Fig 1.
The portrayal of the interactions among the insect predator and prey involving the intraguild predation (IGP) system.
As a shared prey both chironomid and mosquito larvae (Diptera) are consumed by the insect predators (Heteroptera) individually, as well as a part of the IGP system. Initial observations on single prey predator experiments were followed by the intraguild predation experiments under the varied habitat conditions represented in below.
Fig 2.
Illustration of the habitat conditions used to evaluate the influence of the habitat complexity on the IGP system.
Four different habitat conditions in the glass aquaria using vegetations (V), vegetations and pebbles (V+P), pebbles (P) and open conditions (O) were created in the glass aquarium. The condition (O) is used as simple condition reflects no habitat complexity in contrast to the rest three. Glass aquarium: Experimental mesocosm Water– 35L tap: pond; (pH– 7.6 to 8.2; temperature observed 29–32°C) Observation on predation was measured for 24 h. for each replicate.
Table 1.
(a) The logistic regression equations representing the variations in the shared prey consumed (preycon) by the IG predators against the prey density (preyden), predator density (predden) and predator combination (predcomb) and habitat complexity (habitat) as explanatory variables.
Predator combinations were (i) only IG prey and shared prey ii) both IG predator and IG prey with shared prey iii) only IG predator and shared prey. The level of significance assumed to be 0.025. The prey and predator combinations are shown in the suffix. (b) Significant values of the parameters of the model (in bold) were deduced through the Wald’s Chi-square test represented below. Here, the prey predator combinations were, mosq–Mosquito larvae, rus–D. rusticus, Chiro–chironomid larvae, ran- R. filiformis, lacco–L. griseus.
Table 2.
The logistic regression on the IG prey consumed (anicon) against shared prey density (preyden), predator density (predden) and habitat complexity (habitat) as the explanatory variables.
The level of significance is 0.025. (b) Significant values of the parameters of the model (in bold) were deduced through the Wald’s Chi-square test represented below. Here, the prey predator combinations were, mosq–Mosquito larvae, rus–D. rusticus, Chiro–chironomid larvae, ran- R. filiformis, lacco–L. griseus.
Fig 3.
The observed (unfilled bar) and expected (filled bar) number (mean ± SE) of mosquito larvae mortality at low (50 individuals) and high (200 individuals) density in heteropteran IGP using D. rusticus (D), R. filiformis (R), and L. griseus (L) separately as IG predators and ten individuals of A. bouvieri as IG prey at low (2 individuals) and high (4 individuals) of IG predator density.
The secondary y-axis represents Observed/Expected value (O/E) of shared prey mortality. S = Simple; V = Only macrophytes; P = only pebbles; C = Complex; E = Expected value; O = Observed value; O/E = Observed/ expected value.
Fig 4.
The observed (unfilled bar) and expected (filled bar) number (mean ± SE) of chironomid larvae mortality at low (50 individuals) and high (200 individuals) density (primary y-axis) in heteropteran IGP using D. rusticus (D), R. filiformis (R), and L. griseus (L) separately as IG predators and ten individuals of A. bouvieri as IG prey at low (2 individuals) and high (4 individuals) of IG predator density.
The secondary y-axis represents Observed/Expected value (O/E) of shared prey mortality. S = Simple; V = Only macrophytes; P = only pebbles; C = Complex; E = Expected value; O = Observed value; O/E = Observed/ expected value.
Fig 5.
Mortality of shared prey (A—mosquito larvae, B- chironomid larvae) in IGP system in complex habitat conditions (v–vegetation, p–pebbles and v+p—vegetation and pebbles) against simple conditions expressed as a ratio (k–value, mean ± SE) for the three IG predators in two density (L– 2 individuals and H—4 individuals) under low and (50 individuals) high (200 individuals) prey density. The horizontal lines in each graph represents the reference value of 1, equivalent to the value of no difference between the complex habitat condition and open condition.
Fig 6.
Mortality of IG prey (A. bouvieri) in presence of different shared prey (A. mosquito larvae and B. chironomid larvae) in complex habitat conditions (v–vegetation, p–pebbles and v+p—vegetation and pebbles) against open conditions expressed as a ratio (k–value, mean ± SE) for the three IG predators, in IGP system, in two density (L– 2 individuals and H—4 individuals) under low and (50 individuals) and high (200 individuals) prey density. The horizontal lines in each graph represents the value of 1.
Fig 7.
The ‘multiplicative risk model’ measures (pA, pB, pA+B) for the IGP system with different shared prey (A. mosquito larvae and B. chironomid larvae) in complex habitat conditions (v–vegetation, p–pebbles and v+p—vegetation and pebbles) against open conditions expressed as a ratio (k–value, mean ± SE) for the three IG predators (S—D. rusticus, R—R. filiformis and L—L. griseus), in two density (L– 2 individuals and H—4 individuals) under low and (50 individuals) and high (200 individuals) prey density. The dashed lines in each graph represent the reference value of 1, equivalent to the value of no difference between the complex habitat condition and open condition.
Table 3.
The results of t-test using mosquito larvae as shared prey in the IGP system with different habitat conditions (v–vegetation, p–pebbles and v+p—vegetation and pebbles) against open condition.
Table 4.
Results of the t-test using chironomid larvae as shared prey in the IGP system with different habitat conditions (v–vegetation, p–pebbles and v+p—vegetation and pebbles) against open condition.