Population Cycles of Forest Lepidoptera: A Maternal Effect Hypothesis

Abstract

Summary1. Many species of forest Lepidoptera have cyclic population dynamics. Although there are numerous potential causes, including interactions with predators, parasitoids, pathogens, and food-plant quality, strongly density-dependent interactions are often difficult to demonstrate. Both autocorrelation analysis and attractorreconstruction methods have recently been applied to a number of species' time series. Results suggest that complex dynamics, i.e. cycles or deterministic chaos, may be more prevalent than once thought, and that higher-dimensioned models are necessary. 2. We develop a two-dimensional difference equation model that relates the average quality of individuals to patterns of abundance. The delayed density dependence is caused by transmission of quality through generations via maternal effects. We show that the maternal effect model can produce patterns of population fluctuations similar to those displayed by one class of host-parasitoid models. 3. We review empirical evidence for maternal and quality effects in dynamics of forest Lepidoptera. We fit the maternal effect and delayed logistic models to six species of forest moths for which delayed density dependence and maternal or quality effects have been found. The maternal effect model was a good predictor of the period of the oscillations for the species that we examined. We discuss why models of this type give better fits to moth cycles than do first order models with added delays.

Changes in maternal investment in eggs can affect population dynamics

“…In the presence of environmental fluctuations, the lag created by the delayed life-history effect typically also increases population variability and decreases its predictability (Benton et al 2001b;Beckerman et al 2002). In addition, maternal effects can theoretically lead to long-term deterministic population dynamical patterns such as population cycling seen in forest Lepidoptera and many microtine rodents (Ginzburg & Taneyhill 1994;Ginzburg 1998;Inchausti & Ginzburg 1998). Understanding the causes of fluctuations in population size and the interplay between the environment and density dependence is a key goal of current population ecology (Saether 1997;Bjørnstad & Grenfell 2001;Coulson et al 2001;CluttonBrock & Coulson 2002;Greenman & Benton 2003) and is crucial for predictive population modelling for management.…”

“…Inference has typically been made from information contained in time-series, such as the period and shape (e.g. time reversibility) of population cycles (Ginzburg & Taneyhill 1994;Ginzburg 1998;Inchausti & Ginzburg 1998;Turchin & Hanski 2001;Shaw et al 2004), or the relationship between population perturbations or size and the life history of cohorts of individuals (Albon et al 1987;Myers et al 1998;Erelli & Elkinton 2000;Forchhammer et al 2001;Beckerman et al 2002Beckerman et al , 2003Reid et al 2003). A number of experiments have been conducted to investigate the strength of maternal influence on individual performance in a range of animals (e.g.…”

Food-supplementing parents reduces their sons' song repertoire size

“…When this is the case, the reproduction and survival of individuals reflect not only current environmental conditions, but also the environmental conditions experienced by their progenitors (reviews in Mousseau & Fox 1998;Lindströ m 1999;Metcalfe & Monaghan 2001), which can significantly affect population dynamics (Lindströ m 1999;Beckerman et al 2002;Benton et al 2005). Population models incorporating intergenerational effects typically assume there is a positive relationship between the parental environment and offspring quality (Ginsburg & Taneyhill 1994). However, several studies have shown that, in order to produce more offspring or lessen the burden on themselves, parents may produce poorer quality offspring when conditions are favourable because it is precisely when conditions are favourable that offspring quality is least likely to affect recruitment (Bernardo 1996;Sinervo et al 2000;Plaistow et al 2006;Russell et al 2007).…”

Delay driven spatiotemporal chaos in single species population dynamics models

“…U (x, t) → U (x − ct) ∪ U (x + ct). Consider, for instance, the front propagating to the right, U (x, t) = U (ξ) where ξ = x − ct, which is the solution of the following equation (in dimensionless variables): 14) corresponding to the conditions at in nity as U (ξ) → 0 for ξ → ∞ and U (ξ) → 1 for ξ → −∞.…”

“…Delayed density dependence is thought to be one of the main factors causing population uctuations (Berryman and Turchin 1997). The most commonly considered causal mechanisms are resource competition (Hansen et al 1998), cannibalism (Briggs et al 2000), and maternal e ects (Ginzburg and Taneyhill 1994) where the nutritional environment of the parental generation can in uence the growth and reproductive potential of the next generation. Delays may also occur as a consequence of developmental time and/or interaction between individuals of di erent stages (Royama 1981, Hastings 1984.…”