L22. Isthmus of Panama

Question 1

Isthmus of Panama

Answer 1

• dry land connection between North and South
  America
• Was created 17ma due to Caribbean plate tectonics
• results of tectonic events
• mountains, volcanoes at plate boundaries
• barrier to trans-oceanic circulation

Question 2

Ocean circulation changes

Answer 2

• tropical circulation of warm water is blocked and deflected north (gulf stream)
• cold on the pacific side

Question 3

Implications of circulation changes

Answer 3

• increased temperature difference between warm Caribbean and cool pacific
• deflection of gulf stream increase moisture in northern latitudes

Question 4

Land bridge effects on biological systems

Answer 4

direct effects:
- land bridge as a barrier to dispersal
- land bridge as a corridor for dispersal

Indirect effects
- climatic changes, geological changes lead to subsequent changes in distribution, ecology

Question 5

Isthmus Barrier impact of evolution

Answer 5

• isolation of populations of marine invertebrates
• related species in several groups isolated across isthmus
• snapping shrimp
• completely different species on each side of ocean due to circulation (pacific: pelagic, Caribbean: corals, mangroves, seagrasses)

Question 6

Pre-link Fauna

Answer 6

• 3ma
• both continents had diverse fauna of large mammals, birds

But species filling these niches in North America were almost entirely different than the species filling these niches in South America because

Question 7

Starting the interchange

Answer 7

• establishment of isthmus allows these faunas to move into other continent
• mixing of previous isolated communities
• interaction and competition of previously isolated species

Question 8

Isthmus as a corridor

Answer 8

the great American biotic interchange

Question 9

Heralds and legions

Answer 9

heralds: early colonizers (island hopping)
legions: main invasion group (walkers and crawlers)
- north: shrews, rabbits, mice, squirrels, bears, deer, large cats and dogs
- south: porcupines, opssums, manatees

Question 10

Aftermath of the exchange

Answer 10

• at least 50% of South American mammals are descendants of ancestors that came from North America
• several extinctions in South American mammal fauna
• birds, reptiles, amphibians not as affected

Question 11

Change in ecosystem after change

Answer 11

• mountain building in central america
• rain shadow, elevation differences in habitat
• climate changes
• expansion of rainforest in south and central america

Question 12

Recent exchanges

Answer 12

• several groups moved across since first establishment
• ex. igaunas, hummingbirds, salamanders

Question 13

Human changes (new barriers)

Answer 13

Canal and Gatun lake
- well protected/maintain
- buffer zone of protected land on either side of canal provides fresh water, but also protects habitats and species

Question 14

PRISM

Answer 14

• Panama Research and Integrated Sustainability Model
• Putting many different types of models from many different fields to make across field connections
• Ex. Bio, economics, poli-sci, web analytics everything