BIOL 2060 Lecture Notes - Lecture 5: Log-Normal Distribution, Competitive Exclusion Principle, Species Richness

64 views7 pages
2 Aug 2016
Department
Course
Professor
Ecology - Unit 5
Pg. 422-433
-community: is an association of potentially interacting species in habiting some
defined area, at some particular scale over some specific period of time
ounderstanding pop. Level processes is critical to understanding pop. Level
patterns  not sufficient to understand communities  many complex
relationships and interactions
- as species are lost from a community, there is a potential of a loss of an ecological
function
oecological function: any number of biological, chemical or physical processes
that occur in an ecosystem, typically relevant to human needs or uses
-community structure: number of species, relative abundance of species, kinds of
species comprising a community
16.1 - Species abundances and diversity
- a combination of the number of species and their relative abundance defines species
diversity
-species diversity: a measure of diversity that increases with species eveness and
species richness
-species richness (s): the number of species in a community or collection
- ecologist refer to three stages of diversity:
oalpha (α): measure diversity of one community (ex. Just grassland)
obeta (β): measure of differences among communities within a
region/landscape
β= / αϒ
ogamma (ϒ ): measure diversity of entire region (ex. Grasslands, shrubland
and wetland patches in a very large park)
- guilds: group of organisms that all make their living in a similar way
oex. Seed eating animals in boreal forest
ocan be from closely related species or taxonomically diverse
Patterns of species abundances
- first to look if there is evidence of dominance
odominance: when a species is more common than any other species in a
community
rare in communities to have a species that is very abundant, most
species are moderately abundant  “minimal community structure”
will be visually obvious:
determined by counting individuals, assessing biomass, or
estimating basal area
omethod used is determined by research question
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 7 pages and 3 million more documents.

Already have an account? Log in
if a certain species is dominant, that species will drive most
interactions in that community
- most species in a community will be moderately abundant (Preston 1948, 1962a,
1962b)
ofocused in understanding abundances of different species in relative rather
than absolute terms  graphed the frequency distributions of a number of
species given relative abundance  plotted on log scale
results: mound shape, most abundant type of species was moderately
abundant
oPreston’s curves are lognormal distributions
- The more you sample a community, the more species you find
oLots of sampling needed to find a rare sample
Result: sampling scheme often result in under-representation of rare
species  ecologist need to do substantial amounts of sampling
- Robert May (1975):
oLognormal distribution is the product of many environmental variables
acting upon populations of many species  statistical expectation
- G. Suigihara (1980):
oLognormal distribution of distribution is the consequence of a species within
a community subdividing niche space  result: very few very abundant
species
- Lognormal distribution is important because it allows us to predict the distribution
of abundance among species
An integrative index of species diversity
- define species diversity based off of 2 factors:
oSpecies richness
oSpecies evenness: the relative abundance of the different species within a
community
Inverse of dominance
A community that is even is one that doesnt have an dominant species
- Diversity is generated through an increase in the number of species and through an
increase in the evenness of these species
-Shannon-Wiener index:
oH’ = -
H’ = value of the Shannon-wiener diversity index
Minimum value = 0
oValue of a community with a single species
oWill increase as species richness and evenness increase
= the proportion of the ith species
= the natural log of
= the number of species in the community
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 7 pages and 3 million more documents.

Already have an account? Log in

Get access

Grade+
$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
1 Booster Class
Class+
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
1 Booster Class