The global distribution of angiosperm genome size is shaped by climate

Bhadra S., Leitch I.J., Onstein R.E.

Angiosperm diversity arises from trait flexibility and repeated evolutionary radiations, but the role of genomic characters in these radiations remains unclear. In this opinion article, we discuss how genome size can influence angiosperm diversification via its intricate link with cell size, tissue packing, and physiological processes which, in turn, influence the macroevolution of functional traits. We propose that integrating genome size, functional traits, and phylogenetic data across a wide range of lineages allows us to test whether genome size decrease consistently leads to increased trait flexibility, while genome size increase constrains trait evolution. Combining theories from molecular biology, functional ecology and macroevolution, we provide a framework to better understand the role of genome size in trait evolution, evolutionary radiations, and the global distribution of angiosperms.

Gomez M.S., Brown M.J., Pironon S., Veselý P., Bureš P., Elliott T.L., Zedek F., Pellicer J., Forest F., Lughadha E.N., Leitch I.J.

SummaryAngiosperms with large genomes experience nuclear-, cellular- and organism-level constraints that may limit their phenotypic plasticity and ecological niche. These constraints have been documented to vary across lineages, life-history strategies, ecogeographic patterns and environmental conditions. Therefore, we test the hypotheses that extinction risk is higher in large-genomed compared to small-genomed species, and that the effect of genome size varies across three selected covariates: life form, endemism, and climatic zones.We collated genome size and extinction risk information for a representative sample of angiosperms comprising 3,250 species, which we analyzed alongside life form, endemism and climate variables using a phylogenetic framework.Angiosperm genome size is positively correlated with extinction risk, a pattern driven by a signal in herbaceous but not woody species, regardless of climate and endemism. The influence of genome size is stronger in endemic herbaceous species, but is relatively homogenous across different climates. Beyond its indirect link via endemism and climate, genome size also influences extinction risk directly and significantly.Genome size may serve as a proxy for difficult-to-measure parameters associated with resilience and vulnerability in herbaceous angiosperms. Therefore, it merits further exploration as a useful biological attribute for understanding intrinsic extinction risk and augmenting plant conservation efforts.

Taylor A., Weigelt P., Denelle P., Cai L., Kreft H.

Summary Plant life and growth forms (shortened to ‘plant forms’) represent key functional strategies of plants in relation to their environment and provide important insights into the ecological constraints acting on the distribution of biodiversity. Despite their functional importance, how the spectra of plant forms contribute to global gradients of plant diversity is unresolved. Using a novel dataset comprising > 295 000 species, we quantify the contribution of different plant forms to global gradients of vascular plant diversity. Furthermore, we establish how plant form distributions in different biogeographical regions are associated with contemporary and paleoclimate conditions, environmental heterogeneity and phylogeny. We find a major shift in representation of woody perennials in tropical latitudes to herb‐dominated floras in temperate and boreal regions, following a sharp latitudinal gradient in plant form diversity from the tropics to the poles. We also find significant functional differences between regions, mirroring life and growth form responses to environmental conditions, which is mostly explained by contemporary climate (18–87%), and phylogeny (6–62%), with paleoclimate and heterogeneity playing a lesser role (< 23%). This research highlights variation in the importance of different plant forms to diversity gradients world‐wide, shedding light on the ecological and evolutionary pressures constraining plant–trait distributions.

Šmarda P., Klem K., Knápek O., Veselá B., Veselá K., Holub P., Kuchař V., Šilerová A., Horová L., Bureš P.

Summary Polyploidy plays an important role in plant evolution, but knowledge of its eco‐physiological consequences, such as of the putatively enlarged stomata of polyploid plants, remains limited. Enlarged stomata should disadvantage polyploids at low CO2 concentrations (namely during the Quaternary glacial periods) because larger stomata are viewed as less effective at CO2 uptake. We observed the growth, physiology, and epidermal cell features of 15 diploids and their polyploid relatives cultivated under glacial, present‐day, and potential future atmospheric CO2 concentrations (200, 400, and 800 ppm respectively). We demonstrated some well‐known polyploidy effects, such as faster growth and larger leaves, seeds, stomata, and other epidermal cells. The stomata of polyploids, however, tended to be more elongated than those of diploids, and contrary to common belief, they had no negative effect on the CO2 uptake capacity of polyploids. Moreover, polyploids grew comparatively better than diploids even at low, glacial CO2 concentrations. Higher polyploids with large genomes also showed increased operational stomatal conductance and consequently, a lower water‐use efficiency. Our results point to a possible decrease in growth superiority of polyploids over diploids in a current and future high CO2 climatic scenarios, as well as the possible water and/or nutrient dependency of higher polyploids.

