The behaviour and wing morphology of the meadow brown butterfly (Maniola jurtina L.) in Britain : the influence of weather and location
Understanding the influence of climate and weather on butterfly abundance and distribution, as well as the morphological, physiological and life-history traits associated with populations living in different geographic and climatic areas, is critical to the consideration of how they respond to environmental change. Using Maniola jurtina as a model species, research was conducted to determine the effect of meteorological variables on the behaviour of this species in south central England and north west Scotland, and to determine whether variation in wing morphology is adaptive in terms of thermoregulatory efficiency. Temperature, solar radiation and wind speed were recorded simultaneously with timed behavioural observations, which were made on transect walks and whilst following individual butterflies. Thoracic temperatures were recorded in the field, and wing size and darkness determined using digital image analysis. Warm-up rates of butterflies of known wing morphology were determined under laboratory conditions. In the north, conditions are cooler, cloudier and windier; habitat is more restricted and butterflies were found to be at lower density than in the south. Temperature and solar radiation intensity influenced duration of flight, feeding and basking (butterflies in both regions used both dorsal and lateral basking postures), with the largest effects being shown for the southern popUlation. Males from both regions flew for significantly longer than females and northern males flew for significantly longer than those from the south. Northern butterflies are larger and darker than those from the south, but there is no significant difference in thoracic temperatures between the regions. Smaller, darker butterflies were active at lower air temperature and solar radiation intensity than larger, paler individuals. Although northern butterflies show morphological and behavioural adaptations to marginal weather conditions and low population density, a model of egg production estimates that fecundity of northern females is reduced by 16% compared to those in the south.
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