Evolution of specialization in lycaenid butterfly-ant mutualism

I examined two lycaenid butterfly-ant mutualisms to gain insight into the evolution and maintenance of specialized associations between these two groups.;The North American lycaenid, Glaucopsyche lygdamus, associates facultatively with a diversity of ant species. A cost-benefit analysis of larvae tended by different ant species revealed that stability of the interaction and survivorship benefits to larvae depended upon the identity of the attendant ant. Large, aggressive species (Formica obscuripes, F. podzolica) frequently displaced smaller, timid species (F. 'neogagates', Tapinoma sessile). F. podzolica and T. sessile were the most effective ant guards while F. obscuripes reduced larval survivorship below that of untended larvae. All ant species conferred similar costs to developing prepupae. Results suggest that local specialization on the most predictable and effective ant species may be favored and reasons for its apparent absence are discussed.;The Australian lycaenid, Jalmenus evagoras, has specialized, obligate associations with Iridomyrmex ants. Trials conducted at a field site near Brisbane revealed that specificity between larvae and ants was due to aggression or indifference by most ant species in the community toward larvae. Ant specialization by butterflies was examined in oviposition choice tests. Females from Brisbane oviposited preferentially on trees with their natal ant over trees without ants or with attendant species from other Australian localities. When offered the same ant species from different localities, preferences were less pronounced, but also suggested local specialization. Implications for host ant shifts and lycaenid diversification are discussed.;The attractiveness of G. lygdamus and J. evagoras larvae to attendant ants was strongly influenced by the nutritional state of ant colonies. Responses were consistent with the known composition of food rewards secreted to ants by larvae, suggesting that larvae may increase their ant guard by producing food rewards containing limiting ant nutrients.;Patterns of association between lycaenids and ants in Australia were examined in light of the functional roles of attendant ants in local communities. Obligately ant-associated lycaenids were tended almost exclusively by ecologically dominant ants, while facultative mutualists associated with a broad range of ants. A mechanism to explain the evolution of specialization with ecologically dominant ants is proposed.