Environmental Variance of Community Structure
Redundancy analysis (RDA) modelling was applied to Hellinger transformed
observational data with respect to five environmental explanatory
variables (wind speed, solar radiation, temperature, humidity, and field
edge effects). While the model was statistically significant (F = 3.94,
p< 0.001), it only explained 14% of the variance. All
environmental variables are well represented by the axes but did not
match the spread of communities in the model. The effect of sites on
community composition appeared to be low since there was no distinct
clustering with this variable. However, the model including temporal
variables explained 65.2 % (R2 adj = 53.9%) of the
variance (Figure 4a) was significant (F = 5.79, p< 0.001); and
so were first 7 axes (ANOVA, p< 0.001). Most of the temporal
variance was explained by sampling date (ANOVA, p< 0.001).
Models that included date improved the explained variance by more than
45%. Time of day was also significant (ANOVA, p< 0.03), with
ellipses depicting a small gradient across the communities (Figure 4a).
General trends in insect community composition across the season showed
consistent presence of solitary bees and Hemiptera, while the abundance
of Syrphids and other Diptera, as well as observed Apis melliferashowed more seasonal variation (Figure 4b). While Formicidae (ants) were
generally rare or absent, there was a large surge in their abundance on
flowers for one week (May 18th). Coleoptera and
Lepidoptera consistently showed low levels of occurrence on strawberry
flowers (Figure 4b).