Social Parasitism : Blue Butterflies in Ant Colonies
Biology 342 Fall 2011
Ellen Levkoy & Rachel Strominger
Phylogeny attempts to provide an evolutionary pathway by which the behavior and species in question developed .
Origin of Parasitism in Maculinea
The evolution of parasitic myrmecophily in large blue butterflies can be determined by phylogenetic analysis. The common ancestor of this clade used dorsal organ secretions to attract ants with a nectary substance. This trait has been reduced in Maculinea blues, but still exists to some extent . Maculinea blues have developed two alternative strategies of parasitism during the larval stage. M. teleius and M. arion use the derived ancestral trait of organ secretion to act like a “cuckoo,” and are fed directly by worker ants. M. alcon have evolved to be predatory, residing at the edges of the nest and coming in to feed on ant larvae and other food.
Genetic analysis has identified Maculinea as a monophyletic group within Phengaris. Five species within the Maculinea genus exhibit similar food-plant and host-ant associations during the larval stage (M. arion, M nausithous, M. teleius, M. alcon, M. rebeli). All of these species parasitize Myrmica (M. rubra, M ruginodis, M. scabrinodis, M. rugulosa) colonies, but variations between species of Maculinea butterfly of ant species-specificity exist. Some variation has been found between species within the Maculinea genus as to larval stages, their acceptance by various Myrmica colonies. [4, 14, 12, 9, 5]
Researchers hypothesize that acoustical mimicry evolved after semio-chemical mimicry. The Maculinea, whose larvae resemble Myrmica larvae, first gained entry into the nest by tricking the ants into taking them for Myrmica larvae. Then, they evolved to get better treatment by mimicing the sounds made by queen ants, (as distinct from worker ants), prompting guarding and feeding by worker ants, even to the expense of their own larvae and workers. Worker ants have been known to preferentially feed Maculinea caterpillars over their own kind when resources are scarce. [2a]