Ecology 14 Biogeography & Biodiversity Ralph Kirby

Diversity of plant communities Similar climates support similar communities Thus vegetation is correlated to climate This is Biogeography –Aim is to understand the patterns Historical –Origin, dispersal and extinction of groups Ecological –Distribution and interaction of contemporary organisms

Why do these patterns exist Candolle –Temperature and available water Köppen –Fixed on climate Merriam –Elevation important Northward – average temperature Southward – Heat tolerance Clements & Shelford –Animal and Plants together as single unit BiomeWhittaker –Minimum of 9 terrestial biomes –Specific pattern Mean annual temperature Mean annual precipitation

Köppen System

Clements & Shelford Major Biomes of the World

Whittaker –Precipitation versus Temperature Holdridge –Life Zones Average daily temperature Annual precipitation Potential evapotranspiration ratio Biotemperature

Terrestial Ecosystems are reflected in their dominant plants Three general plant life forms –Trees –Shrubs –Grasses Ratio decides ecosystem –Forest Closed canopy of trees –Woodland/Savanna Codominance of trees and grass Ratio varies –Shrubland Shrubs –Grassland Grass –Desert Absence of plant cover Caused by advantages and disadvantages of each type of plant in a particular environment –Grasses Higher ratio of photosynthetic tissue Less supportive tissue –Trees Higher ratio of supportive tissue Less photosynthetic tissue Height advantage –Shrubs Intermediate but better in more extreme climates

Leaves Based on cost to plant versus climate/sunlight See Figure 24.4 –Deciduous Distinct growing season –Winter deciduous Temperate regions with low temperature dormancy Leaves shed during winter –Drought deciduous Seasonal rainfall areas of tropics and subtropics Leaves shed during dry season –Evergreen Needleleaf Type –Very short growing season –Or very nutrient limited environment Broadleaf Type –No distinct growing season

Wallace –Based on biodistribution Driven by continental movement over time –Six regions PalearcticNearcticNeotropicalEthiopianOrientalAustralian –Or three regions Neogea –Neotropical Notogea –Australian Metagea –Arctic –Ethiopean –Oriental

Aquatic systems Based on physical environment –Freshwater Depth Flow of water Separate into –Streams & rivers –Ponds, lakes & wetlands –Saline Coastal –Transition zone Estuaries etc –Diversity of ecosystems Open –Vertical –Horizontal All are linked

Species based on major taxonomic groups vary in greatly –Note microorganisms Wrong estimate Distribution of species not even –Variation in species richness Terrestrial decreases from equator to pole –Age of community Ice Ages –Heterogeneity of environment –Climate stability –Ecosystem productivity

This supports decrease from equator to pole for North America Effectively related to a number of factors seen before –Annual temperature –Solar radiation –Precipitation Best correlate actual evapotranspiration rate

Plots of North American species richness with latitude north

Plots for Evapotranspiration rate and species richness in North America

Terrestrial systems –Basically water and temperature –Thus altitude is also important Marine environments –Latitude similar –Inverse to productivity –Importance of seasonality UpwellingMixing However species diversity operates at many different scales –From communities –To biomes Hard to measure when time is taken into account –Migration etc

Need to plot to manage resources Land –Tends to splitting Sea –Broad Usually as follows –Eco-regions Domains –Divisions Provinces

Can use pollen to look at ecosystems history Predict effect of climate changes