Bureš P., Ozcan M., Šmerda J., Michálková E., Horová L., Plačková K., Šmarda P., Elliott T.L., Veselý P., Ćato S., Norouzi M., Sheidai M., Zedek F.

Elliott T.L., Zedek F., Barrett R.L., Bruhl J.J., Escudero M., Hroudová Z., Joly S., Larridon I., Luceño M., Márquez-Corro J.I., Martín-Bravo S., Muasya A.M., Šmarda P., Thomas W.W., Wilson K.L., et. al.

Abstract Background and Aims While variation in genome size and chromosome numbers and their consequences are often investigated in plants, the biological relevance of variation in chromosome size remains poorly known. Here, we examine genome and mean chromosome size in the cyperid clade (families Cyperaceae, Juncaceae, Thurniaceae), which is the largest vascular plant lineage with predominantly holocentric chromosomes. Methods We measured genome size in 436 species of cyprids using flow cytometry and augment this data with previously published datasets. We then separately compared genome and mean chromosome sizes (2C/2n) amongst the major lineages of cyperids and analyzed how these two genomic traits are associated with various environmental factors using phylogenetically-informed methods. Key Results We show that cyperids have the smallest mean chromosome sizes recorded in seed plants, with a large divergence between the smallest and largest values. We found that cyperid species with smaller chromosomes have larger geographical distributions and that there is a strong inverse association between mean chromosome size and number across this lineage. Conclusions The distinct patterns in genome size and mean chromosome size across the cyperids might be explained by holokinetic drive. The numerous small chromosomes might function to increase genetic diversity in this lineage where crossovers are limited during meiosis.

Peng Y., Yang J., Leitch I.J., Guignard M.S., Seabloom E.W., Cao D., Zhao F., Li H., Han X., Jiang Y., Leitch A.R., Wei C.

Grassland ecosystems cover c. 40% of global land area and contain c. 40% of soil organic carbon. Understanding the effects of adding nutrients to grasslands is essential because they provide much of our food, support diverse ecosystem services and harbor rich biodiversity. Using the meadow steppe (grassland) study site of Inner Mongolia, we manipulated seven key nutrients and a cocktail of micronutrients to examine their effects on grassland biomass productivity and diversity. The results, explained in structural equation models, link two previously disparate hypotheses in grassland ecology: (1) the light asymmetry competition hypothesis and (2) the genome size-nutrient interaction hypothesis. We show that aboveground net primary productivity increases predominantly from species with large genome sizes with the addition of nitrogen, and nitrogen plus phosphorus. This drives an asymmetric competition for light, causing a decline in species richness mainly in species with small genome sizes. This dynamic is likely to be caused by the nutrient demands of the nucleus and/or the scaling effects of nuclear size on cell size which impact water use efficiency. The model will help inform the best management approaches to reverse the rapid and unprecedented degradation of grasslands globally.

Guo Q., Qian H., Zhang J.

Aim What factors may affect species range sizes remains a central question in ecology and biogeography. Particularly, whether and how species richness may regulate average species range size remains largely elusive. Here, we explore the relationship between species diversity and species range size at a global extent and discuss its implications and significance for ecology and management. Location Worldwide. Taxon Plants and various groups of animals. Methods We used published data on plant richness and range size from around the world and synthesized related literature to assess the richness–range size relationships. We used paired t-tests and spatial autoregressive models in data analyses. We conducted a series of partial regressions to partition the variation in species ranges explained by paired independent variables (i.e. species richness versus latitude, species richness versus temperature or species richness versus temperature variability). Results A negative relationship between species diversity (richness) and species range size is nearly ubiquitous. In most cases, species diversity was a better predictor for species range size than latitude, temperature or temperature variability. Main conclusions The diversity predictor works well for different taxonomic groups, regions, continents, and for both terrestrial and marine biomes. High species diversity could imply stronger species interactions such as competition which limit the range sizes of constituent species. A nearly universal negative richness–range size relationship thus has significant implications for species invasion biology and conservation.

