competition Flashcards
types of species interactions
- competition (-1,-1)
- predation (-1,+1)
- parasitism (-1,+1)
- mutualism (+1,+1)
- commensalism (0,+1), can be indirect, one species benefits from the presence of another
- neutralism (0,0), doesn’t occur
competition
occurs when a number of organisms of the same or different species utilise common resources that are in short supply (Krebs, 1978)
Intraspecific competition
competition between individuals of the same species
interspecific competition
- competition between individuals of different species
- controlled by many different physical and biological factors
- cost of interspecific competition is reduced success and fecundity
replacement series experiments
the effect of varying the proportion of each of two species is explored while keeping overall density the same
competitive exclusion principle
the instance where two species which make their livings in identical ways are unable to live in a stable fashion (May 1981)
competition between diatoms
- Asterionella formosa when grown alone in a culture flask establishes a stable population
- when Synedra ulna is grown alone it does the same
- when grown together, Synedra drives Asterionella to extinction
- concentration of silicate is a limiting factor as important for growth, Synedra are able to maintain populations at much lower concentrations of silicate
interspecific competition in plants, experimental designs used to study below and above ground dry weights (biomass)
- grown alone (control) = 100%
- root competition = 65%
- shoot competition = 47%
- root and shoot competition (31%)
character displacement
= the principle that two species are more different when they occur together than when they are separated geographically
e.g. Fenchel (1975), two mud snail species with similar length of shells were grown together, one grew bigger shells, the other grew smaller shells. This reduced competition by varying particle size eaten
niche partitioning
= select prey species that occupy different physical areas
e.g. insectiverous passerines
alleopathy
= where plants can produce chemicals that inhibit the growth of other plants, either metabolites or toxins
e.g detrimental effect on apple tree seedlings when watered through turf compared to being watered directly or through soil
Bracken
- most widely distributed vascular plant in the world
- ancient plant
- carcinogenic
- beneficial to biodiversity
- alleopathic, produces phytotoxins that accumulate in the soil from decomposition of leaves in winter, killing germinating seeds
rhododendron
- introduced in 1700s
- highly invasive
- alleopathic
