Invasive Species

Competition 

for space and resources with native species

Predation

rats, cats, and mongoose account for 43% of recorded bird extinctions

Disease

50% of native Hawaiian birds extinct due to avian malaria

Invasion meltdown

occurs when invasive species allow increases the rate of establishment of other invasive species in the same ecosystem

a community-level phenomenon

disturbance and more invasive species in a cycle

The invasional meltdown hypohtesis predicts

• More rapid population growth for interacting invasive
  • greater impact on the native community
  • increased establishment of other introduced species

Diverse ecosystems resist 

invasive species and diseases because more niches filled 

Not every introduced species becomes invasive

• exotic species/non indigenous/alien: from another part of the world

• acclimatized species: has adapted to new environment

• Naturalized species: well established but not a threat

Invasive species

expanding range and population

a threat to native species

Do invasive species evolve

Collected seeds from source trees in China(native
range), Georgia, Texas and Louisiana.
• grown in field for 14 years and then measured
size, seed production, leaf chemistry and defense
chemicals.
• Invasive genotypes, especially those from recently
colonized areas, were larger than native
genotypes and more likely to produce seeds but
had lower quality, poorly defended leaves.