Flashcards in Final Deck (170)
What is nutrition mutualisms?
Two species exchange nutrients, or one species is rewarded in some way for improving the nutritional status of another
What are some examples of nutrition mutualisms?
-mycorrhizae and N2 fixing bacteria
-Corals- symbiosis with zooxanthellae
-deep sea tube worms
Mutualism will only arise if
pw(sm) + qw(um) > w(nm)
-w(nm): fitness of individuals in a nonmutualistic population
-p: proportion of successful mutualists (W(sm))
-q: proportion of unsuccessful mutualists (w(um))
The major exploitative interactions include
predation, herbivory, and parasitism
Key predator adaptations affect the ___, ___, and ___ of prey.
detection, capture, consumption
Mutualisms generally evolve to facilitate
reproduction, energy/nutrient acquisition, or protection from exploitative interactions
Mutualisms can be
obligate or facultative; specialized or general
What is an ecological community?
a group of interacting species that co-occur in a particular place
What parameters describe communities?
-composition: what species are present?
-structure: how do those species interact with each other?
What is direct filtering determined by?
environmental tolerances of the species
What is indirect filtering mediated by?
interactions with other species that are subject to filtering
What do neutral models of community composition assume?
-communities are random combos of species physiologically able to live in the same place
-two mechanisms determine species membership in communities- dispersal in ecological time and speciation in evolutionary time
-if communities are altered, they do not necessarily recover the same community structure
What do niche-based models of community composition assume?
-biological interactions (ex: competition) shape (and are shaping) the niches of coexisting species and so determine community composition
-"ghost of competition past" may give the appearance of competition not being important in the current community (i.e. that niches are already well separated or even randomly distributed) via competitive exclusion and character displacement some time in the past
Under a neutral model of community structure
species associate at random
In a neutral model
the niches are arranged at random, so that some niches are very similar, and others very different
In a niche-based model
the niches are over- or hyper-dispersed in niche space
Which is more likely: competitive hierarchy or competitive networks?
Coexistence is possible by ___ the niche
Coexistence is also possible is resources are ___ and OVERALL niche overlap is ___
What are some ways to pack species into diverse communities?
-increase overlap: possible if resources (k) are large enough and overlap does not exceed some threshold
-decrease niche breadth: a.k.a. become more specialized
*can happen via character displacement
-extend range along resource axis: a.k.a exploiting resources not used by other species
*can happen via character displacement/directional selection
Environmental filtering and competition have ___ effects on community composition
If environmental filtering dominates over competition,
phylogenetic clustering is more likely
-closely related groups will have similar traits and so pass through environmental filter together
If competition dominates over environmental filtering,
phylogenetic over- dispersion is more likely
-only phylogenetically and therefore ecologically different species are found within guilds in the community
What is community heritability?
the proportion of the variation in a characteristic of the community (such as herbivore diversity) that is explained by genetic variation in the population of a particular species (e.g. plants)
How does community heritability affect community structure?
via "community genetics"
What is facilitation?
a process in which the presence of one species INCREASES the probability that another occurs in the community, usually by mediating competition
How does mutualism operate like facilitation?
lessens the effects of competitive interactions
What are keystone predators?
eat other competitively dominant predators, thus allowing coexistence of a diverse community
What is apparent competition?
two similar species are negatively impacted by the action of a shared predator or herbivore
-good example of an indirect interaction between two species (one that is mediated via another species)