The structure and dynamics of a water beetle community in a ...

calculated from the total number of species with aquatic adults (note, however, that sampling
effort was very different among methods). In larvae, 29% of species was common to all
methods, 14% of species was collected exclusively by activity traps (especially large
Dytiscidae), 3% by box trap, 29% by handnet sampling, and 31% of species was unique for
box trap and handnet sampling taken together. The highest number of species of adults was
sampled by activity traps; in larvae, handnet sampling collected the highest number of
species, followed by activity traps (Appendix 1).
Rarefaction analyses revealed that the sample sizes obtained by each method were
sufficient to gain good estimates of the total number of species detectable by the method
(Table 1). In adults as well as in larvae, the rarefaction curves and species richness estimators
ICE and Chao2 converge (Figs. 2 and 3; other popular estimators ACE and Chao1 performed
very similarly). In rarefaction-based analyses, the light trap had the lowest number of species
of aquatic adults as well as the lowest adult diversity at the level of 400 individuals. Other
methods yield considerably higher numbers of species and diversity values and perform
similarly at this level. In the larvae, the number of species was lowest in the box trap data and
highest in the handnet data. The diversity of larvae sampled by activity traps was
considerably higher than by box trap and handnet (Figs. 4 and 5).
Fig. 2 – Sample-based rarefaction curves for data from the four collecting methods (mean observed number of
species and 95% confidence interval as thin black lines, ICE=thick dashed black line, Chao2=thick dashed gray
line).
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