Transcript Native and Invasive Plants

Native and Invasive Plants
Invasive plant
•
Ability to spread aggressively outside its
natural range
• Especially in new habitat
Invasive plant
•
Lack insects, diseases and foraging animals
Where are they a problem?
Disrupted habitats
• Thrive on
disturbed sites like
construction areas
and road cuts
Why are they a problem?
•
Threaten native plants and animals
• Insects, micro-organisms, birds, etc…
•
Alter habitats and reduce biodiversity
Native Plants
Plants growing here for a long time
 >500 years
◦ Christopher Columbus (1492)
Native Plant Databases
http://www.se-eppc.org/southcarolina/
 http://www.scnps.org/
 http://www.namethatplant.net/
 http://www.wildflower.org/collections/coll
ection.php?start=0&collection=SC&pagec
ount=10&pagecount=100
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Biodiversity

The diversity of animals is linked to the
diversity of plants
◦ Greater number of plant species means less
competition and increased niches
Biodiversity
2.5 acres of Amazonian rainforest
supports 473 species of trees
 Only 134 species of trees in Pennsylvania

Biodiversity
Trophic level is the position an
organism occupies in food chain.
First trophic level: Plants

Plants capture sun’s energy and turn it
into food for the rest of us
Biodiversity
Second trophic level: Herbivores

Transfer energy from plants to predators
and parasites in higher trophic levels
◦ Mainly insects
Biodiversity
Worldwide, 37% of animal species are
herbivorous insects
 Pound for pound, insects contain more
protein than beef
 96% of birds rely on insects and spiders
to feed young

Keystone Species

Keystone species essential role in
maintaining diversity
◦ Robert T. Paine research

Tidal pool on Pacific Coast
◦ Simple ecosystem
Keystone Species
Simple Ecosystem
◦ Rivet example

Some rivets on airplane more important
than others
◦ Seat versus engine
Keystone Species
Simple Ecosystem
 Removing some species had little effect
on populations of remaining species
 But removal of a predatory starfish
(Pisaster ochraceus) caused a collapse of
half the remaining species’ population
Keystone Species
Complex System
 No central players
◦ Jenga example

How vital a
block’s role to the
tower’s stability is
based on the
presence of other
blocks
Keystone Species
Complex System
 Every time block is removed, role and
importance of other blocks changes
 Almost any species can be a keystone
species depending on circumstances
Trophic Cascades
The impact on other species when
removing a keystone species
◦ Predator example
Yellowstone wolf population reduced
 Moose spend less time looking around

◦ More time grazing
Overgrazing led to erosion, impacting
streams, fish, plants, etc.
 http://www.twp.org/

Non-Native (Alien)
Aliens colonize areas faster than natives
 Alien plants interact minimally with
ecosystem and pass along very little
energy to herbivores (2nd trophic level)

Non-Native (Alien)
“Pest-free” ornamentals are primarily
selected for landscape
 It takes time for insects to adapt to
specific chemical composition of leaves

Non-Native (Alien)
Paperbark tea tree
introduced to
Everglades in 1900
 Presently, 8 species
of arthropods feed
on leaves, opposed
to 409 back in
Australia

Non-Native (Alien)

90% of herbivorous insects are specialists
that have evolved with a plant
Non-Native (Alien)

Insects develop ability to overcome
physical and chemical defenses of host,
but limited to feed on that host only
◦ Mainly due to leaf chemistry

Insects develop enzymes that detoxify
chemistry
Non-Native (Alien)
Tannins in oak leaves would bind protein
if we eat them, starving us
 Lima beans contain cyanide unless boiled
 Cucumber leaves are lethal

Non-Native (Alien)
10% of insect
herbivores are
generalists that eat
several types of plants
 Ability to produce
very powerful gut
enzymes called
mixed-function
oxidases
 Feed on many alien
plants, but not
enough

Non-Native (Alien)
Compare diversity and biomass of insects
on 4 woody natives versus 5 aliens
 Native plants produce 4x more biomass
 Supported 3.2x more species
Non-Native (Alien)
Compare diversity and biomass of insects
on 4 woody natives versus 5 aliens
 In terms of caterpillars (most important
to birds), 35x more than alien plants
 Natives produced 2x as many generalists
Non-Native (Alien)


A plant can become
native regardless of
origins
Norway maple
introduced from Europe
in 1756
 Still has few insect feeders
 Compare to 80 millions
years of coevolution, 250
years isn’t much
Non-Native (Alien)
Native applies to local regions
 Human influence is too rapid for adaption

Non-Native (Alien)
Birds eat fruit after reproduction
 Most species depend on insect protein
for egg laying and feeding young and
nesting

Non-Native (Alien)
Non-invasive qualities of alien does not
make it native
 Clematis vitalba introduced 100 years ago
 Supports 40 herbivores in homeland but
only 1 after 100 years since introduction
here
http://www.wildflower.org/collections/
 http://www.wildflower.org/collections/coll
ection.php?start=0&collection=SC&pagec
ount=10&pagecount=100
 http://www.se-eppc.org/
 http://www.dnr.sc.gov/invasiveweeds/illega
l1.html
 http://www.scnps.org/
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
http://arstechnica.com/science/2013/03/by
-building-fairy-circles-termites-engineertheir-own-ecosystem/
Fragmentation Biological Dynamics of
Forest Fragments Project
 Island ecosystem stability
 http://www.stri.si.edu/english/research/faci
lities/affiliated_stations/bdffp/
