Predicting extinction risk of butterflies and moths (Macrolepidoptera) from distribution patterns and species characteristics

An extensive follow-up study of day- and night-active Macrolepidoptera was performed during 2004 at the Kullaberg Nature Reserve located in the south-western part of Sweden. Butterflies were surveyed in an area of 100 km(2) and night-active moths were trapped in the core area of the reserve. Macrolepidopteran species resident in the area in the 1950s were compared with species resident in the area in 2004. As much as 159 of 597 species (27%) resident in the area in 1950s were not found at all in 2004 and 22 species (4%) had colonised the area. Butterflies exhibited a disastrous decline with a loss of 45% of the fauna, and day-active species had declined more than night-active species had. Species distribution pattern and species characteristics were used to predict the probability that a species had become extinct or colonised the area. Species limited to one or a few food plants, with a short flight-period or restricted to non-forest habitats were all associated with a high extinction risk. Species occurring in fewer European countries and recorded from few provinces in Sweden were all associated with a higher extinction risk compared with ubiquitous species. For expanding species (colonisers), the best predictor was their distribution area in Sweden and colonising species were more likely to be limited to a few provinces in the southernmost part of Sweden. Species extinct from Kullaberg also have decreased in Finland and species that had colonised Kullaberg also have increased in Finland, while the species with no change in Kullaberg are also relatively constant in Finland. Indeed, the macrolepidopteran fauna was severely reduced in the last 50 years and almost 70% of the habitat specialists were lost. For red-listed species the situation was found to be alarming. Almost 70% of red-listed species, resident in the area in the 1950s, was not found in 2004. This study highlights that species composition changes rapidly even in protected nature reserves and that similar changes in the macrolepidopteran fauna seem to occur over large areas.