Kelp retained broad genetic diversity after a heatwave, with localized shifts
Western Australian kelp samples collected across 16 years show broad genetic stability around the severe 2011 marine heatwave. Some genetic markers nevertheless changed, particularly at warmer northern locations. The observational study finds patterns consistent with thermal selection, while population declines and migration remain possible contributors to those localized shifts.
Science··Morning
Broad genetic diversity survived the heatwave
Western Australian populations of Ecklonia radiata, a large brown seaweed that forms underwater forests, retained broadly stable genetic diversity across the severe 2011 marine heatwave. A peer-reviewed observational study in Scientific Reports compared samples spanning 2006–2022. Within that overall stability, particular genetic markers changed in frequency. The strongest shifts occurred at warmer northern sites, where the heatwave’s ecological effects had been greatest.[1]
Repeated samples followed localized genetic changes
The analysis used 18,384 genetic markers from 322 individuals collected at Jurien Bay, Marmion and Hamelin Bay. These locations provided a 16-year comparison before and after the heatwave. At some comparable markers, southern populations moved toward genetic patterns characteristic of warmer northern populations. A subset of the changes involved markers previously associated with temperature. For most markers, variation over time did not follow the changes expected from this extreme warming event.[1]
Several processes can shape the observed shifts
The researchers interpret the directional shifts as consistent with selection for heat tolerance. Genetic drift during population declines and limited migration could also have contributed. Some years had very few samples, and the statistical models explained only a small share of overall genetic variation. These observations distinguish localized responses from a broad loss of diversity, while leaving the populations’ resistance to future heatwaves unresolved.[1]
