Les niches écologiques des Carabides en milieu forestier. II. Composante trophique et organisation générale des niches.

Abstract

This paper continues the overall study of the niches of forest carabid beetles, by investigating the trophic component of the niche. Forest carabids are mainly predators on primary consumers, especially litter saprophages. Although opportunist, they strongly differ in their specialization patterns, so that food niches of large-, medium-and small-sized species are well distinct. The niche differentiation along the food axis is to some extent complementary to that along the time axis, and so the four niche components together result in a remarkable final differentiation in forest, and even in a complementarity among the dominant species in the beechwood. A carabid community appears to be an organized set, structured around the central niche of the dominant species. Niche organization grows from a successional stage towards the climax stage. The grassland in process of afforestation harbours an heterogeneous, poorly organized community, where species are likely competing. In the beech-wood, on the contrary, the carabid community is distinguished by its homogeneity, and its stable niche organization. Carabid beetles, especially the large species, seem to play an important role in regulating populations of primary consumers active at the ground surface. Thus, the stability of their communities may also help to stabilize sapro-and phytophage communities at the level of the litter layer in forests.