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• Climates and Biomes• Individual species distributions

–Invasive species

Lecture 3:Distributions and abundance Climates and Biomes

• Climate varies tremendously over globe– abiotic factors such as rainfall and temperature

• Enormous impact on plants and animalsand the resulting communities

Two big factors affect global climate:1. Curvature of the earth -->temp gradient2. Tilt of Earth axis --> Seasons

Climates and Biomes

• Global temp differences create windand drive atmospheric circulation

• formation of distinct temperature andmoisture “bands” from low to highlatitudes

• Results in distinctive plant assemblagesthat are also formed in these distinctzones = BIOMES

Biomes• Major categories of world’s distinctive plant

assemblages• Different biomes correlate well with climatic

factors• Illustrate how organisms match their environments

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Biomes• Tundra

– Very seasonal, very cold, very dry• Taiga (Boreal Forest, N. Coniferous Forest)

– Highly seasonal, very vold, lots snow• Temperate

– Seasonal, temperature fluctuates, rain+snow– Grasslands & Forests

• Tropical– HOT!, little seasonality, rainfall varies– Savannas, Rainforests, and Deserts

• Deserts– Hot & Dry, distributed throughout the world

Individual Distributions

• There are different scales of individualsdistributions:– Geographic– Regional– Populations (habitat-related)– Individual locations (e.g. territories)

Worldwide Continental

RegionCluster/Population

Locality IndividualLocations

Individual Distributions

• How do we study what factors determine thedistributions of organisms?

• Old way: Leibig’s law of the minimum– Look where organisms are found and ask why– Hypothesis: distribution of organism determined by

single environmental factor for which the organismhas narrowest range of control or adaptability

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Individual Distributions

• Leibig’s law of the minimum– Use tolerance curves to determine which

environmental factors organism wasinfluenced by: GRAPH

– Problem: focuses on abiotic conditionsand the physiology of organisms but doesnot consider potential effects of otherfactors

– Realized vs. potential performance -GRAPH!

Individual Distributions• Alternative way to Leibig:

– Look where organisms are NOT found andask why

– Hypothesis: distribution of organismsdetermined by factors keeping them out of orfrom being successful in other areas

Individual Distributions• Factors that can limit species distributions:

–Abiotic env. conditions• Temperature, water, nutrients, etc.

–Species Interactions• predation, competition, disease, etc.

–Dispersal barrier• Land or water barriers

–Behavior• Habitat selection/preference

DesertsNumber/km2

Red Kangaroo Distribution andAbundance - Australia

Distribution of DesertConditions - Australia

>2010-205-101-50.1-1<0.1

Abiotic factors limiting distribution

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Abiotic factors limiting distributionBarnacle Distributions and Climate - UK

Chthamalus sp. –southern species

Balanus sp. – northernspecies Colder water

Warmer water

Species interactions & distributions

Red Kangaroo Abundance relative to a predator – DingosDingos Absent Dingos Present

Kangaroo Density#/km2

Distance from Fence (km)

4

8

12

16

102030 10 20 30

Dispersal limiting distributions

Gypsy moth distribution before and after human-inducedintroduction to the U.S.

Before introduction to U.S. After introduction to U.S.

Habitat selection limiting distributions

addition of shelter

C = control,

E = experimentaladdition)

Result: Kangaroo ratprefers open areas,pocket mice prefersheltered areas

Kangaroo rat

Pocket mouse

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Distributions - CA examples

• California Salamanders ( Ensatina eschscholtzi spp.)

– Ring Species• Monterey Pines (Pinus radiata)

• Likely have both biotic & abiotic constraints

Individual Distributions• How do we determine which factors limit species

distributions?• Can do transplant experiments or change

conditions to distinguish between differentfactors

Dispersal?

Behavior?

Other organisms?

Abiotic factors?

“Natural Experiments”

• Introduced Species– Overcome dispersal barrier– Novel species interactions– Different abiotic conditions– -->Alters distribution dramatically!

• Examples– Kudzu vine (Pueraria montana)– Cane Toads! (Bufo marinus)