Abstract Herbivory is particularly threatening to young plants that lack the resources needed to survive attack. Seeds and seedlings should thus benefit greatly from using pre-attack cues to induce defense prior to damage. Locomotion mucus from slugs, generalist herbivores that consume young plants, has been shown to speed germination, slow growth, and increase both chemical defenses and resistance to herbivores in several herbaceous plants. Whether woody species exhibit similar responses has not been tested. Arion subfuscus, an invasive slug in the eastern USA, is a major herbivore of young sugar maples (Acer saccharum); we explored the effect of its locomotion mucus on Ac. saccharum seeds and seedlings. We exposed sugar maple seeds and seedlings to mucus and measured germination speed and rate, seed susceptibility to slugs, seedling emergence, growth, chemical defenses, and foliar susceptibility to Lymantria dispar and Ar. subfuscus. Contrary to our expectations and previous findings with herbaceous species, we found that mucus had no effect on these performance or resistance traits. Habituation to repeated cue exposure or the limited coevolutionary history between Ac. saccharum and Ar. subfuscus could be the reason for the lack of an observed response by the plants. Further studies should investigate the effects of kairomones using a short-term cue exposure procedure or by using a woody plant species and native slug herbivore with coevolutionary history. Understanding how woody plants respond to kairomones would provide insight into the risk and defense strategies used by long-lived species in crucial early life stages.

Shifts in pollinator composition and associated colour preferences can support flower colour polymorphism (FCP) across environmental gradients and along flowering seasons. We explored the geographical and seasonal turnover of insect visitors in Anemone coronaria, a geophyte that flowers mainly in red, purple, and white. In Israel, southern populations have red flowers whereas some northern populations are colour polymorphic. Southern populations bloom later than northern ones, and red flowers appear later than non-red flowers. We predicted corresponding changes in colour preferences of A. coronaria's pollinators, from non-red in northern sites and early in the season to red in southern sites and in late season. We created experimental arrays of red, purple, and white A. coronaria flowers in three field sites (northern, central, and southern regions of the species' distribution) and three time-points (early, mid, and late season) over 2 years. We recorded flower colour choices of insect visitors. Insect colour preferences varied among locations and time points. Bees and flies visited the flower arrays primarily during early season in the northern and central sites, where bees preferred purple flowers. Beetles visited the flowers mostly during late season in the southern site and preferred red flowers there. As predicted, A. coronaria's purple flowers received more early-season visits in the north, and red flowers received more late-season visits in the south. These spatio-temporal trends are consistent with the species' FCP pattern. A. coronaria's broad pollinator fauna may enhance reproductive success across the plant's wide geographical distribution and long flowering season.

Abstract Mosses contribute to a multitude of ecosystem functions, and their structural and functional traits, such as shoot density or water storage capacity, can play an important role in performing these functions. It is widely known that mosses substantially reduce surface runoff and soil erosion, so the impact of mosses on soil hydrology is expected to be important worldwide. Nevertheless, it is poorly understood how moss species with different traits affect soil erosion and soil water fluxes. Therefore, this study aimed to assess the impact of the two moss species, Thuidium tamariscinum and Rhytidiadelphus loreus, on soil erosion, surface runoff, and water percolation and to investigate the influence of their structural traits. We conducted ex situ rainfall simulations with infiltration boxes that contain undisturbed topsoil samples. The two moss species differed significantly in their structural traits, with R. loreus showing longer shoots and branches, greater cushion height, and larger leaf area, while T. tamariscinum had a higher number of branches. Surprisingly, their water storage capacities were similar despite these morphological differences, suggesting a possible interplay of morphological features and trait resemblances, though the underlying mechanisms require further study. R. loreus and T. tamariscinum exhibited a comparable mitigating effect on sediment discharge and surface runoff, while moss cover had no significant influence on water percolation, regardless of species. Shoot density significantly correlates with reduced surface runoff, highlighting the key role of moss colony structure in hydrological processes.