Vidal-Russell R., Tadey M., Urfusová R., Urfus T., Souto C.P.

Relationships between genome size and environmental variables suggest that DNA content might be adaptive and of evolutionary importance in plants. The genus Larrea provides an interesting system to test this hypothesis, since it shows both intra- and interspecific variation in genome size. Larrea has an amphitropical distribution in North and South American deserts, where it is most speciose. Larrea tridentata in North America shows a gradient of increasing autopolyploidy; while three of the four studied South American species are diploids, Larrea divaricata, Larrea nitida, Larrea ameghinoi, and the fourth is an allopolyploid, Larrea cuneifolia. We downloaded available focal species' georeferenced records from seven data reservoirs. We used these records to extract biologically relevant environmental variables from WorldClim at 30 arc seconds scale, to have a broad characterization of the variable climatic conditions of both regions, and a climatic envelope for each species. We estimated relative DNA content index and relative monoploid genome values, by flow cytometry, of four most abundant Larrea species throughout their respective ranges. Then we winnow the bioclimatic dataset down to uncorrelated variables and sampled locales, to analyse the degree of association between both intra- and interspecific relative DNA content and climatic variables that are functionally relevant in arid environments using Pearson correlations, general linear and mixed effects models. Within the genus Larrea, relative DNA content increases with rising temperature and decreases with rising precipitation. At the intraspecific level, all four species show relative DNA content variation across climatic conditions. Larrea is a genus that shows genome size variation correlated with climate. Our results are also consistent with the hypothesis that extreme environmental pressures may have facilitated repeated whole genome duplication events in North America, while in South America, reticulate evolution, as allopolyploidization, and speciation might have been climate-dependent since the Oligocene.

Sklenář P., Ptáček J., Klimeš A.

Genome size of alpine plants is not related to their resistance against frost and heat. Genome size is a variable trait in angiosperms, and it was suggested that large genome size represents a constraint in stressful environments. We measured genome size and resistance to frost and heat in 89 species of plants from tropical and temperate alpine habitats. Genome size of the species, ranging from 0.49 pg to 25.8 pg across the entire dataset, was not related to either frost or heat resistance in either group of plants. Genome size does not predict resistance to extreme temperatures in alpine plants and is thus not likely to predict plant responses to climate changes.

Ten Caten C., Holian L.A., Dallas T.

Abundance–occupancy relationships predict that species that occupy more sites are also more locally abundant, where occupancy is usually estimated following the assumption that species can occupy all sampled sites. Here we use the National Ecological Observatory Network small-mammal data to assess whether this assumption affects abundance–occupancy relationships. We estimated occupancy considering all sampled sites (traditional occupancy) and only the sites found within the species geographic range (spatial occupancy) and realized environmental niche (environmental occupancy). We found that when occupancy was estimated considering only sites possible for the species to colonize (spatial and environmental occupancy) weaker abundance–occupancy relationships were observed. This shows that the assumption that the species can occupy all sampled sites directly affects the assessment of abundance–occupancy relationships. Estimating occupancy considering only sites that are possible for the species to colonize will consequently lead to a more robust assessment of abundance–occupancy relationships.

Cobos M.E., Barve V., Barve N., Jiménez-Valverde A., Nuñez-Penichet C.

Data exploration is a critical step in understanding patterns and biases in information about species’ geographic distributions. We present rangemap, an R package that implements tools to explore species’ ranges based on simple analyses and visualizations. The rangemap package uses species occurrence coordinates, spatial polygons, and raster layers as input data. Its analysis tools help to generate simple spatial polygons summarizing ranges based on distinct approaches, including spatial buffers, convex and concave (alpha) hulls, trend-surface analysis, and raster reclassification. Visualization tools included in the package help to produce simple, high-quality representations of occurrence data and figures summarizing resulting ranges in geographic and environmental spaces. Functions that create ranges also allow generating extents of occurrence (using convex hulls) and areas of occupancy according to IUCN criteria. A broad community of researchers and students could find in rangemap an interesting means by which to explore species’ geographic distributions.

Carta A., Mattana E., Dickie J., Vandelook F.

