Genome size is positively correlated with extinction risk in herbaceous angiosperms.

Angiosperms with large genomes experience nuclear-, cellular-, and organism-level constraints that may limit their phenotypic plasticity and ecological niche, which could increase their risk of extinction. Therefore, we test the hypotheses that large-genomed species are more likely to be threatened with extinction than those with small genomes, and that the effect of genome size varies across three selected covariates: life form, endemism, and climatic zone. We collated genome size and extinction risk information for a representative sample of angiosperms comprising 3250 species, which we analyzed alongside life form, endemism, and climatic zone variables using a phylogenetic framework. 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 is associated with 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.

Adaptation strategies of leaf traits and leaf economic spectrum of two urban garden plants in China.

BACKGROUND: Previous studies of the relationships between traits have focused on the natural growth conditions of wild plants. Urban garden plants exhibit some differences in plant traits due to environmental interference. It is unknown whether the relationships between the leaf traits of urban garden plants differ under distinct climates. In this study, we revealed the variation characteristics of the leaf functional traits of trees, shrubs, and vines in two urban locations. Two-way ANOVA was used to reveal the response of plant leaf traits to climate and life forms. Pearson correlation analysis and principal component analysis were used to calculate the correlation coefficient between the leaf functional traits of plants at the two locations. RESULTS: Leaf dry matter content (LDMC) and vein density (VD) of different life forms in Mudanjiang were higher than those in Bozhou (P < 0.05), and the relative water content (RWC) in Bozhou was higher, whereas vein density (VD) of trees and shrubs in the two urban locations was significant (P < 0.05), but the vines were not significant. The photosynthetic pigments of tree and shrub species were larger in Mudanjiang, but the opposite was true for the vines. Both leaf vein density (VD) and stomatal density (SD) showed a very significant positive correlation in the two urban locations (P < 0.01), and both were significantly positively correlated with specific leaf area (SLA) (P < 0.05); and negatively correlated with leaf thickness (LT), and the relationship between pigment content were closer. CONCLUSION: The response to climate showed obvious differences in leaf traits of different life forms species in urban area, but the correlations between the traits showed convergence, which reflects that the adaptation strategies of garden plant leaves to different habitats are both coordinated and relatively independent.

Evidence linking life-form to a major shift in diversification rate in Crassula.

PREMISE: Plants have evolved different ecological strategies in response to environmental challenges, and a higher lability of such strategies is more common in plant groups that adapt to various niches. Crassula (Crassulaceae), occurring in varied mesic to xeric habitats, exhibits a remarkable diversity of life-forms. However, whether any particular life-form trait has shaped species diversification in Crassula has remained unexplored. This study aims to investigate diversification patterns within Crassula and identify potential links to its life-form evolution. METHODS: A phylogenetic tree of 140 Crassula taxa was reconstructed using plastid and nuclear loci and dated based on the nuclear DNA information only. We reconstructed ancestral life-form characters to estimate the evolutionary trends of ecophysiological change, and subsequently estimated net diversification rates. Multiple diversification models were applied to examine the association between certain life-forms and net diversification rates. RESULTS: Our findings confirm a radiation within Crassula in the last 10 million years. A configuration of net diversification rate shifts was detected, which coincides with the emergence of a speciose lineage during the late Miocene. The results of ancestral state reconstruction demonstrate a high lability of life-forms in Crassula, and the trait-dependent diversification analyses revealed that the increased diversification is strongly associated with a compact growth form. CONCLUSIONS: Transitions between life-forms in Crassula seem to have driven adaptation and shaped diversification of this genus across various habitats. The diversification patterns we inferred are similar to those observed in other major succulent lineages, with the most-speciose clades originating in the late Miocene.

Forest cover resilience to climate change over India using the MC2 dynamic vegetation model.

It is imperative to understand the climate change impact on the forest ecosystem to develop appropriate mitigation and management strategies. We have employed a process-based dynamic vegetation modeling (MAPSS-CENTURY: MC) approach to project change in vegetation life forms under projected climate conditions that attained 81% overall accuracy. The present and projected climate conditions suggested highly resilient/stable forest covers in wet climate regimes and moderately resilient in dry semi-arid regions. Several forested grids in the seasonally dry tropical forest in the Eastern Ghats and dry Deccan peninsula regions are estimated to be less resilient, which may experience a regime shift toward scrub and grassland. The future prediction demonstrated an upward temperature shift in the Western Himalayas and trans-Himalaya, which may facilitate forest spread at higher elevations. Although the forest cover resilience may increase in future climate conditions, the disturbances in several regions in the Deccan Peninsula and the Eastern Ghats may trigger forest to scrub and grassland transition. The inaccuracy in model simulation in the Western Himalayas could be attributed to coarse resolution grids (0.5°) failing to resolve the narrow climate niches. The spatially explicit model simulation provides opportunities to develop long-term climate change adaptation and conservation strategies.

Plant Community of Pine Forests (Pinus kochiana, Pinaceae) of Dagestan.

