Importance of habitat quality and landscape factors for a monophagous shield bug on a rare host plant

Abstract: Understanding the factors affecting species distribution and at what scale a species respond to these factors is a major challenge in conservation biology. I studied the distribution and abundance of a monophagous shield bug Canthophorus impressus at three spatial scales: host plants, patches and circular landscapes (area ca. 3 km2), to determine the relative importance of the different spatial scales and how habitat quality, amount and spatial configuration affect the distribution of C. impressus. Influence of habitat characteristics on occurrence and abundance of the bug was analysed with separate generalised linear mixed models. The data show that effects of habitat quality and amount dominate over configuration in determining the distribution of C. impressus. The bug prefers large host plants in warm conditions on a plant scale and abundant host plants in a landscape scale, whereas patch scale was not important for the distribution of the bug. Management should aim to preserve sites with abundant host plants and promote large host plants with low to moderate grazing. To secure sufficient number of host plants in the landscape, high densities of suitable habitat such as semi-natural grasslands should be preserved. This study suggests that analyses of multiple spatial scales are crucial for identifying appropriate actions for successful conservation of species living in fragmented habitats.