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THE GENETICS AND COST OF CHEMICAL DEFENSE IN THE TWO‐SPOT LADYBIRD ( ADALIA BIPUNCTATA L.)
Author(s) -
Holloway Graham J.,
Jong Peter W.,
Ottenheim Mart
Publication year - 1993
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.1993.tb02149.x
Subject(s) - biology , chemical defense , body weight , predation , zoology , botany , ecology , herbivore , endocrinology
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 a and cov a . All four characters were associated with high levels of V a , but the cov a values were mixed, some being negative and others positive. Principal‐component analysis indicated the operation of factors constraining the cov a 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.