Today’s Lecture • Communities • Ecosystems Community Ecology Communities are populations that live and interact in the same place at the same time. Smaller communities are nested within larger communities. Communities – spatial scales - a specific group • Cliff dwelling birds • Microbial communities • Plant communities Communities • Organisms do not live in isolation – Associations can be based on need • Butterflies and plants • Parasites and hosts • Flowers and pollinators – Associations can also be due to sharing similar requirements • Soil types • moisture Niche • All the biotic and abiotic resources a species needs to survive, remain healthy and reproduce – Light – Temperature – Moisture – Food… Fundamental vs realized niche No two species can have identical niches! Limiting resources • Any environmental resource that restricts the ecological niche of a species Species’ Interactions: Competition, Symbiosis, Predation • Intraspecific • Interspecific Factors Limiting Distribution Biotic Competitive exclusion – a species is prevented from occupying an area due to a competitive interaction with another Biotic and abiotic factors can restrict niches Fig. 54-3 EXPERIMENT Chthamalus Balanus High tide Chthamalus realized niche Balanus realized niche Ocean Low tide RESULTS High tide Chthamalus fundamental niche Ocean Low tide Competitive exclusion – a species is prevented from occupying an area due to a competitive interaction with another Gallium ssp. Reducing Competition – Niche partitioning • Temporal – nocturnal vs diurnal – Predatory mammals – Woodland flowers • Spatial – species use different microhabitats – Wading birds – Fish Reducing Competition Frequency Green sunfish Largemouth bass Bluegill Prey size Werner, 1977 Amer. Nat. 111:553 Reducing Competition Frequency Green sunfish small Largemouth bass Bluegill Prey size Werner, 1977 Amer. Nat. 111:553 Reducing Competition med Frequency Green sunfish small Largemouth bass Bluegill Prey size Werner, 1977 Amer. Nat. 111:553 Reducing Competition med Frequency Green sunfish small Largemouth bass Bluegill Prey size Werner, 1977 Amer. Nat. 111:553 Prey size small large inshore Green sunfish Microhabitat Bluegill Largemouth bass Deep, open water Werner, 1977 Amer. Nat. 111:553 Character displacement reduces interspecific competition On islands where 2 species of finches do not co-occur, birds have similar beak depths On islands where they are both found beak depths differ Predation Predation strategies include speed, ambush and lures Predation avoidance strategies include cryptic and aposomatic coloration Fig. 54-5 (a) Cryptic coloration Canyon tree frog (b) Aposematic coloration Poison dart frog (c) Batesian mimicry: A harmless species mimics a harmful one. Hawkmoth larva Green parrot snake (d) Müllerian mimicry: Two unpalatable species mimic each other. Cuckoo bee Yellow jacket Fig. 53-8, p. 1154 Herbivory • Herbivory (+/– interaction) refers to an interaction in which an herbivore eats parts of a plant or alga • It has led to evolution of plant mechanical and chemical defenses and adaptations by herbivores Symbiosis • Symbiosis is a relationship where two or more species live in direct and intimate contact with one another – Parasitic – Mutualistic – Commensal Fig. 54-1 Fig. 54-7 (a) Acacia tree and ants (genus Pseudomyrmex) (b) Area cleared by ants at the base of an acacia tree Fig. 54-8 Diversity vs Richness • Diversity is about number of species AND species evenness • Richness is only number of species • Two communities with 100 individuals and 10 species: – First on has 91 individuals of one species and 1 of all the others – Second has 10 individuals in 10 species – Which is more diverse? Fig. 54-9 A B C D Community 1 A: 25% B: 25% C: 25% D: 25% Community 2 A: 80% B: 5% C: 5% D: 10% California Floristic Province 2,124 endemic plant species Community Dynamics • Trophic structure – Food chains – Food webs • • • • Community Dominants Ecosystem Engineers Keystone Species Facilitators Food chain Quaternary consumers Carnivore Carnivore Tertiary consumers Carnivore Carnivore Secondary consumers Carnivore Carnivore Primary consumers Herbivore Zooplankton Primary producers Plant Phytoplankton A terrestrial food chain A marine food chain Food Web Humans Smaller toothed whales Baleen whales Crab-eater seals Birds Leopard seals Fishes Sperm whales Elephant seals Squids Carnivorous plankton Euphausids (krill) Copepods Phytoplankton Community Dynamics • Trophic structure – Food chains – Food webs • • • • Community Dominants Ecosystem Engineers Keystone Species Facilitators Fig. 54-22d 4 Spruce-dominated forest – Community Dominants Ecosystem Engineers RESULTS Number of species present Keystone Species EXPERIMENT 20 15 With Pisaster (control) 10 5 Without Pisaster (experimental) 0 1963 ’64 ’65 ’66 ’67 ’68 ’69 ’70 ’71 ’72 ’73 Year Number of plant species Fig. 54-18 8 6 4 2 0 (a) Salt marsh with Juncus (foreground) (b) With Juncus Without Juncus Diversity in time Succession– directional change in community structure through time, but outcome is unpredictable Fig. 54-22-4 Early successional species– rapid colonization and/or growth 1941 1907 2 1 Pioneer stage, with fireweed dominant, low N, OM 0 1860 Dryas stage 5 10 15 Kilometers Glacier Bay Alaska 1760 4 Spruce stage – invades Alder Late successional species– slow colonization and/or growth 3 Alder stage symbiosis with nodule forming bacteria – but reaching equilibrium doesn’t mean that the community is static - A forest is a mosaic of successional stages (sensu Forman) Secondary succession – Gaps from, trees dying, ice, windfall Final successional stage is a state of flux, a mosaic of patches -Landscape