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Evolution and plasticity in an acidifying ocean

WHOI 9-11 June 2015 - 3rd OAPI meeting: Experiments on contemporary marine organisms have demonstrated many complex and often negative responses to elevated CO2 levels, i.e., conditions that could occur in the average open ocean within the next 300 y
by

Hannes Baumann

on 10 June 2015

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Transcript of Evolution and plasticity in an acidifying ocean

Factorial breeding designs to track 'who is who' - estimate proportion of additive genetic variance
Focus on early life stage morphometric traits (e.g. size) -> relation to overall fitness not clear
Factorial crosses + replication = unwieldy experimental designs
All
is
lost
Three strawmen
NOT all is lost.
There IS reason to worry.
We HAVE some tools.
2014
2013
2013
Natural selection experiments on clonal uni-cellular species
Evidence for de novo evolution, multiple genetic pathways
500+ generations - not an option for most metazoans
Evolutionary responses observed!
e.g., Lohbeck et al. (Nat Geosci 2012, Evolution 2013), Jin et al. (Evolution 2013)
Differential OA sensitivities between strains or populations
Trichodesmium
strains
Hutchins et al. Nat Geosci 2013
Wild vs. disease resistant oyster strains
Baltic vs. Norwegian cod
populations
Parker et al. Mar Biol 2011
3rd OAPI meeting 9-11 June 2015 Woods Hole
Frommel et al. Nat Clim Change 2012, Mar Biol 2012
Suggests:
heritable genetic variation with respect to OA sensitivity exists
Shifts in genotypic composition (evolution) due to OA - trade offs?
Estimating the evolutionary potential
a.k.a. Heritability
h2 = additive genetic / total phenotypic variance
Responds to
selection
Sunday et al. PLOS One 2011
Kelly et al. GCB 2013
Atlantic Silverside
(
Menidia menidia
)
Impractical
CO2 sensitivity known (survival)
Rear all crosses in a common replicated environment
Figure out who's who later
Quantitative sampling
Microsatellites (n=9)
Genotyping everybody
Animal model
"Survival under high CO2 was more similar between genetically related vs. unrelated individuals"
h2 = 0.20
maternal effects insignificant
*
* first h2 estimate
of survival under
OA for a metazoan
2015
Genomic & transcriptomic approaches
Varying expression levels of functional genetic groups -> indicate plastic response on the cellular level, heritable variation needs to be shown
How do pCO2 responsive loci relate to fitness?
Next-generation sequencing -> not only for model species
e.g., Todgham & Hofmann J Exp Biol 2009; Benner et al. Phil Trans R Soc 2013
e.g., Pespeni et al. PNAS 2013
Pespeni et al. PNAS 2013
7 days of selection
ubiquitous shifts in allele frequencies
little morphometric or survival differences
Single nucleotide polymorphisms (SNPs) in single genes related to known functional protein classes
Lipid metabolism
Ion homeostasis
Likely an adaptation to varying CO2 conditions along the Californian Coast
Major
challenges
Acidification is only one
of many potential stressors
1
Evolutionary adaptation to other stressors may promote or constraint adaptation to acidification
e.g., food availability can modify CO2 sensitivity in bivalves, fish
What about copepods?
II
Species interaction will
modify selection pressure to OA
We only have a limited picture about the sensitivity of some stages, not whole life
-> fitness consequences
unclear
III
OA sensitivities
are stage-specific
Experiments
:
abrupt, extreme change
Reality
:
gradual change,
short-term variability
IV
What selection differential?
h2 = 0.5
h2 = 0.12
h2 = 0.43
h2 = 0.14
h2 = 0.09
Transgenerational effects are truly ubiquitous in nature
Jablonka & Raz
Q Rev Biol
2009; Salinas et al.
Non-genetic Inheritance
2012
Transgenerational acclimation to high CO2 has been shown in the laboratory
Clownfish larvae
(Miller et al. Nat Clim Change 2012)
Green sea urchin larvae
(Dupont Mar Biol et al. 2013)
Sydney rock oyster larvae
(Parker et al. Mar Biol 2012)
But does it happen in the wild?
Adults collected from the field

Offspring reared in the lab

Parallel field monitoring

2 years
10 exp

~400 vs 2,000 µatm CO2
Transgenerational acclimation is not just a laboratory phenomenon!
Its existence suggests that organisms need it. Perhaps to cope with seasonal CO2 variability?
Implication I: how useful are broodstocks?
Implication II: Does TGP prevent adaptation?
Selection differentials?
Trade-offs?
Spatial approaches
Temporal, palaeontological approaches
Genetic, molecular approaches
Full transcript