A willow drawing from 1786: the earliest depiction of intraspecific trait variation in plants?

Background and Aims:

The study of intraspecific trait variation (ITV) in plants has a long history, dating back to the 4th century BC. Its existence was widely acknowledged by the end of the 18th century, although systematic and experimental studies commenced only a century later. However, the historiography of ITV has many gaps, especially with regards to early observations and visual documents. This note is a contribution to fill that gap.

Methods:

The botanical works of Johann Wolfgang von Goethe (1749-1832), a German writer and naturalist, were subjected to close reading. This included all publications and unpublished sources related to botany between 1785 and 1832 (e.g. notes, drafts, diaries, letters, drawings). This material is accessible in the multi-volume historical-critical edition of Goethe’s studies in natural science (“Leopoldina-Ausgabe”).

Key Results:

A diary entry from 9 September 1786 described changes in leaf morphology along an elevation gradient in the Bavarian Alps. The leaves of an unidentified species of willow (Spix sp.) and gentian (Gentiana sp.), respectively, were said to become narrower with increasing elevation; leaves also stood further apart on twigs, and the latter became thinner. A crude drawing of two willow twigs illustrated the differences. Goethe conjectured that the differences were due to environmental conditions.

Conclusions:

Goethe’s notes were anecdotal, and it is unclear whether the observed plant individuals actually belonged to the same species. Nevertheless, the notes represent an early and clear articulation of the hypothesis that changes to environmental conditions can cause ITV in a natural plant population. The drawing may be the earliest visual record of environmentally-mediated plant ITV in the wild.