Invasive species Flashcards
How are species introduced to new locations?
Acclimation societies, botanical gardens, zoos etc.
Agriculture
Biological control
Erosion control
Forestry, agroforestry
Horticulture / ornamental / nursery
Intentional release
Military
Transportation of animals, food, habitats, pets, etc.
How are plants, mammals, birds and reptiles introduced to new locations?
Plants: mainly horticulture / ornamental, forestry and agriculture
Mammals: mainly through transportation and intetional release
Birds: mainly through transport, intentional release or biological control
Reptiles: Transportation and biological control
4 classifications for non-native (alien) species
Casual
Naturalized
Invasive
Transformer
classification - casual
non-native plants that can reproduce but not disperse widely, usually persisting only through human assistance (wether for agriculture or as ornamentals)
classification - naturalized
plants that are self-sustaining at the original point of establishment and which can disperse but not dominate a habitat
classification - invasive
naturalized species that expands from the site of original arrival into intact or semi-intact vegetation (regardless of demonstrated impacts); usually becomes a significant component of the habitat
classification - transformer
an invasive species with significant ecological impact
Traits associated with invasiveness of plants
fitness
size
growth rate
shoot allocation
leaf-area allocation
physiology
What makes a species invasive? (possible factors)
Geography of origin
Taxonomy (phylogeny and history of invasions by family/genus)
The ability to reproduce both asexually as well as sexually
Consistency in fecundity
Fast growth
Short time to reproduction
Seed size (smaller = more invasive)
High dispersal ability
Phenotypic plasticity and rapid evolution
Tolerance of a wide range of environmental conditions (generalist)
Ability to live off a wide range of food types (generalist)
Association with humans
What makes an ecosystem susceptible to invasion?
Propagule pressure: the number of alien propagules available
Species diversity
Disturbance
Changes in nutrients or resources
Lack of natural predators of non-native species
Brown tree snake - Boiga irregularis
Accidental introduction to Guam Island (W. Pacific)
Generalist predator: Juveniles mainly feed on lizards and amphibians (in particular, frogs); adults prey on birds, mammals (bats, pets). (Westbrook and Ramos 2005).
Egg clutches of 10 or more
Can reproduce year-round in tropics
No natural predators in Guam
Miconia calvescens
Native to tropical America
Imported to Tahiti in 1937 as an ornamental
Flowers and fruits multiple times per year -Multiple growth forms
Early reproduction, massive fruit loads, tiny seeds
Bird dispersed fruits
Seeds can be dormant in soil
Large leaves shade out native vegetation
Covers >65% of the Tahitian islands!
Falcataria moluccana / Paraserianthes falcataria / Albizia falcataria
N-fixing legume
Planted for agroforestry / forestry
Extremely rapid growth (6 cm DBH / yr)
High seed production
Increased nutrient cycling rate (positive reinforcement like many invasives)
Increases N and decreases P availability in soil
Results in “fundamentally new and different ecosystems”
Which control measures work best on invasive plants?
Out of burning, cut and/or removal and herbicide, herbicides are the most effective treatment on invasive plants
