Alien plants in checklists and floras: towards better communication between taxonomists and ecologists

Invasion ecology is one of the most rapidly developing branches of ecology (Williamson, 1996; Rejmánek & al., in press). Recent developments in this field have brought about the need to standardize terminology (Richardson & al., 2000). The awareness of the importance of biological invasions dates back to De Candolle (1855) and Darwin (1859), but the field was set on firm ground in the middle of the 20th century by the work of Charles Elton (1958), followed in the last quarter of the century by international programs, notably those co-ordinated by SCOPE (Drake & al., 1989) and the Global Invasive Species Programme (GISP; Mooney, 1999; Mooney & Hobbs, 2000; McNeeley & al., 2001). Plant geographers studying plants associated with people have given attention to issues of terminology since the 19th century (Thellung, 1905, 1918/1919; Holub & Jirásek, 1967; Schroeder, 1969), well before invasion ecology was recognized as a subdiscipline of ecology, and before basic knowledge of the processes driving invasions started to be accumulated. The past few decades have seen a rapid increase in the number of studies devoted to plant invasions, but the accumulating body of knowledge has unfortunately also spawned increasing confusion in terminology (Pyšek, 1995; Richardson & al., 2000). The search for a precise lexicon of terms and concepts in invasion ecology is not driven by concerns of just semantics. Invasions are a global phenomenon and comparison of geographically distant regions and their introduced biota is a crucially important methodological Alien plants in checklists and floras: towards better communication between taxonomists and ecologists