Biology and anthropology of plant invasions - Invasive Plants: Ecological and Agricultural Aspects - page 215

ously defined as 1) the act of scattering, spreading, separating in different
directions [3], 2) the spread of animals, plants, or seeds to new areas [2], 3)
outward spreading of organisms or propagules from their point of origin or
release [8], iv) the outward extension of a species' range, typically by a chance
event [8]. I defined the dispersal as the search by plant propagules (e.g., seeds,
buds) for opportunity space.

Colonization
The process of colonization includes three activities: recruitment, establish-
ment and reproduction at the new locality. Colonization could be defined as 1)
(of plants and animals) to become established in (a new environment) [2], 2)
the successful invasion of a new habitat by a species [8], 3) the occupation of
bare soil by seedlings or sporelings [8].

Recruitment
Recruitment is the 1) seedling and bud shoot emergence, and 2) the influx of
new members into a population by reproduction or immigration [8].

Establishment
Establishment

is the process of growing and reproducing successfully in a

given area [8].

Enduring occupation of a locality
Several modes of long-term presence at a locality are possible. An invading
species can have an enduring presence for more than one generation in the
same locality. This long-term presence is often facilitated by plant traits that
allow the formation of soil propagule (e.g., seed) pools. A species present in
one locality can also expand its range into new localities.

Local selection and adapted phenotypes

Once a species successfully occupies a local site of some time period, the
action of selection pressures result in local adaptation in favor of particular
genotypes and phenotypes. The selection pressures these populations experi-
ence in the invasion and occupation phases derives from biological, abiotic and
human selection pressures. This local selection also acts on the variable phe-
notypes of that invading species and selects adapted biotypes that occupy that
space into the future. Some of the consequences of this local evolution and
adaptation include increases in locally-adapted phenotypes, range expansion
beyond the locality, and population shifts in the local community as a conse-
quence of altered neighbor interactions.
The biology of the invasion process as presented in this section is rational
and experimentally tractable. What is less apparent is the human component of
the selection process that creates opportunity spaces into which invasive spe-