Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Ecological fitting wikipedia , lookup
Molecular ecology wikipedia , lookup
Introduced species wikipedia , lookup
Biodiversity action plan wikipedia , lookup
Occupancy–abundance relationship wikipedia , lookup
Latitudinal gradients in species diversity wikipedia , lookup
Habitat conservation wikipedia , lookup
Island restoration wikipedia , lookup
Assisted colonization wikipedia , lookup
Aggregations on larger scales…. Metapopulation • Definition: A group of interconnected subpopulations • Sources and Sinks Metapopulation - interconnected group of subpopulations sink source McKillup and McKillup 2000 Oecologia Predictable recruitment gradients - bluehead wrasse Thalassoma bifasciatum St. Croix www.reef.org Hamilton et al. 2006. Marine Ecology Progress Series 306: 247-256 Population Level 1. Population size 2. Spatial aspects - metapopulation connectivity - sources, sinks (larval dispersal Community Structure - Important Factors to Consider • Species that determine structure foundation species, interacting species • Processes: Competition, predation, disturbance, disease, parasitism, facilitation • Environmental influences: temperature, salinity, light, water energy, depth, nutrient regime Foundation species coral seagrass salt marsh grass mussels COMPETITION LIMITING RESOURCES (1) Renewable - e.g., copepods exploiting diatom population (2) Non-renewable - space on a rock exploited by long-lived sessile species Limiting Resources Limiting Resources Outcomes of Competition COMPETITIVE DISPLACEMENT - one species outcompetes another for a resource COEXISTENCE - two species exploit different resources, some process allows two species to exploit same resource without displacement Interference vs. Exploitation Competition Interference - one species overgrows another, interspecific territoriality, agonistic interaction Exploitation (scramble) - one species eats a prey resource more efficiently than another CONSEQUENCES OF COMPETITION Extinction: usually local, habitat shift Coexistence: "niche shift" - character displacement evolution of shift in morphology or behavior Variable Environment: Unstable, but can permit coexistence (“Paradox of the plankton” - coexistence of many phytoplankton species, despite nutrient limitation) EVIDENCE FOR INTERSPECIFIC COMPETITION 1. EXPERIMENTAL MANIPULATIONS remove hypothetical competitor (e.g., barnacles) 2. LABORATORY DEMONSTRATIONS e.g., growth experiments with one and multispecies combinations disadvantage is lack of field conditions 3. DISPLACEMENTS IN NATURE - e.g., invasive species, increase of resource exploitation in estuaries. Problem - other factors could be atwork 4. CONTIGUITY OF RESOURCE USE e.g., "adjacent niches" - could arise by evolutionary change Predation SPATIAL SCALE Relation of Predation to Competition Predation suppresses competitive success of superior species over inferior species, especially if predator prefers competitively superior prey DISTURBANCE Usually refers to physical change in environment that causes mortality or affects reproduction (storm, ice scour). SPATIAL SCALE OF DISTURBANCE Habitat wide (storms, ice, oil spill) Localized in patches (horeshoe crabs, logs) EFFECT CAN BE SIMILAR TO PREDATION Suppresses effect of competition (Intermediate disturbance-predation effect) Intermediate DisturbancePredation Hypothesis Low levels of disturbance or predation: Competitive dominant species takes over Intermediate levels: Promotes coexistence, more species present High levels: most individuals removed, reduces total number of species Succession Predictable order of appearance and dominance of species, usually following a disturbance. Examples of disturbance and colonization: volcanism--> coral colonization; deep-sea invertebrate colonization Deposition of sand --> colonization by burrowers SOME MODES OF SUCCESSION (1) Early species modify unoccupied habitat, which facilitates colonization by later species (bioturbation) primary succession SOME MODES OF SUCCESSION (2) Inevitable colonization of successively competitively superior species, following some initial community secondary succession. Later species tolerate competition, lower resources. Factors in succession 1. Initial colonists - properties: not specialized, high reproductive rate, dispersal-oriented 2. Later colonists - better competitors that displace earlier species? 3. Prevention of invasion - good competitor? Good at resisting predation? Environment altered, which prevents further colonists from invading? 4. Is there a climax community? Assemblage of competitively superior species? Resistant to predators? Evidence for such communities? Dominance? SOME MODES OF SUCCESSION (3) When patterns exist, they are an accidental result of a variety of interactions, including priority effects, seasonal colonization, random change Membranipora sp. Direct versus Indirect Effects Direct effects: Predator consumes prey, prey population decreases Indirect effects: Sea otter consumes urchins; as a consequence, seaweed prey of urchins increases in population size Density mediated indirect effect: Density at one feeding level increases, which reduces prey of another species, and, in turn results in an increase of the prey of the second species Trait-mediated indirect effect: Presence of a predator, causes prey to be active less and feed less on their own prey, so prey of second species increase in abundance, even though the second species did not decline (their feeding activity declined). Ecosystem level • Ecosystem: group of interdependent biological communities and abiotic factors in a single geographic area that are strongly interactive. • Nearly all ecosystems have primary producers (mainly photosynthetic), secondary producers (herbivores), and carnivores. Material escaping this cycle is material to be decomposed in the saprophytic cycle. • Food webs may be controlled by top-down processes where top predators have strong effects or bottom-up processes where changes in primary production drive changes in food web. • Strong top-down linkages or bottom-up linkages generate a tropic cascade through the food web. The End