spatial component in aquatic insect assemblage
variation These findings suggest caution in the application of biomonitoring data to
conservation planning. Although landscape and regional scale structuring of aquatic
insect communities may be weak, it does not preclude the existence of smaller scale
spatial structuring driven by local dispersal processes.