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OBJECTIVES Species Diversity at scales above local Regional effects on local SD Equilibrium theory + Island Biog. Theory Regional SD Latitudinal SD Continental SD Global SD
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What explains great variation in species richness over the earth? Figure 1
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Multiple scales of species diversity Local Regional Latitudinal Continental Global
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Many factors influence regional and local species richness.
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Local diversity as f (regional diversity). Figure 2
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Comparing diversities of communities in similar habitats in different regions can reveal regional effects. Figure 3
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Saturation of local communities hypothesis: test how local and regional diversity relate. Figure 2 Figure 4
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Variation in local species diversity depends on regional diversity. ***Are these local communities saturated? Figure 5
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Equilibrium theories: diversity reflects a balance between processes that add vs. remove species. ***What processes add species? speciation immigration What processes subtract species? extinction emigration Differences in diversity between communities reflect differences in relative rates of these processes.
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*** What is the pattern? What two equilibrium factors may explain it? Figure 6
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Equilibrium theory of island biogeography: # species = balance of immigration on a regional scale vs. extinction on local scale. Figure 7
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Islands closer to the mainland support more species because of higher immigration rates. Figure 8
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Larger islands support more species because of lower extinction rates. Figure 9
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Which hypotheses are illustrated in Figure (a) + (b)? Figure 10
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*** Do experimental results support ETIB? Figure 11
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Applications of Island Biogeography Theory to: Terrestrial systems mountain tops as islands fragmented remnants as islands Design of nature reserves
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Regional-scale patterns of diversity also reflect: Habitat heterogeneity Suitability of physical conditions Isolation from centers of diversity
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***What are three patterns in regional species diversity? What factor accounts for each pattern? Figure 12
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How do patterns of species richness differ among taxa? Why? Figure 13
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***What are major changes among regions from Tertiary to present? What accounts for them? What are major differences today? Figure 14
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***Why did climate change during the Ice Age contribute to Europe’s low species richness? Figure 15
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What is relationship between tolerance of low temperature / rainfall and extinction? Figure 16
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Multiple scales of species diversity Local Regional Latitudinal Continental Global
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***What is latitudinal gradient in woody species diversity? What explains it? Figure 17
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Hypotheses to explain latitudinal gradient in species diversity… Time and stability Heterogeneity in space and time (Vegetation and food complexity) Herbivore and pathogen pressure Competition/niches Disturbance
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Multiple scales of species diversity Local Regional Latitudinal Continental Global
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How do history + biogeography + climate change influence species diversity?
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History of life is gauged by geologic time scale. Cretaceous 150mya Cambrian 600mya --> Permian 286mya
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Equilibrium theory in continental communities: balance between speciation and extinction on regional scale Figure 21
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Has diversification been faster in tropics than temperate area? Figure 22
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***Has diversity been constant? What is role of extinction vs. additions? Figure 18
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Did species richness increase through time? To what did richness correspond? All species turned over during this time period. Figure 19
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Catastrophes --> what are consequences - short- and long-term? ***Asteroid impact--> extinctions of what? Figure 20
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Multiple scales of species diversity Local Regional Latitudinal Continental Global
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Continental drift --> positions of continents change over geologic time. Climate changes too --> influences geography of evolution Figure 23
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Continental drift changed routes of dispersal via separation + joining. Figure 24
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Wallace: Major zoogeographic regions reflect long-term evolutionary isolation. Figure 25
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Exchanges of biotas after joining of continents: e.g. The Panama land bridge Figure 26
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***How explain same body form in multiple continents? Convergence or divergence? Figure 27
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Climate change influences distributions of organisms. How does the historical extent of climate zones help to explain global patterns of species richness? Figure 28
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Where does more diversification occur? Why? How does this relate to more species near 0 than at higher latitudes? Figure 29
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Climate change in N.A. shifted species diversity; Miocene drier with grasslands. Fig Figure 30
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Oak trees shifted their distributions after end of most recent glacial period. Figure 31
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How does ‘dispersal limitation’ explain differences in post-glacial expansion? A,b = small; c,d = large seeded species Figure 32
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How does climatic history determine species distributions + community composition? Figure 33
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