community ecology exam 3

Ecological network

Depicts/ quantifies interactions among species in a community, ex: pollinator/ plant, parasite/ host, food webs, seed dispersal etc…

Network topology

structural properties of networks, important to understanding how decisions impact communities and understand species connections, ex food chain length, nestedness, connectedness, link density.

Food webs

Depicts all feeding interactions among organisms in a community

Food web data types

connectedness, energy flow, functional

connectedness

presence or absence of links, not super accurate

energy flow

amount of organisms/ biomass moving from one species to another, difficult to quantify

Functional

quantifies strength of links between species, allows for predictions of how communities might respond to changes, very difficult.

Trophic cascade (top down)

non adjacent trophic level effects the abundance or biomass of a lower level, by driving down the lower level’s predator population.

Sink webs

Objective bounds, all links that lead up to one node of interest

source webs

objective bounds, all links that stem from one node of interest

Green (autotroph) Food web

Fast energy channels

Brown (detritus) food webs

Slow energy channels

Resolution in food webs

most food webs are not sorted into distinct trophic levels, they use calculated trophic position, this is due to omnivory.

Aggregated nodes

Aggregated due to being functionally/ ecologically similar or becuase at low levels taxonomy is difficult

Data on strength of interactions may lack resolution

• hard to quantify

• ingested vs assimilated

• temporarily unavailable (prey switching)

• strong vs weak interactions

Body size in food webs

Optimal foraging theory supports the idea that food web position can be predicted based off of body mass, certain sized predators eat certain sized prey. Not all, ex pack hunters, scavengers, ants, filter feeders.

Keystone species

heterotroph with a disproportionally large impact on the community relative to its biomass

dominant species

autotroph with a large effect on the community due to its large abundance / biomass

Foundation species

non replaceable, many links to other species, non trophic/ mutualistic interactions, occurs near base of food web.