Abstract
The domed fitness functions are suggested to describe developmental patterns of progeny parasitoids in relation to host age at oviposition in solitary koinobint parasitoids that are engaged in single parasitism, but few studies have investigated the applicability of the functions as related to superparasitism. The present study was designed to compare fitness functions between single parasitism and superparasitism by examining developmental patterns of Meteorus pulchricornis (Wesmael) (Hymneoptera: Braconidae) progeny in relation to the beet armyworm, Spodoptera exigua Hübner (Lepidoptera: Noctuidae), either singly parasitized or self-superparasitized as second–fifth instar larvae. Selfsuperparasitism caused deleterious effects on the fitness-related traits of parasitoid progeny, as demonstrated by a prolonged egg-to-adult emergence time, a smaller body size, and shorter longevity of the emerging adults, and decreased survival to adult emergence. While the domed fitness function was detected for development time, survival, adult body size, and longevity in relation to host larvae that were singly parasitized, the function was observed only for progeny survival in relation to host larvae that were self-superparasitized. This study suggests that developmental fitness functions with selfsuperparasitism can deviate from those with single parasitism in solitary koinobiont parasitoids.
Highlights
Among the most important trade-offs faced by organisms is whether to grow larger at the cost of extended development time or to develop more rapidly at the cost of reduced size (Abrams and Rowe 1996)
Where the relationship between body size and host stage at oviposition was best fitted by a quadratic curvilinear function for offspring parasitoids engaged in single parasitism, it was best fitted only by a linear function for the counterparts involved in selfsuperparasitism (Figure 1C, D; Table 1)
Our experiments show that self- progeny parasitoids are larger in body size in superparasitism in M. pulchricornis had dele- superparasitized aphid hosts than counterparts terious effects on the development of in singly parasitized aphids without a corresponding increase in development time (Bai and Mackauer 1992; Mackauer and Chou 2001)
Summary
Among the most important trade-offs faced by organisms is whether to grow larger at the cost of extended development time or to develop more rapidly at the cost of reduced size (Abrams and Rowe 1996). The studies observe that the fitness functions differ markedly between (and within) koinobiont and idiobiont parasitoids in response to ecophysiological characteristics of the host species, including host size, growth potential at parasitism, immunity, and feeding ecology (Harvey et al 2004; Pennacchio and Strand 2006). Fitness functions for solitary parasitoids attacking hosts with the potential to grow considerably larger than the adult parasitoid are distinctly dome-shaped (or may even decrease with host size in extreme cases) because progressively larger hosts possess more potent immunological defenses, or else they may be less nutritionally compatible for parasitoid development (and survival) than younger hosts (Strand 2000; Harvey et al 2004). The model gains strong support in numerous studies of solitary parasitoids involved in single parasitism (Smilowitz and Iwantsch 1975; Harvey et al 1994, 1999, 2004; Pandey and Singh 1999; Chau and Mackauer 2001; Elzinga et al 2003; Harvey et al 2004; Liu and Li 2006, 2008; Chen et al 2011), but few studies have yet investigated the applicability of this model to the parasitoids engaged in superparasitism
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