Comparative fecundity, clutch size, ovariole number and egg size of Dacus tryoni and D. jarvisi, and their relationship to body size

Abstract

Dacus tryoni (Frogg.) (Diptera: Tephritidae) is the main tephritid pest of cultivated fruits in Australia. D. jarvisi (Tryon) is also able to infest these fruits. Some factors influencing the rate at which D. tryoni and D. jarvisi exploit patches of host fruits were examined to determine whether one species may have an advantage when they exploit the same fruits in the field. Measurements of the intrinsic rate of increase, ovariole number, clutch size and egg size and the influence of body size on these parameters were made for both species in the laboratory. Up to 10 weeks of age D. tryoni produced twice as many eggs as D. jarvisi, most during a peak 3-5 weeks after adult emergence. The difference in fecundity up to 10 weeks can be explained partly by the higher number of ovarioles in D. tryoni (38/ovary) compared to D. jarvisi (27/ovary). In addition D. tryoni produces smaller eggs than D. jarvisi and distributes them in smaller clutches; 3-4 eggs/clutch vs 10-15. In both species there was a positive correlation between ovariole number and body size (as measured by wing length). By contrast, egg size remained constant over a broad range of body sizes. The influence of these life history differences on the interaction between D. tryoni and D. jarvisi in the field is discussed.

Selection Strategies of Parasitized Hosts in a Generalist Parasitoid Depend on Patch Quality but Also on Host Size

“…Indeed, host size is correlated with offspring size in P. vindemmiae (Grandgirard et al, 2002). Even if size is not sufficient to precisely evaluate the fitness of individuals (Roitberg et al, 2001), fitness and size are usually strongly correlated (Fitt, 1990;Petersen and Hardy, 1996). Therefore, D. radicum could be fitter hosts for P. vindemmiae females than D. melanogaster, which would explain why D. radicum pupae are more often accepted even when they are already parasitized.…”

Foraging and Oviposition Decisions in the Parasitoid Aphytis lingnanensis: Distinguishing the Influences of Egg Load and Experience

“…Although a variety of modelling approaches have been used, existing models may be broadly grouped by their choice of the parameter to be optimized (the 'currency'): (i) fitness gained per clutch (the single host maximum or 'Lack solution'; Charnov & Skinner 1984Parker & Courtney 1984; Waage & Ng load and experience. Fitt 1986Fitt , 1990 Recent studies have employed quantitative genetic techniques to investigate the influence of egg load on host range. An exception occurs for some proovigenic insects (i.e.…”

Differences in Body Size and Egg Loads of Rhagoletis indifferens (Diptera: Tephritidae) From Introduced and Native Cherries

“…Despite differences in egg loads, bitter cherry and sweet or tart cherry ßies produced similar sized eggs. In other Diptera, including tephritids, egg size does not vary with female size (Krainacker et al 1989, Fitt 1990, Saunders et al 1999, but this is not true in all insects (references in Honȇ k 1993).…”

“…As a result, sweet and tart cherry ßies likely have greater reproductive potential in nature, a concern for commercial cherry growers. Positive adult body size-fecundity patterns have been observed for at least 10 other tephritids under laboratory conditions: Ceratitis capitata (Wiedemann); Bactrocera (Dacus) dorsalis (Hendel) (Krainacker et al 1989, Chua 1992; B. tryoni (Froggatt); B. jarvisi (Tryon) (Fitt 1990); Anastrepha obliqua (Macquart); A. ludens (Loew); A. serpentina (Wiedemann) (Liedo et al 1992); A. suspensa (Loew) (Sivinski 1993); Rhagoletis juglandis Cresson (Alonso-Pimentel et al 1998); and Toxotrypana curvicauda Gerstaecker (Jimé nez-Pé rez and Villa-Ayala 2006). Here, we show that the positive adult body size-fecundity pattern occurs for R. indifferens in nature, where nutrition may not maximize egg loads as in the laboratory (see study 4).…”

“…For example, the larger fruit size of sweet and tart cherries could result in larger pupae and subsequently larger adult body size for ßies infesting the introduced versus native cherries. This is important because adult body size in insects, including tephritids, is positively correlated with fecundity (egg load, eggs laid over a signiÞcant portion of the oviposition period or over the lifetime, depending on the author) (Honȇ k 1993, Krainacker et al 1989, Fitt 1990, Liedo et al 1992, Ameneshewa and Service 1996, Armbruster and Hutchinson 2002, Bochdanovits and De Jong 2003, Calvo and Molina 2005. Higher fecundity could contribute to higher ßy densities on particular hosts, which in this case would have negative economic consequences for commercial cherry growers.…”