Genome size exhibits extensive variation across the tree of life. Previous studies have predominantly focused on interspecific comparisons. However, the ecological drivers and adaptive implications of its variation, particularly within a single species, have received less attention.
In a study published in Physiologia Plantarum, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences investigated the intraspecific genome size variation and its role in ecological adaptation in the hexaploid plant Rorippa indica (R. indica). Their findings indicated that plants can adapt to tropical environments by significantly enlarging their genomes.
The researchers conducted a comprehensive study on 952 individuals from 97 different populations of R. indica. By integrating flow cytometry, plastome-based phylogeography, repetitive sequence analysis, and reciprocal transplant experiments, they investigated natural patterns of genome size variation and adaptive mechanisms in plants.
The researchers identified a continuous range of genome sizes within R. indica, which correlated closely with geography, climatic gradients, and lineage history. Tropical lineages of R. indica consistently possessed larger genomes compared to their temperate counterparts from northern regions. Further analysis revealed that the genome expansion was primarily driven by the amplification of specific sequences, including 45S rDNA and Ty1 retrotransposons.
A critical common garden experiment, where plant strains with different genome sizes were transplanted to both Xishuangbanna (tropical) and Kunming (temperate) sites, provided the functional evidence. In the stable, warm tropical environment of Xishuangbanna, the large-genome strains produced significantly more seeds, demonstrating a clear adaptive advantage.
The study provides insights into how genome size interacts with the environment. It suggests that under global warming species or populations with larger genomes might be favored due to their increased reproductive output.
"Our findings suggest that 'big' and 'small' genomes are not just neutral variations but reflect distinct adaptive strategies shaped by natural selection," said Prof. XING Yaowu of XTBG. "Genomic expansion appears to be a positive response to the relatively stable conditions of the tropics."
First published: 26 October 2025
