31. Macroecology Flashcards
macroecology
the large-scale study of species abundance and distribution
creating ecological niche models (ENMs)
- Identify niche of species of concern.
- Determine distribution of environmental conditions through geographic range of concern.
- Combine information to produce map of potential distributions of species of concern.
applications of ENMs: predicting the spread of the invasive mitten crab throughout North America
- The mitten crab (Eriocher sinensis) is native to Asia
• Spread through world via shipping ballast water
• Where could it invade in North America?
• Herborg et al. (2007) used data on distribution of crab in Asia to model areas of suitable habitat - Broader predicted distribution in North America based on levels of 12 environmental variables
- Narrower predicted distribution when life history considered
• Mitten crabs are catadromous (spawn in ocean water,
live in freshwater → opposite of salmon!)
• Likely only to be found <355km from ocean
limitations of ENMs
- Focuses on realized niches (where the species has existed before); does not consider the fundamental niche
- Even harder to model rare species because we will have few observations from which to gather environmental data
broad definition of “the island”
Any portion of isolated habitat - mountain tops, lakes, land islands
relationship between species richness and island area and island isolation
- Species richness increases with island area
2. Species richness decreases with island isolation (distance from mainland and other islands)
latitudinal diversity gradient patterns
- Species richness generally increases from middle and high latitudes to the equator.
- Most groups of organisms are more species-rich in the tropics than they are at higher latitudes.
- Well-documented decline in species richness as one moves from low to high latitudes.
potential mechanisms of latitudinal diversity patterns
- time and area effects
- land mass
- rates of extinction
- rates of diversification
land mass
- tropical ecosystems are generally older and disturbed less frequently.
- Tropics include greater area of both land and water.
- Temperatures more uniform across range of tropical latitudes
rates of extinction
• Speciation rate increased due to stronger biotic interactions in tropics.
• Some evidence for this, but data lacking.
• Variety of other possible mechanisms that may
generate increased species diversification in tropics, through increased speciation rates, decreased extinction rates, or both.
ecological niche modelling
combining information about a species’ current distribution and niche requirements with spatial information to predict invasion and range expansion
- consider range of tolerance, fundamental niche, realized niche, global patterns of environmental conditions,
why predict potential invaded areas?
Know where to focus monitoring programs to detect and remove the invader (stop the spread)
other applications of ENMs
- Can be used to direct researchers to areas in
which rare species may be found. - Can highlight areas where species could move to
under future environmental conditions (e.g. changing climate) - Beyond a single species distribution, can examine broader patterns of diversity across large geographic scales
examples of relationship between species richness and island area
- number of bird species increased with log island area
- number of beetle species increased with island area
- number of fish species increased with lake area
why does increased area = increased species richness
Larger areas …
• Likely have more resources
• Can support larger populations, less vulnerable to extinction
• Have greater niche diversity (support more species richness)
