Study Notes on Species Distribution and Historical Factors

Introduction to Historical Distribution of Species

Discussion of a group called the cryptobranchi.
- These organisms are related to each other.
Explanation of distribution based on fossil record.
- Notation of a significant location at the junction between North America and Russia.
- Discovery of fossil cryptobranchi in this area, indicating a historical significance.

Implication of historical distribution of giant salamanders across a land bridge.
- Reference to the Bering Land Bridge.
Explanation of how extinction events have led to species separation.
- Reformation of the Bering Straits.
- The gap once served as a bridge for species dispersal.

Importance of understanding extinction as a factor in species distribution.
Overview of additional factors affecting species distribution:
1. Range Expansion
2. Dispersal
3. Vicariance

Introduction of Starlings as an example of range expansion.
- Noted as non-native to North America; originally from Europe.
- Description of their aggressive behavior and social dynamics.
- Size comparison: Similar to or slightly smaller than a robin.
Historical introduction of starlings:
- Brought over by the Shakespeare Society of New York in 1896.
- Released into Central Park.
Timeline of their range expansion:
- 1920: Moved inland.
- 1930: Reached the Great Lakes region.
- 1940: Extended westward.
- 1950: Reached northern areas.
- 1960: Encroached on Alaska.
- 1970: Established presence in Alaska.
Characterization of the range expansion:
- A significant example of a species adapting to various habitats.
- Differentiation between artificial and natural range expansions.

Current trend of species moving north due to climate change.
- Benefits certain species by creating new habitats.
- Notable examples of amphibians moving north as a result of rising temperatures.
- Early breeding attributed to warming effects.

Overview of historical glacial coverage from 18,000 years ago.
- Hash lines on a map represent ice cover and permafrost extent.
- Notable areas impacted included northern Europe, covering countries such as Italy and France.
Description of permafrost:
- Defined as a layer of ice just below the ground.
- Significant regions, especially in Siberia, contain permafrost, inhibiting plant and animal movements.
- Climate change causing permafrost melt, impacting human infrastructure (e.g., cities sinking).

Examination of brown bears during glacial periods.
- Original distribution limited to Greece, Italy, Spain, and North Africa.
- Expansion occurred post-ice age as permafrost receded:
- Growth of wooded areas allowed bears to spread northwards.
Presence of bears in Great Britain historically and extinction due to hunting.
- Current debates on potential reintroduction of bears into the UK.

Concept of disjunct or relic populations arising from expansion events.
- Example of the long-toed salamander:
- Distribution illustration showing a few isolated population clusters reflecting historical dispersion.
Discussion on queen snakes as another example:
- Distribution predominantly on the east side of the Mississippi River, with a separate population in the Ozarks.
- Historical consideration of populations likely existing west of the Mississippi that became isolated due to landscape changes.

Opportunity for students to ask questions about range expansion and distribution processes.
Announcement of the conclusion of the lecture for that day, an atypical decision by the instructor.