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LECTURE OVERVIEW

Basic statement:

Humans are increasingly moving about the world. As they do so, they may either accidentally or intentionally introduce organisms, including plants, into places in which they have never occurred. Sometimes these introductions are harmless, but many times the introduced organisms negatively affect native species and ecosystems.

Key ideas:

In the last few centuries a number of plants have been introduced accidentally through the inclusion of weed seeds in imported crop seeds, on or in imported animals, or in soil from other countries that was loaded onto ships as ballast and then dumped here in exchange for cargo. Non-native plants have also been introduced intentionally for ornamental and agricultural purposes. Most introduced plants do not establish and reproduce, but many do form extensive "natural" colonies and are considered "non-native invasive plants." These invasive plants compete with native species for resources such as light, water, nutrients, pollinators, and seed dispersers. They may also alter hydrology, geomorphic processes, and disturbance frequencies and intensities in native ecosystems, all of which can severely affect native species. Non-native invasive plants are considered to be a significant threat to biodiversity.

Important terms:

Non-native invasive plants

Biological invasions

Restoration

LECTURE OUTLINE

Introduction:

Definitions: (from:Executive Order on Invasive Species, Feb 4. 1999)

• "Alien species" means, with respect to a particular ecosystem, any species, including its seeds, eggs, spores, or other biological material capable of propagating that species, that is not native to that ecosystem.
• "Ecosystem" means the complex of a community of organisms and its environment.
• "Introduction" means the intentional or unintentional escape, release, dissemination, or placement of a species into an ecosystem as a result of human activity.
• "Invasive species" means an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.
• "Native species" means, with respect to a particular ecosystem, a species that, other than as a result of an introduction, historically occurred or currently occurs in that ecosystem.
• "Species" means a group of organisms all of which have a high degree of physical and genetic similarity, generally interbreed only among themselves, and show persistent differences from members of allied groups of organisms.

What is the Problem? (Some examples)

• Displace native species (change biodiversity): better competitors, aggressive seed dispersal and vegetative propagation
  

Change ecosystem properties or processes Tamarisk, Saltcedar (Tamarix spp.): changes hydrology : deep rooting tree or shrub that removes large amounts of water from rivers-- dries riparian areas and excludes native species Malaleuca quinquenervia: changes fire regimes (forms dense stands in wetlands): is highly flammable, causing fires were they normally were rare.

inflorescence of T. parviflora

shrub of T. parviflora

• Pathogens: native species are not resistant to the disease-causing agent (examples for trees)
• Dutch elm disease (Ophiostoma ulmi)
• White pine blister rust (Cronartium ribicola)
• Chestnut blight (Cryphonectria parasitica)
• Balsam wooly Adelgid (Adelges piceae)
• Alter genetic make up (change evolution)
• Alien white mulbery (Morus alba) hybridizes with the native red mulberry ( Morus rubra) and coul eliminate native species by "genetic swamping"

How did the problem arise?

1. International Trade: inadvertent
   example: Dutch elm disease probably came in shipment of elm veneer from Europe
2. International Travel: inadvertent
3. "Reclamation"-- effort to "improve" environmental conditions
   examples: Lombardy poplar planted as wind row (not invasive)
   Tamarisk introduced as source of wood, shade, as an ornamental and for erosion control
4. Economic-- new crop tree
5. Aesthetic: Horticultural importation
   examples: scotch broom, European Mountain ash, tamarisk

Control/Management

1. Exotic pests: bring in biological control agent that "controls" invasive species in its native range:
   example: Saltcedar leafbeetles from China eat Tamarisk. What if beetles cause additional problems
2. Inspection/restrictions on travel and trade"
   example: trade restrictions on Siberian wood to prevent introduction of pests
   inspect vehicles (bottom of boats for aquatic plants)
3. Genetic breeding: selectively breed trees for resistance against exotic diseases (mimic disease resistance mechanisms in hosts where disease is native)
   example: white pine blister rust, Dutch elm disease??
   

4. Eradication: physically remove plants example: Attempts with tamarisk have limited success

Spring Lake before treatment

Spring Lake after treatment

4. Herbicides: chemically kill plants
example: Environmental and health concerns

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