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Week 9 lecture 1 Biogeography and Island Species Richness - General Biology

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  • What is biogeography?

    Biogeography is the study of ecological structure and processes at large geographic scales, focusing on species composition and diversity across different locations.

  • How does species richness relate to area in biogeography?

    Species richness generally increases with increasing area sampled, often demonstrated by island studies.

  • What types of 'islands' are studied in biogeography besides geographic islands?

    Islands can include mountain ranges, plateaus, isolated lakes, and habitat fragments created by humans, all acting as isolated habitats.

  • Why are log transformations used in species-area relationships?

    Because species richness and area data are often non-linear, log transformations help linearize the relationship for analysis.

  • How do species richness slopes differ between islands and mainland?

    Islands tend to have a steeper slope in species richness vs. area, indicating higher species richness per area compared to mainland.

  • What is the Equilibrium Theory of Island Biogeography?

    Developed by MacArthur and Wilson, it explains island species richness as a balance between immigration rates and extinction rates.

  • How does island proximity affect immigration rates?

    Islands closer to the mainland have higher immigration rates because species can disperse more easily.

  • How does island size affect extinction rates?

    Larger islands have lower extinction rates due to greater resource availability and niche partitioning.

  • What happens to immigration rates as the number of species on an island increases?

    Immigration rates decrease as the number of species present increases, due to fewer new species available to colonize.

  • What is the predicted species richness for an island that is near and large?

    An island that is near and large is predicted to have the highest species richness due to high immigration and low extinction rates.

  • What was the Krakatau test in island biogeography?

    It was a test of the equilibrium theory where bird species recolonized Krakatau island after a volcanic eruption, matching predicted species richness.

  • What did the Mangrove island experiments in Florida demonstrate?

    They showed that near islands regained insect species faster than far islands after fumigation, supporting the theory that proximity affects immigration rates.

  • How does species biology affect extinction rates on islands?

    Primary producers and smaller organisms tend to have lower extinction rates, while higher trophic level species and those with mutualistic partners have higher extinction rates.

  • How does species biology affect immigration rates?

    Good dispersers like birds and wind-dispersed plants have higher immigration rates, while amphibians and freshwater fish have lower immigration rates.

  • What are the two main ways oceanic islands form?

    Oceanic islands form as continental islands (land breaking from continents) or volcanic islands (new land from volcanic activity).

  • Why might continental islands have greater species richness than volcanic islands?

    Continental islands start with species already present, while volcanic islands rely solely on immigration to gain species.

  • What other processes can create island-like habitats?

    Islands can form from sediment accumulation (e.g., coral or mangrove barriers), landslides, or erosion creating isolated lakes or mountain tops.

  • Why can biodiversity vary among islands at similar distances from the mainland?

    Regional processes, geographic history, and temporal changes affect species richness beyond just distance and island size.

  • What is species turnover in island biogeography?

    Species turnover is the rate at which species are replaced on an island, reflecting ongoing immigration and extinction dynamics.

  • How does habitat fragmentation relate to island biogeography?

    Habitat fragmentation creates isolated patches that function as 'islands', affecting species richness through altered immigration and extinction rates.