SPATIAL AND TEMPORAL COOCCURRENCE OF COMPETITORS IN SOUTHERN AFRICAN DUNG BEETLE COMMUNITIES

1. Co-occurrence of 11 species of crepuscular-nocturnal medium-sized t unnelling dung beetles from two core functional groups that vary in th eir rate of dung burial was examined at a range of spatial and tempora l scales to identify the likely extent to which competition for dung m ight affect the structure of beetle communities of subtropical pasture . 2. At the largest scale, clear seasonal co-occurrence and similar ha bitat preferences (soil type and vegetation associations) were found a mongst the species. 3. Medium- and fine-scale distributions of the spe cies were investigated across nine blocks of dung-baited traps dispers ed over a 400 ha tract of open cattle pasture, on deep sandy soil in N atal, South Africa. Traps were baited overnight and cleared in the mor ning in two series of three successive days. 4. There was marked varia tion in mean numbers caught within and between each 3-day trapping per iod, and also between blocks in the total number of beetles (pooled ov er species) or individual species caught per block. The spatial relati onship for total beetles between blocks persisted for several days, bu t not several weeks. 5. Significant intraspecific aggregation was appa rent for all species at the medium spatial scale amongst individual pa ds and between blocks over the 400 ha, but at the finest spatial scale (within blocks) most species were randomly distributed on most occasi ons, irrespective of the abundance of the species. The actual level of aggregation was thus found to increase at higher spatial scales. 6. P airwise species comparisons showed little or no positive association o n the majority of occasions and negative pairwise associations were ex ceedingly rare. Positive association between the two functional groups was stronger, however, and positive species association at the commun ity-wide level was evident on most occasions. 7. There was thus some e vidence of independent spatial aggregation patterns amongst individual species on a medium spatial scale (400 ha), but not on a fine scale ( 100 m2). Intraspecific/functional group aggregation tended to be great er than interspecific/functional group aggregation at all scales of an alysis. Despite this, beetle densities in a considerable proportion of pads in the field would indicate, based on previous experimental evid ence, that significant levels of inter- and intraspecific/functional g roup competition for dung is likely to occur. Thus, the aggregative be haviour of species documented here is not predicted to significantly d iminish the level of interspecific competition within and between the two functional groups in this system.