IENE 2016

The maintenance of habitat connectivity is desirable in facilitating seed dispersal for the conservation of many species and plant communities. Occasional long-distance dispersal (LDD) events, although rare and stochastic processes, are important for habitat colonization and the maintenance of genetic connectivity.  Minor rural road networks constitute an important landscape element, and have gained recent attention for their role in potential LDD events. As minor roads are maintained by anthropogenic inputs, they possess novel environments which provide habitat conditions advantageous to some plants, depending on their life history attributes. Seed dispersal by ants, or myrmecochory, is a significant ant-plant mutualistic relationship that occurs in many ecosystems worldwide. In myrmecochory, a food ‘reward’, in the form of a specialized fleshy appendage called an elaiosome, is attached to the seed. Attracted to this food reward, ants move seeds into their nests to consume the elaiosomes, and then discard the seeds into the surrounding area. The extent to which ants may facilitate occasional LDD in road corridors largely depends on the habitat conditions which prevail in relation to human disturbances.

In Australia and elsewhere, minor roads are maintained by anthropogenic inputs, often in the form of periodic soil disturbances form roadwork’s activities.  Field studies were conducted in a typical fragmented agricultural landscape in southern New South Wales, which contained a large network of minor rural roads and associated remnant vegetation. 24 road segments were selected that possessed both disturbed and undisturbed zones. Seeds of Acacia pycnantha, a common myrmecochorous shrub, were offered to ants at multiple bait stations in both zones to ascertain seed fates, seed dispersal distances, and to identify the main seed dispersing ant species. As expected, ant species richness was greater in the undisturbed zones. However disturbance tolerate species were present in large numbers in the disturbed zones. Mean seed dispersal distances was greater in the disturbed zone (mean 35m, maximum 120m), where large meat ants (Iridomyrmex purpureus) were responsible for most of the seeds dispersed, and appeared to thrive in habitat conditions as a result of soil disturbances from roadworks. Field observations also recorded secondary dispersal events away from nests – which may further aid in seed dispersal. The implications this study in terms of developing a better understanding of the importance of this mutualism, and role of minor rural roads in promoting LDD, will be discussed.