REPRODUCTIVE PATTERNS AND RESOURCE-ALLOCATION IN TROPICAL BUTTERFLIES- INFLUENCE OF ADULT DIET AND SEASONAL PHENOTYPE ON FECUNDITY, LONGEVITY AND EGG SIZE

The reproductive patterns and resource allocation strategies of three closely related tropical satyrine butterflies, Mycalesis terminus, M. sirius and M. perseus, were studied under laboratory and semi-laborato ry conditions. We first examined the influence of two adult food sourc es, sugar (25% honey solution) and rotting fruit, on the oviposition p attern, fecundity, longevity, egg size and reproductive effort in the west-season forms of M. terminus and M. sirius. We then compared the r eproductive traits between the two seasonal phenotypes (wet- and dry-s eason form) of M. perseus fed only on the rotting fruit diet. In this species females of the dry-season form diapause as adults whereas thos e of the wet-season form usually reproduce directly. Availability of s ugar or rotting fruit in the adult diet of M. sirius had no significan t effect on any of the reproductive traits. However, in M. terminus di et had two major effects: availability of sugar increased longevity, w hile females fed on rotting fruit tended to maintain constant egg weig ht over time. Differences in response to adult diet in these two speci es correspond with their behaviour in the field: M. sirius adults rare ly feed at nectar sources or on rotting fruit, whereas those of M. ter minus readily feed on rotting fruits. Hence, availability of rotting f ruits to adult M. terminus may enhance reproductive success since fema les appear to produce better quality offspring (i.e. lay larger eggs o ver time). In M. perseus, post-diapausing females of the dry-season fo rm had reduced realised and potential fecundity, laid proportionally f ewer eggs, and had a shorter oviposition period compared with the wet- season form. Egg weight increased with female age in the wet-season fo rm but declined in the dry-season form. Although the dry-season form l aid larger eggs it still had a much lower reproductive effort, indicat ing that diapause imposes a substantial cost to reproduction. We tenta tively conclude that this cost is the result of an adjustment in resou rce allocation between soma (body size and structure to increase longe vity) and reproductive reserves acquired during the larval feeding per iod. Comparison of the reproductive patterns between the three species (i.e. when both seasonal form and adult diet are standardised) reveal ed striking similarities in many traits, including oviposition pattern , potential fecundity, reproductive effort and survival. However, ther e were substantial differences in allocation strategies, with M. perse us partitioning its reproductive effort into many smaller eggs. Differ ences in these reproductive strategies are associated with the preferr ed habitats of each, and we suggest that habitat uncertainty and limit ed breeding opportunities may have selected for higher fecundity in M. perseus.