From Songlines to genomes: Prehistoric assisted migration of a rain forest tree by Australian Aboriginal people

Abstract

BackgroundPrehistoric human activities have contributed to the dispersal of many culturally important plants. The study of these traditional interactions can alter the way we perceive the natural distribution and dynamics of species and communities. Comprehensive research on native crops combining evolutionary and anthropological data is revealing how ancient human populations influenced their distribution. Although traditional diets also included a suite of non-cultivated plants that in some cases necessitated the development of culturally important technical advances such as the treatment of toxic seed, empirical evidence for their deliberate dispersal by prehistoric peoples remains limited. Here we integrate historic and biocultural research involving Aboriginal people, with chloroplast and nuclear genomic data to demonstrate Aboriginal-mediated dispersal of a non-cultivated rainforest tree.ResultsWe assembled new anthropological evidence of use and deliberate dispersal of Castanospermum australe (Fabaceae), a non-cultivated culturally important riparian tree that produces toxic but highly nutritious water-dispersed seed. We validated cultural evidence of recent human-mediated dispersal by revealing genomic homogeneity across extensively dissected habitat, multiple catchments and uneven topography in the southern range of this species. We excluded the potential contribution of other dispersal mechanisms based on the absence of suitable vectors and current distributional patterns at higher elevations and away from water courses, and by analyzing a comparative sample from northern Australia.ConclusionsInnovative studies integrating evolutionary and anthropological data will continue to reveal the unexpected impact that prehistoric people have had on current vegetation patterns. A better understanding of how traditional practices shaped species’ distribution and assembly will directly inform cultural heritage management strategies, challenge “natural” species distribution assumptions, and provide innovative baseline data for pro-active biodiversity management.

Extensive Genetic Connectivity and Historical Persistence Are Features of Two Widespread Tree Species in the Ancient Pilbara Region of Western Australia

“…Indigenous Australians have occupied the Pilbara for at least 50 thousand years [ 113 ] and may have been important dispersers of some plant species [ 114 ]. Relatively little recognition has hitherto been given to the potential impacts of this means of dispersal on the present distributions of species and their genetic diversity, but it is likely that people have impacted the current biogeography of plant species, mobilising them for their use as food, medicine or for totemic purposes [ 114 , 115 , 116 , 117 ]. Combined with extreme meteorological events, these features provide a context for understanding the LDD observed in widespread Pilbara plant species and can form the basis of future hypotheses regarding genetic connectivity amongst the Pilbara flora.…”

Archaeobotany of Aboriginal plant foods during the Holocene at Riwi, south central Kimberley, Western Australia

“…Whitau et al (2017) suggest that the isolated occurrence of a M. nesophilus tree in the cave may have been a consequence of human behaviours, intentional or incidental. Aboriginal agency in the dissemination of trees in Australia has been suggested for Adansonia gregorii (boab) (Rangan et al 2015) and Castanospermum australe (black bean) (Rossetto et al 2017) supporting the argument of anthropogenic origin for the M. nesophilus at Riwi. It is possible that other plants may have grown in the cave in the past, however, no root structures were encountered during excavation and the structure of the cave, diminishing sunlight and water availability, suggests that incorporation of modern and prehistoric seed rain into the macrobotanical assemblage is improbable.…”

Reimagining the relationship between Gondwanan forests and Aboriginal land management in Australia's “Wet Tropics”

“…An abundance of historical documents and oral history testimonies describe the forced relocation of Rainforest Aboriginal People to stations and missions, and the genocide of hundreds, if not thousands, of Aboriginal people from the region (e.g., Loos, 1982), likely leading to a bias in pre-contact demographic estimations. Third, Rainforest Aboriginal Peoples (Aboriginal Australian people originating from the rainforest regions of Far North Queensland), in part based on oral histories passed down from Aboriginal Elders (Pannell, 2008;Nunn and Reid, 2016;Rossetto et al, 2017), have emphasized the fact that the environments of this region are a product of generations of Aboriginal land management. Future archeological and ethnohistorical work may therefore reveal an even greater extent of pre-colonial human occupation across the Wet Tropics, as has been demonstrated elsewhere in the tropical world (Heckenberger et al, 2003;Bush et al, 2015;Koch et al, 2019).…”

“…Research is also underway to test hypotheses of cultural imprints on key rainforest plants, and a similar multidisciplinary approach has now identified a recent and rapid dispersal of black bean (Castanospermum australe) based on its narrow genetic diversity and wide distribution across dissected territory in northern New South Wales (Figure 4) (Rossetto et al, 2017). Black bean is commonly found in economically useful tree clusters in the Wet Tropics, and Aboriginal oral histories and exchange networks provide a clear cultural framework for a distribution that is highly unlikely to be the result of natural dispersal mechanisms (Rossetto et al, 2017). This demonstrates the potential for innovative transdisciplinary research, with Aboriginal knowledge of landscape histories at its core, to further document the cultural heritage of the Wet Tropics Bioregion following trends in other tropical forest zones.…”