The rate of carbon assimilation in leaves (A) is a key trait central to a plant's economic strategy that has downstream impacts on the regional and global cycling of carbon and other nutrients. Most previous paleoecological studies estimate A from nearest living relatives or leaf vein density.
We present a method for reconstructing A using gas-exchange modeling that requires both measured (stomatal size and density, leaf δ13C) and inferred (e.g., atmospheric CO2 concentration) inputs. We apply this method to ten extant taxa and nine fossil taxa representing common angiosperms of the exquisitely preserved mid-Miocene (~15.9 Ma) flora at Clarkia in northern Idaho, USA.
Application to extant taxa produces estimates of A that are near measured values on the same leaves (R2 = 0.89 across all taxa). Median reconstructed A for fossil taxa range from 9.5–21.7 µmol m–2 s–1 with 95% confidence intervals ~+51%/–38% indicating that most species are statistically indistinguishable. Sensitivity tests show that our method is most reliable when CO2 is well-constrained, but when that is impractical, taxa within single sampling horizons (with a presumed fixed CO2 concentration) can be organized by A into a relative rank order with tighter confidence intervals (~+16%/–14%).
Following this relative approach at Clarkia, we reconstruct high A for taxa whose modern relatives are characterized by rapid growth and/or riparian habitats (Castanea and Platanus) and corroborate previous interpretations on the ecology of taxa whose modern relatives are less known (Quercus simulata).
Climate change poses challenges to grasslands, including those of the North American Great Plains Region, where shifts in species distributions and fire dynamics are expected. Our present analysis focuses on remaining grasslands within this largely developed and agricultural region. The differential responses of C4 and C3 grass species to future climate conditions, particularly in habitat suitability and flammability, are critical for understanding ecosystem changes.
We used species distribution models to predict shifts in habitat suitability for 37 grass species under future climate scenarios and assessed flammability traits in a free-air CO2-enrichment study, focusing on species' physiological responses to elevated CO2, warming, and drought.
Our models predicted that C4 species will retain higher habitat suitability, while C3 species will decline. Leaf-level flammability analysis showed that species with higher water-use efficiency under elevated CO will have lower flammability than under non-elevated, potentially decreasing the predicted rate of fire spread when such species dominate. In contrast, species with higher growth rates but lower water-use efficiency may be more flammable. Species-specific responses varied within functional types. Anticipated shifts in species distributions suggest C4 species will become more dominant, potentially altering competitive dynamics and reducing C3 diversity. Changes in flammability under future conditions are expected to influence fire regimes, with a predicted decrease in mean community rate of spread due to the dominance of less-flammable C4 species.
These findings highlight the need for adaptive fire management and conservation strategies to maintain biodiversity and ecosystem function in North American grasslands under climate change.
Lichen-forming fungi of genus Botryolepraria build no compact thalli, yet elevate and display algal symbionts upon their open, aerial mycelium. Although Botryolepraria occurs worldwide, the construction of its unique somatic form has not been examined in detail. We applied light microscopy and SEM to better understand how it is built and stabilized and how phycobionts are distributed during development.
Specimens were examined with light microscopy, conventional SEM, and cryo-field emission SEM. Symbiont identity was corroborated by obtaining and comparing nucleotide sequences with those in the NCBI database.
Hyphal branches grew centripetally toward clusters of algal symbionts, while other branches grew centrifugally outward before further bifurcating to produce additional hyphal branches that reoriented centripetally toward algal clusters. Anastomosis of hyphae, tip to tip or laterally via short bridging connections, occurred frequently. The lichen was irregularly but often densely covered with thread-like hydrophobic materials that resemble certain forms of plant epicuticular waxes. Repeated interpenetration of suspended algal clusters by anastomosing mycobiont hyphae separated and distributed phycobiont cells within the expanding reticulum. Fungal ITS and LSU and algal rbcL sequences suggest closest proximity of mycobiont and phycobiont to Botryolepraria neotropica and Pseudostichococcus monallantoides, respectively, for the material studied.
Anastomosis of hyphae, in regions where algae are absent and at the surfaces of expanding phycobiont clusters, stabilizes the soma of Botrylopraria as a three-dimensional lattice. The dense covering of hydrophobic materials over an open aerial mycelium suggests adaptation to avoid surface condensation and optimize gas exchange.
