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BIOGEOGRAPHIC DISTRIBUTION CONTROLS

A. INTRODUCTION

Biogeography

• study of the geographic distribution of biological organisms
  
  
• global biome patterns
  Image credit: U.S. Department of Agriculture Natural Resources Conservation Service (2005) World soil resources map index. http://soils.usda.gov/use/worldsoils/mapindex/index.html

Geographic Range

the spatial extent of where an organism lives



range may change over time due to



• successful colonization of new areas
  
  

• extirpation and extinction

Ecological Niche

• the combination of conditions required for an organism to survive and reproduce
  
  
• food (energy and nutrients)
  
  
• habitat
  
  
• temperature, sunlight, moisture

B. DISPERSAL & COLONIZATION

Find better habitat; avoid competition



Accessibility



Colonization requires an available ecological niche & successful reproductionn

C. ABIOTIC INFLUENCES (p. 303-309)

Moisture

Temperature

photosynthesis rate



respiration rate

Sunlight

Soil Nutrients

Adaptations (p. 315-316, 324-327) leaf characteristics root characteristics deciduous/evergreen habit reproductive habits Image credit: Gary M. Stolz. U.S. Fish & Wildlife Service Digital Library System. http://images.fws.gov/default.cfm?library_id=none&CFID=3302570&CFTOKEN=37370443

D. BIOTIC INFLUENCES (p. 316-317, 327-328)

Competition

• food, water, nesting space, ground space

Mutualism

• interactions between species that benefit both species

• e.g. flowering plants & pollinators

Commensalism

• one species benefits from a second species, but the second species is unaffected by the first

• e.g. epiphytes in tropical rainforests gain support and access to sunlight

Predation and Parasitism

• one organism benefits at the expense of another

E. DISTURBANCES & ECOLOGICAL SUCCESSION

Disturbances events that disrupt an ecosystem wildfire boreal coniferous forests Mediterranean (Cs) climates fuel load: litter & living organisms ignition most often due to lightning adaptations to survive fire wind, flooding Image credit: U.S. Fish & Wildlife Service Digital Library System. http://images.fws.gov/default.cfm?library_id=none&CFID=3302570&CFTOKEN=37370443
Ecological Succession directional change in mix of plants & animals at a place , repeated colonization, establishment & extirpation pioneer community: first colonizers hardy, fast-growing; short-lived species create conditions that favor other organisms easily disrupted, low diversity community	Image credit: U.S. Forest Service Superior National Forest http://www.fs.fed.us/r9/forests/superior/storm_recovery/ blowdown_images.php

• over time, community changes to:

• slower-growing species with longer life spans

• increasing diversity and stability

• climax community - "end" of succession; in reality:

• true climax communities rarely form due to frequency of disturbances

• disturbances rarely affect entire ecosystems, just patches

• disturbances rarely set ecosystems back to square one

F. SUMMARY

Major controls over geographic distribution of species

• ability to disperse and colonize suitable habitats

• abiotic influences: moisture, temperature, sunlight, nutrients

• biotic influences: competition, mutualism, commensalism, predation/parasitism

• disturbances and ecological succession