Evolution of phenotypic variance: non-Mendelian parental influences on phenotypic and genotypic components of life-history traits in a generalist herbivore

Abstract

Non-Mendelian parental effects are a form of phenotypic plasticity that influences offspring development and modifies their phenotype. They could have major evolutionary impact by changing the process of selection and the correspondence between offspring genotypes and phenotypes. To examine the influence of parental effects on life-history traits in the obliquebanded leafroller, Choristoneura rosaceana (Harris), three successive generations were raised in a constant laboratory environment, the first and subsequent generations being produced by field-raised and laboratory-raised parents, respectively. Between-generation variation in phenotypic means, variances and among-and within-family variance components were used to assess the magnitude of the influence of parental effects on allelic expression. The differences between parent-offspring regressions derived using parents from the first and second generations were used to estimate the directionality of the influence of parental effects on the family means of the traits.It appears that parental effects influenced the mean and variance of life-history traits at population and family levels. For development time and within-family diapausing propensity, the families of parents developing in a specific environment (laboratory or field) were apparently affected by a similar parental effect. For larval growth rate and pupal weight, it appears that different parental effects transmitted by field parents influenced the family means. Consequently, parental effects transmitted by field parents did not change the correspondence between the offspring phenotypic and breeding values in the first two traits but modified this relationship in the later traits. Parental effects influenced simultaneously the range of phenotypes produced by a genotype and its mean phenotype. Therefore, they may represent a major developmental mechanism by which organisms adapt to unpredictable and predictable environments.

Host-Plant Quality Influences Diapause and Voltinism in a Polyphagous Insect Herbivore

“…Given the potential increases in fitness accrued by producing an extra generation (Roff 1980(Roff , 1983 we might expect host choice by C. rosaceana to match the probability of bivoltinism on a particular host. Our results are in broad agreement with a previous study of neonate dispersal of C. rosaceana (Carrière 1992b) in which there was no relationship between larval preference and subsequent performance. 3), although neonate dispersal levels were lowest from chokecherry, the host that maximizes the probability of a second generation.…”

“…It feeds on a wide variety of deciduous tree species, is a pest of fruits and nuts (Schuh and Mote 1948, Pree and Roberts 1981, Kaethler et al 1982, Madsen et al 1984, Onstad et al 1985, AliNiazee 1986, Rice et al 1988, and is an occasional pest of coniferous tree seedlings (Simeone and Engelken 1959). Neonates emerge after ഠ2 wk, and larval dispersal on silk threads appears to be a dominant mode of dispersal and host choice (Carrière 1992b). The life cycle of C. rosaceana in the Quebec City area (46Њ48Ј N, 71Њ21Ј W), where the present study was conducted, is as follows.…”

“…Specifically, firstand second-instar larvae are the only stages susceptible to diapause induction. More recently, Carrière (1992a) demonstrated that, for a population in the Okanagan Valley of British Columbia, the instar in which larvae entered diapause varied among host-plant species, although he found no variation in the proportion of larvae entering diapause on different host plants. Above 15 h of light per day, most larvae do not enter diapause, and continue development.…”

“…Studies of an Oregon population have shown that there is a critical photoperiod of between 14 and 15 h of light per day; at 14:10 h light : dark, all larvae enter diapause. Finally, there are both genetic and nongenetic parental effects that contribute to variability in diapause in C. rosaceana (Carrière 1994, Carrière andRoitberg 1994). The critical photoperiod can be modified slightly by altering temperature (Gangavalli and AliNiazee 1985).…”

Summer diapause induced by high temperatures in the oriental tobacco budworm: ecological adaptation to hot summers

“…Newly hatched larvae were reared in groups in the Petri dishes with diet until the 3 rd instar, after which they were separated and placed in individual glass tubes to prevent cannibalism46. H. assulta colonies had been maintained for more than 6 generations in the laboratory before the start of the experiments to reduce the possible influence of the host source47.…”