Thermal tolerance in the keystone species Daphnia magna-a candidate gene and an outlier analysis approach.
Changes in temperature have occurred throughout Earth's history. However, current warming trends exacerbated by human activities impose severe and rapid loss of biodiversity. Although understanding the mechanisms orchestrating organismal response to climate change is important, remarkably few studies document their role in nature. This is because only few systems enable the combined analysis of genetic and plastic responses to environmental change over long time spans. Here, we characterize genetic and plastic responses to temperature increase in the aquatic keystone grazer Daphnia magna combining a candidate gene and an outlier analysis approach. We capitalize on the short generation time of our species, facilitating experimental evolution, and the production of dormant eggs enabling the analysis of long-term response to environmental change through a resurrection ecology approach. We quantify plasticity in the expression of 35 candidate genes in D. magna populations resurrected from a lake that experienced changes in average temperature over the past century and from experimental populations differing in thermal tolerance isolated from a selection experiment. By measuring expression in multiple genotypes from each of these populations in control and heat treatments, we assess plastic responses to extreme temperature events. By measuring evolutionary changes in gene expression between warm- and cold-adapted populations, we assess evolutionary response to temperature changes. Evolutionary response to temperature increase is also assessed via an outlier analysis using EST-linked microsatellite loci. This study provides the first insights into the role of plasticity and genetic adaptation in orchestrating adaptive responses to environmental change in D. magna.
Laboratory of Aquatic Ecology, Evolution and Conservation, University of Leuven, Ch. Deberiotstraat 32, 3000 Leuven, Belgium.
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M
Jansen
Laboratory of Aquatic Ecology, Evolution and Conservation, University of Leuven, Ch. Deberiotstraat 32, 3000 Leuven, Belgium.
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AN
Geerts
Environmental Genomics Group, School of Biosciences, University of Birmingham, Birmingham, B15 2TT, United Kingdom.
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A
Rago
Laboratory of Aquatic Ecology, Evolution and Conservation, University of Leuven, Ch. Deberiotstraat 32, 3000 Leuven, Belgium.
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Spanier
Laboratory of Aquatic Ecology, Evolution and Conservation, University of Leuven, Ch. Deberiotstraat 32, 3000 Leuven, Belgium.
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Denis
Laboratory of Aquatic Ecology, Evolution and Conservation, University of Leuven, Ch. Deberiotstraat 32, 3000 Leuven, Belgium.
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De Meester
Environmental Genomics Group, School of Biosciences, University of Birmingham, Birmingham, B15 2TT, United Kingdom.
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http://orcid.org/0000-0002-1716-5624
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Orsini
D000818:Animals; D005075:Biological Evolution; D057231:Climate Change; D003621:Daphnia / Q000235:genetics*; D020224:Expressed Sequence Tags; D015870:Gene Expression; D005838:Genotype; D060106:Lakes; D018895:Microsatellite Repeats; D008957:Models, Genetic; D013696:Temperature; D000071436:Thermotolerance / Q000235:genetics*
adaptation; climate change; contemporary evolution; crustaceans; gene structure and function; molecular evolution