The plant community of Dagestan pine forests, comprising 590 vascular plants species, was examined based on materials from field studies performed from 2012 to 2019. Taxonomic, biomorphological, florocoenotic, and geographical characteristics of the plant community showed its boreal and Mediterranean nature. Mesotrophic and eutrophic plants predominated in terms of soil fertility and mesophytes and mesoxerophytes, in terms of soil water availability. Species of different altitudinal belts, including forest, meadow, and mountain-steppe belts, were observed in the plant community of pine forests. The plant community included 22 species listed in the Red Books of the Russian Federation and the Republic of Dagestan, 82 relict species, and 76 endemics.

Ecological and phylogenetic constraints determine the stage of anthetic ovule development in orchids.

PREMISE: Unlike most flowering plants, orchid flowers have under-developed ovules that complete development only after pollination. Classical studies reported variation in the stage in which ovule development is arrested, but the extent of this variation and its evolutionary and ecological significance are unclear. METHODS: Here, we used light microscopy to observe ovule development at anthesis for 39 species not previously studied and surveyed the literature gaining information on 94 orchid species. Tropical and temperate members of all five orchid subfamilies as well as species with contrasting pollination strategies (rewarding versus deceptive) and life forms (epiphytic versus terrestrial) were represented. We analyzed the data using statistical comparisons and a phylogenetic generalized least square (PGLS) analysis. RESULTS: Apostasioideae, the sister to the rest of the orchids, have mature ovules similar to other Asparagales, while under-differentiated ovules are present in the other subfamilies. Ovule developmental stages showed high variation even among closely related groups. Ovules were more developed in terrestrial than in epiphytic, in temperate than in tropical, and in rewarding than in deceptive pollination orchid species. This latter comparison was also significant in the PGLS analysis. CONCLUSIONS: These results suggest that ovule developmental stage in orchids can be shaped by ecological factors, such as seasonality and pollination strategy, and can be selected for optimizing female reproductive investment.

The role of perennation traits in plant community soil frost stress responses.

BACKGROUND AND AIMS: Herbaceous plants can survive periods of prolonged freezing as below-ground structures or seed, which can be insulated from cold air by soil, litter or snow. Below-ground perennial structures vary in both form and their exposure to soil frost, and this structural variation thus may be important in determining the responses of plant communities to frost stress. METHODS: We conducted a suite of snow removal experiments in a northern temperate old field over 3 years to examine the relative freezing responses of different plant functional groups based on below-ground perennation traits. A litter removal treatment was added in the third year. Species-level percentage cover data were recorded in May, June and September then pooled by functional group. KEY RESULTS: Snow removal decreased total plant cover, and this response was particularly strong and consistent among years for tap-rooted and rhizomatous species. The snow removal responses of cover for plants with root buds and new recruits from seed varied from positive to negative among years. The cover of rootstock plants consistently increased in response to snow removal. Rhizomatous species were generally the most vulnerable to litter removal. CONCLUSIONS: This study is the first to explore the effects of variation in frost severity on the responses of different plant perennation trait functional groups. The responses of herbaceous species to frost may become increasingly important in northern temperate regions in the coming decades as a result of declining snow cover and increasing temperature variability. Our results reveal substantial variation in responses among perennation trait functional groups, which could drive changes in species abundance in response to variation in soil frost.

Plasticity in the growth habit prolongs survival at no physiological cost in a monocarpic perennial at high altitudes.

BACKGROUND AND AIMS: Monocarpic plants are those that flower, produce seeds and then die. Although most monocarpic plants are annual or biennial, some of them are perennial. However, relatively little is known regarding the biology of monocarpic perennials. Pyrenean saxifrage (Saxifraga longifolia) is a monocarpic perennial that is well adapted to high-mountain ecosystems. Here, we evaluated altitudinal changes in clonality in various populations growing in their natural habitat with particular emphasis on the physiological costs of clonal growth. METHODS: We assessed the percentage of clonal plants in nine populations growing in their natural habitat, as well as the plant stress response of clonal and non-clonal plants, in terms of photoprotection and accumulation of stress-related phytohormones, in a 3-year study at Las Blancas (2100 m a.s.l.). We also evaluated the influence of plant size on the activation of defensive responses to biotic and abiotic stresses. KEY RESULTS: We found that 12 % of Pyrenean saxifrage plants growing at the highest altitudes (2100 m a.s.l.) produced lateral rosettes which survived the flowering of the main rosette and shared the same axonomorphic root, thus escaping monocarpic senescence. This clonal growth did not worsen the physiological performance of plants growing at this altitude. Furthermore, increased plant size did not negatively affect the physiology of plants, despite adjustments in endogenous stress-related phytohormones. In contrast, maturity led to rapid physiological deterioration of the rosette, which was associated with monocarpic senescence. CONCLUSIONS: This study shows that the evolution of clonality has allowed Pyrenean saxifrage to survive harsh environmental conditions and it provides evidence that harsh environments push plant species to their limits in terms of life form and longevity.

Is the evolution of carnivory connected with genome size reduction?

