THE GENETICS AND COST OF CHEMICAL DEFENSE IN THE TWO-SPOT LADYBIRD (ADALIA BIPUNCTATAL.)

Abstract

Ladybirds (Coccinellidae) defend themselves against attack by vertebrate predators by exuding a fluid from the femero-tibial joints. This fluid carries a noxious or toxic alkaloid. The amount of fluid produced during a single attack can be very high (up to 20% of fresh body weight), and the weight of the self-synthesized alkaloid can amount to several percent of the weight of the fluid. A study was carried out on these two defense characters and two other fitness characters (body weight and growth rate) to demonstrate a cost to defense in the form of genetic trade-offs between characters. The two sexes were analyzed separately, and a jackknife procedure was used to attach errors to the estimates of V and cov . All four characters were associated with high levels of V , but the cov values were mixed, some being negative and others positive. Principal-component analysis indicated the operation of factors constraining the cov values in males, and further possible reasons for the appearance of so many positive values are explored. A matrix analysis showed that the genetic variance/covariance matrices of the two sexes were significantly different from each other. Breeding values derived from sons plotted on breeding values from daughters had correlation coefficients significantly less than +1. This finding indicated that a substantial amount of sex-dependent gene expression was occurring.

The effect of novel environment and sex on the additive genetic variation and covariation in and between emergence body weight and development period in the cowpea weevil, Callosobruchus maculatus (Coleoptera, Bruchidae)

“…Sex-limited G-matrix structure has been noted elsewhere (Holloway et a!., 1993). It is possible that different constraints operate in the two sexes, with energy being used in different ways (Maynard Smith et a!., 1985).…”

“…In many insect species, however, sexual dimorphism in life history traits, such as emergence body weight or development period, is often very evident. In addition to this, Holloway et al (1993) showed that estimates of additive genetic variation and covariation in and between life history traits differed between the sexes in a population of the two-spot ladybird, Adalia bipunctata. This suggests that each sex may be subject to a different set of constraints that is reflected in the structure of the life history genetics.…”

Foraging in a complex environment - semiochemicals support searching behaviour of the seven spot ladybird

“…1-1), which thus serves a dual role in C. septempunctata chemical ecology as an enemy repellent and aggregation pheromone (Al Abassi et al, 1998). The amount of reflex fluid emitted by ladybirds in response to an attack can be very high (up to 20% of fresh body weight), and the weight of the alkaloid can amount to several percent of the weight of the fluid (Holloway et al, 1993). The potential aposematic cues present in the multiple-component defence secretion of C. septempunctata have been investigated in feeding experiments with Japanese quail, Coturnix coturnix japonicus ( Marples et al, 1994).…”

Effect of reflex bleeding of a predatory ladybird beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), as a means of avoiding intraguild predation and its cost

“…In the field, larvae often face limited aphid availability (Osawa, 1989;Yasuda and Shinya, 1997;Jansen and Hautier, 2008). In this circumstance, one possible way of avoiding intraguild predation more effectively is by reflex bleeding-based protection (Komai, 1956;Holloway et al, 1991Holloway et al, , 1993.…”