Transcript Chapter1

WELCOME TO INVASION BIOLOGY
http://www.biologie.unihamburg.de/bonline/d02/acacia.htm
This course investigates the invasive biology of
alien and in some cases indigenous
organisms. The course content includes
definitions; history and globalisation; the human
dimension; characteristics; ecology; impacts;
management; predictions; restoration; national
and international context.
COURSE EXPECTATIONS







make regular use of the discussion forum - trade
ideas and resolve problems
be sure to submit assignments before the due
date - late assignments will not be marked
NB name your assignments using your first
name, leaving no spaces eg sallyalienplants.doc
assignments must be typed in aerial font, size 12,
using 1.5 line spacing
check the course outcomes and the study
questions at the end of each chapter to gauge
your own progress
the educator will check and respond to e-mails
daily between 2-4pm and will be online during
this time for discussion
the educator will make every effort to mark
assignments timeously (within two weeks after
the due date)
•
•
Introduced/alien species: Introduced species are those that
move into an area from which they don’t originate, and have
never previously occurred.
An invasive alien species has most likely been introduced by
human action to an area where it did not previously occur
naturally (i.e. not indigenous).
•
•
•
It is capable of establishing a breeding population in the
new location without further intervention by humans,
Becomes a pest in the new location, threatening the local
biodiversity.
The term invasive alien species is most often applied to
plants and larger animals, but less well-known microscopic
and microbial species can also be invasive.
•
•
The term invasive usually implies harm,
either actual or potential. This harm may
be manifested in ecological, economic or
social impacts.
Some indigenous species may become
invasive under certain conditions, such
as environmental change. This change
often occurs as a result of human
influence
• e.g. Pied Currawongs of Australia
expanded their range drastically in the
20th century because of human
changes to the landscape causing
large declines in populations of smaller
birds that were being preyed upon by
the Currawongs. A good local example
is the Hadeda Ibis
THE NEED FOR DEFINITION





There is a lot of confusion in the scientific
literature, policy documentation and internet
resources around what exactly defines an
invasive species.
The need for a definition for invasive alien
species resulted from a need to control or
manage them.
Many terms have been used interchangeably
to describe the same concept (e.g. nonindigenous, exotic, alien) and other terms
used to describe unrelated concepts (e.g.
invasive, naturalized, imported).
These varying definitions have caused (and
continue to cause) confusion and controversy.
A clear understanding of the key concepts in
biology, ecology and biogeography relating to
invasion of alien species is thus essential.
CONFUSION

Most confusion has been concentrated on the word
invasive (Richardson et al, 2000a). Most widely used
definitions include statements relating to two or more of
the following:



1. The species’ alien status
2. Ability or potential to establish themselves and
overcome barriers to reproduction, dispersal and
population increase in the new environment
3. The ability or potential to cause harm to the
environment and/or human health
Are aliens
from outer
space?
THE TENS RULE
It is estimated that of the species introduced to a
new environment:



10% become established,
of these 10% become invasive,
and of these 10% cause substantial damage.
This is referred to as the ‘tens rule’ (Wiliamson
and Fitter, 1996).
www.jubisha.co.jp/hangten/
Many species have been introduced to new
environments over the centuries, and very few
have become invasive.
TWO MAIN GROUPS OF DEFINITIONS OF ‘INVASIVE’
EXIST, BASED ON DIFFERENT PRINCIPLES:
a) BIOLOGICAL/ECOLOGICAL
PRINCIPLES:

These definitions are objective and
have measurable criteria.

“Invasive species are a subset of
naturalised species that produce
reproductive offspring, often in very
large numbers, are able to disperse
considerable distances from parent
populations, and thus have the potential
to spread over a large area” (Pyšek et al,
2004).
Note that this definition has no
implied impact.
b)ANTHROPOCENTRIC (HUMAN-CENTERED)
PRINCIPLES:


These definitions focus the attention of policy
makers on the biggest impacts:

“Invasive alien species are non-indigenous
organisms that cause, or have the potential
to cause, harm to the environment,
economies, or human health” (Global
Invasive Species Programme).

Many impacts are however not readily
measurable, or if they were then the
problem would arise as to applying a
monetary value.
This definition has however been widely adopted including
Executive Order 13112 of 1999, signed by President Clinton.
ANTHROPOCENTRIC DEFINITIONS - THE PROBLEM
Reliance on human interactions for definitions results in
them often not being consistent, especially when impacts
are both beneficial and detrimental, and species may be
considered a nuisance wherever they occur simply because
they are a nuisance elsewhere (Colautti and MacIsaac,
2004).
http://www.iatge.de/index.html?aktuell/veroeff/ie/lehner92c.html
GENERAL DEFINITIONS (Pysek et al, 2004)
unless otherwise stated:
Invasion ecology is the study of how organisms spread into
habitats to which they are not indigenous (Alpert et al, 2000)

An invasion is the geographical expansion of a species into an
area not previously occupied by it (Vermeij, 1996)

Indigenous species (native): originated, evolved or arrived
(from an area in which they are indigenous) in a given area
without human intervention
Photo: Charl Cilliers

GENERAL DEFINITIONS cont.
•
Alien species (exotic, introduced, non-native, nonindigenous): taxa in a given area whose presence
there is due to human involvement, or which have
arrived there without the help of people from an area
in which they are indigenous. Taxa can be alien to any
definable geographical area, e.g. continents, islands,
bio- or ecoregions, or any political entity (e.g.
countries).
Human involvement in this case does not include
habitat changes, global warming, etc.
Carcinus maenus, the European
Green Crab, was introduced to North
America in the 1800's. This predator
now ranges from Nova Scotia to
Delaware.
Photo Credit: Paul Erickson
GENERAL DEFINITIONS cont.