AbstractSeeds show important variation as plant regenerative units among species, but their evolutionary co-variations with other plant characteristics are still poorly understood. Whilst a positive association of seed mass with genome size (GS) and life forms has already been documented, a broad-scale quantification of their evolutionary correlation and adaptive selection has never been conducted. Here, we tested for correlated evolution of seed mass and GS towards distinct selective regimes related to life form in angiosperms. In particular, we tested the hypothesis that the selection toward lighter seeds and smaller genomes is stronger for annual plants, ensuring high regenerative potential. Using multivariate evolutionary models over a dataset containing 3242 species, we showed an overall positive correlated evolution of seed mass and GS deviating from a pure drift process. Instead, evolutionary changes in seed and genome sizes were driven by adaptive selection towards optimal values differing among life forms. Specifically, the evolutionary optima towards which the seed and genome sizes evolve show a covariation toward small values in annuals, intermediate values in perennial herbs and a trade-off between seed mass and GS in woody plants. Moreover, the evolutionary correlation between seed mass and GS is strongest in annuals as an adaption to complete their life cycle in a short time window, when environmental conditions are favourable for regeneration and development to maturity. The asymmetry in the correlated evolution acting on seed and genome sizes due to life form could explain how life-history traits interplay with functional traits and how plants have evolved diverse successful life-history strategies.

Greimler J., Temsch E.M., Xue Z., Weiss-Schneeweiss H., Volkova P., Peintinger M., Wasowicz P., Shang H., Schanzer I., Chiapella J.O.

The grass Deschampsia cespitosa is a variable taxon out of which many varieties, subspecies and endemic species have been separated. In this paper, the variation in genome size (GS) and ploidy of this grass including several of its subspecies and two related species in Eurasia was investigated by flow cytometric (FCM) measurements. GS and ploidy data were also related to specific environments and reproduction mode. Ploidy levels found by FCM were confirmed by chromosome counts of diploid (2n = 28) and tetraploid (2n = 52) samples. Seminiferous (seed bearing) D. cespitosa was mainly diploid (GS between 3.754 and 5.438 pg/1C). GS variation in diploids showed a geographic pattern with a significant difference (H = 41,441, P < 0.001) between European (median = 4.377 pg) and Asian (median = 4.881 pg) accessions. Genome size (1C) in tetraploids ranged from 7.9426 to 9.0399 pg. Tetraploid seminiferous D. cespitosa was found mostly in disturbed habitats in western and southern Europe, while tetraploids in Asia were registered in wet Arctic habitats. Genome size (1C between 8.3278 and 8.8603 pg) of the pseudoviviparous plants (spikelets produce plantlets asexually) of wet habitats in central and northern Europe indicated tetraploidy. A putative triploid (GS 6.6817 pg) was detected in Iceland. Summing up, we found a high variation in GS on the geographic scale with significant regional differences in diploid D. cespitosa. Among the tetraploids, the asexually reproducing plants were bound to specific habitats, while the seminiferous plants showed a habitat preference similar to the diploids.

Zedek F., Veselý P., Tichý L., Elliott T.L., Garbolino E., Ruffray P., Bureš P.

Ultraviolet-B radiation (UV-B, wavelength 280-315 nm) is a clastogen (chromosome-breaking factor) that has accompanied life on Earth throughout its entire history (Lomax, 2012). Plants need to cope with UV-B almost permanently, as they are sessile organisms whose survival is directly dependent on solar radiation. The susceptibility to clastogens may depend on the type of chromosomes (Zedek and Bures, 2018).

Hu L., Xu T., Cai Y., Qin Y., Zheng Q., Chen T., Gong L., Yang J., Zhao Y., Chen J., Chen Z., Wu Y., Yang Z.

Corlett R.T.

Yao Y., Guo W., Gou J., Hu Z., Liu J., Ma J., Zong Y., Xin M., Chen W., Li Q., Wang Z., Zhang R., Uauy C., Baloch F.S., Ni Z., et. al.

Fujiwara T., Liu H., Zhu R., Schneider H.

