Temporal Dynamics of the Origin and Domestication of Sweet Potato and Implications for Dispersal to Polynesia

Abstract

In a study focussed on the origin of Ipomoea batatas (L.) Lam. (the sweet potato) and its close relatives [1], the authors claimed that a specimen of sweet potato collected by Banks and Solander in 1769 in Polynesia was distinct and along with some other varieties had levels of genetic variation of more than 100,000 years. This timeframe, along with several other lines of evidence, was interpreted, by the authors, as questioning human-mediated transport of the sweet potato to Polynesia within the last 1,000 years. This aspect of the paper received widespread media coverage as well as a number of critical remarks, and correspondence. The criticism questioned whether claims in the paper were justified. Here, three authors from the paper take the opportunity to fully explain the reasoning for calling into question the need to invoke human mediated transport of the sweet potato to Polynesia. Iterative nature of long-distance dispersal and storage root evolution in IpomoeaOur study of sweet potato and its wild relatives is part of a much larger taxonomic [2-10] and phylogenetic study of Ipomoea worldwide, to be published later this year. During the last four years, we have become aware of the prevalence of naturally occurring long distance dispersal within and across the phylogenetic breadth of Ipomoea and we provide two examples in the paper [1]. The significance of this highly iterative process is that disjunct distribution patterns of closely related species (e.g. disjunction patterns between Polynesia and the American continent) are not uncommon in Ipomoea, and therefore a species native to America but also present in Polynesia (whether it is a crop or not) is not that surprising. However, the prevalence of naturally occurring long distance dispersal in Ipomoea, in itself, does not preclude the sweet potato arriving in Polynesia via human mediated dispersal within the last 1,000 years. What we claim, though, is that the probability of it dispersing naturally to Polynesia is already high given the prevalence of naturally occurring dispersal of close relatives across vast distances, and becomes even more so within the timeframe since it diverged from its closest relative, I. trifida.In addition, during our field studies [2-10] we became aware of one other aspect of Ipomoea biology: the independent evolution of tubers in different species in various clades across the reuse, remix, or adapt this material for any purpose without crediting the original authors. preprint (which was not peer-reviewed) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, The copyright holder has placed this . http://dx