The effect of ant association on the population genetics of the Australian butterfly Jalmenus evagoras (Lepidoptera: Lycaenidae)

Abstract

Populations of the myrmecophilous lycaenid Jalmenus evagoras Donovan were assessed for genetic structure at three hierarchical spatial scales: sites, geographically-defined subpopulations, and subpopulations defined by species of mutualistic ant-associate. Estimates of Wright's FST generated from multilocus electrophoretic data revealed low, though significant, amounts of genetic structure. Most structure was observed at the level of geographic subpopulations, suggesting that adult butterflies do not exhibit preferential mating and oviposition along the lines of ant associate. The genetic structure data, together with estimates of Nei's genetic distance (D) for pairwise site and subpopulation comparisons, suggest that J. evagoras populations are spatially and temporally dynamic. These patterns are considered in the context of extinction and recolonization models. The extreme patchiness of J. evagoras populations stems from the stringent requirements of both host plant and host ant, contributing to an extinction/ recolonization process. We discuss the key parameters influencing genetic cohesion versus differentiation under an extinction/recolonization regime, including mode of butterfly dispersal, site turnover rate, and the effects of host dispersal and phenology. This system provides a model of population-level consequences of certain mutualistic interactions as well as of a class of patterns arising from an extinction/recolonization process.