AbstractAmong the lineages of the tree of life, land plants exhibit a remarkably high genomic disparity because of their distinct evolutionary trajectories in the phylogenetic history of their major lineages. The macroevolutionary pattern of genomic evolution has been mainly investigated to obtain insights into well‐studied lineages such as angiosperms, but little attention has been given to many important lineages such as bryophytes. This study was designed to resolve this gap by comparing the genomic evolution trajectories of mosses and liverworts. Thus, a data set comprising chromosome number and genome size was compiled, including previously published and newly generated data that were used to trace the phylogenetic history of these two parameters among mosses and liverworts via ancestral state reconstruction and phylogenetic comparative analyses. Contrasting patterns of chromosome number and genome size evolutions were detected between the two sister lineages. Mosses accumulated high chromosome number disparity via repeated whole‐genome duplications and descending dysploidy but maintained a small genome size. By contrast, the chromosome number of liverworts was highly conserved, and heterogeneous trends in genome size evolution were identified among major lineages. These contrasting patterns may be partly explained by the difference in genomic dynamics: Active dynamics enables genome downsizing and reorganization in mosses, whereas genome stability leads to the accumulation of large genomes in liverworts. The results of this study confirmed the distinct trends of genomic evolution in bryophytes.

Winterfeld G., Tkach N., Röser M.

Abstract Nuclear genome sizes of 54 representative species from 44 genera of the monocot order Poales were investigated by flow cytometry. Small holoploid genomes with < 2 pg/2C are characteristic of the Poales; only some families have larger 2C values, although this is not consistently the case. The sizes of monoploid genomes as well as mean DNA content per chromosome (MC) show a similar pattern. A comparison of the genome size data with current molecular phylogenetic data suggests that small monoploid genomes (1Cx < 0.4 pg) and small chromosomes (MC ≤ 0.05 pg), as found in some families, are likely the ancestral features of the order Poales. Conspicuous increases in genome size occurred particularly in the Poaceae (grasses) and to a lesser extent in the xyrid clade and the Restionaceae. According to previous phylogenomic studies, the Poaceae are characterized by a whole-genome duplication (WGD) called ρ, which is absent in all other Poales families. However, it is clear from the 1Cx values that the ρ event is not, or no longer, associated with a significant increase in the minimum 1Cx genome sizes of grasses compared to other Poales families. Future studies need to clarify whether the smallest 1Cx values in the Poaceae are due to a secondary reduction of the nuclear genome after the ρ event and whether the relatively large minimal 1Cx values of the xyrid clade were caused by a further WGD within Poales.

Lin Y., Chen Y., Zhao Y., Wu W., Yang C., Zheng Y., Huang M.

Bauhinia s.s. belongs to the Cercidoideae subfamily, located at the base of the Leguminosae family. It displays a variety of growth habits and morphologies, and is widely utilized as both ornamental and medicinal plants globally. The objective of this research is to uncover chloroplast genomes of species from Eastern Asia and Southern Africa, thereby advancing our understanding of the diversity within this genus. This study sequenced Bauhinia purpurea, Bauhinia brachycarpa var. microphylla, Bauhinia variegata var. candida, Bauhinia galpinii, and Bauhinia monandra using the Illumina platform and conducted the construction of phylogenetic trees as well as the estimation of divergence times. Compared to Asian species, the IR regions of African species underwent a contraction of approximately 100–400 bp. The phylogenetic analysis indicated that Asian and African species clustered into two distinct clades, with high support. The divergence of Bauhinia s.s. species occurred in the late Paleocene, and the rps18 and cemA genes were under positive selection. Six hypervariable regions were screened for evolutionary studies and the super-barcode data were used for species delimitation. The results revealed certain differences between African and Asian species in their chloroplast genomes of Bauhinia species.

Xiao Q., Fer T., Guo W., Chen H., Li L., Zhao J.

AbstractUnderstanding the proximate and ultimate causes of genome size (GS) variation is the focus of much research. However, the extent and causes of intraspecific variation in GS is debated and poorly understood. This study aims to test the large-genome constraint hypothesis through the variations of intraspecific GS. GS was measured in 53Roscoea tibeticapopulations from the Hengduan Mountains using flow cytometry. Stomatal size and density were collected from the wild populations and common garden populations. Associations between GS and environmental factors, stomatal traits were explored. We found that high GS 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 the variations in GS. The stomatal traits measured in the wild were significantly correlated with GS, but no such correlations were detected in the common garden. Populations in the common garden have larger stomatal size and lower stomatal density. Populations with smaller GS present larger degree of stomatal traits variation from wild to common garden. Our findings suggests that intraspecific GS has experienced adaptive evolution driven by environmental stress and the evolution of intraspecific GS can be explained by the large-genome constraint hypothesis. Smaller GS is more advantageous to the alpine ginger to adapt to alpine habitat and thrive in changing habitat.

