Abstract
Over millennia, Indigenous peoples have dispersed the propagules of non-crop plants through trade, seasonal migration or attending ceremonies; and potentially increased the geographic range or abundance of many food species around the world. Genomic data can be used to reconstruct these histories. However, it can be difficult to disentangle anthropogenic from non-anthropogenic dispersal in long-lived non-crop species. We developed a genomic workflow that can be used to screen out species that show patterns consistent with faunal dispersal or long-term isolation, and identify species that carry dispersal signals of putative human influence. We used genotyping-by-sequencing (DArTseq) and whole-plastid sequencing (SKIMseq) to identify nuclear and chloroplast Single Nucleotide Polymorphisms in east Australian rainforest trees (4 families, 7 genera, 15 species) with large (>30 mm) or small (<30 mm) edible fruit, either with or without a known history of use by Indigenous peoples. We employed standard population genetic analyses to test for four signals of dispersal using a limited and opportunistically acquired sample scheme. We expected different patterns for species that fall into one of three broadly described dispersal histories: (1) ongoing faunal dispersal, (2) post-megafauna isolation and (3) post-megafauna isolation followed by dispersal of putative human influence. We identified five large-fruited species that displayed strong population structure combined with signals of dispersal. We propose coalescent methods to investigate whether these genomic signals can be attributed to post-megafauna isolation and dispersal by Indigenous peoples.
Highlights
Historical plant dispersal by Indigenous peoples has been recorded in many different parts of the world and there is a growing recognition that ancient Indigenous populations had a significant influence on the composition and distribution of ecosystems [1–8]
The patterns we found in P. queenslandica were consistent with long-term faunal dispersal and the species was not considered a candidate for further study (Table 3)
The genomic signals we found in C. australe confirm the utility of our workflow, in which extensive Indigenous dispersal has already been demonstrated [32]
Summary
Historical plant dispersal by Indigenous peoples has been recorded in many different parts of the world and there is a growing recognition that ancient Indigenous populations had a significant influence on the composition and distribution of ecosystems [1–8]. Molecular studies have sought to reconstruct the demographic history of food plant species to investigate the origins and processes of domestication [22–25]. These studies generally focus on crops that have been extensively genotyped and for which different cultivars are well-described (for example [26–30]). Little work has been carried out on the human-mediated dispersal of non-crop species ( see [31–35]) This could be in the form of “assisted migration” which is the movement of a species outside it’s natural range, “introduction” which is the establishment of new populations within a species’ existing range and “reinforcement” which is the planting of propagules from one population into another [36]. Retracing propagule dispersal by pre-colonial Indigenous peoples (hereon referred to as ‘Indigenous dispersal’) is important for cultural resource recognition and management and can yield insights to the long-term evolutionary impacts of translocations that can be applied to restoration activities
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