Insect Diversity in Changing Landscapes

University dissertation from Ekologiska institutionen, avdelningen för zooekologi Lunds universitet

Abstract: During recent decades, concern about the loss of biodiversity has increased. To change this negative trend there is an urgent need for effective conservation measures and there are ample evidence that conservation of organisms without an understanding of their ecology and behaviour is impossible. At the Kullaberg Nature Reserve in the south-western part of Sweden butterflies exhibited a disastrous decline with a loss of 45% of the fauna during the last 50 years. Considering all Macrolepidoptera, extinction rate was 7 times higher than the colonisation rate. Mark release recapture studies in Småland show that realistic estimates of dispersal distance often are underestimated and a study-area of at least 50 km2 are required to obtain realistic dispersal data for burnet moths (Zygaenidae). To obtain adequate measures of dispersal, the marked population should be large, preferably over 500 recaptured individuals. In the warm July 2003 burnets were more mobile, with 2.14 and 2.18 times higher between habitat patch dispersal rates compared to July in 2004 when the temperature was below normal. For the specialised solitary bee Andrena hattorfiana a pollen budget was calculated and used to predict critical resources for a given size of the specialised bee population. The local bee populations were dominated by small local populations. Only 16% of the patches were occupied four consecutive years and only one patch had a local bee population >20 females all four years. Both the size of the host plant population and the bee population had strong and independent effects on extinction probability. Colonisations occurred more frequent at larger host plant populations. During the four year study the bee declined severely, but the host plant was relatively constant. The most important farm characteristics to predict species richness of butterflies and solitary bees were the density of the plant Knautia arvensis, the proportion of grazed semi-natural grassland (negative) and the proportion of meadows with late harvest (after mid-July). People managing agricultural biodiversity can encompass high species richness of pollinating insects and support red-listed species by preserve and restore areas with a high density of K. arvensis and manage at least 20% of the grasslands as traditional hay meadows or left ungrazed.

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