REPRODUCTIVE ALLOCATION FROM RESERVES AND INCOME IN BUTTERFLY SPECIESWITH DIFFERING ADULT DIETS

Allocation of stored and incoming nutrients to reproduction determines an organism's age-specific fecundity curve. In holometabolous insects , differences among species in the shape of the curve are correlated w ith differences in the potential importance of adult food to reproduct ion. I examined allocation patterns underlying this association. Speci fic changes throughout life in body mass and reproductive effort were predicted to result from use of stored vs. incoming nutrients for repr oduction and other metabolic needs at each age. Data for three nymphal id butterfly species, Euphydryas editha, Speyeria mormonia, and Helico nius charitonius, were compared with the predictions. These three spec ies differ in adult diet and fraction of oocytes mature at adult emerg ence (hence, potential for adult nutrients to be used to make eggs), w ith E. editha showing the least potential for use of adult nutrients i n egg production and H. charitonius showing the greatest potential. Fo r all three species, body mass declined with age, although nonlinearly for E. editha. This indicated that metabolic expenditures were greate r than intake at all ages, and that a constant fraction of stored nutr ients was allocated to reproduction and other metabolic uses at each a ge for E. editha. Reproductive effort also declined with age for all t hree species. The specific patterns seen suggested that incoming nutri ents may be stored, to some extent, early in life and then used late i n life by both S. mormonia and H. charitonius. The similarity between S. mormonia and H. charitonius is rather surprising, given the qualita tive differences in adult diet and suggests either that qualitative ag e-specific allocation patterns for incoming vs. stored nutrients may b e independent of adult diet quality, or that the observed patterns are constrained by phylogenetic relatedness of these two species.