_______ is the ubiquitous driver of biodiversity
linkage density =
= actual # links / # species
palatable species benefit from association with non-palatable species
When might we expect predation to be a key driver in community structure?
when predators select competitively dominant species
Murdoch Alternate Green World Hypothesis
the plants do it, they are prickly and taste bad
partners require the association to reproduce or survive
a reciprocal evolutionary interaction between two or more species, trait of one species evolves in response to trait of another species
When might we expect predators to have little impact?
when prey is not limited by competition
Ants and Acacia, facultative mutualists mostly, sometimes obligate
infrequent, large-magnitude, short duration events of increased resource availability
Neighbourhood habitat amelioration
other species are going to reduce "harmful" abiotic stressors-- make more hospitable
Dynamic stability hypothesis
Elton, more disturbance, lower food chain length
Pyramid of Numbers, who?
= actual # of links / total possible links
Yucca and yucca moths are an example of _______ mutualists
grizzly bears, protecting them protects others too
positive interactions between species of the same trophic guild
a change in abundance that propagates at least three trophic levels
experimentally removed predation but kept the fear to demonstrate powerful non-consumptive effects
assimilation efficiency is the proportion of ...
proportion of primary production ingested that goes into the bloodstream
Trait Mediated Indirect Effects
induced defences; non-consumptive effects of predators
UBC studied mycorrhizal networks, potential competitors helps each other
Bertness and Callaway
made conceptual models of the stress gradient hypothesis
Hairston, Smit and Slobodkin Hypothesis
strong top-down control of terrestrial herbivores by predators allow plants to flourish, green world
Ecological efficiency =
= energy at one trophic level / energy at trophic level right below it
Snails and algae, reaffirmed keystone species
consumption efficiency is the proportion of...
proportion of energy ingested
Are stressful or peaceful environments more likely to have mutual associations
Pyramid of Numbers, what?
lowest trophic levels have the highest number of individuals/biomass/size
partners benefit, but not all require the association
Three categories of mutualists
by necessity, by physical association, by currencies
What is the stress gradient hypothesis?
with increasing abiotic stress, positive interspecific interactions become more frequent and important, and competition interactions become less frequent and important
production efficiency is the proportion of ...
proportion of energy in bloodstream that goes into new biomass
Pisaster, coined Keystone Species; trophic cascades