Genetic Diversity of Stream Fish

Populations in the Mid-Atlantic Region

Suzanne Christ, Mark Bagley, Frank McCormick

US Environmental Protection Agency,National Exposure Research Laboratory

Cincinnati OH

What does genetic diversity have to do with

vulnerability assessments?

ReVA Endpoints:– Resource Productivity– Clean Drinking Water– Biodiversity

What does genetic diversity have to do with

vulnerability assessments?

ReVA Endpoints:– Resource Productivity– Clean Drinking Water– Biodiversity

Biodiversity

Genes

Species

Ecosystem

Genetic Diversity

• Variation in the heritable portion of measurable traits that exists among individuals within a species.– Genetic diversity within populations – Genetic diversity among populations

• Examples: eye color, height, blood type, HIV resistance

Gilpin and Soule’s (1987) Extinction Vortex Model (Adaptation and inbreeding vortices)

Δ Environment Δ Genetic Diversity Δ Vulnerability

Ne

Demographic randomness

EXTINCTION

Genetic Drift Inbreeding

Heterozygosity

Inbreeding depression

Adaptation( Environment tracking)

Population size Density Replacement rate variability

Spatial distribution of genetically distinct resource populations (ESUs)

Spatial distribution of genetically distinct resource populations (ESUs)• Unique resources

• Biodiversity “Hotspots”

Spatial distribution of stressors

Relative vulnerabilities of populations

What does genetic diversity have to do with

vulnerability assessments?

• Indicator of population’s future “environmental buffering” ability

• Reflective of past population stressor history• Defines the fundamental biological unit that

we wish to assess (the population)– Prioritization based on uniqueness and

vulnerability

Genetics of Creek Chubs in a Coal Mining Region of the Mid-

Atlantic

Photo courtesy of Ohio Dept. Natural Resources

Semotilus atromaculatus

• Are there distinct population resources in the MAIA region?

• Do watershed boundaries (HUCs) predict stream population boundaries?

• Do levels of genetic diversity differ among sites?

• What is the relationship between genetic diversity and environmental condition?

Study Questions

• Five watersheds assessed in MAIA pilot

• 10 sample sites• Part of EMAP-MAIA

97-98 sampling• Wadeable streams

(second and third order)

Study Area

Major Environmental Concerns

• 10-28 fish sampled per site

• 590 bp of mitochondrial Cyt-B gene sequenced

• AFLP fingerprints based on 109 polymorphic markers

• Genetic differences within and among sites assessed by Analysis of Molecular Variance

Genetic Analyses

Population genetic structure

Mitochondrial DNA

Nuclear DNA

Population genetic structure

Among Regions64.8%

Within Sites

27.8%

Among SitesWithin Regions

7.4%

Partitioning of Genetic Variance: Mitochondrial DNA

Partitioning of Genetic Variance: Nuclear DNA

8.0%

86.6%

Among Regions

5.4%

Within Sites

Among SitesWithin Regions

• Are there distinct population resources in the MAIA region? YES

• Do watershed boundaries (HUCs) predict stream population boundaries? NOT 1:1

• Do levels of genetic diversity differ among sites?

• What is the relationship between genetic diversity and environmental condition?

Study Questions

0.74

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Average Genetic Similarity

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Nitrogen (ug/ L)

6.56.76.97.17.37.57.77.98.18.38.5

pH

6.56.76.97.17.37.57.77.98.18.38.5

pH

Each site characterized with 25 environmental measures

Principal Components Analysis

Principal component

Variation explained

Variables

1 (Geochemistry) 37.4%Conductivity, aluminum, calcium, chloride, potassium, magnesium, sodium, sulfate

2 (N/P/C) 24.3%Nitrate, total nitrogen, total phosphorus, organic carbon

3 (Latitudinal clines) 14.1%Latitude, elevation, channel slope, silica, zinc

4 (Spatial scale) 11.8%Watershed area, stream width, stream depth

5 (pH-Ammonium) 6.7%pH, Ammonium

6 (Substrate condition)

6.3%Pebble size, embededness, percent riffle

Stepwise multiple regression nuclear DNA diversity

PCA FactorPartial

r2 Model r2 F P>F

PCA 3 (Latitudinal clines)

0.433 0.433 6.10 0.039

PCA 2 (N/P/C) 0.349 0.792 12.06 0.010

PCA 5 (pH/Ammonium)

0.184 0.976 45.6 0.005

• Are there distinct population resources in the MAIA region? YES

• Do watershed boundaries (HUCs) predict stream population boundaries? NOT 1:1

• Do levels of genetic diversity differ among sites? YES

• What is the relationship between genetic diversity and environmental condition? APPEARS TO BE STRONG

Study Questions

Complete Study • 3 stream minnows• MAIA and WAP• To be completed later this year

Acknowledgements

Betsy Smith (ReVA)Tony Leonard (Sobran, Univ. of Cincinnati)EMAP program

More info: bagley.mark@epa.gov513 569 7455