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,
• Publikační typ
• časopisecké články MeSH

Rapidly radiated groups are usually accompanied by unclear lineage and taxa delineation, which complicates their better understanding in terms of biodiversity, evolutionary processes, and taxonomic treatment. The most species-rich orchid subtribe, Pleurothallidinae, exemplifies an extremely diverse group with a complex evolutionary history associated with Andean orography. Here we combined multi-loci phylogeny reconstruction (HybSeq), genome-wide traits (inferred by flow cytometry), spatial analyses, and biogeography to investigate the evolutionary intricacy of one clade of Pleurothallidinae orchids. To achieve deep insights, we performed multiple species tree reconstruction approaches with the implementation of custom scripts to reveal sources of topological discrepancies and alternative evolutionary scenarios. The phylogeny clearly resolves the delimitation of the main evolutionary lineages corresponding to the accepted genera, with the exception of the genus Specklinia, which is divided into three distinct monophyletic lineages whose taxonomic treatment is proposed. Genome-wide characters (especially genome size) show an association with precipitation seasonality in a geographical context, and partial endoreplication, a unique character of orchids, is geographically restricted to the Andes, Central America, and the Caribbean. Specifically, the Andean region exemplifies the prevalence of bigger genome size and higher GC content, resulting from a higher proportion of species with partial endoreplication. The Andean origin of the clade was also revealed by biogeographic analysis. Our comprehensive approach has provided deep insights into the evolution of this clade and may be a useful tool for unraveling the intricate evolutionary history of similarly complex lineages.

• Klíčová slova
• Andes, GC content, HybSeq, Pleurothallidinae, endoreplication, evolution, genome size, spatial analysis,
• MeSH
• biologická evoluce * MeSH
• délka genomu MeSH
• fylogeneze * MeSH
• genom rostlinný * genetika   MeSH
• molekulární evoluce MeSH
• Orchidaceae * genetika   klasifikace   MeSH
• Publikační typ
• časopisecké články MeSH

BACKGROUND: Genome size is influenced by natural selection and genetic drift acting on variations from polyploidy and repetitive DNA sequences. We hypothesized that centromere drive, where centromeres compete for inclusion in the functional gamete during meiosis, may also affect genome and chromosome size. This competition occurs in asymmetric meiosis, where only one of the four meiotic products becomes a gamete. If centromere drive influences chromosome size evolution, it may also impact post-polyploid diploidization, where a polyploid genome is restructured to function more like a diploid through chromosomal rearrangements, including fusions. We tested if plant lineages with asymmetric meiosis exhibit faster chromosome size evolution compared to those with only symmetric meiosis, which lack centromere drive as all four meiotic products become gametes. We also examined if positive selection on centromeric histone H3 (CENH3), a protein that can suppress centromere drive, is more frequent in these asymmetric lineages. METHODS: We analysed plant groups with different meiotic modes: asymmetric in gymnosperms and angiosperms, and symmetric in bryophytes, lycophytes and ferns. We selected species based on available CENH3 gene sequences and chromosome size data. Using Ornstein-Uhlenbeck evolutionary models and phylogenetic regressions, we assessed the rates of chromosome size evolution and the frequency of positive selection on CENH3 in these clades. RESULTS: Our analyses showed that clades with asymmetric meiosis have a higher frequency of positive selection on CENH3 and increased rates of chromosome size evolution compared to symmetric clades. CONCLUSIONS: Our findings support the hypothesis that centromere drive accelerates chromosome and genome size evolution, potentially also influencing the process of post-polyploid diploidization. We propose a model which in a single framework helps explain the stability of chromosome size in symmetric lineages (bryophytes, lycophytes and ferns) and its variability in asymmetric lineages (gymnosperms and angiosperms), providing a foundation for future research in plant genome evolution.

• Klíčová slova
• Angiosperms, CENH3, asymmetric and symmetric meiosis, bryophytes, centromere drive, chromosome size, ferns, genome size, gymnosperms, lycophytes, post-polyploid diploidization,
• MeSH
• biologická evoluce MeSH
• centromera * genetika   MeSH
• chromozomy rostlin * genetika   MeSH
• cykasy genetika   MeSH
• délka genomu * MeSH
• fylogeneze MeSH
• genom rostlinný * genetika   MeSH
• histony genetika   metabolismus   MeSH
• kapradiny genetika   fyziologie   MeSH
• Magnoliopsida genetika   MeSH
• meióza * genetika   MeSH
• molekulární evoluce * MeSH
• polyploidie MeSH
• rostliny genetika   MeSH
• selekce (genetika) MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• histony MeSH

BACKGROUND: Species of the carnivorous family Lentibulariaceae exhibit the smallest genomes in flowering plants. We explored the hypothesis that their minute genomes result from the unique mitochondrial cytochrome c oxidase (COX) mutation. The mutation may boost mitochondrial efficiency, which is especially useful for suction-bladder traps of Utricularia, but also increase DNA-damaging reactive oxygen species, leading to genome shrinkage through deletion-biased DNA repair. We aimed to explore the impact of this mutation on genome size, providing insights into genetic mutation roles in plant genome evolution under environmental pressures. METHODS: We compiled and measured genome and mean chromosome sizes for 127 and 67 species, respectively, representing all three genera (Genlisea, Pinguicula and Utricularia) of Lentibulariaceae. We also isolated and analysed COX sequences to detect the mutation. Through phylogenetic regressions and Ornstein-Uhlenbeck models of trait evolution, we assessed the impact of the COX mutation on the genome and chromosome sizes across the family. RESULTS: Our findings reveal significant correlations between the COX mutation and smaller genome and chromosome sizes. Specifically, species carrying the ancestral COX sequence exhibited larger genomes and chromosomes than those with the novel mutation. This evidence supports the notion that the COX mutation contributes to genome downsizing, with statistical analyses confirming a directional evolution towards smaller genomes in species harbouring these mutations. CONCLUSIONS: Our study confirms that the COX mutation in Lentibulariaceae is associated with genome downsizing, probably driven by increased reactive oxygen species production and subsequent DNA damage requiring deletion-biased repair mechanisms. While boosting mitochondrial energy output, this genetic mutation compromises genome integrity and may potentially affect recombination rates, illustrating a complex trade-off between evolutionary advantages and disadvantages. Our results highlight the intricate processes by which genetic mutations and environmental pressures shape genome size evolution in carnivorous plants.

• Klíčová slova
• Genlisea, Pinguicula, Utricularia, Carnivory, Lentibulariaceae, chromosome size, cytochrome oxidase, genome size, recombination rate, smallest genomes,
• MeSH
• délka genomu * MeSH
• fylogeneze MeSH
• genom rostlinný * MeSH
• Magnoliopsida genetika   MeSH
• molekulární evoluce MeSH
• mutace MeSH
• respirační komplex IV genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• respirační komplex IV MeSH