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Lecture 7

BIOC63Fall2013 Lecture 7 Notes.docx

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Biological Sciences
Karen Williams

BIOC63Fall2013 Lecture 7 Notes: Invasive Species Invasive species (biotic exchange)  Expected changes for 2100 in the main 5 drivers of biodiversity change  o Biggest biotic exchange in the Mediterranean  most threatened by invasive species Definitions  Native species o Native to a given region if its presence there is a result of only natural processes, without human intervention  Introduced species o Not a threat to ecosystems in their introduced range  Invasive species o Are a threat to native competitors in an introduced range Biological invasion  Natural phenomenon  Hugely sped up after industrial revolution and increased travel in he 20 century Scale of invasion, continental o Native and introduced plant species richness o  Ontario has the highest percentage of established alien species 32% o o Most of those are plants o 4% mammals  starling, house sparrow, mouse, rate o examples of non native birds  house barrow, starling 1 o o Ontario, QB and BC have the most introduced plants by province/territory   islands have higher percentages of alien species Pathways of plant introductions in CA   typical course of invasion o intentional introductions  mostly ornamental or landscaping plants o unintentionsal introduction  with plant products 2  i.e. contaminated in seeds, wood, garden supplies etc. Typical pattern of invasive establishment o o nominal time in years, is not fixed for all invasive species to 25 years as in this graph  it could be higher o reach peak population at carrying capacity (when they have taken up all the niches that they can occupy)  invasive establishment is extremely rapid until it hits a peak populationlog growth Reasons for ecological success Enemy Release Hypothesis (ER)  native species frequently out competed   generalist enemies will feed on native competitors and less on the study species, allowing the study species to thrive and outcompete the native competitor   no evolutionary change  no change 3  i.e. only 3% herbivory on DSV but up to 14% in MW change occurs  no change  fungi and viruses o most plant species looked at in this experiment have higher levels of pathogen by fungi in thei native range than in their introduced range o o the fungal load drops to very very little in the neutralized range and very few fungi from neutralized range can feed on the plant species Evolution of increased competitive ability (EICA) o evolution to invest less in defense  toxin, hairs, spikes o evolution to invest more ino growth and reproduction o significant decrease in
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