Influences of climate change on light availability are often overlooked; yet, understory species may experience shifts in irradiance as rising temperatures influence phenology and community composition. Light management is crucial for seedling success, and a whole-plant approach can help elucidate consequences of light on plant performance. Rhododendron minus is an evergreen shrub native to the Southeast United States that grows from rock outcrops to the understory. We conducted two experiments to unravel influences of light on plant function: (i) a manipulative greenhouse experiment on seedlings from a sun-exposed provenance examining pigments, plant architecture, and biomass patterns under shade, ambient, and supplemental light and (ii) a common garden experiment comparing pigments of mature plants from six provenances differing in latitude, elevation, climate, and solar radiation. We used multispectral imaging to estimate anthocyanin through the normalized difference anthocyanin index (NDAI) and chlorophyll through the normalized difference vegetation index (NDVI). Supplemental light seedlings had significantly higher NDAI than shade and ambient seedlings, but there was no significant treatment effect on NDVI or total biomass. Supplemental light seedlings also exhibited leaf movements that reduced projected surface area over time. This work highlights the importance of anthocyanins and plant architecture in allowing seedlings to maintain similar performance across light environments. In our common garden experiment, plants from northern, colder provenances had higher NDAI compared to warmer, southern provenances. We suggest that interactions between temperature and irradiance likely drive intraspecific variation in NDAI across the range, indicating that climate change could influence future pigment evolution.

Abstract Hybridization is a key mechanism in the adaptive evolution of weeds and invasive species. The evolutionary success of hybrids may be shaped by selection on functional traits, interacting with maternal genotype and ecological context. We performed experimental hybridization and common garden field experiments to assess phenotypic variation on functional traits, and the strength and direction of linear and quadratic selection acting on them, in bidirectional crop–weed hybrids and their parents of Raphanus sativus, across two contrasting environments: agrestal (agricultural) and ruderal (human-disturbed uncultivated area), over two years. Bidirectional hybrids exhibited overall greater values for size-related traits than their parents, with similar flowering time and no significant effects of cross direction. Selection acted on multiple functional traits through both linear and quadratic components, with broadly similar patterns across environments and cross types, although selection tended to be slightly stronger in hybrids than in weeds. Intraspecific crop–weed hybridization, regardless of cross direction, can increase weediness in weedy radish by enhancing plant size, thereby increasing competitive ability and potential interference with crops. Our findings highlight how hybridization and selection shape plant evolution, influencing the potential introgression of crop alleles into wild or weedy gene pools. Understanding the hybridization process and the mechanisms that control it is crucial for managing the evolutionary outcomes of crop-weed hybridization.

Background and AimsStomata are specialized epidermal structures typically restricted to aerial organs of vascular plants. Their absence on roots has long been regarded as a general anatomical rule. Although rare reports in certain dicotyledonous taxa have described root stomata, these occurrences have been considered transient or developmentally anomalous. Within Apiaceae, no confirmed occurrence has previously been documented. This study aimed to investigate the anatomical presence of stomata on the primary roots of Conium maculatum L. seedlings.MethodsSeedlings of C. maculatum derived from wild-collected populations and genebank accessions were examined using light microscopy. Transverse sections and epidermal surface preparations were prepared to confirm root identity and epidermal features. Taxonomic identity was verified using morphological traits and molecular data (ITS and rps16 sequences).Key ResultsMorphologically distinct stomata with characteristic guard cells were observed on the primary root. Their distribution was sparse and irregular. Root identity was supported by the overall anatomical organization of the examined sections, including a uniseriate epidermis and a broad parenchymatous cortex. Stomatal complexes were consistently detected across all examined accessions of the species.ConclusionsThis study provides the first anatomically verified and reproducible report of stomata on the primary root of C. maculatum within Apiaceae. These findings expand current knowledge of root epidermal anatomy in the family and indicate that further comparative surveys will be necessary to determine the taxonomic extent of this trait.

