Chapter 9: Population Distribution and Abundance

Question 1

Distribution

Answer 1

geographic area where individuals of a species occur

Question 2

Abundance

Answer 2

number of individuals in a given area

Question 3

Population

Answer 3

a group of individuals of the same species that live in a particular area and interact with each other

Question 4

Population Size

Answer 4

number of individuals

Question 5

Population Density

Answer 5

Number of individuals per unit area

Question 6

What are some problems that are had in population density studies?

Answer 6

-The total area occupied may not be known
-It is often difficult to know how far organisms or their gametes travel

Question 7

How do they determine an area for population density studies?

Answer 7

An area is delimited based on best available knowledge of the species

Question 8

Why can it be hard to determine what an individual is?

Answer 8

-Aspen trees produce clones (genetically identical copies) when new plants grow from root buds. A grove of Aspens may all be from the same individual
-Other organisms can do this too

Question 9

How is an individual defined?

Answer 9

-Product of a Single Fertilization

Question 10

Name of single genetic individual

Answer 10

Genet

Question 11

Members of a genet that are independent physiologically, each member is called a….

Answer 11

ramet

Question 12

Absolute Population Size

Answer 12

actual population abundance

Question 13

Relative Population Size

Answer 13

number of individuals in one time period or place relative to the number in another

Question 14

What are relative population size estimates based on?

Answer 14

-estimates are based on data presumed to be correlated with absolute population size
-Ex: number of cougar tracks in an area or number of fish caught per unit of effort

Question 15

Methods for estimating abundance

Answer 15

1. Area-based counts
2. Distance Methods
3. Mark and Recapture Studies

Question 16

Methods for estimating abundance: Area Based Counts

Answer 16

individuals in a given area or volume are counted
-used most often to estimate abundance of plants
-Quadrants: sampling areas of specific size; must be a good representation of the entire area and are chosen at random or placed on a grid
-Individuals are counted in several quadrants; counts are averaged to estimate population size

Question 17

Methods for Estimating Abundance: distance methods

Answer 17

Distance of individuals from a line or point are converted into estimates of abundance
-Line Transects: observer travels along a randomly place line, counts individuals and determines distance from the line
-A detection function converts distance measurements into an estimate of the absolute population size

Question 18

Methods for Estimating Abundance: Mark and Recapture Studies

Answer 18

are used for mobile organisms
-a subset of individuals are captured again and the ratio of marked to unmarked individuals is used to estimate population size

Question 19

Example of Mark and Recapture Study

Answer 19

-23 butterflies are captured and marked
-Later, 15 butterflies are captured, 4 of them marked
-Population is estimated

Question 20

Dispersal

Answer 20

movement of individuals into (immigration) or out of (emigration) an existing population

Question 21

Metapopulation

Answer 21

group of geographically isolated populations linked by dispersal

Question 22

Geographic Range

Answer 22

species might consist of one or multiple metapopulations

Question 23

Dispersion

Answer 23

spatial arrangement of individuals in a population

Question 24

Regular Dispersion

Answer 24

individuals are evenly spaced throughout their habitat

Question 25

Random Dispersion

Answer 25

individuals are randomly spaced

Question 26

Clumped Dispersion

Answer 26

more common in natural populations

Question 27

How many locations do endemic species occur in?

Answer 27

one location only, no where else on earth

Question 28

What all does geographic range include?

Answer 28

all the areas a species occupies during all life stages

Question 29

What may be the cause of patchy distribution?

Answer 29

abiotic factors

Question 30

Species Distribution Models

Answer 30

useful if the geographic range of a species is unknown or to predict spread of a pest species, or shifts in ranges due to climate change

Question 31

Example of a species distribution model

Answer 31

distributions of chameleons in Madagascar. a model used mapped environmental data along with "habitat rules" for each species to accurately predict the distribution of 11 species

Question 32

What determines distribution and abundance?

Answer 32

habitat suitability

Question 33

Abiotic factors

Answer 33

moisture, temperature, pH, light, nutrients, etc.

Question 34

What influences habitat suitability?

Answer 34

food availability

Question 35

What organisms affect species distribution?

Answer 35

Herbivores, predators, competitors, parasites, and pathogens

Question 36

What can interact to determine species distribution and abundance?

Answer 36

Abiotic and biotic factors

Question 37

Disturbance

Answer 37

events that kill or damage some individuals, creating opportunities for other individuals to grow and respond

Question 38

Continental Drift

Answer 38

Wallace 1860 observed very different animal species on the Philippines and New Guinea , even though they are very close together

Question 39

What caused continental drift?

Answer 39

discovery that two islands were on different tectonic plates, and have been close together for a relatively short amount of time

Question 40

Migration

Answer 40

type of dispersal in response to seasonal variation in resources; involves round-trip movement of whole population

Question 41

Dispersal Limitation

Answer 41

a species' limited capacity for dispersal can prevent it from reaching areas of suitable habitat

Question 42

Van der Veken et al. 2007

Answer 42

-27 populations of English Bluebells were established experimentally in suitable habitat in 1960 -After 45 years, 11 populations persisted, hundreds or thousands of individuals -suggests that dispersal limitation prevented the bluebells from reaching habitats where they could thrive

Question 43

Metapopulation

Answer 43

a set of spatially isolated populations linked to one another by dispersal

Question 44

How are metapopulations formed?

Answer 44

-some populations are sources of individuals that disperse to other populations -other populations are sinks that receive more immigrants than the number of emigrants they produce -individual populations may be prone to extinction but the meta population persists

Question 45

Levins (1969,1970)

Answer 45

represented meta population dynamics in terms of extinction and colonization of patches

Question 46

Model Assumptions of Levins 1969-1970

Answer 46

-a very large (infinite) number of identical habitat patches -all patches have an equal change of getting colonists (spatial arrangement of patches doesn't matter) -all patches have an equal chance of extinction

Question 47

Habitat Fragmentation...

Answer 47

can result in metapopulations -patches become smaller and more isolated; colonization rate may decrease and extinction rates increase

Question 48

Isolation By Distance

Answer 48

patches located far from other patches were less likely to be colonized; few patches separated by more than 2 km from an occupied patch were colonized during that period

Question 49

Why is patch size important to metapopulations?

Answer 49

larger patches were more likely to be colonized; small patches had highest rate of extinction

Question 50

Rescue Effect

Answer 50

high rates of immigration from a nearby patch that protects a small population from extinction