Midterm 2

• study of biotic and abiotic interactions between organisms and their environment • typically involves measuring distribution and abundance in various environments and what resources are available to organisms

• +- Territoriality • +- Predation • • • Parasitism • ++ Mutualism • • 0 Commensalism

• Maintenance of home range and defense against intruders • Individuals maintain territories to: – protect a feeding area – breeding site – a specific nest site

• Mobile and non-mobile predators • search for prey using chemical, mechanical and/or visual stimuli

• Diet breadth - rule: food scarce, increase breadth (or when food is plentiful - focus on nutritious items) • Time spent in a patch - rule: greater the distance between patches, spend more time in a given patch • Size selection - maximize energy intake, usually leads to selection for intermediate size

• Characteristics that increase resistance to predation are SELECTED for • Examples of adaptation are: – crypsis (camouflage) – deceit – escape responses • Mimicry • Müllerian (not known in marine organisms) and Batesian • mechanical defense • inducible defense • chemical defence • Visual cues

• Toxic compounds • Conspicuous colour plus chemical defense • Many very poisonous marine organisms are brightly coloured (aposematic colouration) • These defenses (chemical and mechanical) vary with latitude, habitat and oceanic basin • Organisms without such defences may hide or grow fast (e.g. sponges, seaweeds) to enhance survival

• Parasites evolve to reduce damage to host • Commonly involve complex life cycles with more than one host • Parasites may invade specific tissues, such as the reproductive tissue of the host

• Commensal crab and fish live in this burrow of Urechis caupo

• Coral + zooxanthellae • cleaner fish + predators

• Destruction of important species, e.g., shellfish disease attacks • Removal of ecologically important species (example: removal of key grazer) • Interaction with other factors such as climate change & pollution (? Sea star wasting disease)

• Competition • Predation • Parasitism • Disturbance • Facilitation • Larval dispersal (unique to ocean) • Larval settlement

• Group of individuals that are affected by the same overall environment and are unconnected with other populations of the same species. • Changes in populations come from survival, birth, death, immigration and emigration • Marine populations are dynamic • Survival of adults is a major factor in populations • Many marine species produce hundreds of thousands of eggs per female • Reproduction is seasonal and corresponds to food and environmental factors • Population size and extinction are closely related - low density of adult individuals can result in population extinction • Many marine species spawn eggs & sperm in the water if density is low the likelihood of sperm fertilizing an egg is low

• exponential growth • logistic growth • random change

Correlation between population size, density & fitness

• Communities are organized around the habitat or around foundational species • 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

• These organisms play a role in facilitation which is a + + relationship. - E.g. retention of water by seaweeds at low tides for small organisms to remain moist

• Many marine organisms have planktonic larvae that can disperse across large areas. • Suitable substrate upon which these larvae can settle is a limiting factor in marine communities. • There are many factors that can result in good and bad recruitment and this can result in affecting adult population sizes

• Renewable - e.g., copepods exploiting diatom population • Non-renewable - space on a rock exploited by long-lived sessile species

• Competitive exclusion - one species outcompetes another for a resource • eg. extinction • Coexistence - two species exploit different resources, some process allows two species to exploit same resource without displacement • eg. “niche shift” - character displacement - evolution of shift in morphology or behaviour

• Niche structure - predictable partitioning by co-existing species of a habitat into subhabitats • Extensive coexistence with apparent resource limitation

• Field experiments - remove hypothetical competitor (e.g., barnacles) • Laboratory experiments - e.g., growth experiments with one and multispecies combinations -disadvantage is lack of field conditions • Displacement in nature- e.g., invasive species, increase of resource exploitation in estuaries. • Problem - other factors could be at work. • Contiguity of resource use - e.g., “adjacent niches” • could arise by evolutionary change

• Predation or Herbivory can suppress the competitive success of superior species over inferior species, especially if predator prefers competitively superior prey • E.g. Piaster ochraceus & Mytilus californianus or sea urchins, sea otters & seaweeds (keystone species), or removing urchins results in dominance of a fast growing seaweed • Seasonal influx of predators can decimate some local communities • E.g. Migratory seabirds in the intertidal zone

• Usually refers to physical change in environment that causes mortality or affects reproduction (storm, ice scour). • Habitat wide (storms, ice, oil spill) • Localized in patches (horseshoe crabs, logs) • Suppresses effect of competition (Intermediate disturbance-predation effect)