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Transcript
Lecture 3: Distributions and abundance • Climates and Biomes • Individual species distributions –Invasive species Climates and Biomes • Global temp differences create wind and drive atmospheric circulation • formation of distinct temperature and moisture “bands” from low to high latitudes • Results in distinctive plant assemblages that are also formed in these distinct zones = BIOMES Climates and Biomes • Climate varies tremendously over globe – abiotic factors such as rainfall and temperature • Enormous impact on plants and animals and the resulting communities Two big factors affect global climate: 1. Curvature of the earth -->temp gradient 2. Tilt of Earth axis --> Seasons Biomes • Major categories of world’s distinctive plant assemblages • Different biomes correlate well with climatic factors • Illustrate how organisms match their environments 1 Biomes Individual Distributions • Tundra – Very seasonal, very cold, very dry • Taiga (Boreal Forest, N. Coniferous Forest) • There are different scales of individuals distributions: – Highly seasonal, very vold, lots snow • Temperate – Geographic – Regional – Populations (habitat-related) – Individual locations (e.g. territories) – Seasonal, temperature fluctuates, rain+snow – Grasslands & Forests • Tropical – HOT!, little seasonality, rainfall varies – Savannas, Rainforests, and Deserts • Deserts – Hot & Dry, distributed throughout the world Worldwide Continental Individual Distributions • How do we study what factors determine the distributions of organisms? Cluster/ Population Locality Region • 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 organism has narrowest range of control or adaptability Individual Locations 2 Individual Distributions • Leibig’s law of the minimum – Use tolerance curves to determine which environmental factors organism was influenced by: GRAPH – Problem: focuses on abiotic conditions and the physiology of organisms but does not consider potential effects of other factors – Realized vs. potential performance GRAPH! 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 Individual Distributions • Alternative way to Leibig: – Look where organisms are NOT found and ask why – Hypothesis: distribution of organisms determined by factors keeping them out of or from being successful in other areas Abiotic factors limiting distribution Red Kangaroo Distribution and Abundance - Australia Number/km2 >20 10-20 5-10 1-5 0.1-1 <0.1 Distribution of Desert Conditions - Australia Deserts 3 Abiotic factors limiting distribution Barnacle Distributions and Climate - UK Chthamalus sp. – southern species Balanus sp. – northern Colder water species Species interactions & distributions Red Kangaroo Abundance relative to a predator – Dingos Dingos Absent Dingos Present 16 Kangaroo Density #/km2 12 8 4 Warmer water 30 20 10 10 20 30 Distance from Fence (km) Habitat selection limiting distributions Dispersal limiting distributions Gypsy moth distribution before and after human-induced introduction to the U.S. Before introduction to U.S. After introduction to U.S. addition of shelter C = control, Kangaroo rat E = experimental addition) Result: Kangaroo rat prefers open areas, pocket mice prefer sheltered areas Pocket mouse 4 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 different factors 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) 5