‘Aliens’, ‘Natives’ and ‘Artificial Habitat’- Revisiting the Legacies of H.C. Watson and S.T. Dunn

Nimal R. Chandrasena

Keywords:

‘Aliens’; H. C. Watson; S. T. Dunn; ‘invasive species’; invasions; weeds

Abstract:

Hewett Cottrell Watson, a British botanist and phyto-geographer, might rightfully be the first to apply the term ‘alien’ to denote ‘foreign’ species introduced to Britain, which successfully established at various locations in the isles with or without man’s help. Botanists recognize Watson for his monumental work Cybele Britannica, written in four volumes over 12 years (1847-1859). While applying the term ‘alien’, along with ‘natives’ (indigenous species), ‘denizens’ (long-term residents, introduced species, who might be considered ‘naturalized) and ‘colonists’ (species, colonizing agricultural land and habitat occupied by humans), Watson discussed in detail how difficult it is to assign ‘nativeness’ to any species. Stephen Troyte Dunn, who wrote ‘Alien Flora of the British Isles’ in 1905, partly adopted H. C. Watson’s categorization of species. Both worked without much knowledge of the geological and fossil evidence of plants but agreed that all species, even ‘natives’, may have been immigrants sometime in the past. All of Watson and Dunn’s ‘alien’ species have several things in common. They are all highly productive (fertile), pioneering or colonizing taxa, which can establish and thrive in disturbed environments (‘artificial habitat’, sensu S. T. Dunn), from which they perpetuate themselves. Knowledge about the ‘foreign’ components of a country’s flora is ecologically important to understand how species adapt to new environments and influence others. Both Watson and Dunn emphasized the remarkable ability of some introduced to spread, unassisted by man’s activities, while others, like ‘shadows of men’, appear to ‘follow the plough’. The ‘colonization process’ of these highly successful plants gets them into trouble in the minds of some, who prefer to attribute other meanings, such as ‘invasions’ to these “foreign” species. A dip into history shows that Watson and Dunn discussed introduced plants without disparaging them. Like humans, colonizing taxa are good at what they are genetically predisposed to do, i.e., adapt and survive even under stressful environments. They are no more ‘alien’ than we are. They are also no more ‘invasive’ than we are. As one historian (Alfred Crosby) noted, these species may even help heal the wounds on the earth, torn apart by the real ‘invaders’ – those ‘wretched ingrates’ (humans).