Hersch‐Green E.I., Fay P.A., Hass H.B., Smith N.G.

Summary Affecting biodiversity, plants with larger genome sizes (GS) may be restricted in nutrient‐poor conditions. This pattern has been attributed to their greater cellular nitrogen (N) and phosphorus (P) investments and hypothesized nutrient–investment tradeoffs between cell synthesis and physiological attributes associated with growth. However, the influence of GS on cell size and functioning may also contribute to GS‐dependent growth responses to nutrients. To test whether and how GS is associated with cellular nutrient, stomata, and/or physiological attributes, we examined > 500 forbs and grasses from seven grassland sites conducting a long‐term N and P fertilization experiment. Larger GS plants had increased cellular nutrient contents and larger, but fewer stomata than smaller GS plants. Larger GS grasses (but not forbs) also had lower photosynthetic rates and water‐use efficiencies. However, nutrients had no direct effect on GS‐dependent physiological attributes and GS‐dependent physiological changes likely arise from how GS influences cells. At the driest sites, large GS grasses displayed high water‐use efficiency mostly because transpiration was reduced relative to photosynthesis in these conditions. We suggest that climatic conditions and GS‐associated cell traits that modify physiological responses, rather than resource–investment tradeoffs, largely explain GS‐dependent growth responses to nutrients (especially for grasses).

Lan W., Mo Q., Jin M., Wen Y., Yang M., Ma H., Huang H., Huang M.

The genus Impatiens, which includes both annual and perennial herbs, holds considerable ornamental, economic, and medicinal value. However, it posed significant challenges for taxonomic and systematic reconstruction. This was largely attributed to its high intraspecific diversity and low interspecific variation in morphological characteristics. In this study, we sequenced samples from 12 Impatiens species native to China and assessed their phylogenetic resolution using the complete chloroplast genome, in conjunction with published samples of Impatiens. In addition, a comparative analysis of chloroplast genomes were conducted to explore the evolution of the chloroplast genome in Impatiens. The chloroplast genomes of 12 Impatiens species exhibited high similarity to previously published samples in terms of genome size, gene content, and sequence. The chloroplast genome of Impatiens exhibited a typical four-part structure, with lengths ranging from 146,987 bp(I. morsei)- 152,872 bp(I. jinpingensis). Our results identified 10 mutant hotspot regions (rps16, rps16-trnG, trnS-trnR, and rpoB-trnC) that could serve as effective molecular markers for phylogenetic analyses and species identification within the Impatiens. Phylogenetic analyses supported the classification of Impatiens as a monophyletic taxon. The identified affinities supported the taxonomic classification of the subgenus Clavicarpa within the Impatiens, with subgenus Clavicarpa being the first taxon to diverge. In phylogenetic tree,the Impatiens was divided into eight distinct clades. The results of ancestral trait reconstruction suggested that the ancestral traits of Impatiens included a perennial life cycle, four sepals and three pollen grooves. However, the ancestral morphology regarding fruit shape, flower colour, and spacing length remained ambiguous. Our study largely supported the family-level taxonomic treatment of Impatiens species in China and demonstrated the utility of whole chloroplast genome sequences for phylogenetic resolution. Comparative analysis of the chloroplast genomes of Impatiens facilitated the development of molecular markers.The results of ancestral trait reconstruction showed that the ancestor type of habit was perennial, the number of sepals was 4, and morphology and number of aperture was 3 colpus. The traits of capsule shape, flower colour, and spur length underwent a complex evolutionary process. Our results provided data support for further studies and some important new insights into the evolution of the Impatiens.

Zedek F., Šmerda J., Halasová A., Adamec L., Veleba A., Plačková K., Bureš P.

Abstract 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.

Morton J.A., Arnillas C.A., Biedermann L., Borer E.T., Brudvig L.A., Buckley Y.M., Cadotte M.W., Davies K., Donohue I., Ebeling A., Eisenhauer N., Estrada C., Haider S., Hautier Y., Jentsch A., et. al.

