1. Plant Ecology - Chapter 16
Landscape Ecology

2. Landscape Ecology
Study of the spatial distributions of individuals, populations, and communities, and the causes and consequences of those spatial patterns

3. Island Biogeography
Equilibrium theory of island biogeography by MacArthur & Wilson (1967)
Island size and isolation both play important roles in determining number of species present on “islands”
Number of species is a balance between immigration and extinction, which vary with island size and isolation

4. Island Biogeography: Predictions
Number of species should eventually become constant through time
Continual turnover of species, extinction vs. immigration
Large islands should support more species than small islands
Species number should decline with remoteness (isolation) of an island

5. Island Biogeography

6. Island Biogeography
Remoteness a strong influence (bird species more impoverished on far rather than near islands)

7. Island Biogeography
But it takes time to establish the species equilibrium (new island being slowly colonized by new species)
Local evolution, speciation processes also must be considered (fruit flies on Hawaiian islands - more important than immigration, extinction)

8. Metapopulation Theory
The population size of a species on any “island” is a result of local population dynamics, plus immigration minus emigration
The population on an “island” may go extinct, but new immigrants may repopulate

9. Metapopulation Theory
The equilibrium between immigration and extinction determines the number of surviving populations on different islands, their average size, and the total size of the metapopulation

10. Metapopulation Theory
Source and sink
populations
- some populations may not be self-sustaining

11. Metapopulation Theory

12. Metapopulation Theory
Do plant populations have high enough rates of migration, extinction to have an impact on distributions and population sizes?

13. Metapopulation Theory
Prediction 1: If extinction rates are dependent on the frequency of occupied patches, those species occurring in many patches will have large populations when present
For most plant species, studies show that occupancy and abundance are positively correlated

14. Metapopulation Theory
Prediction 2: If immigration, extinction depend on frequency of occupied patches, patch occupancy by a species should have a bimodal distribution
Core species - common; satellite species - rare

15. Metapopulation Theory
Prediction supported at small scales (< 1 km2), but not at larger scales
Spatial structure and dispersal OK at small scale, but not at larger scale - immigration and extinction rates of plants too low for model

16. Metapopulation Theory
Konza Prairie
Species-time-area relationships
Number of species observed in plot each year won’t change, but extinction/immigration will result in new species being observed in plots over the years
Larger plots have more species
Larger plots contain metapopulations of all species in landscape, small plots do not

17. Conservation & Reserves
Forest fragmentation and species richness?
SLOSS - single large or several small reserves
Which gives the most protection per area?

18. Conservation & Reserves
Island biogeography
Metapopulation theory

19. Conservation & Reserves
Testing concepts in Brazil

20. Conservation & Reserves
Corridors can also be important - connectivity - seeds for dispersal into sink regions

21. Conservation & Reserves
Bigger should be better
More species, larger populations, less chance of extinction
Reality: take whatever size you can get

22. Conservation & Reserves
Edge effects
Higher mortality near edges - wind, pathogens
More prone to invasive species - unprotected edges - fewer barriers to seed dispersal