Elena Haeler



Dormancy induction in female meadow brown butterflies Maniola nurag and M. jurtina

In Sardinia, adult females of the two butterfly species Maniola nurag and M. jurtina perform a reproductive summer dormancy, i.e. they do not oviposit before autumn. With this strategy they survive summer-drought during which grass, the caterpillar’s food resource, is scarce. While M. nurag is endemic on the island, M. jurtina is widespread over Europe and populations of climatically cooler regions usually do not perform an aestivation. In this study I investigate the influence of day length and the availability of fresh grass as a food resource for the offspring on dormancy induction and egg-laying strategy. I expected that long daylength and the lack of grass (=summer conditions) would promote aestivation and therefore delay egg deposition. For the experiment, 150 females were collected from Sardinia (M. nurag + M. jurtina) and Austria (M. jurtina) and kept under three controlled conditions: long-day (LD = L16:D8) with fresh grass, long-day without grass, and short-day (SD = L11:D13) with fresh grass. The long-day treatment prolonged dormancy of Sardinian females from a mean of 24d (SD) to 72d (LD). Concomitantly, average adult lifespan was extended from 56d (SD) to 117d (LD); one female butterfly actually lived for eight months. Fresh grass had no effect on reproductive dormancy. M. jurtina from Austria did not show a reaction to the different treatments (average lifespan: 54d, days until oviposition: 16d), they behaved similar to short-day females from Sardinia. I conclude that reproductive summer dormancy in Mediterranean Maniola butterflies is induced by long-day, while day length has no effect on the timing of egg-laying of Central European individuals.