ASSIGNMENT

Assignment

Assignment

Introduction

For the design and declaration of conservation areas as well as for planning habitat management it is important to quantitatively know the habitat preferences of the focal species. To take into account the requirements of as many species as possible, it would be of great advantage if one would either (i) find one or several species whose habitat requirements cover those of a large number of other species or if one could (ii) identify a common set of habitat parameters that is important for the occurrence of many species. Ideally such common habitat parameters should be easy to measure. Only then they may be of practical value in applied conservation biology.

In this study, we compared the habitat preferences of different insect species [Coleoptera (beetles), Diptera (Flies), Diptera - Tipulidae (Crane flies), Trichoptera (Caddis)] in the same region by applying identical methods. To identify common explanatory variables that predict the occurrence probability of these species, we first tested the transferability of the specific 'species models' to other species within the same insect group. We tested how well the incidence of one species can be predicted by the occurrence probability of another species. The 'best' models within each group were then tested for transferability between the different groups. Additionally, we tested the predictive power of the predictor variable 'habitat type' as an easy and often available measure for conservation practice.

Although in the different 'species models' different key factors determine habitat suitability, some models were successfully transferred and were able to reasonably predict the distribution of other species. The habitat preferences of the burnet moth Zygaena carniolica were particularly well suited for the prediction of suitable habitats for all other species. In addition, the predictor variable 'habitat type' played a dominant role in all models. Models using this aggregated predictor variable may well predict suitable habitat for all species.

The increasing and irreversible loss of biodiversity is one of the major current environmental problems. It results in an urgent need for efficient decision making to protect valuable areas. Conservation has to succeed in strong competition with alternative land uses and under substantial constraints (e.g. low monetary funds). This is especially true for grassland systems in Central Europe. Thus, priorities in the declaration of protected areas have to be set. For this aim, appropriate and reliable decision criteria need to be developed to maintain the species diversity in selected conservation areas (with as little expenditure in area and money as possible, see e.g. Kleyer et al., 2007; Schröder, Rudner, Biedermann, Kögl, & Kleyer (2007) and Rudner, Biedermann, & Kleyer (2004); Rudner, Biedermann, Schröder, & Kleyer; 2007).

To reach the aim of protecting as many species as possible in the conservation of grasslands, habitat requirements of a very large number of single species has to be considered simultaneously (Bobbink & Willems, 1993). To overcome this problem, one could imagine two scientific approaches: (a) the identification of single species - so-called umbrella species - which are representatives for others with respect to habitat requirements (Bonn & Schröder, 2001; Fleishman, ...