Genome-Wide Adaptation to a Complex Environmental Gradient in a Keystone Phytoplankton Species

Area of Science:

• Marine biology
• Evolutionary genetics
• Population genomics

Background:

• Marine phytoplankton are crucial for global primary production and biogeochemical cycles.
• The genetic basis of phytoplankton adaptation to fluctuating coastal environments is poorly understood.
• The Baltic Sea represents a unique natural experiment for studying adaptation in brackish waters.

Purpose of the Study:

• To investigate the genomic underpinnings of adaptation in the diatom Skeletonema marinoi colonizing the Baltic Sea.
• To identify genes under selection in response to environmental gradients in the Baltic Sea.
• To understand the role of salinity and other factors in local adaptation.

Main Methods:

• Combined population genomics with experimental transcriptomics.
• Utilized target capture of the entire nuclear genome and pooled shotgun sequencing.
• Performed genotype-environment association analyses and laboratory common garden experiments.

Main Results:

• Identified over 1000 genes with signals of selection in response to Baltic Sea environmental gradients (salinity, temperature, nutrients).
• Locally adapted genes are involved in diverse metabolic processes, including signal transduction, cell cycle, and homeostasis.
• Significant overlap was found between locally adapted genes and salinity-responsive genes, implicating salinity in adaptation.

Conclusions:

• Local adaptation in phytoplankton to complex coastal environments is driven by widespread changes across multiple metabolic pathways.
• The Baltic Sea salinity gradient plays a significant role in the local adaptation of Skeletonema marinoi.
• This study provides insights into the evolutionary genetics of phytoplankton adapting to environmental change.