Phylogeographic differentiation versus transcriptomic adaptation to warm temperatures in Zostera marina, a globally important seagrass.
Populations distributed across a broad thermal cline are instrumental in addressing adaptation to increasing temperatures under global warming. Using a space-for-time substitution design, we tested for parallel adaptation to warm temperatures along two independent thermal clines in Zostera marina, the most widely distributed seagrass in the temperate Northern Hemisphere. A North-South pair of populations was sampled along the European and North American coasts and exposed to a simulated heatwave in a common-garden mesocosm. Transcriptomic responses under control, heat stress and recovery were recorded in 99 RNAseq libraries with ~13 000 uniquely annotated, expressed genes. We corrected for phylogenetic differentiation among populations to discriminate neutral from adaptive differentiation. The two southern populations recovered faster from heat stress and showed parallel transcriptomic differentiation, as compared with northern populations. Among 2389 differentially expressed genes, 21 exceeded neutral expectations and were likely involved in parallel adaptation to warm temperatures. However, the strongest differentiation following phylogenetic correction was between the three Atlantic populations and the Mediterranean population with 128 of 4711 differentially expressed genes exceeding neutral expectations. Although adaptation to warm temperatures is expected to reduce sensitivity to heatwaves, the continued resistance of seagrass to further anthropogenic stresses may be impaired by heat-induced downregulation of genes related to photosynthesis, pathogen defence and stress tolerance.
Faculty of Biosciences and Aquaculture, Nord University, Universitetsalleen 11, Bodø, 8049, Norway. Alexander-Jueterbock@web.de.
A
A
Jueterbock
Institut für Populationsgenetik, Vetmeduni Vienna, Veterinärplatz 1, Vienna, 1210, Austria.|Institute for Evolution and Biodiversity, University of Münster, Hüfferstr. 1, Münster, 48149, Germany.
S U
SU
Franssen
Integrated School of Ocean Sciences (ISOS), Kiel University, Leibnizstr. 3, Kiel, 24098, Germany.
N
N
Bergmann
Institute for Evolution and Biodiversity, University of Münster, Hüfferstr. 1, Münster, 48149, Germany.
J
J
Gu
Shoals Marine Laboratory, University of New Hampshire, Durham, NH, 03824, USA.|Groningen Institute for Evolutionary Life Sciences, Ecological and Evolutionary Genomics Group, University of Groningen, P.O. Box 11103, Groningen, 9700 CC, The Netherlands.
J A
JA
Coyer
GEOMAR Helmholtz-Centre for Ocean Research Kiel, Evolutionary Ecology of Marine Fishes, Düsternbrooker Weg 20, Kiel, 24105, Germany.
T B H
TB
Reusch
Institute for Evolution and Biodiversity, University of Münster, Hüfferstr. 1, Münster, 48149, Germany.
E
E
Bornberg-Bauer
Groningen Institute for Evolutionary Life Sciences, Ecological and Evolutionary Genomics Group, University of Groningen, P.O. Box 11103, Groningen, 9700 CC, The Netherlands.
J L
JL
Olsen
D000222:Adaptation, Physiological; D005060:Europe; D009656:North America; D010802:Phylogeny; D058974:Phylogeography; D013696:Temperature; D059467:Transcriptome; D035962:Zosteraceae / Q000235:genetics*
RNAseq; common-garden experiment; differential expression; global warming; heatwave; transcriptomics