Appendix A. Comparison of life-history of golden vs. wild-type Plodia interpunctella larvae.
We conducted a series of experiments comparing the biology of two phenotypic morphs of the moth Plodia interpunctella, as used to assess the effects of competition between parasitized and unparasitized larvae on survival of host larvae and host population dynamics. We present the results of comparisons of body size and development time between unparasitized wild and golden hosts. We assess any differences in response to parasitoid attack in the two phenotypic morphs, specifically their encapsulation response. Finally we ask whether there are differences in survival between wild type and golden larvae in response to resource limitation.
Comparison of unparasitized wild type and golden larvae
The mean body size ( ± SE) of individually reared golden larvae was slightly, but significantly larger than wild type larvae (female wing vein length: golden 4.38mm ± 0.04, Wild 4.17 mm ± 0.03, t = -4.7261, 99, P < 0.05 (Lewis 2005)), but golden larvae emerged as smaller adults following competition (female dry mass: wild 3.07 ± 0.05 mg, golden 2.57 ± 0.58 mg Mann-Whitney, Z = -5.523, n = 288, 492, P < 0.05). From an independent study of competition experiments between either golden or wild larvae, there was significant difference in development times to adult eclosion between the two color morphs (females: wild 25.88 ± 0.36 days, golden 25.42 ± 0.63 days Mann-Whitney, Z = -0.733, n = 113, 24, P = 0.46).
Comparison of parasitoid attacked wild type and golden larvae
The encapsulation rates of individually reared wild and golden larval hosts were not significantly different (wild 5.5%, golden 4.46%, χ = 0.00, df = 1 P < 0.05). The development times of larvae that successfully encapsulate a parasitoid were not significantly different from unparasitized Plodia larvae (unpara., 23.74 ± 0.34 days, encap., 25.05 ± 0.65 days Mann-Whitney, Z = 0.000, n = 96, 6, P = 1). Similarly, the size of golden adult moths that develop from larval hosts that successfully encapsulate a parasitoid are not significantly different from adults that develop from unparasitized larvae (unpara., 3.09 ± 0.13 mg, encap., 2.92 ± 0.08 mg Mann-Whitney, Z = -1.270, n = 202, 62, P = 0.204), which indicates that hosts that encapsulate parasitoids do not appear to bear a cost in their final size at eclosion. However, due to the small sample size it is not possible to test what effects density and inter-class competition have on encapsulation rates.
Survival of unparasitized wild type and golden larvae
The larval to adult survival of golden Plodia is not significantly different to wild Plodia under all competitive conditions (wild 0.754 ± 0.038 vs. golden 0.713 ± 0.046 proportion survived, paired t tests, proportional survival; t23, 1 = 0.901, P = 0.37). There was a significant interaction between the host phenotype and the competitor ratio, where either morph had higher per capita survival when rare (GLM F49, 7 = 28.655, P < 0.04).
Overall, we conclude that any differences in the life-history of the two phenotypic morphs studied here – wild vs. golden – are negligible.
LITERATURE CITED
Lewis, Z. 2005. Sexual selection and sexual conflict in the Lepidoptera, PhD Thesis, University of Leeds, UK.