Plant invaders can promote invasion success through interactions with soil-biota (i.e. soil-conditioning), forming feedback, which can change in strength and direction over time. Thus, native plant responses to invader soil-conditioning dynamics may be dependent on the degree of invasion and could additionally be mediated by plant functional traits. To investigate the temporal dynamics of invader-soil-conditioning and the role of traits in mediating plant responses, we conducted a greenhouse experiment focusing on Oncosiphon pilulifer, an invasive annual forb spreading across the Southwestern United States and Western Australia. We grew Oncosiphon and six native plants in live whole soil vs sterilized whole soil inocula from an existing Oncosiphon invasion gradient, with four levels of invasion ranging from uninvaded, small patches, large monocultures, and the origin point of invasion resulting in a space-for-time substitution. We measured plant biomass, mycorrhizal root colonization, and leaf and root traits. We found native plant growth was reduced with soil from patchily invaded soils, while mycorrhizal root colonization rates were reduced with Oncosiphon monoculture soil. Oncosiphon itself experienced reduced growth over the course of invasion, with consistently low root colonization. Our trait analysis suggests that an interaction between root and leaf traits can mediate plant vulnerability to invader impacts on soil-biota.

Coastal wetland plants are adapted to fluctuating and often harsh environmental conditions. In urban wetlands, plant functional groups display a range of physiological and morphological strategies in response to abiotic stress. However, differences amongst functional groups and the coordination between leaf traits, nutrient status, and environmental variation remain poorly understood in these systems. This study evaluates trait-environment relationships in three dominant species-Acrostichum danaeifolium (fern), Dalbergia ecastaphyllum (nitrogen-fixer shrub), and Laguncularia racemosa (halophytic tree)-across contrasting wetland soils and seasonal periods in a tropical urban reserve. We measured leaf gas exchange, specific leaf area (SLA), nutrient content, and photosynthetic nitrogen use efficiency (PNUE) across wet and dry periods on two soils in the Ciénaga Las Cucharillas Natural Reserve, Puerto Rico. Soil bulk density, salinity, and bioavailable nutrients were also quantified. Multivariate analyses (principal component analysis) were used to assess trait covariation. Species differed significantly in morphological and physiological traits. L. racemosa exhibited the highest assimilation rates, PNUE, and succulence, consistent with an acquisitive resource-use strategy. In contrast, A. danaeifolium showed high SLA and water content but conservative stomatal behaviour and lower PNUE, indicative of a shade-tolerant strategy. Dalbergia ecastaphyllum maintained high water-use efficiency during the dry period and exhibited adaptive responses to slightly and moderate saline soils, indicative of a nutrient acquisitive strategy. Soil type influenced elemental availability but had limited effects on photosynthetic rates. Trait differentiation amongst coexisting wetland species reflects contrasting resource-use strategies shaped by both seasonality and soil environment. These findings underscore the functional diversity and adaptive capacity of tropical wetland vegetation under urban and hydrological pressures.

[This corrects the article DOI: 10.1093/aobpla/plaf066.].

Parasitic organisms are of interest in evolutionary biology, often displaying drastic modifications in morphology, physiology, genomes, and ecology. These properties, however, make them challenging from a systematics perspective. Mycoheterotrophy, in which plants become non-photosynthetic parasites on fungi, is an excellent example, and this unique life history has evolved numerous times in the orchid family. Here, we focused on Stereosandra, a genus of mycoheterotrophic orchid comprising a single species, S. javanica, about which little is known. Stereosandra has been placed in the orchid tribe Nervilieae, along with the leafy, autotrophic Nervilia, and the leafless, mycoheterotrophic Epipogium. We characterized the first complete plastid genome for Stereosandra and used nuclear sequence capture to determine its relationships within Nervilieae. This study presents the first genetic data ever produced for Stereosandra. The plastid genome exhibits rampant gene losses, pseudogenes, and reduced size relative to Nervilia but not to the extent seen in Epipogium. There is evidence of relaxed negative selection in six genes in Stereosandra, including matK, which functions in Group IIA intron removal of seven plastid genes, four of which have been lost or pseudogenized in this species. Applying mixture models, plastid genomes provided weak support for a sister position of Stereosandra to a clade of Epipogium + Nervilia. Nuclear phylogenomic analyses provided strong support for the same relationships. Ancestral state reconstruction revealed clear evidence that mycoheterotrophy evolved multiple times in the tribe from leafy ancestors. This study provides a previously unidentified, convergent instance of the evolution of full mycoheterotrophy in plants. We discuss the results in the context of proposed models of reductive plastid genome evolution and the genomic and evolutionary consequences of radical life history shifts in heterotrophic plants.