Cryptogenic species (mostly microscopic taxa or those with
poor taxonomic resolution): species that are not demonstrably
indigenous or alien (Carlton, 1996).
• Note that the term ‘Cryptogenic’ has been mistakenly
used to mean an introduced species whose original
home is not known, i.e. of unknown geographic
origin, even though it is clearly recognized as nonindigenous
www.calacademy.org/
research/izg/SFBay2K/Molgu...
GENERAL DEFINITIONS cont.
Casual alien species: taxa that may flourish and even reproduce
occasionally as aliens outside cultivation or captivity in an area,
but that eventually die out because they do not form selfreplacing populations, and rely entirely on repeated
introductions for their persistence
www2002.stoke.gov.uk/…/pages/chaffinch01.htm
•
The Chaffinch was originally
introduced to the Cape from England
by Cecil John Rhodes. A small
population survives in the vicinity of
Tokai forest, but numbers seem to
be declining.
GENERAL DEFINITIONS cont.
•
Naturalized species (established, feral): alien
species that sustain self-regenerating
populations for a reasonable period of time,
unsupported by and independent of humans
Feral species (usually mammals, birds and fish,
also insects): species that have lapsed into a
wild form from a domesticated one
www.texasoutdoorsman.com/
Staff-Articles/Russe...
•
GENERAL DEFINITIONS cont.
•
Invasive species: a subset of naturalized species that produce
reproductive offspring, often in very large numbers; capable of
dispersal or movement over considerable distances from the
parent populations; have the potential to spread over a large
area
•
•
Note: Organisms should be labelled ‘invasive’ with reference
to a given geographic locality. Organisms that spread
previously, but do not spread currently because the total
range of suitable habitats and landscapes have been
occupied, should still be termed invasive because local
eradication will undoubtedly lead to re-invasion.
Note: This definition infers no connotation of impact,
although many invasive species do have impact.
GENERAL DEFINITIONS cont.
•
Transformers (plants): a subset of invasive plants (not
necessarily alien) that change the character, condition,
form or nature of ecosystems over a substantial area.
Several categories of transformers may be distinguished:
excessive users of resources (water, light, oxygen),
donors of limiting resources (nitrogen), fire promoters or
suppressors, sand stabilizers, erosion promoters, etc.
GENERAL DEFINITIONS cont.
•
Pests (harmful, problem, noxious):
taxa (not necessarily alien) that grow
or live in sites where they are not
wanted and which have economic or
environmental impact or both. For
plants, the term ‘weed’ is used.
DIFFICULTIES IN DETERMINING WHETHER AN
ORGANISM IS INDIGENOUS OR ALIEN:

Taxonomic resolution i.e. whether the species evolved or
migrated into the area without human intervention. In the case
of alien species, they have been moved to an area through
direct or associated human activity. It is not always easy to
determine if a species is indigenous or alien especially if their
taxonomy is not resolved e.g. smaller organisms such as
viruses, bacteria, fungi, algae, protozoa, arthropods and
plankton. Those species without defined taxonomy are
therefore labelled as cryptogenic

Gene level invasions (covered in Chapter 6) and the
spread of alien genotypes (species with different genetic
composition but similar physical attributes to the
indigenous species) within ranges of the indigenous
species. This leads to hybridisation between the
indigenous and alien species, complicates the
classification of a species as indigenous or alien.
Genetically modified versions of indigenous organisms
are often listed under non-indigenous species
The plant on the left side of the
photograph is a natural form of
Arabidopsis thaliana, while that on
the right side is a genetically
engineered variant whose leaf
shape has been modified through
the insertion of a homeobox gene.
DIFFICULTIES IN DETERMINING IF AN
ORGANISM IS INDIGENOUS OR ALIEN:
•
•
Geographic scale: When organisms encroach on habitats
in which they were not previously recorded, they can be
termed colonizers (ecological perspective), invaders
(biogeographical perspective), or weeds (anthropogenic
perspective)
Space and time: A species may well be invasive at one
locality at one time, but not invasive under other situations
ARE INVASIONS BY ALIENS DIFFERENT TO THOSE BY
INDIGENOUS SPECIES?

Although basic processes of geographic spread and increase
in range is essentially the same for both alien and indigenous
species, alien species have certain attributes that make them
need further and closer management attention.

The major differences between indigenous and alien species
are that indigenous species have co-evolved natural enemies,
predators and symbiotic relationships, whereas aliens are
usually without any of these.
 Alien species are therefore at an advantage since they have
left all their natural predators behind (Richardson et al,
2000b).
Chapter 1 Definitions
Next
Chapter 2 History, globalisation and GMOs
Chapter 3 The human dimension
Chapter 4 Pathways of introduction
Chapter 5 Characteristics of invasive alien species
Chapter 6 The ecology of biological invasions
Chapter 7 Impacts of invasive alien species
Chapter 8
Chapter 9
Chapter 10
Chapter 11
Chapter 12
I hope that you found chapter 1 informative and that
you will enjoy chapter two!