Stream Fish Stream Fish DiversityDiversity

Ecological Principles of Ecological Principles of DiversityDiversity

1.1. Principle of Limiting SimilarityPrinciple of Limiting Similarity - - There is a limit to the similarity of There is a limit to the similarity of coexisting competitors; they cannot coexisting competitors; they cannot occupy the exact same niche.occupy the exact same niche.

2.2. Niche Separation / DifferentiationNiche Separation / Differentiation -Competitors use different resources -Competitors use different resources to coexist.to coexist.

3.3. Environmental heterogeneityEnvironmental heterogeneity - - Creates more niche possibilities; Creates more niche possibilities; therefore, higher environmental therefore, higher environmental diversity leads to higher species diversity leads to higher species diversity. diversity.

Purpose, Hypotheses, and Purpose, Hypotheses, and PredictionPrediction

PURPOSE: Test the idea that increased PURPOSE: Test the idea that increased environmental/physical diversity (niche space) leads to environmental/physical diversity (niche space) leads to increased species diversity.increased species diversity.

Hypotheses and predictionsHypotheses and predictions   HH11: Fish diversity is determined by competition for niche space : Fish diversity is determined by competition for niche space

and the principle of limiting similarity.and the principle of limiting similarity.

Prediction: There will be a significant positive correlation Prediction: There will be a significant positive correlation between fish diversity and physical habitat diversity. between fish diversity and physical habitat diversity.

  

Other Possible Other Possible HypothesesHypotheses

The fish assemblage is structured by:The fish assemblage is structured by: Predation or number of trophic levelsPredation or number of trophic levels FloodingFlooding Glacial and geographic history (age of Glacial and geographic history (age of

the stream, and its history of isolation)the stream, and its history of isolation) (more are possible…use your knowledge (more are possible…use your knowledge

of ecology to think of a few more)of ecology to think of a few more)

Habitat Parameters that Habitat Parameters that Could Influence Species Could Influence Species

CompositionComposition1. Physical (1. Physical (our our

focusfocus)) Water depthWater depth Current Current

velocityvelocity Substrate typeSubstrate type

1. Physical (extra)1. Physical (extra) TemperatureTemperature

2. Chemical2. Chemical Dissolved ODissolved O22 IonsIons pHpH

3. Biological 3. Biological Other organisms Other organisms

presentpresent Nutrient inputNutrient input Nutrient cyclingNutrient cycling

Note: We are not measuring all factors, so this is not a completetest of the hypothesis (we can support but not falsify).

Background for Background for CalculationsCalculations Diversity addresses 1) how many categories exist, Diversity addresses 1) how many categories exist,

and 2) how evenly the categories are represented.and 2) how evenly the categories are represented. For example, we may have 2 communities with 7 For example, we may have 2 communities with 7

species (species richness = 7) and 21 total species (species richness = 7) and 21 total individuals, but each species may not be individuals, but each species may not be represented evenly.represented evenly.

Community 2 Species Diversity Histogram

0

2

4

6

8

10

12

1 2 3 4 5 6 7

Species

Num

ber o

f Ind

ivid

uals

More Diverse

Less Diverse

A.

E.

H.

G.

C.

F.

B.

D.

A.

E.

H.

G.

C.

F.

B.

D.

H’= 1.38

H ’= 0.41

H ’= 0.69H’= 1.39

H’ = 1.10

H’= 1.39

H ’= 1.24

H’ = 1.61

Diversity CalculationsDiversity Calculations For the fish assemblages and habitat For the fish assemblages and habitat

parameters we calculate diversity using the parameters we calculate diversity using the following equation:following equation:

HH’’=-=-∑ p∑ pii lnlnppii

Where pWhere pi i = # of individuals in a category/total # = # of individuals in a category/total # of individualsof individuals

Is There a Correlation Between Is There a Correlation Between Habitat Diversity and Species Habitat Diversity and Species

Diversity?Diversity? Today, we will compile fish diversity and Today, we will compile fish diversity and

habitat diversity results from all groups in habitat diversity results from all groups in our lab. our lab.

This correlation will only involve two or This correlation will only involve two or three data points, so it will probably not be three data points, so it will probably not be significant. Therefore, we also will significant. Therefore, we also will examine some data from a previous year to examine some data from a previous year to increase sample size (n).increase sample size (n).