Documenting the flora of a diversity hotspot: Richard Thomas Lowe (1802–1874) and his botanical exploration of Madeira island

Abstract

AbstractOceanic island floras often exhibit remarkable concentrations of endemic diversity, provide spectacular examples of rapid evolutionary radiations and harbour floras under significant threat due to anthropogenic pressures. They have attracted the interest of biologists for centuries, but their floras continue to yield new taxa and, at a global scale, the extent of their plant diversity remains imperfectly known. Both natural characteristics and historical factors have shaped the development of knowledge of island floras. In this paper, we investigate the approach of Richard Thomas Lowe (1802–1874), to documenting the flora of Madeira island in the North Atlantic. Lowe collected abundantly in Madeira between 1826 and 1873, resulting in several works on Madeira's flora, published from the 1830s. At a time when taxonomic research on island floras was often based on limited collections made during brief expeditions, Lowe's research on the flora, spanning almost half a century, was exceptional. In this study, 2579 herbarium specimens collected by Lowe were georeferenced and used to investigate temporal, spatial and taxonomic patterns in Lowe's collecting activities. We also examine the distribution of specimens by Lowe to other botanists. Some biases are evident in Lowe's collecting efforts, with steep slopes under‐sampled and coastal sites over‐sampled. These reflect constraints imposed by topography and transport links. These limitations aside, Lowe's work on the Madeiran flora was conducted in a systematic manner, resulting in a comprehensive study of the entire flora. His approach was distinctly modern: he gathered and studied all available information in herbaria and in the published and unpublished writings from earlier visitors; his initial fieldwork was conducted widely to gain knowledge of all habitats and their floras; later fieldwork focussed on less‐explored and most promising areas; duplicates were sent to other botanists, facilitating taxonomic exchanges on critical taxa; and his later fieldwork focussed on plant groups where taxonomic problems had been detected. As a result of Lowe's sustained and systematic approach, he is the single most prolific contributor to the study of Madeira's endemic flora. His approach is a model to documenting island floras still relevant today. Areas poorly sampled by Lowe were areas that were difficult to access, which also protected them from anthropic destructive activities and allowed them to serve as refuges for endemic flora. Those areas deserve particular attention in efforts to complete the survey of Madeira's plant diversity, using technological advancements such as drones to prospect areas that are otherwise still largely inaccessible.