PREMISE: As repeatedly shown, the remarkable variation in the genome size of angiosperms can be shaped by extrinsic selective pressures, including nutrient availability. Carnivory has evolved independently in 10 angiosperm clades, but all carnivorous plants share a common affinity to nutrient-poor habitats. As such, carnivory and genome reduction could be responses to the same environmental pressure. Indeed, the smallest genomes among flowering plants are found in the carnivorous family Lentibulariaceae, where a unique mutation in cytochrome c oxidase (COX) is suspected to promote genome miniaturization. Despite these hypotheses, a phylogenetically informed test of genome size and nutrient availability across carnivorous clades has so far been missing. METHODS: Using linear mixed models, we compared genome sizes of 127 carnivorous plants from 7 diverse angiosperm clades with 1072 of their noncarnivorous relatives. We also tested whether genome size in Lentibulariaceae reflects the presence of the COX mutation. RESULTS: The genome sizes of carnivorous plants do not differ significantly from those of their noncarnivorous relatives. Based on available data, no significant association between the COX mutation and genome miniaturization could be confirmed, not even when considering polyploidy. CONCLUSIONS: Carnivory alone does not seem to significantly affect genome size decrease. Plausibly, it might actually counterbalance the effect of nutrient limitation on genome size evolution. The role of the COX mutation in genome miniaturization needs to be evaluated by analysis of a broader data set because current knowledge of its presence across Lentibulariaceae covers less than 10% of the species diversity in this family.

Meta-analysis of the differential effects of habitat fragmentation and degradation on plant genetic diversity.

Genetic diversity is a key factor for population survival and evolution. However, anthropogenic habitat disturbance can erode it, making populations more prone to extinction. Aiming to assess the global effects of habitat disturbance on plant genetic variation, we conducted a meta-analysis based on 92 case studies obtained from published literature. We compared the effects of habitat fragmentation and degradation on plant allelic richness and gene diversity (equivalent to expected heterozygosity) and tested whether such changes are sensitive to different life-forms, life spans, mating systems, and commonness. Anthropogenic disturbance had a negative effect on allelic richness, but not on gene diversity. Habitat fragmentation had a negative effect on genetic variation, whereas habitat degradation had no effect. When we examined the individual effects in fragmented habitats, allelic richness and gene diversity decreased, but this decrease was strongly dependent on certain plant traits. Specifically, common long-lived trees and self-incompatible species were more susceptible to allelic richness loss. Conversely, gene diversity decreased in common short-lived species (herbs) with self-compatible reproduction. In a wider geographical context, tropical plant communities were more sensitive to allelic richness loss, whereas temperate plant communities were more sensitive to gene diversity loss. Our synthesis showed complex responses to habitat disturbance among plant species. In many cases, the absence of effects could be the result of the time elapsed since the disturbance event or reproductive systems favoring self-pollination, but attention must be paid to those plant species that are more susceptible to losing genetic diversity, and appropriate conservation should be actions taken.

Meta-Análisis de los Efectos Diferenciales de la Fragmentación y Degradación del Hábitat sobre la Diversidad Genética de las Plantas Resumen La diversidad genética es un factor clave para la supervivencia y evolución de las poblaciones. Sin embargo, la perturbación antropogénica de los hábitats puede dañar esta diversidad, volviendo a las poblaciones más susceptibles a la extinción. Con el objetivo de evaluar los efectos globales de la perturbación del hábitat sobre la variación genética de las plantas, realizamos un meta-análisis basado en 92 estudios de caso obtenidos de la literatura publicada. Comparamos los efectos de la degradación y fragmentación del hábitat sobre la riqueza de alelos y la diversidad de genes (equivalente a la heterocigosidad esperada) de las plantas y probamos si dichos cambios son sensibles para diferentes formas de vida, tiempos de vida, sistemas de apareamiento y preponderancia. La perturbación antropogénica tuvo un efecto negativo sobre la riqueza de alelos, pero no sobre la diversidad genética. La fragmentación del hábitat tuvo un efecto negativo sobre la variación genética, mientras que la degradación del hábitat no tuvo efecto. Cuando examinamos los efectos individuales en los hábitats fragmentados, la riqueza de alelos y la diversidad genética disminuyeron, pero esta disminución estuvo vinculada fuertemente con ciertas características de las plantas. Específicamente, los árboles de larga vida y las especies auto-incompatibles fueron más susceptibles a la pérdida de la riqueza de alelos. De manera contraria, la diversidad genética disminuyó en especies comunes de vida corta (hierbas) con reproducción auto-compatibles. En un contexto geográfico más amplio, las comunidades de plantas tropicales fueron más sensibles a la pérdida de la riqueza de alelos, mientras que las comunidades de plantas de zonas templadas fueron más sensibles a la pérdida de diversidad de genes. Nuestra síntesis mostró respuestas complejas a la perturbación del hábitat entre las especies de plantas. En muchos casos, la ausencia de efectos podría ser el resultado del tiempo transcurrido desde el evento de perturbación o los sistemas reproductivos que favorecen la auto-polinización, pero se le debe prestar atención a aquellas especies de plantas que son más susceptibles a la pérdida de la diversidad genética, para así poder realizar las acciones de conservación apropiadas.