DOES ANT DISPERSAL OF SEEDS IN SCLEROLAENA-DIACANTHA (CHENOPODIACEAE)GENERATE LOCAL SPATIAL GENETIC-STRUCTURE

Sclerolaena diacantha is unusual in that it can exhibit contrasting di aspore dispersal at adjacent sites. At most sites, the diaspores merel y fall to the ground where secondary dispersal occurs. However, at som e sites ants actively collect the diaspore that contains a food body a nd subsequently thousands of seeds accumulate on the long-lived ant mo unds. The study evaluated the patterns of local spatial genetic struct ure within and among replicated sites with and without ant dispersal. Spatial autocorrelation, relatedness coefficients and gene correlation statistics based on four polymorphic allozyme loci showed that local spatial structure was minimal at two sites without ant dispersal. In c ontrast, moderate local spatial structure was apparent at one of the a nt-dispersed sites whereas weak spatial structure was detected at the other. Restricted diaspore dispersal centred on long-li led ant mounds may explain the observed spatial structure at the first site whereas other forces appear to have contributed to the erosion of spatial stru cture at the second site. This multisite spatial study highlights the complexity of the interacting forces that may create or erode genetic structure in natural plant populations.