Global warming permits range expansions of tropical marine species into mid-latitude habitats, where they are, however, faced with cold winter temperatures. Therefore, tolerance to cold temperatures may be the key adaptation controlling zonal range expansion in tropical marine species. Here we investigated the molecular and physiological response to cold and heat stress in a tropical symbiont-bearing foraminifera that has successfully invaded the Eastern Mediterranean. Our physiological measurements indicate thermal tolerance of the diatom symbionts but a decrease in growth for the foraminifera host under both cold and warm stress. The combined (‘holobiont’) transcriptome revealed an asymmetric response in short-term gene expression under cold versus warm stress. Cold stress induced major reorganization of metabolic processes, including regulation of genes involved in photosynthesis. Analyses limited to genes that are inferred to belong to the symbionts confirm that the observed pattern is due to changes in the regulation of photosynthesis-related genes and not due to changes in the abundance of the symbionts. In contrast to cold stress, far fewer genes change expression under heat stress and those that do are primarily related to movement and cytoskeleton. This implies that under cold stress, cellular resources are allocated to the maintenance of photosynthesis, and the key to zonal range shifts of tropical species could be the cold tolerance of the symbiosis. A free Plain Language Summary can be found within the Supporting Information of this article.
Bibliographical noteFunding Information:
This work was supported by ISF grant no. 941/17, and BMBF‐MOST Cooperation in Marine Sciences grant numbers: 3‐15275 and 3‐15274. The authors thank the support provided to D.T. by the Mediterranean Sea Research Centre of Israel.
This work was supported by ISF grant no. 941/17, and BMBF-MOST Cooperation in Marine Sciences grant numbers: 3-15275 and 3-15274. The authors thank the support provided to D.T. by the Mediterranean Sea Research Centre of Israel.
© 2021 British Ecological Society
- biogeographical expansion
- cold temperature limitations
- global warming
- large benthic foraminifera
- thermal stress
- transcriptomic signature