Ants cannot account for interpopulation dispersal of the arillate pea Daviesia triflora

Estimating distances and rates of seed dispersal, especially long-distance dispersal (LDD), is critical for understanding the dynamics of patchily distributed populations and species' range shifts in response to environmental change. Daviesia triflora (Papilionaceae) is an ant-dispersed shrub. The ant Rhytidoponera violacea was recorded dispersing its seeds to a maximum distance of 4.7 m, and in more intensive trials seeds of a related species from the study area, to a maximum of 8.1 m. Microsatellite DNA markers and population assignment tests identified interpopulation immigrants among 764 plants on 23 adjacent dunes bearing D. triflora, and 13 interpopulation seed dispersal (LDD) events (1.7%) were inferred. The distance between source and sink populations ranged from 410 m to 2350 m (mean 1260 m). These distances exceed ant dispersal distances by two to three orders of magnitude but are comparable with previous measurements of LDD for two co-occurring wing-seeded (wind-dispersed) species from the same system. The observed distances of seed dispersal in this arillate species demonstrate the significance of nonstandard dispersal mechanisms in LDD and the independence of these from primary dispersal syndromes. The likely role of emus in dispersal of the many 'ant-dispersed' species in Australia is discussed.