Intraspecific competition in the speckled wood butterfly Pararge aegeria: Effect of rearing density and gender on larval life history

Abstract

In insects, the outcome of intraspecific competition for food during development depends primarily upon larval density and larval sex, but effects will also depend on the particular trait under consideration and the species under study. Experimental manipulations of larval densities of a Madeiran population of the speckled wood butterfly Pararge aegeria confirmed that intraspecific competition affected growth. As densities increased P. aegeria adults were smaller and larval development periods were longer. Sexes responded differently to rearing density. Females were more adversely affected by high density than males, resulting in females having smaller masses at pupation. Survivorship was significantly higher for larvae reared at low densities. No density effect on adult sex ratios was observed. Intraspecific competition during the larval stage would appear to carry a higher cost for females than males. This may confer double disadvantage since females are dependent on their larval derived resources for reproduction as they have little opportunity to accumulate additional resources as adults. This suggests that shortages of larval food could affect fecundity directly. Males, however, may be able to compensate for a small size by feeding as adults and/or by altering their mate location tactics.

The Mothematics of Female Pheromone Signaling: Strategies for Aging Virgins

“…Females can potentially use cues other than their own mating status to adjust signaling effort: if females can perceive the signals of competing females, there is potential for more complex signaling strategies than the ones modeled by us (Harari et al 2011). Experimental manipulation of juvenile environments can also prove informative (Gibbs et al 2004).…”

Effect of larval crowding on the life history traits of Sesamia nonagrioides (Lepidoptera: Noctuidae)

“…Under conditions of restricted food supply, many lepidopteran larvae extend their development and consequently their feeding period in order to attain a critical size for metamorphosis (Fischer & Fiedler, 2001;Bauerfeind & Fischer, 2005). In addition, larval crowding during development causes a reduction in female pupal and adult weight in a number of species (Leonard, 1968;Peters & Barbosa, 1977;Fisher & Fiedler, 2001;Agnew et al, 2002;Gibbs et al, 2004). However, the results of these studies are contradictory, so it is unclear whether these effects are caused by the group density per se or by the reduced availability of food.…”

“…However, the results of these studies are contradictory, so it is unclear whether these effects are caused by the group density per se or by the reduced availability of food. In Pararge aegeria (L.) for example, high larval crowding resulted in lower survival and a longer developmental period (Gibbs et al, 2004). Tammaru et al (2000) found that crowding during early larval development strongly delayed larval growth in Epirrita autumnata and reduced pupal weight.…”

“…Numerous studies on the effects of the stress of larval crowding have demonstrated both direct and indirect effects on the performance of Lepidoptera. The most obvious are the direct effects of a low survival rate, prolonged larval period and low pupal weight (Mercer, 1999;Tammaru et al, 2000;Gibbs et al, 2004;Bauerfeind & Fischer, 2005). Rearing larvae in overcrowded conditions are linked indirectly with adult fitness, specifically small adult size, reduced fecundity and lowperforming offspring (Quring & McNeil, 1984;Boggs, 1997;Fisher & Fiedler, 2001).…”

Effects of intraspecific competition of prey in the dynamics of a food chain model

“…Griffith and Poulson 1993), wood butterfly (cf. Gibbsac et al 2004) also used to take part in intraspecific competition. The intraspecific competition among prey is incorporated in the model through the theta-logistic growth rate of prey.…”