Invasive Species 2

Understand the interactions between various species and their environment by studying community measures and parameters.
Familiarize with handouts such as the Examples of Enemy Release.

The introduced fireweed can allocate resources towards growth and reproduction rather than defense mechanisms.

Origin: Native to Eurasia; introduced in 1890 by Shakespeare enthusiasts.
Economic Impact: Causes agricultural losses and disease transmission (bacterial, fungal, affecting humans and livestock).
Parasitic Worms: 79 species present in their native range; only 35 in North America.

The removal of natural enemies leads to increased competitive ability for the invasive species.
Example: California Poppy
- Conducted a common garden experiment comparing native poppy populations from California with those that invaded Chile.
- Findings: California natives were smaller when grown alongside Chile invaders because they allocated more resources to defense (more trichomes, etc.).

Invasive Lady Beetle in British Columbia
   - Parasitism Rates:
     - Invasives: 4.6% parasitism (due to microsporidia fungal infection)
     - Natives: 32% parasitism
   - Explanation: Natives may have not evolved with these parasites, resulting in higher rates of parasitism.

Removal of enemies leads to selection for increased competitive ability.
Example: Yellow-star thistle
- Displays anti-herbivore defense mechanisms including production of chemicals, thorns, trichomes, and phytochemicals (like phenolics, latex) which serve to reduce herbivory.
- Over time, invasive species exhibit reduced expression of these defenses leading to a shift in resource allocation from defense to competition.

Mutualistic Facilitation: Invasive species may depend on mutualists, while recipients may accommodate new mutualists from the local region.
Positive Feedback: Illustrated by Old World Bluestems; the introduction changes microbial community which inhibits native growth, thereby enhancing the success of the invaders.
Invasional Meltdown: The occurrence where one invasion facilitates another.
Empty Niche Hypothesis: Gaps left open in the ecosystem can be filled by invasive species.
Novel Weapons Hypothesis: Can be understood through classic studies like that of Ragan Callaway focusing on Spotted Knapweed in the US. This invasive species exhibited larger growth due to allelopathic chemicals which inhibited germination of native species.

Natives can serve as biotic filters that resist invasion through various mechanisms.
Exploitative Competition: Native pine trees have been shown to repel non-native pine trees in Argentina, although further planting increased non-natives.
Predation: Native red rock crabs consume non-native green crabs off the coast of Oregon, although green crabs out-reproduce the natives.
Mutualism: Non-native fig trees fail to establish in Florida without the necessary mutualistic fig wasps.

Biotic Resistance: Interactions with other species can provide resistance against invaders by way of enemies or competitors.
New Associations: Invasive species may face challenges from their ecological interactions.

Was the species introduced by human activity?
What impacts has the species had? Consider human health, biodiversity, and more.

Negative impacts on new ecosystems.
High adaptability signals that it might be invasive.
Highly competitive nature.
Generalist and r-selected biological traits indicating rapid reproduction and generational turnover.

Resource allocation strategies of the species.
Presence or absence of natural enemies that may assist in its establishment.
Specific adaptations that correlate with the discussed hypotheses.
Traits at the population level that indicate invasiveness.
Mechanisms of introduction (human involvement, ecological disturbances).
Potential for monopolization of resources (monoculture scenarios).
Climate matching criteria indicating the invasive species' spread potential.
Dependence on human-intervention for survival and proliferation, and its ability to spread independently.