assemblage of species found in the same area and presumably interacting 

-includes: plants, animals, fungi, bacteria, protists, etc.

Proportion of a given species in the community= P(i)

• fire
• flood
• landslide
• human clearing of the land

1. colonization of an open habitat: carried out by colonizing, r-selected, or "pioneer" species 

2. site of modification: soil stabilized and improved. Microclimate improved. 

3. continuing colonization by new species.

4. competition between earlier and later colonizers. 

5. community changes: earlier colonizers lose to later-colonizing species that are better competitors

6. further site modification. 

7. further colonization & further community change

8. Climax community when there are no longer major changes in community. 

• sample size and effort
• ability to capture or locate the species in question
• taxonomic knowledge

When we are discussing diversity, what forms of life contribute most significantly to this pool of species?

The answes:

• arthropods, but especially insects
• mollusks
• flowering plants
• note that prokaryote diversity is mostly unknown.

1. Environmental Harshness

2. Succession

3. Latitude/Atitude

• as temperature, salinity, pH, moisture, light intensity and chemicals reach extremes, diversity declines
• Biodiversity can be an indicator of pollution or othter environmental degradation

• as communities develop over time diversity increases, but reaches a peak prior to climax.
• recall again, the intermediate disturbance concept. 

• diversity declines with increasing latitude and altitude, with some exceptions. 
• fifty-perecent of biodiversity of the Earth is located in 7% of the Earth's surface in the tropical latitudes

we mean high numbers of endemic species (species found uniquely in these areas):

• tropical areas near the equator
• islands
• mediterranean type ecosystems

• is a region in Eurasia bordered on the north by Russia, on the southwest by Turkey, on the west by the Black Sea, on the easy by the Caspian Sea, and on the south by Iran.
• The Caucasus includes the Caucasus Mountains and surrounding lowlands. 

by sample size and taxonomic errors

SO generally speaking, as we increase sample size, we find more species. 

1. Species Richness

2. Evenness or Equitability 

1. immigration
2. local extinction

• the earliest immigrants to arrive on an island, just as in succession, are r-selected species
• that is, species with high dispersal rates, small bodied, with fast growth, and high reproductive rates.
• This is all r-selected (don't forget that)
• But by contrast, they are poor competitors

• the extinction rate will be low at first. There will be many open habitats and little competition.
• as populations of established species grow, competition will increase. Some species will be competitively excluded. There will be also lower average population sizes resulting in an increase in stochastic extinctions.
• finally, the more species there are, the larger the number than go extinct. 

1. local population extinctions are commong events
2. movements of individuals among populations are common
3. populations on a given habitat patch routinely undergo local extinction, but these routinely undergo local extinction, but these extinctions are balanced by immigration from other local populations.
4. species diversity on a habitat patch is therefore a balance between extinction and recolonization.

the three main issues are:

1. size
2. shape
3. connectivity to other preserves.

• according to the species/area relationship, the larger the preserve, the more species it can accommodate.
• in addition, we want our preserve to be able to accommodate populations of large plants, large animals and all trophic levels. 

• the best shape for a wildlife preserve is roughly, circular, rather than oblong.
• an oblong shape maximizes the edge to area ratio (the opposite is true for circles)

• many species migrate seasonally from winter to summer ranges, or by following the rains in tropical habitats.
• therefore, wildlife preserves must not only include both seasonal ranges, but must include the corridors that allow wildlife to move from one area to another.