ecology exam 4 pt 3 (community -> similarity matrix)

community

all of the organisms interacting in a given area

the community is what kind of concept?

spatial concept

what kind of descriptions are used for landscape community structure?

broad-scale

consistent floristic composition

although communities in a hilltop or valley are distinct, the communities on TWO hilltops/valleys are quite similar

association is a type of community with what characteristics?

A) relatively consistent species composition

B) uniform, general appearance (physiognomy)

C) distribution that is characteristic of a particular habitat

organismic concept of communities

communities are integrated units → development of a community through time (succession) was viewed as development of the organism

*think of the community as its OWN organism, evolving over time with different parts of the community functioning together

in organismic concept, transitions between communities are ______, with few species in common

narrow

what suggestion can be made about evolution in organismic concept?

a common evolutionary history and similar fundamental responses + tolerances for the component species can be suggested by this concept

→ mutualism + coevolution are important to the association

this means that two species that are NOT similar to each other may still evolve alongside each other and need each other for survival because there are a few species in common between that transition

individualistic/continuum concept

states that the relationship among coexisting species is due to similarities in their requirements + tolerances not to strong interactions or common evolutionary history

species distributions along environmental gradients do not ______, but represent what?

cluster

→ independent responses of species

*in other words, there will still be dynamics happening between species but that doesn’t mean they evolved together or that they rely on one another to evolve because they each adapted to the environment on their own (evolutionary divergence), but just so happen to live in the same area

sorensen’s coefficient of community (CC) is based on species ______ or _______

presence or absence

what is the sorensen’s coefficient of community formula?

CC = 2c/(s₁ + s₂)

what is the sorensen’s coefficient of community formula telling you?

the number of species common to both communities (2c) / (the number of species in community 1 (s₁) + the number of species in community 2 (s₂)

what do the ranges in the sorensen’s coefficient of community formula mean?

CC ranges from 0-1

1.0 = when the species composition of the two communities is identical

0 = no similarity at all

percent similarity (PS)

based on the relative abundance of species within the communities being compared

what range does PS have?

ranges from 0 = communities have no species in common

100 = when the relative abundance of the species in the two communities is identical

similarity matrix

used when comparing more than two communities