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 / Niche Separation / DifferentiationDifferentiation -Competitors use -Competitors use different resources to coexist.different resources 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 leads to increased species environmental/physical diversity leads to increased species diversity.diversity.

Hypotheses and predictionsHypotheses and predictions   HH11: Fish diversity increases with habitat diversity in the physical : Fish diversity increases with habitat diversity in the physical

environment, due to competition for niche space and the environment, due to competition for niche space and the principle of limiting similarity.principle of limiting similarity.

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

Nu

mb

er o

f In

div

idu

als

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’= 0.69

H’= 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 Today, we will compile fish diversity

and habitat evenness results from all and habitat evenness results from all groups in our lab. groups in our lab.

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