[Science news] - The origin of Oxalis corniculata

Oxalis corniculata, known as creeping woodsorrel, is a common weed, despised by horticulturists worldwide. It grows in gardens and as a plantpot hitchhiker in nurseries and garden centres. It has spread widely and currently has the third largest distribution of any vascular plant species. However, its native origins are obscure. New research sheds light on the origin of this ubiquitous weed.

We gathered evidence from sources going back centuries and even millennia. Herbarium specimens, literature (including Renaissance herbals), archaeobotany and traditional medicine, and all have provided clues to the native range of O. corniculata.
We found no strong evidence that O. corniculata grew in Europe before the 15th century, or in the Americas before the 19th century. However, there is direct archaeobotanical evidence of the plant in south-east Asia at least 5,000 years ago. This points to an East Asian origin, which fits with the distribution pattern of Oxalis section Corniculatae, which is largely circum-Pacific.

Physical evidence for the native origins of a species has its limitations and biases. We would therefore welcome complementary research on the global genetic diversity of O. corniculata. This would further clarify how this species has evolved and migrated over geological epochs and millennia of human history.