Unformatted text preview: Species Populations, Interactions, and Communities Communities Species Diversity, what it is, how it occurs Spatial patterns of species diversity Species Interactions Limiting factors to species Properties of species communities Species Diversity & Community Stability How disturbance shapes communities Case Study: Case Study: Does diversity matter? Do more diverse communities recover differently? Hypotheses Methods Results Results Are their hypotheses rejected? Conclusions/Applications Conclusions/Applications What can we induce from this finding? Why is this important to environmental issues? Species Diversity Species Adaptation & Natural Selection Mutation Nonrandom mating Genetic drift Migration Species Diversity Species Limiting Factors Limiting Limit availability of food, space, mates and safety Examples? Adaptation Adaptation
Through natural selection, species become adapted to a specific range of ecological parameters Indicator Species Indicator The presence/absence of different species indicates the structure of a community and ecosystem Habitats Habitats A place or set of environmental conditions in which a particular species lives Also known as an ecological niche Endemic species Ecological Niches Ecological Competitive Exclusion Competitive Different Species can’t occupy the exact same niche at the same time/space forever One has to adapt or die out • Resource partitioning Specialists vs. Generalists Specialists Some species are more specifically adapted to their habitat’s environmental parameters Why are generalists and invasive species so successful? invasive Norway Rat (usually brown) Kudzu Speciation and Diversity Speciation Constant rates of genetic mutation, combined with different rates of change in environment New ecological niches are created, or old ones pushed closer together This is the process that drives the creation of new species Galapagos Finches Galapagos Speciation Speciation Usually takes a relatively long time for new species to emerge Sometimes the rate of speciation can be accelerated – Punctuated Equilibrium Geographic Separation / Allopatric Speciation Allopatric
A previously connected population becomes geographically separated or isolated Human Example: Redheads Human Isolated population Random mutation in genes that control pigmentation Succeeded in areas with low sunlight (Scotland) Sympatric Speciation Sympatric Sharing habitat, but one species has more chromosomes than the other. Genetic Drift Genetic Similar but separated species will become more genetically unique over time Cheetah have particularly narrow genetic traits, esp. in immune system Selection Pressure Selection Changes in an environmental parameter Each species will react in a different way according to their genetic traits If pressure is significant and long lasting, will lead to new species Selection Pressure Selection Selection Pressure Selection
Plants & animals grown for food are an example of what kind of selection pressure? Taxonomy Taxonomy A systematic way of naming different species Usually descriptive Species Competition Species Over space, food and mates Intraspecific & interspecific competition The Effect of Predation The One species preying on another has affects on both Usually a dynamic equilibrium between predator & prey populations Predation & Agriculture Predation Outbreaks of insect pests that eat crops sometimes linked to a lack of predators (and of course, an abundance of food) Example: mites & strawberries Predation and Life Stages Predation Species may have different prey and predators depending on their level of development Larvae/juveniles/adu lts Barnacle larva and adults Adaption to Predation Adaption Avoid being eaten Speed, hiding, armor, poison Predator Coevolution Predator Predator and prey often evolve new strategies to eat/not get eaten Sometimes can be beneficial to prey, e.g., tropical fruit trees and fruit bats Other species interactions Other Coevolution between species can become very specific leading to a dependence of one species on the other Keystone Species Keystone Species interactions have important effects on ecosystem diversity Some species appear to have more significant effects than other Known as ‘keystone species’ Keystone Species A keystone holds a structure together If you remove the keystone, the structure becomes unstable Keystone Species Keystone Can prey on a species that would otherwise dominate system, Can affect vegetation in area Can provide food during Kelp forests, orcas sea otters and periods of stress sea urchins Population Growth Population A species’ population will grow as long as there are sufficient resources and growth outpaces predation The limit of population growth is known as the biotic potential Reproductive Strategies and Population Growth Population Species adapt to environmental pressures by evolving different ways of producing offspring Communities & Species Diversity Species What is species diversity? How do we measure species diversity? How is this related to abundance? Geographical Patterns of Species Diversity Species General rule: diversity increases as you approach equator Shallow water habitats (e.g, coral reefs) more diverse than deeper water habitats http://www.youtube.com/watch?v=4Rt2zHOJiQw http://vimeo.com/6806286 http://www.unep-wcmc.org/climate/bioadaptation.aspx Species Patterns & Community Structure Community Individuals within species, as well as different species are distributed in different patterns in a community Species Patterns Species Why do individuals have different patterns of distribution? Community Structure Community As temperature, precipitation and Mt. Union, PA topography changes, so will the types of habitat found in a given place Habitat Patches Habitat Large enough patches of habitat will contain a core, big enough to support plants and animals normally found there Small patches of habitat are conservation issue Ecotones Ecotones where two habitats meet blending of each one’s characteristics Typically high species diversity Edge Effect Edge One habitat can have an effect on another beyond their boundary Changes in vegetation, temperature, moisture and species Conservation issue Community Diversity and Complexity Complexity Recovery correlated with species diversity But community complexity is also important Community Complexity Community
What makes a community complex? Multiple trophic levels Many species with similar niches This also makes a community more likely to be resilient (but not always) Community Productivity Community Primary Productivity and Net Primary Productivity Depends on temperature, moisture & light Community Stability Community Stability not the same as resilience Resilience is the ability to recover from a disturbance Community Change Community Original paradigm was that if an area was undisturbed by humans, it would reach a steady state ‘climax community’, changing only with climate Old growth forests Community Change Community New understanding that communities are far more dynamic Some patterns take place slowly, and are hard to discern Succession Succession Change in community structure and function is known as succession Primary and secondary succession Communities and Disturbance Communities What is disturbance? Different Levels of disturbance Intermediate disturbance is usually best for species diversity and complexitywhy? Disturbance adapted species Disturbance Able to do well in disturbed environments Some species, esp. plants, depend on certain types of disturbance, such as fire ...
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- Fall '10
- Ecology, Community Structure Community, Community Change Community