Understanding the proximate and ultimate causes of genome size variation has been the focus of considerable research. However, the extent and cause of intraspecific variation in genome size are debated and poorly understood. This study aimed to test the role of genome size in adaptation through variations in intraspecific genome size. Genome size was measured in 53 Roscoea tibetica populations from the Hengduan Mountains using flow cytometry. Stomatal size and density data were collected from wild and common garden populations. Associations among genome size, environmental factors, and stomatal traits were explored. We found that high genome size variability was positively correlated with most environmental factors but negatively correlated with solar radiation during the growing season. The environment, rather than geography, significantly influenced variations in genome size. Stomatal traits measured in the wild were significantly correlated with genome size, but no such correlations were detected in the common garden. Populations in the common garden had larger stomatal sizes and lower stomatal densities. Populations with smaller genome size presented a larger degree of stomatal trait variation from the wild to the common garden. Our findings suggest that intraspecific genome size has undergone adaptive evolution driven by environmental stress. A smaller genome size is more advantageous for the alpine ginger to adapt to and thrive in changing alpine habitats.

• Klíčová slova
• Roscoea tibetica, adaptation, common garden, environmental factors, intraspecific genome size, stomatal traits,
• MeSH
• délka genomu * MeSH
• fyziologická adaptace * genetika   MeSH
• genom rostlinný * MeSH
• průduchy rostlin genetika   MeSH
• zázvor lékařský * genetika   MeSH
• Publikační typ
• časopisecké články MeSH

BACKGROUND AND AIMS: The Greater Cape Floristic Region is one of the world's biodiversity hotspots and is considered poor in polyploids. To test this assumption, ploidy variation was investigated in a widespread Cape shrub, Dicerothamnus rhinocerotis (renosterbos, Asteraceae). The aim was to elucidate the cytotype distribution and population composition across the species range, and to assess differences in morphology, environmental niches and genetics. METHODS: Ploidy level and genome size were determined via flow cytometry and cytotype assignment was confirmed by chromosome counting. Restriction site-associated DNA sequencing (RADseq) analyses were used to infer genetic relationships. Cytotype climatic and environmental niches were compared using a range of environmental layers and a soil model, while morphological differences were examined using multivariate methods. KEY RESULTS: The survey of 171 populations and 2370 individuals showed that the species comprises diploid and tetraploid cytotypes, no intermediates and only 16.8 % of mixed populations. Mean 2C values were 1.80-2.06 pg for diploids and 3.48-3.80 pg for tetraploids, with very similar monoploid genome sizes. Intra-cytotype variation showed a significant positive correlation with altitude and longitude in both cytotypes and with latitude in diploids. Although niches of both cytotypes were highly equivalent and similar, their optima and breadth were shifted due to differences mainly in isothermality and available water capacity. Morphometric analyses showed significant differences in the leaves and corolla traits, the number of florets per capitulum, and cypsela dimensions between the two cytotypes. Genetic analyses revealed four groups, three of them including both cytotypes. CONCLUSIONS: Dicerothamnus rhinocerotis includes two distinct cytotypes that are genetically similar. While tetraploids arise several times independently within different genetic groups, morphological and ecological differences are evident between cytotypes. Our results open up new avenues for questions regarding the importance of ploidy in the megadiverse Cape flora, and exemplify the need for population-based studies focused on ploidy variation.

• Klíčová slova
• Elytropappus rhinocerotis, Stoebe clade, Asteraceae, Compositae, Gnaphalieae, RADseq, South Africa, flow cytometry, ploidy level, renosterbos, renosterveld,
• MeSH
• Asteraceae * genetika   MeSH
• délka genomu MeSH
• diploidie * MeSH
• ekosystém * MeSH
• genetická variace MeSH
• genom rostlinný MeSH
• tetraploidie * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH