Phenotypic plasticity and fitness in egg parasitoids

Abstract

-Several proxies can be used to estimate the fi tness of egg parasitoids: size, longevity, fecundity, mating ability and vagility. All these proxies are positively correlated with the lifetime fi tness gain of an individual. However, the phenotypic plasticity, which is the ability of a genotype to produce distinct phenotypes depending on environmental conditions, may alter the value of these proxies. Host related factors (host species and quality), competition and duration of development will infl uence the proxies expressed by a given phenotype. When the phenotype is modifi ed by the temperature at which an individual develops, the resulting phenotype will vary based on the life history strategy of the parasitoid. While in koinobiont species an increase in size is positively correlated with longevity and fecundity, the reverse occurs with idiobiont parasitoids. Using size as a proxy could thus be misleading depending on the factors that infl uence the size of the adult.KEY WORDS: Fitness, proxy, reproduction, longevity, phenotype Most optimality models are based on the assumption that organisms optimize some physiological or behavioral characteristics in order to maximize their lifetime fi tness (Stephens & Krebs 1986). Fitness, defi ned here as the success of an individual in passing on copies of its genes to future generations (Bolhuis & Giraldeau 2005), is therefore used as a measure of success and any change in the morphology, physiology or behavior of an animal that increases its lifetime fi tness is expected to be positively selected. This concept is central in behavioral ecology and both direct fi tness and inclusive fi tness are recognized. Direct fi tness refers to the fi tness gained by an individual through the production of its own offspring while inclusive fi tness refers to the sum of the direct fi tness plus the indirect fi tness gained by the reproduction of nondescendant relatives (Krebs & Davies 1997).Insect parasitoids are good organisms to test hypothesis in behavioral ecology as the expression of behaviors associated with host localization and parasitization are directly linked to a gain in fi tness. Indeed, fi nding and successfully parasitizing a host results in additional progeny and therefore in an increase in fi tness (Godfray 1994). Another research area where measures of fi tness are used for parasitoids is applied ecology and in particular biological control (Roitberg et al 2001). When comparing different species or genotypes within a species for their potential in biological control programs, measures of fi tness can be used to assess their capacity to multiply and control a targeted pest.However, measuring directly fi tness is a diffi cult and timeconsuming process. One would have to measure the relative performance of genotypes and quantify their representation in a population over several generations (Hoffman 1994). In general, proxies that give absolute values, such as size, longevity, fecundity etc., are used to approximate the fi tness of an individual. The different...

Review of Anaphes Haliday (Hymenoptera: Mymaridae) with key to species in Europe and a world catalogue

“…Phenotypic and other types of variation is also well documented in other genera of Mymaridae, e.g., Segoli & Rosenheim (2015) for metatibia length in one species of Anagrus, and in other families of egg parasitoids, e.g., Boivin (2010) and Abram et al (2016, and references therein) discussed variation in various feature due to host, phenology, etc. Johnson et al (1987) showed that host-related antennal variation occurs in a polyphagous egg parasitoid, Telenomus alsophilae Viereck (Platygastridae, Telenominae).…”

Quality assessment of Riptortus pedestris (Hemiptera: Alydidae) eggs cold-stored at different temperature and relative humidity regime

“…However, cold-stored eggs can lose water as they age, and parasitism of such eggs may decrease with time (Kivan and Kilic, 2005;Boivin, 2010), making the use of storage conditions able to preserve the quality of host eggs important.…”

Size-induced reproductive constraints in an egg parasitoid

“…Insect parasitoids, that must develop using the resources available from a single host, show large phenotypic plasticity in their size mostly due to the fact that parasitoids are constrained in their immature development by the resources contained in their host (Godfray, 1994). Such intra-specific differences in size have obvious impacts on their reproductive capacity (Boivin, 2010). Smaller individuals generally have lower probability of gaining access to the other sex (Ramadan et al, 1991;Boivin and Lagacé, 1999) and have a lower fecundity and shorter life expectancy (West et al, 1996;Ellers et al, 2001;Colinet et al, 2007).…”