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FRIMEDBIO-Fri prosj.st. med.,helse,biol

The genomic basis of temperature adaptation across space

Alternative title: Det genomiske grunnlaget for temperaturtilpasning i det geografiske rom

Awarded: NOK 11.7 mill.

Project Number:

315287

Application Type:

Project Period:

2021 - 2025

Partner countries:

How do organisms adapt to their local environment? This question is a main focus of evolutionary biology. It becomes urgent in times of anthropogenic climate change, as we need to predict whether populations and species will be able to adapt to future conditions. To fully understand adaptation, we need to identify the genes responsible for it. In particular, we need to analyse how these genes change across the species range, and find out which populations contain genetic variants that will help them to respond to changing environments in the future. This project aims to contribute towards these goals by studying the genetic basis of temperature adaptation in great detail. We focus on an ideal study species, the marine snail Littorina saxatilis, a key member of marine ecosystems. On the large scale, the species covers a wide range from warm (e.g. Spain) to cold waters (e.g. northern Norway). On the small scale, it occupies cliffs with steep temperature gradients in each location. Our main goal is to identify the genes contributing to temperature adaptation, ask where they are located in the genome, and test whether the genetic basis of temperature adaptation varies across space. For example, we test whether the same genes contribute to adaptation in different geographical locations, and whether adaptation on small scales (shore levels) and large scales (latitudinal gradients) uses the same genes. So far, we have collected snails from a large number of locations across Europe and North America both from the high and the low shore and have sequenced their genomes. We have identified genes potentially contributing to shore level adaptation (small-scale temperature gradients) in Sweden, Spain and Norway. We find that these genes overlap significantly between Norway and Sweden, indicating a similar genetic basis of adaptation; in contrast, in Spain the genetic basis of adaptation appears to be largely different, consistent with Spanish populations having been isolated from Scandinavian populations for a long time. We have also developed a method to study chromosomal rearrangements – large-scale mutations predicted to contribute to adaptation – in pooled whole-genome sequencing data. Using this approach, we could show that chromosomal inversions strongly contribute to shore level adaptation in our system. In addition, we have identified physiological characteristics that differentiate snails from the high and low shore even though they live just meters apart. These include heart rate responses to high temperatures and the time it takes a snail to drop down from a vertical surface when exposed to heat. We have developed assays to measure these traits in large numbers of individuals and are currently applying these to snails from lab crosses. This will allow us to identify and compare the genetic basis of these traits in snails from Sweden, Spain and Norway. We are also currently exposing snails from multiple locations to different temperatures in order to study gene expression profiles. Finally, we have sampled a large number of snails from a population recently introduced to waters unusually warm for this species (Mediterranean), mimicking climate change. We have measured various traits in these snails, including traits reflecting temperature adaptation, and are currently sequencing their genomes. In the next months, we will use these data to identify the origin of this human-introduced population and to test for signatures of recent selection in the genome.

How do organisms adapt to their local environment? This question is a main focus of evolutionary biology. It becomes especially urgent in times of anthropogenic climate change, as we need to predict whether populations and species will be able to adapt to future conditions. To fully understand adaptation, we need to identify the underlying genes and genomic regions. In particular, we need to analyse how adaptive genetic variation is distributed across the species range, and whether genetic variation necessary for responding to future conditions is available locally. The proposed project will make a substantial contribution towards this goal by studying the genetic basis of temperature adaptation across space and in exceptional detail. We will focus on an ideal model system, the marine snail Littorina saxatilis, a key member of marine ecosystems. On the large scale, the species covers a wide latitudinal range from warm (e.g. Spain) to cold waters (e.g. northern Norway). On the small scale, L. saxatilis occupies cliffs with steep temperature gradients in each location. We will identify the genomic regions underlying temperature adaptation and study their distribution in the genome. For that, we will use a set of complementary approaches (genomes scans, QTL mapping, gene expression analysis, cline analysis, and quantitative genetics), allowing for comprehensive insights. We will especially focus on how adaptive variation is distributed across space, testing whether the same genes contribute to adaptation in different geographical locations, and whether adaptation on small scales (shore levels) and large scales (latitudinal gradients) has the same genetic basis. We will also include a population recently introduced to waters unusually warm for this species (Mediterranean), mimicking climate change. Our work will represent a pioneering case study useful for the communities of evolutionary biologists, conservation biologists, and conservation practitioners.

Funding scheme:

FRIMEDBIO-Fri prosj.st. med.,helse,biol

Funding Sources