PATTERNS IN THE DISTRIBUTION, ABUNDANCE AND BODY-SIZE OF CARABID BEETLES (COLEOPTERA, CARABOIDEA) IN RELATION TO DISPERSAL ABILITY

The effects of dispersal ability, measured as two wing size categories (brachypterous vs. macropterous), on the distribution, abundance and body size, and on the relationships between these variables were exami ned in eighty-four species of carabid beetles over twenty-two sites in the northern Iberian peninsula. Geographic ranges of species (restric ted to the northern Iberian peninsula vs. widespread-European or wider range) were also taken into account in the analyses because macropter ous species significantly tended to exhibit wider geographic ranges th an did brachypterous species. Regional distributions were wider in bra chypterous-restricted and brachypterous-widespread species than in mac ropterous-widespread species. The three groups did not differ in abund ance. Differences in regional distributions between groups may be expl ained by referring to a trade-off between dispersal ability and establ ishment ability indicated in the literature. Macropterous species woul d occupy relatively few sites due to a high frequency of unsuccessful colonizations. The relationships between regional distribution and abu ndance were positive for all the three groups, brachypterous-restricte d, brachypterous-widespread and macropterous-widespread species. The r egression line for the last group showed a lower elevation than those for brachypterous-restricted and brachypterous-widespread species. Thi s fact was probably due to differences in regional distributions betwe en groups. No relationship between abundance and body size was signifi cant. Regressions of regional distribution on body size were positive in brachypterous-restricted and brachypterous-widespread carabids, but the relationship was not significant in macropterous-widespread carab ids. These results were interpreted in terms of differences in body si ze-dependency of travelling velocities between flying and running cara bids.