THE EFFECT OF ADULT FOOD LIMITATION ON LIFE-HISTORY TRAITS IN SPEYERIA-MORMONIA (LEPIDOPTERA, NYMPHALIDAE)

Variation in food availability is likely to occur in the wild, and may affect resource allocation to various life history traits. Quantitative adult diet restriction had no effect on life-span or mean individual egg mass, but reduced fecundity in the butterfly Speyeria mormonia. The sum of fecundity plus unlaid oocytes remaining in the ovaries at death declined in direct proportion to the reduction in the adult diet. This indicates that oocytes were resorbed and resources re-allocated away from reproduction under resource stress, since the sum of laid and unlaid eggs for butterflies fed ad libitum did not differ from the number of oocytes present in the ovaries at eclosion. In this nectivorous species, then, life-span is conserved at the expense of reproduction under adult resource stress. Further, for butterflies fed ad libitum, the volume of honey-water imbibed declined with age for both sexes. Daily volume imbibed by females fed ad libitum was directly correlated with daily egg production and life-span, suggesting that factors as yet unexplored may be affecting both resource intake and life history traits when resources are available ad libitum.