mammalogy biogeography

Discussion regarding the timing and preparation for an unspecified upcoming project.
Mention of lab quizzes now available with grading instructions.
- Email lecturer for any grading discrepancies with question number reference.
- Lecturer occasionally manually overrides grades for minor issues.

Overview of four major glacial periods from approximately 1.7 million to 10,000 years ago.
- Most recent glacial period: Wisconsin Glacier left around 10,000 years ago.
- Impacts of glaciation:
- Extensive destruction of living organisms over large areas.
- Altered local climates in areas not covered by glaciers due to glacial presence.
- Cold conditions extended further south than current climate, affecting the ecosystems.
Example of Michigan being completely covered by glaciers leading to new mammal species in post-glacial period.

Concept of glacial refugia, areas that survived glaciation where species persisted, allowing for recolonization.
- Southern Central Wisconsin and northern Illinois identified as refugial zones.
- Notable area: Driftless Area (parts of Wisconsin, Iowa, and Illinois) known for its unique topography.
Importance of dispersal in biogeography:
- Distinction between ecological dispersal (individuals leaving their home range) and biogeographical dispersal (species expanding geographical range).
- Examples of species expanding into previously unoccupied areas due to climate change, such as armadillos moving north.

Two main types of dispersal mechanisms:
- Active dispersal: Individuals move on their own (walking, flying, swimming).
- Passive dispersal: Organisms reach new areas inadvertently (rafting, human transportation).
Types of interchange routes for dispersal:
- Corridors: Areas with minimal barriers allowing for unhindered movement; e.g., movement from Europe to Asia.
- Filter routes: Selective movement where only some species can cross barriers (e.g., deserts, mountain ranges).
- Sweepstakes routes: Low probability pathways for successful dispersal (rafting, flying) and establishment.

Example of Beringia as a land bridge facilitating species movement between Asia and North America.
Panamanian Land Bridge (formed about 2.5 million years ago) serves as a filter route:
- Some northern species migrated southward while adapted species did not move north due to climate challenges.

Definition and significance of centers of origin for taxons, primarily at family or genus levels, aiding in understanding evolutionary conditions and dispersal routes.
- Determining criteria:
- Location of earliest known fossils, fossil history of predecessors, and regions with highest taxon diversity.

Unique characteristics of Michigan's biogeographic zones:
- Comprising a transition zone between boreal forests (north) and deciduous forests (south).
- Two peninsulas surrounded by water serve as barriers to dispersing species.
- Disparity in species across regions (e.g., Arctic shrews and Eastern moles) demonstrates biogeographic isolation.

Major reductions and extirpations of mammalian species due to European influence.
- Examples of extirpated species: fishers, otters, elk, which have now been reintroduced.
- Species like the white-tailed deer and fox squirrels have expanded their ranges resulting in population increases.
- Involvement of land use changes, exploitation, and introductions of non-native species (e.g., Norway rats, house mice).

Variable precipitation patterns and heavy snowfall influence mammalian biogeography.
- Large snowfalls affect mobility and food accessibility for medium to large mammals.
- Energetic bottleneck impacts medium to large herbivores, which can benefit their predators.
- Contrast between long-tailed weasels and short-tailed weasels, with differing hunting strategies based on snow conditions.
- Historical distribution patterns of snowshoe hares versus cottontail rabbits indicate ecological adaptations to snow.

Relationship between species presence on islands versus mainland, influenced by island size and isolation:
- Larger islands typically support more species due to lower extinction rates.
- Proximity to mainland affects immigration rates and species distribution.
Finding of non-flying hibernators generally absent from islands due to difficulty in crossing barriers like ice.

Inventory of mammal species on Apostle Islands as a natural laboratory for biogeography.
- Conclusion: Larger island area positively associated with species number. Degree of isolation had less influence than expected.
- Underrepresentation of non-flying mammals indicates selective pressures at play.

Bats and rodents generally thrive on islands, while large mammals are underrepresented.
Body size variations between island and mainland animals reflect different selective pressures.

Wrap up biogeographical material and plan to continue with the next topics in future discussions.