Phenology—the timing of developmental events—is one of the most effective ways to study the impacts of climate change on plants and ecosystems. However, it remains unknown whether phenology shows a linear or curvilinear response to spring warming.
We measured days to leaf out and flowering for dormant twigs of 12 woody species in seven temperature conditions, representing a wider range of temperatures than in previous studies, and tested whether responses of leaf out and flowering follow linear or curvilinear trends by comparing model fit of linear and second-order polynomial regressions. We also evaluated how the flower–leaf emergence sequence (FLS), the number of days between flowering and leaf out, is affected by temperature.
Overall, warmer temperatures caused earlier flowering for all species and earlier leaf out for many, though there was some lack of response at the extremes of the temperature range. Species varied in whether responses were linear or curvilinear, though flowering responses of most species were best explained by curvilinear models. Due to intraspecific variability in flowering and leaf-out sensitivities, two species exhibited different FLS patterns under different temperature treatments.
These findings suggest that studies investigating climate change and phenology should consider using curvilinear rather than linear models, particularly for flowering. Such curvilinear models may suggest alternative scenarios regarding how warming will impact phenology and ecosystem functions. Variable flowering and leaf-out sensitivities can also affect FLS. Researchers should consider using a wider range of temperatures in dormant twig experiments.
Adaptive radiation in ecologically and morphologically diverse plant lineages presents an opportunity to investigate the rapid evolution of novel floral traits. While some types of floral traits, such as flower color, are well characterized, other types of complex morphologies remain understudied. One example is occluded personate flowers, dorsoventrally compressed flowers with obstructed floral passageways, which have evolved in multiple genera, but have only been characterized from snapdragon.
Our study examined the morphological basis and evolutionary history of personate flowers in a clade of Penstemon species that includes three personate-flowered species. We characterized floral morphology and inferred phylogenetic relationships for 13 species in this group to examine the evolutionary history of personate flowers. We used phylogenomic tests for introgression to examine whether personate-flowered lineages have a history of introgression.
Unlike the personate flowers of snapdragon, personate flowers in Penstemon are produced by deep pleats in the ventral petal tissue that curve the ventral petal surface upward, obstructing the floral tube opening. Our phylogenetic tree suggests that personate flowers evolved in two separate lineages. Phylogenomic analyses indicate incomplete lineage sorting and introgression between certain taxa have contributed to phylogenomic discordance; however, we found little evidence of recent introgression between the two personate-flowered lineages.
Personate flowers in Penstemon have a different morphological basis than those in snapdragon. Personate flowers have evolved multiple times in Penstemon on a rapid evolutionary timescale. The source of genetic variation for repeated shifts may be de novo mutations or pre-existing variants.
The lateral displacement of the Indochina Peninsula, driven by the Indian–Asian plate collision, significantly altered the topography of the Indo-Burma ecoregion, affecting its climate and biological evolution. Despite the renowned biodiversity of the region, spatiotemporal patterns of evolution remain poorly understood.
We analyzed the Engelhardia spicata complex, which has a continuous distribution across Indo-Burma, based on a robust phylogenetic framework comprising 778 individuals from 80 populations, to elucidate spatiotemporal and paleogeological patterns of evolution. We used ancestral area reconstruction to reconstruct the historical biogeography of the species complex and to understand the broader evolutionary history of the Indo-Burma ecoregion.
An initial divergence within the E. spicata complex approximately 26.62 million years ago (Ma) separated a lineage in the Truong Son Mountain Range from one in the Hengduan Mountains and the Shan Plateau. The Shan Plateau and Hengduan Mountain lineages subsequently diverged around 23.03 Ma. These results highlight a three-tiered landform in the Indo-Burma ecoregion, characterized by high-elevation northern regions (Hengduan Mountains, Yunnan-Guizhou Plateau), intermediate-elevation central plateau (Shan Plateau), and low-elevation southern ranges (southern Truong Son Mountains).
Our findings support the tectonic hypothesis that crustal thickening and lateral extrusion of Indochina occurred simultaneously during the Late Oligocene, which led to the formation of the Indo-Burma ecoregion and highlights the biological significance of the resulting three-tiered landform (north-to-south altitudinal gradients) in these regions, providing novel insights into biogeographic patterns in Southeast Asia.
