Lecture+22+-+Biodiversity+posted

Lecture+22+-+Biodiversity+posted - Biodiversity: The 3 BIG...

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Biodiversity: The 3 BIG questions 1. Maintenance - what allows the coexistence of so many species in one habitat? 2. Origin - What causes large scale biogeographic patterns in diversity? 3. Function - Why care about biodiversity?
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Maintenance of diversity: what do we already know? Species coexist when: 1. Species partition resources (intraspecific competition is strong relative to interspecific competition) -this can be resources in the strict sense (food, nutrients) -partitioning of space (high vs. low intertidal) -partitioning of time (different seasons, years, stages of succession) 1. Environments change (or a disturbance happens) faster than the time required for competitive exclusion (seasonality, yeaer to year variation, small-scale disturbance)
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Increased nutrients leads to higher productivity and biomass, but decreased diversity and increased dominance More resources does NOT mean more species : Rothamsted, England Initially, the most abundant species made up only 15% of all biomass After 100 years of fertilization, one species dominated After 50 years of fertilization, one made up half of total biomass Relative abundance __adding resources has actually decreased diversity. This is called the “paradox of enrichment”
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Coexistence can occur when species specialize on different resources to minimize competitive overlap Or when species specialize on a particular type of habitat or time of year (spatial or temporal resource partitioning) __more resource types, not necessarily more resources_______
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Niche partitioning allows species to coexist, leading to increasing diversity when habitat (or resource) diversity is high MacArthur and MacArthur (1961) More niches in forests of diverse heights. Leads to greater number of consumers and compounding species diversity.
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Intermediate disturbance hypothesis Disturbance frequency disturbance-mediated coexistence disturbance-caused extinctions competitive exclusion Competitive exclusion can also be prevented by disturbance / environmental change:
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A fluctuating environment over time can also promote diversity Temporal fluctuations in environmental conditions prevent competitive exclusion by altering the competitive hierarchy.
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This note was uploaded on 11/29/2010 for the course BIOLOGY 1211 taught by Professor Patricelli during the Spring '10 term at UC Davis.

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Lecture+22+-+Biodiversity+posted - Biodiversity: The 3 BIG...

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