Influence of host size on the clutch size and developmental success of the gregarious ectoparasitoid Eulophus pennicornis (Nees)(Hymenoptera: Braconidae) attacking larvae of the tomato moth Lacanobia oleracea (L.) (Lepidoptera: Noctuidae)

Female parasitoids are expected to distribute offspring among hosts in a manner that maximizes fitness. Several theoretical and empirical studies have focussed on clutch-size patterns in hymenopteran parasitoids. In contrast, dipteran parasitoids, which differ from hymenopterans in potentially important ways, have received little attention. The phonotactic tachinid fly Ormia ochracea has been intensively studied for its effects on host crickets, and has recently been the subject of studies of its own reproductive biology. This work suggests a negative relationship between clutch size and progeny fitness (consistent with hymenopterans), but no adjustment of clutch size to host size (different from hymenopterans). However, the repeatability of these patterns and the relationship between fly size and fitness remain to be demonstrated. We examined clutch sizes of O. ochracea larvae in the cricket Teleogryllus oceanicus. Most clutches were smaller than a cricket can support to pupation. Smaller clutches yielded larger offspring and larger wild-caught flies had higher fecundity, supporting the idea that small clutches yield higher fitness. However, although parasitised male crickets were slightly larger than unparasitised males, there was no correlation between cricket size and the number of larvae. Potential reasons for this departure from the patterns found in hymenopteran parasitoids are discussed.

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Phenotypic plasticity in clutch size regulation among populations of a potential invasive fruit fly from environments that vary in host heterogeneity and isolation

Bulletin of Entomological Research ◽

10.1017/s0007485318000329 ◽

2018 ◽

Vol 109 (2) ◽

pp. 169-177 ◽

Cited By ~ 1

Author(s):

M. Aluja ◽

A. Birke ◽

F. Díaz-Fleischer ◽

J. Rull

Keyword(s):

Phenotypic Plasticity ◽

Clutch Size ◽

Fruit Fly ◽

Egg Laying ◽

Host Size ◽

Anastrepha Ludens ◽

Laboratory Population ◽

Size Regulation ◽

Host Fruit ◽

Wild Host

AbstractPhenotypic plasticity is thought to evolve in response to environmental unpredictability and can shield genotypes from selection. However, selection can also act on plastic traits. Egg-laying behaviour, including clutch size regulation, is a plastic behavioural trait among tephritid fruit flies. We compared plasticity in clutch size regulation among females of Anastrepha ludens populations stemming from environments that differed in the degree of predictability in egg-laying opportunities. Clutch size regulation in response to hosts of different sizes was compared among flies from (a) a wild, highly isolated population, (b) a wild population that switches seasonally from a small wild host fruit that varies greatly in abundance to an abundant large-sized commercial host, and (c) a laboratory population. Flies from all three populations adjusted clutch number and size according to host size. However, flies from the heterogeneous wild environment were more plastic in adjusting clutch size than flies from agricultural settings that also laid fewer eggs; yet both populations were more plastic in adjusting clutch size in line with host size when compared with laboratory females. When wild and orchard females encountered the largest host, clutch size was extremely variable and egg regulation did not follow the same trend. Heterogeneity in host availability in space and time appears to be as important as seasonal variation in host size in maintaining plastic clutch size regulation behaviour. In stable environments, there was a clear reduction in the plasticity of these traits.

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