Beetle diversity and historical ecology of woodlands in Flanders

Extensive data on the present-day carabid beetle fauna occurring in woods o f Flanders were compared with a unique data-set of archaeological carabid r emains from a Late and Post-Roman forest at Velzeke (Eastern Flanders), wit hin the framework of a study on the historical ecology of woodlands in Flan ders. Integration of these data on 14 woods revealed that most have been si gnificantly impoverished with respect to their stenotopic woodland beetle f auna. The carabid species' diversity is higher in several small and relativ ely recent woodlands compared to that in larger ancient forests, regardless of whether this diversity is evaluated by rarefaction or by mean species r ichness per standardised year sample data. This pattern is primarily caused by the presence, in forest fragments , of many species from surrounding op en habitats. Typical woodland beetles show a reduced dispersal power (const ant brachyptery) and appear to be strongly linked to larger ancient woods. Knowledge of historical ecological factors, other than actual size of the f orests, further aids the explanation of the observed ground beetle assembla ges in the specific forests or sites. Preliminary results of population gen etics, for the eurytopic forest carabid beetle Abax ater showed significant genetic differentiation between populations (due to reduced gene flow) at a relatively large spatial scale, although genetic erosion cannot (yet?) be observed for this species.