Lecture 10 Interactions And The Niche Flashcards
Ecology
Scientific study of the distribution of abundance of organisms and the interactions that determine their distribution and abundance
3 key factors
Where - distribution
How many - abundance/ diversity
Why there? Interactions
Ecology includes
Individual organisms
Populations ( 1 species)
Communities (>1 species)
Ecosystems
Biomes
Ecology doesn’t include
Biological hierarchy - taxonomy
Subcellular particles, cells, tissues and organs - physiology
Interactions
Classified according to impact of interaction on specie involved : positive, negative or no effect
Classified according to trophic (feeding) or non trophic
Predation (trophic)
Predator consumes individual/ parts of individual of another species (prey) - may or may not involve killing
Prey, carnivory, herbivory, parasitism
Non-trophic: Interspecific competition
Two or more species overlap in use of one or more of the same limited resources leading to reduced growth, reproduction or survival (ie lower fitness) such as competition for food or nesting space or light in plants
Trophic/non-trophic: interspecific facilitation
At least one species benefits from interacting, neither is harmed. Mycorrhizal networks in plants , plant pollinator interactions are mutualistic/ mutualisms - both parties benefit. Commensalism one partner benefits and other is unaffected e.g. shrubs and grasses able to grow under “nurse trees” on savannah protected from harsh sun
Amensalism
One species neg affected by other whilst the other is unaffected by the interaction e.g. seedlings on forest floor unable to grow due to larger plants blocking sunlight - larger plants unaffected. Destruction of plants by elephant as it walks - does not effect elephant.
Symbiosis
One specie lives in/on another - close and long-term biological interaction. May be mutualistic or parasitic.
Mutualistic e.g.mycorrhizal fungi in plant roots plant recieves nutrients and fungi recieves carbohydrates (particularly underpins survival of orchids.)
Parasitic - host symbiosis - many parasites specific to host e.g. human head louse and cannot survive independently from partner (obligate) human head louse has an endosymbiotic bacteria in them vital for B5 synthesis (mutualistic symbiosis)
Example:
African buffalo feeds on savannah grass - herbivory
Oxpeckers eat parasitic ticks off the buffalos back
- parasitism, predation, mutualism
Ox destroys insect nests as it walks. White cattle egret feed on insects disturbed by the buffalos passage
- amensalism and commenalism
Interactions
not binary
often not symmetrical
strength of interaction vary
may be stronger in one direction than another
eg. In UK grey squirrels expert stronger competitive effect on red squirrels.
Interactions shift
Can shift between neg and pos due to enviro conditions e.g. shrubs and trees have amensal or commensal interactions depending on intensity of the sunlight - shade can protect (commenalism) or block photosynthesis (amensalism)
Commensalism
One species positively affected whilst other is unaffected or unharmed e.g. white cattle egret feed on insects disturbed by buffalo walking - egret benefits, buffalo unaffected
Effects of interactions
Population dynamics
Competitive exclusion
Ecosystem function/properties
Community composition
Species distribution
Evolution
Predation and population dynamics
Regulate oneanother - other factors can produce cycling effects too
Competitive exclusion
Can prevent coexistence of species w/strong overlap in resource requirements
Competition, predation and community composition
Interactions can remove dominant species allowing others to persist e.g. starfish preying on mussels reduce their dominance in intertidal communities allowing more species to establish themselves
Interactions and community dynamics
Can drive process of succession over time- changes in communities e.g. due to receding ice caps
Interactions and ecosystems
Reintroduction of wolves into Yellowstone NP caused tritrophic cascade- reduced elk pop. Allowing aspen to recruit and regenerate particularly in riparian zones - wolf acts as keystone species
Evolution
Competition may lead to evolution of differentiated resource use resulting in avoidance of competition and speciat89!.
10 herbs in ginger family live in Costa Rican rainforest all are pollinated by hermit hummingbird they coexist by flowering at different times (different flower phenology) avoiding competition
Niches
In ginger plant - hummingbird example past competition is thought to have resulted in evolution of differentiated niches
In general a species niche can be considered as the role and position a species has in its environment including abiotic and biotic factors. so niches are a product of interactions
How to visually represent niches
1 dimensional: repro success Vs survival fitness (hyperbola)
2 dimensions e.g. precipitation Vs temp
3 dimensions soil pH Vs precipitation and temp
Width of dimension where species maintain fitness can be thought of as “niche breadths”
Narrow niche = specialism
Broad niche = generalist
Fundamental niche = range of abiotic enviro conditions that species (individual/population) can persist in
Realised niche= portion of fundamental niche that can be occupied accounting for biotic factors - almost always smaller and never larger than fundamental niche
Interactions summary
Interactions can be classified according to effect on organisms involved and whether or not they are trophic
Can vary in strength/direction depending on enviro conditions and partners involved
Far reaching effects: pop. Dist. Communities, ecosystems and evolution
Help define a species niche (forming realised niche from fundamental)
