Habitat‐related differences in the adult longevity of two ecotypes of a specialized butterfly

Abstract

AbstractThe life expectancy of adult butterflies is highly diverse. Substantial variation may be found among closely related species, and even on the intraspecific level, where it could be associated with sex, genetic differentiation, diet and weather conditions. We compared the demographic parameters of populations of the regionally endangered Boloria eunomia butterfly living in two different habitats. Across its boreal‐mountane distribution range in Europe, B. eunomia occurs in two ecotypes associated with wet meadows and raised bogs using distinct both larval and nectar plants. We carried out simultaneous studies of both ecotypes through mark–recapture surveys of two large populations in NE Poland, located close to each other. A total number of 1124 and 644 individuals were marked at the bog and meadow sites respectively, and 51 and 33% of them were recaptured at least once. The estimated adult population size of the bog population (about 3000) was twice as large as that of the meadow population, which however was characterized by more than three‐fold higher density. The emergence of imagoes was highly synchronized, and protandry was evident. The sex ratio was slightly male‐biased and the mean capture probability was significantly higher for males. More importantly, the estimated life span of males was considerably shorter than that of females at each site. Finally, both sexes of the ‘meadow’ ecotype lived significantly longer than those from the raised bog. The detected pattern can be related to distinct larval food plants and/or nectar resources, different pressures from predators, genetic variation and morphological differences affecting thermal properties. Further investigations would be useful to reveal if the shorter adult life span translates into reduced viability of bog populations and consequently whether they are potentially more threatened, at least in the southern margins of the distribution range in Central Europe.