People and Plants

Have Martu substantially influenced the distribution, abundance, and genetic diversity of bush tomatoes through both seed dispersal and burning, and how significant is (and has been) this process in shaping both social formations and the choices people make about how to utilize landscapes?

Even in the Western Desert of Australia, where Aboriginal populations historically were among the least dense and most mobile, anthropologists have long suspected that people played a substantial seed dispersal role. Martu talk about their role in seed dispersal, asserting that by scattering the inedible seeds of the fruit of many shrubs and trees, they affect the distribution of those plants such that they could recognize old camp sites or archaeological sites by the presence of such indicator plants. Martu also talk about the importance of fire for continued productivity of many desert plants, especially seed grasses and solanum fruits. While it is well known that Martu shape fire regimes to the benefit of native animals, and that these fire mosaics are localized around pathways of movement--today mainly vehicle tracks, our understanding of how this fire regime affects plants, including food plants, remains limited.

Both the use of fire and fruit processing activities at central places and along corridors of movement may affect the distribution and local abundance of the more preferred species, S. diversiflorum (wamula). Wamula occurs in discrete patches, often in high densities, producing hundreds of kilograms of fruit per hectare. Harvesters often stop to taste the fruits, cleaning as they continue to search, and selecting the best available fruits in terms of sweetness and size. In some patches, production is so great that people obtain extremely high return rates (>2000 kcal/hr) for a week or more, revisiting the patch almost daily during the ripening period. At the end of a collecting trip, fruit harvests are returned to a central place, often a temporary dinner-time camp (DTC), for storage, processing, and initial consumption. It is common practice for Martu to carry these unopened fruits in their vehicles and pockets while foraging in new locations in the days/weeks following the original harvesting event, as well as to transport some proportion of the harvest explicitly for sharing, between community members as well as to family and friends in distant communities. At locations where fruits are processed in bulk, thousands of seeds will be left scattered on the ground, the majority of which will be concentrated around the nexus of the camp’s social interaction – the hearth.

This leads us to suspect that Martu interact with wamula in ways that expand its environmental niche: they disperse significant amounts of seed well beyond the seed shadow of the parent plant, which increases both in-patch fruit density and gene flow between isolated fruit patches, and furthermore, through fire they create more habitat likely to be good for its subsequent growth and reproduction.