Dispersal Mechanisms Worksheet Key

Faculty of Food and Agriculture

Department of Food Production

ENRM 1004: Ecology and Microbiology

Dispersal Mechanisms Worksheet

NOTES:

There are two critical stages in the life cycle of a flowering plant:

1. The transfer of pollen from anther to stigma. Most flowering plants have different types of mechanisms to promote the transfer of pollen from an anther in one flower to a stigma in a different flower, and hopefully this flower will be on a different plant.

2. The dispersal of seeds away from the parent plant.

Plants often solicit the aid of animals, as well as abiotic forces such as wind, to accomplish both of these. With regard to dispersal:

insects insects much less important for dispersal than pollination, but ants often involved in dispersal

birds, mammals, reptiles, and even fish much more important for dispersal than pollination

wind important in both pollination and dispersal

water minor importance in pollination, somewhat greater in dispersal

self-dispersal just like some plants carry out self-pollination, some plants have mechanisms for self-dispersal.

Why is dispersal important?

Avoid competition with parent and siblings

Colonize new habitats

Avoid pathogens and predators

Minimize inbreeding

Units of Dispersal Different plant parts become modified for dispersal.

Seeds are the units of dispersal, and the seeds are released from the fruits ready for dispersal.

Fruits, or parts of fruit, for dispersal.

Other structures sometimes modified for dispersal ovary wall, style, sepals, hypanthium, receptacle, bracts, even whole plant.

The term DIASPORE is used for the unit of dispersal, no matter what it is morphologically,

Methods of dispersal are often tied to certain habitats

Wind prairie/grasslands, mountains, forest trees, weedy areas, most parasitic plants

External attachment to animals forest plants relatively low to ground and even pasture species

Ingestion by animals forest plants, passed through digestive tract of animals

Water plants that grow in wetlands and along streams and float; also transported by irrigation

Ballistic various; some parasitic plants, some forest plants, some weedy plants

Types of Dispersal

Wind Dispersal

Water Dispersal

Animal DispersalPassive

Animal DispersalActive

Mechanical Dispersal

Human Dispersal

Dust-like seeds

Tiny seeds

Samaras

Plumed diaspores

Woolly diaspores

Balloons

Roller plants

Splash cups

Sea currents

Streams

Simple adhesion

Awns, hooks, & barbs

Carrying & caching

Ants (elaiosomes)

Ingestion

Ballistic fruits

Shaker fruits

Hygroscopic

Short-distance dispersal, eg farm machinery.

Long distance dispersal, purposeful or accidental.

Videos

After watching the two videos on invasive species: Invasive exotics in South Florida and Strange days on Planet Earth Invaders answer the following questions:

Bear in mind the following rule:

Tens Rules

For every 10 species imported ---> 1 will be introduced In the 10 introduced --> 1 becomes established Of every 10 established --> 1 becomes a pest Invasive

1. What is an invasive species?

Is non-native and causes economic or environmental harm

2. What are three synonyms of non-native?

exotic, alien, nonindeigenous

3. Name 6 ways humans spread invasive species:

1) trade2) agriculture3) biological4)pets5) accidental

4. Name three ways that an invasive species can cause harm to native species:

1) can be a superior predator2) can overcrowd an organism3) can prey on an organism

5. Name 4 ways invasive plants can be dangerous:

1) displace native plants that once gave food and shelter to native species2) compete for nutrients, sun, space3) increase fire danger by providing more fuel4) affect erosion and flood levels

6. What are two reasons invasive species can spread so rapidly?

1) no natural predators2) utilize unused resources

7. What are some ecological impacts that invasive species have?

Reduces biodiversity and reduces resources available to natives

8. What are some agricultural impacts that invasives have?

Harmful to human food sources

9. What are some ways invasives are harmful to forestry in your country?

Can ruin timber industries in some areas

10. Why does Florida and other Caribbean Islands have so many invasive species?

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11. List some of the invasives found in the Caribbean that have become of increasing concern over the past few years:

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12. Name some ways in which invasive species can be controlled.

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