Figure 2. Combined factor and path analysis for B.
truncatus biomass demonstrating top-down and bottom-up effects of
insecticides and fertilizer, respectively. Top-down effects:
insecticide exposure reduced final crayfish counts, which directly
increased snail biomass by reducing predation, and also indirectly
increased snail biomass by increasing snail habitat H.
verticillata (crayfish ate H. verticillata ). Bottom-up effects:
Fertilizer increased periphyton and H. verticillata , which
increased snail biomass because they are food and habitat, respectively,
for snails. Herbicides reduced H. verticillata , snail habitat,
and, thus, on average, had net negative effects on snails. P-values for
paths in the model are reported below each standardized coefficient. Red
arrows denote significant negative paths; black arrows denote
significant positive paths; dashed arrows denote non-significant
pathways. Boxes represent directly measured variables and circles
represent latent variables. Indicator variables for latent variables
have been omitted from the figure to reduce visual complexity, but are
reported in Table S5. The path model had a good fit to observed data
(CFI = 0.99, χ2 = 26.3, df = 26,p-value = 0.45).