Can the distribution patterns of plants used by humans as food give clues as to whether they are native or introduced?

Abstract

The discovery that Arbutus unedo (Strawberry Tree) was probably introduced to Ireland and Wales by pre-Bronze Age copper miners about 2,400 BC (Sheehy Skeffington & Scott, 2021) has led me to consider whether the distributions of other British and Irish plants might have been extended by the activities of early humans, including hunter-gatherers. Three species have been chosen for study, Blitum bonus-henricus (L.) Rchb. (Good-King-Henry), Bistorta officinalis Delarbre (Common Bistort) and Lathyrus sylvestris L. (Narrow-leaved Everlasting-pea). These have contrasting distributions. The tetrad distributions of the three species were examined for areas where the distribution is coherent, suggesting native status, or broadly random, suggesting introductions. Individual localities were studied for a sample of vice-counties. Natural dispersal methods were also studied as were the likely uses by humans. It was concluded that the Blitum is an archaeophyte that had been introduced as a vegetable by early farmers in the Neolithic or Bronze Age. The Bistorta is a native species that survived the woodland invasion following the Ice Age in refugia in the north of England and, when woodland cover was reduced by man in the Neolithic and Bronze Age, recolonised only limited areas where it came to be used as a vegetable. It was later widely introduced elsewhere as a medicinal plant. The Lathyrus is a native species that had probably been harvested as a vegetable by man in the Mesolithic Age, and cultivated from the Neolithic or Bronze Age. Introductions from other sources were also probable.