Local differentiation in heat response of Laminaria digitata at the range edges

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Local differentiation in heat response of Laminaria digitata at the range edges

Daniel Liesner, L. Fouqueau, M. Valero, M. Roleda,

G. Pearson, K. Bischof, K. Valentin, I. Bartsch

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2

Range shifts

70°N

50°N

30°N

80°W 60°W 40°W 20°W 0° 20°E 40°E

Assis et al. (2018). Projected climate changes threaten ancient refugia of kelp forests … Glob Change Biol.

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3

Local adaptation for heat tolerance?

Do populations of Laminaria digitata differ in short-term

heat tolerance?

Min | mean | max daily SST 2018

W W

Tromsø Bodø

Helgoland Roscoff

Quiberon

Spitsbergen

E.U. Copernicus Marine Service (2019). Global Ocean OSTIA Sea Surface Temperature and Sea Ice Analysis.

Do population genetic characteristics relate

to physiological

responses?

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4

Experimental design

n = 30

TAGTAGTAGTAGTAGTAGTAGTAGTAG ACACACACACACACACACACAC

AACAACAACAACAACAACAAC

TCTCTCTCTCTCTCTCTC n = 12

Billotet al. (1998). Isolation and characterization of microsatellite markers … Mol Ecol.

Coelho et al. (2014). Characterization of fifteen microsatellite markers for the kelp … Conserv Genet Resour.

15°C 19°C 23°C 21°C

day

e xp . tem p (° C)

-5 0 3 6 8 15

15 17 19 21 23

Acclimation Heatwave Recovery

n = 5

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5

Experimental design

Growth PAM

Fluorometry

• F

_v

/F

_m

Hypotheses:

1. Heat resilience decreases with higher latitudes.

2. … and with lower genetic diversity.

Genetic structure and diversity

• Fresh weight

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6

W W

Spitsbergen

Tromsø Bodø

Helgoland

Quiberon Roscoff

Strong structuring between and within

northern and southern clades

Structure analyses, K=2 / K=3

Population genetics: structure

King et al. (2019). Evidence for different thermal ecotypes … J Exp Mar Biol Ecol.

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7

W W

Spitsbergen

Tromsø Bodø

Helgoland

Quiberon Roscoff

0 .2 0 .3 0 .4 0 .5 0 .6

SPT TRO BOD HLG ROS QUI

E x pec ted het er oz y g os it y ( H

e

) A lle lic r ic h n e s s ( A R 2 3 4 5 6

H

_e

AR

mean ± SE, n=11–12, ANOVA, n.s.

Spitsbergen Tromsø Bodø Helgoland Roscoff Quiberon

Population genetics: diversity

Helgoland is

genetically isolated.

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8 mean ± SD, n=5, ANOVA, Tukey HSD

Spitsbergen Tromsø Helgoland Roscoff Quiberon

0.00 0.02 0.04 0.06

Rel ati v e gr ow th rate (g g

-1

d

-1

)

Physiology: growth

15°C 19°C 23°C 21°C

day

Photoperiod?

Fertility?

Slight advantage for Quiberon?

W W

Spitsbergen

Tromsø Bodø

Helgoland

Quiberon Roscoff

Lüning (1988). Photoperiodic control of sorus formation … Mar Ecol Prog Ser.

Schaffelke & Lüning (1994). A circannual rhythm controls growth … Eur J Phycol.

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9

W W

Spitsbergen

Tromsø Bodø

Helgoland

Quiberon Roscoff

Physiology: optimum quantum yield

mean ± SD, n=5, ANOVA, Tukey HSD

0.5 0.6 0.7 0.8 0.9

F

v

/F

m

No stress response in

Helgoland?

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10 Growth

0.00 0.02 0.04 0.06

Rel ati v e gr ow th rate (g g

-1

d

-1

)

Physiology: recovery

5 days at 23°C harmful for all populations.

0.5 0.6 0.7 0.8 0.9

F

v

/F

m

Optimum quantum yield

mean ± SD, n=5, ANOVA, Tukey HSD

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11

Synthesis

pe rf orm a nc e

temperature

Fixed thermal limit

Northern and southern

clades

Subtle

differentiation in marginal populations

Genetic diversity

≠

heat tolerance

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12

Relevance

Bolton & Lüning (1982). Optimal growth and maximal survival temperatures … Mar Biol

Assis et al. (2018). Projected climate changes threaten ancient refugia of kelp forests … Glob Change Biol.

Loss of southern populations

&

range expansion of northern clade?

0 5 10 15 20

0 5 10 15 20 23

R GR (% d

-1

)

Temperature (°C) L.dig. Helgoland

L.dig. Halifax

pe rf orm a nc e

temperature

70°N

50°N

30°N

80°W 60°W 40°W 20°W 0° 20°E 40°E

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