ecology, patch dynamics Ecosystem Ecology Study of the ecological significance of the flow of energy and matter Ecosystems • Ecosystems include the community and the physical environment – Community: focus is on species interactions – Ecosystem: focus is on functional aspects • Functional aspects include: – Energy flow – Nutrient Cycling Decomposers/ detritivores – feed on bits not consumed or that die naturally Decomposition connects all trophic levels • Energy flow is linear, from sun to producer to consumer to decomposer (with some systems receiving energy from another source!) • A lot of energy is converted to heat, and is lost as it moves from one organism to another Energy that reaches the predators has passed through many organisms and feeding levels. Energy is lost at each transfer so energy available to the top is limited relative to those at lower trophic levels • Disturbance • Components of Stability -Resistance -Resilience Ecosystem structure and function Stability and Diversity Time Time Stability and Diversity • In the 1950s ecologists proposed that more complex systems should be more stable – Simple systems more prone to outbreaks – Simple models of predator/prey systems tend to oscillate – More pathways for energy flow Nutrient Cycling • From nutrient “pools” • Nutrients are passed from organisms to organism • All organisms eventually die and become food for decomposers • Nutrients then return to the nutrient pool • Unlike energy, nutrients are recycled. • Limiting nutrients often determine ecosystem dynamics Biogeochemical Cycles • Gaseous carbon, oxygen, sulfur, and nitrogen occur in the atmosphere and cycle globally • Less mobile elements such as phosphorus, potassium, and calcium cycle on a more local level • A model of nutrient cycling includes main reservoirs of elements and processes that transfer elements between reservoirs • All elements cycle between organic and inorganic reservoirs • In studying cycling of water, carbon, nitrogen, and phosphorus, ecologists focus on four factors: – Each chemical’s biological importance – Forms in which each chemical is available or used by organisms – Major reservoirs for each chemical (pools) – Key processes driving movement (flux) of each chemical through its cycle Fig. 55-14c N2 in atmosphere Assimilation NO3– Nitrogen-fixing bacteria Decomposers Ammonification NH3 Nitrogen-fixing soil bacteria Nitrification NH4+ NO2– Nitrifying bacteria Denitrifying bacteria Nitrifying bacteria Eutrophication • Eutrophication is the transformation of an ecosystem from low to high nutrient levels • Increase in nutrient loads can lead to rapid increases in the amount of algae and aquatic plants and reduced water clarity Fig. 55-14d Precipitation Geologic uplift Weathering of rocks Runoff Consumption Decomposition Plant uptake of PO43– Plankton Dissolved PO43– Uptake Sedimentation Soil Leaching Fig. 55-14b CO2 in atmosphere Photosynthesis Photosynthesis Cellular respiration Burning of fossil fuels Phytoand wood plankton Higher-level consumers Primary consumers Carbon compounds in water Detritus Decomposition Effects of change in C cycle • • • • Plants grow faster Hotter, wetter climate Ocean acidification Change in phenology and migration 97% oceans 2% glaciers 1% lakes, rivers, streams Transport over land Solar energy Net movement of water vapor by wind Precipitation Evaporation over ocean from ocean Precipitation over land Evapotranspiration from land Percolation through soil Runoff and groundwater Effects of altered water cycle on ecosystems - Global Glacier melting - Influx of fresh water - Rise in sea level - Change of coastline - More inland lakes - Less circulation What is the Greenhouse Effect? Increases in greenhouse gases will lead to increases in global temperature Data from 2007 IPCC report Climate Change: Faster than expected in 1990s CO2 Concentration Solid lines = observed • Dashed lines = 1990s projections Av Surface Temp IPCC 4 (2007) was limited to science published by early 2006 • Subsequent research shows increasing rates of: Global GHG emissions 3.3% in 2000s, vs 1.3% in 1990s Temperature rise especially in polar regions Ice melt (Arctic: 40% loss since Sea Level Rise (cm) 1980, accelerating 2006-07) Sea-level rise Rahmstorf, Church, et al., Science 2007 1975 1985 1995 2005 IPCC Fourth Assessment Report (2007) was very conservative. Recent studies indicate accelerating change. What are the Consequences? Melting of glaciers and polar ice Since 1850, glaciers in the European Alps have disappeared from more than 30-40% of their former range What are the Consequences? Increased temperature and incidence of heat waves Globally averaged, the earth is ~0.75 C warmer than it was in 1860 What are the Consequences? Sea Level Rise Sea Level Rise What are the Consequences? Melting of glaciers and polar ice Polar bears need sea ice – seals and other marine mammals main food item Documented drop in female weight 1980 = 650lbs 2004 = 507 Minimum weight needed to become pregnant Unprecedented numbers swimming and then found drowned. Global Warming Global Warming Global coupled atmosphere-ocean-ice model Hoegh-Guildberg (1999) What are the Consequences? Shifts in species ranges Edith's Checkerspot Butterfly has been disappearing from the lower elevations and southern limits of its range. Average shift = 35 miles north What are the Consequences? Shifts in biological activity Toads, frogs, and newts spawning early. Spawning was 9 to 10 days earlier over a 17-year period. Marmots are emerging from hibernation on average 23 days earlier than 20 years ago. This coincides with an increase in average May temperatures of about 1.8oF (1oC). Fig. 55-1