envs 100 lecture 13

envs 100 lecture 13 - Today Why are invaders sometimes...

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Today • Why are invaders sometimes harmful? • Restoring invaded ecosystems • Web of Science, Google Scholar 1
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What is exotic? • Everything is native to somewhere • An historical change in rate • Exotic vs. invasive vs. harmful • A spectrum: – Transcontinental (within and across) – Human-assisted range shifts – Human-caused range shifts
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Why do exotics act out away from home? Pampas grass in Uruguayan steppe; Caspian sea beach, no sign of zebra mussels 3
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Enemy release hypothesis Escape from predators and diseases that limit populations at home Evolution of Increased Competitive Ability (EICA) After enemy release, species can evolve reduced investment in defense, increased competitiveness 4
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EICA and purple loosestrife • Plants in U.S. released from weevil • In lab, U.S. plants grow bigger than European plants, have less resistance to weevil 5
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Novel weapons hypothesis Hosts or prey in introduced range lack resistance to the invader 6
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Novel weapons can have severe consequences White-nose syndrome, N. American bats Chytrid disease, global amphibians Has affected 30% of the world’s amphibian species already; problem emergent max 25 yrs ago; source unclear – Japan, Africa? The worst global vert biodiv loss to a disease in history of Earth? 7
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Novel weapons can have severe consequences Rats, cats on islands (pic on R Tasman Island by cat. About 100 there). Have caused many, many extinctions worldwide on islands–of seabirds, reptiles, mammals, land birds.
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envs 100 lecture 13 - Today Why are invaders sometimes...

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