INVASION of the ALIENS! Science or Pseudoscience? by David I. Theodoropoulos
Las Sombras Biological Preserve, Box 337, La Honda, CA
"Alien invaders" are a hot topic. In his book "Alien Invasion" Robert Devine vilifies botanic gardens- Quote:
"Kanapaha, like almost all botanic gardens, is loaded with invasive exotics…By helping fuel the alien invasion, botanical gardens give legitimacy to the dangerous status quo… most botanic gardens are oblivious to the issue of invasive species…"
He claims that you have "a reluctance to discontinue sales of exotic plants that have been big moneymakers" for botanic gardens (Devine 1998:206-208).
Unfortunately, invasion biology, with its irrational fear of the movement of species, is a century out of step with ecological science.
Natural dispersal has been frequent, long-distance, and beneficial (Section Title Slide) (Axelrod 1959; Clark 1988; Clark et al. 1989; Crow et al. 1988; Darlington 1957; Darwin 1948; Davis 1983; Davis 1988; Elias 1994; Elliott-Fisk 1988; Gleason & Cronquist 1964; Kuc 1995; Menard 1974; Munz & Keck 1959; Neill 1969; Orban 1995; Paus 1995; Peglar et al. 1989; Simpson 1942; Thornton 1971). Dispersal is essential to maintaining biodiversity, and has been a powerful driving force of evolution (1).
(Text Slide) Contrary to the antiquated and discredited ecology on which invasion biology rests, natural biota are not coevolved, tightly-integrated, perfectly balanced systems. (Text Slide) All evidence from modern ecology and paleobiology indicates that current species assemblages are recent, non-coevolved aggregations, that species disperse independently, and species interactions form and dissolve readily (Davis 1983; Kellman 1980; Lawton 1998). (Text Slide) All extant species assemblages are resilient and are accustomed to integrating new members (Vermeij 1991). The fossil record is clear (Text Slide) - invasion increases biodiversity (2), and the experimental record indicates that the greater the rate of invasion, the higher the diversity of the resulting assemblages (Robinson & Edgemon 1988). As Turner (1996) stated, "life evolves at the edge of chaos, the area of maximum vitality and change."
(Text Slide) Invasion is identical to entirely natural processes - note this dense, invading monoculture (Photo Slide) - this is our native bracken fern [Pteridium aquilinum] (3). No scientific model can distinguish this from an "alien" invasion. (Text Slide) Again and again, we find "invaders" to be disturbance indicators only, symptoms of industrial abuse of the land (4), integrating ecologically, and with many beneficial effects that are carefully ignored by those promoting a "crisis" (Colwell & Dodd 1995; Essink & Dekker 2000; Francour et al. 1995; Holland et al. 1995; Kuuispalo et al. 1995; Marshall 1991; Peles et al. 1995; Sagoff 1999; Stewart & Samways 1998).
(Text Slide) The data indicate that in all cases, including even the oceanic islands, anthropogenic dispersal has increased biological diversity (Baskin et al. 1995; Harrison 1999; Harty 1993; Hickman 1993; Klick et al. 1989; Moulton & Pimm 1986; Simberloff 1986) (5). The alpha diversity of species counts has risen, beta and gamma diversity have increased, and phylogenetic omega diversity has risen. Novel assemblages have formed, new functional and structural elements have been added to landscapes, and entirely new ecological interactions have arisen.
Anthropogenic dispersal is an essential conservation strategy - at-risk clades need to be naturalized in new regions to prevent extinction, and hyperdiverse preserves established (Theodoropoulos 1993, 1999). There are no theoretical limits to diversity (Cornell & Lawton 1992).