Soil salinization is a growing global challenge that significantly reduces agricultural productivity by impairing seed germination, growth, and yield. While conventional crops have limited tolerance to high salinity, halophytes are promising biological models for developing strategies to sustain agriculture in saline environments and support global food security. This review addresses the potential of halophyte-produced allelochemicals and related signaling molecules to mitigate the impacts of salinization, a topic of growing relevance for sustainable agriculture in a changing climate.
We surveyed and synthesized current research on halophyte allelochemicals and complementary plant-derived molecules and discussed their roles in enhancing resilience to salt stress. Emphasis was placed on distinguishing true allelochemicals from other biologically active compounds and evaluating their applications in plant stress management.
Conventional allelochemicals that are synthesized and released into the environment by halophytes modulate plant responses and may enhance their salt stress resistance. In addition, phytohormones, polyamines, and microbial metabolites have also demonstrated significant hardening effects by enhancing plant tolerance to salinity. Halophytes also provide additional ecosystem benefits as biofuel, forage, or edible crop sources and play a role in phytoremediation.
Using halophyte-derived allelochemicals and complementary signaling molecules offers a viable, environmentally friendly way to increase crop production in saline areas, reduce soil salinization, and conserve freshwater. Future research is expected to focus on optimizing application strategies, evaluating environmental risks, and integrating allelopathy-based approaches into sustainable agricultural systems to enhance crop resilience in the face of climate change.
Biodiversity loss and increasing extreme weather events disrupt the functioning of ecosystems and thus their ability to provide services. While the interplay among various climatic constraints, diversity and productivity has received increasing attention in the last decades, the role of flooding has been overlooked.
In a greenhouse experiment, we manipulated species richness and water regimes to evaluate the influence of flooding on species diversity–productivity relationships. We measured biomass production and partitioned net biodiversity effects into complementarity and selection effects. To link changes in biodiversity effects to underlying mechanisms, we evaluated the contribution of species richness, species identity, functional diversity and community-level traits.
Under flooding, biomass production decreased, and biodiversity effects were less frequently positive. By reducing the incidence of positive complementarity effects, flooding promoted a preponderance of selection effects. Flooding further favored competitive displacement by Phalaris arundinacea; balanced contributions to selection effects from all functional groups at field capacity subsided under flooding when P. arundinacea became the single dominant species. As a result, its acquisitive leaf trait attributes contributed more to selection effects and biomass production under flooding, while root traits contributed less to complementarity effects at field capacity.
As an environmental stressor, flooding promoted the dominance of tolerant species and reduced the incidence of complementary species interactions in the experimental plant communities, clearly modulating the linkage between diversity and productivity.
New insights into biomineral uptake and sequestration are important for understanding how plants grow. Some plants accumulate silica accretions in precise locations in particular cells. Among monocots, controlled biosilicification occurs in several different forms and is restricted to commelinids and orchids.
We utilized energy-dispersive x-ray spectroscopy (EDX/EDS) mapping technology on leaf transverse sections to explore the diverse silica deposition patterns in a range of monocots. The results were evaluated using character optimizations on existing phylogenies.
Our optimization indicates at least two independent evolutionary origins of phytoliths among monocots, with secondary losses in some lineages. Silica that accumulates in the cell lumen occurs mostly in bundle sheath cells or epidermal cells, often associated with sclerenchyma. In Bromeliaceae and Rapateaceae, small phytoliths occur in the walls of occluded epidermal cells overlying sclerenchyma. In Dasypogonaceae, phytoliths accumulate in the lumen of epidermal cells. Cell-wall bound silica occurs in the epidermal cells of some commelinids (Commelinaceae, Cyperaceae and Poaceae). There is a close association between silica deposition and the presence of ferulic acid, except possibly in orchids. Records of high silica concentration in leaves are not always correlated with deposition. We found no silica deposition in leaves of some aquatic commelinids, despite evidence for silica uptake and presence of ferulic acid.
Our ongoing comparative investigations using EDX data not only extend our knowledge about biomineral inclusions in plants, but also highlight their structural and biochemical complexity. This study suggests that the diversity and relatively restricted phylogenetic distribution of monocot phytoliths is at least partly attributable to cell chemistry.
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