Table 1.
Terms in equations. Parasite-induced trait effects on IGP were included by scaling instantaneous predation rates on or by the infected subclass by ρi (appetite) and υi (vulnerability), assuming predation in infected–infected encounters is determined by predator appetite (appetite has priority over vulnerability). Parameter subscripts: 1, IGprey; 2, IGpredator.
| parameter/variable (units) | definition | values taken (reference) |
|---|---|---|
| Si, Ii state variables (per area) | densities of susceptible and infected subpopulations, respectively, of host species i | n.a. |
| Ni state variable (per area) | total population density, species i; initial population Ni = 10 (Si = 9, Ii = 1 or Si = 10, Ii = 0) iterated to equilibrium | n.a. |
| ri (t−1) | intrinsic per capita population growth rate | r1 varied, r2 = 1.0 (reference values: [14]) |
| αij (unitless) | competition coefficient (the effect on species i of species j) | α11 = α22 = 0.005, α12 = α21 = 0.0005 [15] |
| e (unitless) | conversion efficiency of victims of predation or cannibalism into offspring | 0.3 [15] |
| γij (per predator–prey encounter · t−1) | instantaneous rate of predation on species i by species j (before trait modification); subscripts 1 = IGprey, 2 = IGpredator | γ12 = 0.015, γ21 = 0.01 reflecting mutual asymmetric IGP [15] |
| k (per encounter · t−1) | instantaneous rate of cannibalism | 0.01 [15] |
| Ωi (per infection · t−1) | per capita rate of parasite-induced mortality | 0 ≤ Ωi,Ωj ≤ 0.5 (as given, figure 1) |
| βij (per infectious–susceptible encounter) | parasite transmission efficiency to species i from species j | β11 = β22 = 0.05, β12 = β21 = 0.005 |
| υi (unitless) | vulnerability trait modifier (scales predation on infected subclass of species i by susceptibles of j) | 0 ≤ υi ≤ 2 (applied to γ1I2S, γ2I1S) |
| ρi (unitless) | appetite trait modifier (scales predation by infected subclass of species i on infected and susceptible subclasses of j) | 0 ≤ ρi ≤ 2 (applied to γ1S2I, γ1I2I, γ2S1I, γ2I1I) |