Experiments comparing diploids with polyploids and in single grassland sites show that nitrogen and/or phosphorus availability influences plant growth and community composition dependent on genome size; specifically, plants with larger genomes grow faster under nutrient enrichments relative to those with smaller genomes. However, it is unknown if these effects are specific to particular site localities with speciifc plant assemblages, climates, and historical contingencies. To determine the generality of genome size-dependent growth responses to nitrogen and phosphorus fertilization, we combined genome size and species abundance data from 27 coordinated grassland nutrient addition experiments in the Nutrient Network that occur in the Northern Hemisphere across a range of climates and grassland communities. We found that after nitrogen treatment, species with larger genomes generally increased more in cover compared to those with smaller genomes, potentially due to a release from nutrient limitation. Responses were strongest for C3 grasses and in less seasonal, low precipitation environments, indicating that genome size effects on water-use-efficiency modulates genome size–nutrient interactions. Cumulatively, the data suggest that genome size is informative and improves predictions of species’ success in grassland communities.

Volkova P.A., Ivanova M.O., Efimov D.Y., Chemeris E.V., Vinogradova Y.S., Grishutkin O.G., Konotop N.K., Efimova L.A., Tikhomirov N.P., Zueva N.V., Bobrov A.A.

Northing P.C., Pelosi J.A., Venable D.L., Dlugosch K.M.

ABSTRACTPremisePectocarya recurvata(Boraginaceae), a native species of the Sonoran Desert, has served as an important model system for a suite of ecological and evolutionary studies. Despite its relevance as an eco-evolutionary model, no reference genome assemblies in the Cynoglossoideae subfamily have been published.MethodsUsing PacBio HiFi sequencing, we assembled a reference genome forP. recurvataand annotated coding regions with full-length transcripts from an Iso-Seq transcriptome library. We assessed genome completeness with BUSCO and used flow cytometry and K-mer analysis to estimate the genome size ofP. recurvata.ResultsThe chromosome-scale reference genome assembly forP. recurvatawas 216.0 Mbp long with a contig N50 of 12.1 Mbp. Our assembly included 12 primary contigs bounded by telomeres at all ends but one, consistent with the 12 chromosomes documented for the species. The chromosomes covered 158.3 Mbp and contained 30,655 predicted genes. Our measured haploid genome size from the same population was 386.5 Mbp, among the smallest for Boraginaceae. Genomic analyses suggested that this may reflect a recent autotetraploid, such that predicted diploid genome size would be even smaller and similar to the assembly size.DiscussionTheP. recurvataassembly and annotation provide a high-quality genomic resource in a sparsely represented area of the Angiosperm phylogeny. Our new genome will enable future ecophysiology, biogeography, and phylogenetics research.

Givnish T.J.

This article comments on: František Zedek, Jakub Šmerda, Aneta Halasová, Lubomír Adamec, Adam Veleba, Klára Plačková and Petr Bureš, The smallest angiosperm genomes may be the price for effective traps of bladderworts, Annals of Botany, Volume 134, Issue 7, 31 December 2024, Pages 1131–1138, https://doi.org/10.1093/aob/mcae107

Simpson K.J., Mian S., Forrestel E.J., Hackel J., Morton J.A., Leitch A.R., Leitch I.J.

Summary Increasing genome size (GS) has been associated with slower rates of DNA replication and greater cellular nitrogen (N) and phosphorus demands. Despite most plant species having small genomes, the existence of larger GS species suggests that such costs may be negligible or represent benefits under certain conditions. Focussing on the widespread and diverse grass family (Poaceae), we used data on species' climatic niches and growth rates under different environmental conditions to test for growth costs or benefits associated with GS. The influence of photosynthetic pathway, life history and evolutionary history on grass GS was also explored. We found that evolutionary history, photosynthetic pathway and life history all influence the distribution of grass species' GS. Genomes were smaller in annual and C4 species, the latter allowing for small cells necessary for C4 leaf anatomy. We found larger GS were associated with high N availability and, for perennial species, low growth‐season temperature. Our findings reveal that GS is a globally important predictor of grass performance dependent on environmental conditions. The benefits for species with larger GS are likely due to associated larger cell sizes, allowing rapid biomass production where soil fertility meets N demands and/or when growth occurs via temperature‐independent cell expansion.