Bees in a landscape context : what do bees need and who needs them?

The interaction between plant and pollinator is generally mutualistic. The plant becomes pollinated or gets its pollen grains dispersed and the pollinator gets food rewards consisting of nectar or pollen. Many plants and crops are dependent on pollinators for fruit set and must therefore have efficient pollinators in their surroundings. There are many groups of animals that include pollinating species; however, bees are often referred to as the most effective pollinating group. Their effectiveness is partly because of their dependence on floral food resources both for larval development and adult survival. In addition to high abundance, high diversity of bees has been shown to be important for effective and stable pollination services of crops and wild plants. The importance of identifying what is affecting the bee composition and distribution in a landscape is therefore obvious. In addition to food resources, bees need suitable nesting habitats for reproduction and often external substrates for the construction of brood cells. On Earth, there are bees on every continent except Antarctica and 17,500 species are so far identified (Michener 2007). Despite the high diversity of bees with great variation in food and nesting requirements one factor has been found to frequently explain the diversity of bees; heterogeneity. In general, on a regional scale, bee diversity increases with higher heterogeneity in the landscape. Highly heterogeneous environments, provides high diversity of food and nesting resources, which can support more species. However, bee communities will differ in their response to changes in the landscape depending on species composition, habitat and continent. Therefore knowledge about the bees’ basic ecology and life-history is important for interpreting results and planning conservation measures