Species-Richness Correlations of Six Different Taxa in Swedish Seminatural Grasslands

An important question in conservation biology is whether the biodiversity of different taxa is correlated. We studied the extent to which the number of species of six different taxa-plants, birds, butterflies, bumblebees, ground beetles, and dung beetles-in 31 Swedish seminatural grasslands covary, and whether species diversity can be related to habitat variables. During 1996 and 1997, we surveyed plants and animals with appropriate techniques for each taxa and mapped the grassland habitat. In general, correlations between taxa were few. Grassland plant diversity (currently used as an indicator for conservation value) was only significantly positively correlated to total bird diversity. Bumblebee diversity was significantly positively related to both total and grassland butterflies, whereas there was a significant negative relationship between grassland birds and dung beetles. Plants, birds, bumblebees, and butterflies showed significant similarities in patterns of species composition, as did birds, butterflies, grassland butterflies, and ground beetles. The total number of plants and both subsets of birds (total and grassland) were significantly positively related to area, whereas there was a significant negative association between area and dung-beetle diversity. The diversity of both butterflies and bumblebees was significantly negatively related to the proportion of short-grazed field layer. Bumblebees showed a positive relationship with junipers, whereas ground beetles and grassland birds were negatively associated with trees. The total number of bird species was positively influenced by the occurrence of shrubs. Our results suggest that neither the species richness of grassland plants nor that of any other of the surveyed taxa can be used as an indicator for total biodiversity in seminatural grasslands. The lack of similar patterns of species composition among taxa also makes it difficult to define functional groups with similar habitat demands. Until we have more detailed knowledge of the demands of species and taxa, it is important that we direct management efforts so that we provide a wide spectrum of grassland characteristics.