The
intrinsic rate of natural increase of an insect population.
Intrinsic rate of increase (r) increased with increasing temperature; from 0.1543, 0.1600 and 0.1518 females per female per day at 24 +- 0.5 AdegC, 27 +- 0.5 AdegC but declined at 32 +- 4 AdegC.
These results showed that the
intrinsic rate of increase (r) of L.
The main parameter of the life table is represented by the
intrinsic rate of population increase ([r.sub.m]), which is defined as the innate increase capacity of a population under ideal conditions; in other words, it corresponds to the population biotic potential (Price, 1984; Pedigo and Zeiss, 1996).
Treatment Population growth parameter (a,b) T [R.sub.o] YieldGard VT 41.96 [+ or -] 0.17 a 621.16 [+ or -] 44.33 b PRO[TM] PowerCore[TM] 41.60 [+ or -] 0.15 a 490.30 [+ or -] 56.50 c Non-Bt corn 39.98 [+ or -] 0.22 b 854.16 [+ or -] 58.46 a Treatment Population growth parameter (a,b) [r.sub.m] [lambda] YieldGard VT 0.153 [+ or -] 0.003 b 1.17 [+ or -] 0.002 b PRO[TM] PowerCore[TM] 0.146 [+ or -] 0.003 c 1.16 [+ or -] 0.003 c Non-Bt corn 0.169 [+ or -] 0.002 a 1.18 [+ or -] 0.002 a (a) T = mean generation time (days); [R.sub.o] = net reproductive rate (females per female per generation); [r.sub.m] =
intrinsic rate of population increase (per day) and [lambda] = finite rate of population increase (per day).
Parameters Results Net reproductive rate ([R.sub.o]) 223.64 [female]/[female] Mean generation period (T) 36.50 d
Intrinsic rate of natural increase ([r.sub.m]) 0.145 [female]/[female]/d Doubling time ([D.sub.T]) 4.78 d
The results of statistical analysis revealed significant differences in sublethal effects of the synthetic and botanical insecticides on the net reproductive rate (F = 8.271; df = 6, 37; P < 0.001), the
intrinsic rate of increase (F = 8.619; df = 6,37; P < 0.001), and the finite rate of increase (F = 8.688; df = 6, 37; P < 0.001).
Under the assumption of zero fishing mortality, the conditional
intrinsic rate of increase parameter, r, was estimated at 0.00%/yr and was not significantly different from zero based on the 95% confidence interval (P>0.05) (Table 5).
Intrinsic rate of natural increase = r = Ln(Nt)-Ln(N0)/t Doubling time of population in days = tD = 0.6931/r Nt = N0-e rt where Nt and N0 = final and initial populations, Generation time = Gent't = 1 / Divisions day-1 Divisions day-1 = Div.
In the black region of each graph, the hyperparasitoid
intrinsic rate of increase is not great enough for it to invade the host-parasitoid system.
Chaoborus extract Trait Absent Present Juvenile body length Time to maturity -0.52 0.29 Mean clutch size 0.11 -0.04 Reproductive effort -0.17 0.19
Intrinsic rate of increase 0.28 0.09 Juvenile body depth Time to maturity -0.47 0.34 Mean clutch size 0.02 -0.15 Reproductive effort -0.23 0.15
Intrinsic rate of increase 0.26 0.13 Juvenile tailspine length Time to maturity -0.34 -0.01 Mean clutch size -0.09 0.29 Reproductive effort -0.36 0.24
Intrinsic rate of increase -0.08 0.29 In the presence of the extract, time to maturity was positively correlated with both body length and depth, possibly indicating a cost.
Life table parameters such as
intrinsic rate of increase ([r.sub.m]), mean generation time (TG), finite rate of increase ([lambda]), and doubling time (DT) were calculated using Equations 1 to 4 of Birch (1948) and Carey (1993).
