Population genetics & responses to ice-age variability in North Pacific pollock

and Pacific cod

W.S. Grant, I.B. Spies, L. Hauser & M.F. Canino

Department Biological Sciences, U of A, Anchorage

School of Aquatic and Fishery Sciences, U of W, Seattle

Alaska Fisheries Science Center, NOAA, Seattle

0.001 0.001 0.0010.001

Space km

0.10.11.01.0

1010

DayDay

MonthMonth1 1

10 10

100 100 1,000 1,000

10,00010,000100,000100,000

Years

Matingencounters

Year-classstrength

Larval drift

Adult movementAdult movement

ClimateClimateshiftsshifts

Ice ageIce ageseparationsseparations& extinctions& extinctions

Sources of Genetic Population Structure

100100

1,0001,000

Populationabundancecycles

(NOAA)

Decadal variability

Ice-age Temperatures

Ice-age Temperatures

USGS• Decrease in plankton productivity

• Elimination of near-shore nursery areas

Contraction-expansion

• Population growth • Low genetic diversity• Haplotypes related to refugia

• High diversity• Haplotypes related to one another

Extinction

Cool Warm

Multiple southern refugia

• Population growth • Low diversity• Connections to refugia• Hybrid zone

• High diversity• Closely related haplotypes

Extinction

Geneticdivergence

Local refugia

• High diversity• Unique haplotypes• Genetic mosaic

• High diversity• Closely related haplotypes

Small refugia

Geneticdivergence

Pollock

NW Pacific Aleutians NE Pacific n = 87 n = 142 n = 155

NW Pacific Aleutians NE Pacific NEP south n = 68 n = 107 n = 104 n = 67

Pacificcod

Mitochondrial DNA sequences

Pollock Pacific codCOI 630 bp ND2+Cytb 1510 bp

Pollock Pacific cod

Amonggroups

5.8%

Amongindividuals

93.6%

Amongpops0.6% 9.8%

1.8%

88.5%

4 Groups

Pollock Pacific cod

Amonggroups

5.8%

Amongindividuals

93.6%

Amongpops0.6% 18.6%

2.2%

79.2%

NW Pacific vs. Others

Pollock Pacific cod

Amonggroups

5.8%

Amongindividuals

93.6%

Amongpops0.6%

Gene 0.74-0.78 0.95-0.98diversity

Pi 1.2-1.4 4.6-6.0

18.6%2.2%

79.2%

NW Pacific vs. Others

Coalescent gene tree

Expanding Ne Constant Ne

0 1 2 3 4 5 6 7 8 90 1 2 3 4 5 6 7 8 9

tt11 tt22tt33

0 1 2 3 4 5 6 7 8 90 1 2 3 4 5 6 7 8 9

expectedobserved

Pollock

NW Pacific Bering Sea-Aleutians NE Pacific

Pollock

NW Pacific Bering Sea-Aleutians NE Pacific

Pacific Cod

NW Pacific Aleutians NE Pacific NEP south

NW Pacific Aleutians NE Pacific NEP south

T2 T3 T4 T5

2Nn(n – 1)

E(Tn) =

Bayesian estimates of historical Ne

PollockNW Pacific Bering Sea-Aleutians NE Pacific

Bayesian Skyline Plots of Female Ne LGM

NW Pacific Aleutians NE Pacific NEP southPacific cod

PollockNW Pacific Bering Sea-Aleutians NE Pacific

Bayesian Skyline Plots of Female Ne LGM

Summary

• Greater gene flow in pollock

• Southern refugia

• Northern Pacific cod refugia?

• Recent population expansions

• Contact zone in W Bering Sea