Early-career researchers (ECRs) play a vital role in advancing macrophyte research, bringing fresh perspectives, collaborative skills, and innovative methods to the field. Across marine and freshwater realms, macrophytes function as ecosystem engineers and key indicators of ecosystem health, yet they are declining due to a plethora of threats. As those who will shape the future of the field, ECRs are well-positioned to identify existing knowledge gaps and future priorities for the field in macrophyte research in a creative, integrative, and sustainable manner (both for the ecosystems and the ECRs themselves). Here, we present a unified perspective informed by the results of an international survey of 147 ECRs, capturing how ECRs see the field of macrophyte research at present and envision its future, including priorities for the field and how to overcome systemic barriers that ECRs face. Across realms and regions, ECRs currently use classical methods (e.g., field work, statistics) to study a wide range of topics including biodiversity, biotic interactions, and anthropogenic impacts. Regardless of research topic, ECRs are aware that technological advances are reshaping how research is conducted but acknowledge that they are not a silver bullet. Such advances should be harnessed to complement classical approaches, particularly taxonomy and field work. However, ECRs face structural barriers, including job insecurity and funding constraints, that disproportionately impact researchers in resource-limited regions within an already underrepresented field. Addressing these barriers and strengthening science-society connections is essential for the field’s future, and requires collaborative, interdisciplinary, and innovative research grounded in a strong ecological foundation.
The invasive alien species Alternanthera philoxeroides (Mart.) Griseb. exhibits extremely vigorous growth and regenerates clonally from stem fragments, forming dense mats in aquatic environments and causing serious impacts on agriculture and ecosystems. To understand the physiological mechanisms that drive its growth and invasiveness, we compared A. philoxeroides with two congeneric reference species across three complementary approaches: (1) growth analysis under emergent conditions, comparing leaf area and dry weight over 1–3 weeks; (2) gas exchange, chlorophyll fluorescence, and P700 absorbance (an indicator of photosystem I redox activity) measurements under emergent conditions; and (3) underwater photosynthesis measurements using leaves grown under emergent and submerged conditions. Alternanthera philoxeroides exhibited higher relative growth rate (RGR) than the control species, primarily attributable to a higher net assimilation rate (NAR) supported by greater CO2 assimilation capacity in the leaves. The leaf weight ratio (LWR) was lower than that of the control species, indicating preferential biomass allocation to stems. Under submerged conditions, leaf function declined with no formation of new leaves, and A. philoxeroides did not actively utilize HCO₃⁻ for photosynthesis. These results suggest that A. philoxeroides prioritizes rapid stem elongation supported by high photosynthetic capacity. In aquatic environments, rather than relying on underwater photosynthesis, it adopts an escape strategy involving stem elongation to deploy leaves above the water surface. This coordinated physiological and morphological strategy likely underlies its successful invasion across aquatic and riparian habitats. This understanding of the invasiveness strategy A. philoxeroides provides a basis for the development of effective management and control measures.
Nutrient uptake traits shape plant competition, yet nutrient acquisition and internal allocation strategies remain poorly resolved for invasive seagrasses, limiting predictions of responses to eutrophication. Over the past two decades, the exotic seagrass Halophila stipulacea has rapidly colonized the Mediterranean and Caribbean, occasionally displacing native species. Competition for inorganic nitrogen, particularly ammonium, may therefore drive future meadow composition and functioning.Using a novel split-chamber incubation system, we compared leaf and root ammonium (15NH4+) uptake kinetics and internal nitrogen transfer among three native Caribbean seagrasses (Thalassia testudinum, Halodule wrightii, Syringodium filiforme) and the exotic H. stipulacea. We further synthesized published ammonium uptake and transfer data to contextualize our findings.Leaf uptake exceeded root uptake by nearly an order of magnitude across species. Native species exhibited high root uptake affinity and balanced internal allocation, consistent with nutrient-conservative strategies in oligotrophic enivronments. In contrast, H. stipulacea showed lower root uptake but exceptionally high maximum leaf uptake rates and strong root-to-leaf transfer at elevated ammonium, indicating opportunistic aboveground allocation under nutrient pulses. Some species displayed non-saturating uptake kinetics, suggesting uptake capacity may be underestimated under eutrophic conditions. Our synthesis revealed substantial inter- and intraspecific variability and showed 80% of seagrass species lack kinetic parameters.Native Caribbean seagrasses are likely competitively favoured under low to moderate ammonium concentrations, whereas H. stipulacea may gain a context-dependent advantage under nutrient enrichment. These findings illustrate how trade-offs between nutrient-use efficiency and flexibility shape invasion potential highlight critical mechanistic data gaps for predicting future seagrass dominance and ecosystem functioning.
Aquatic plants are a diverse and important component of freshwater ecosystems and have evolutionary histories and adaptive strategies that differ substantially from those of terrestrial plants. Although this has led to increased interest in the genetic diversity and adaptive traits of aquatic plants, the evolutionary processes and underlying mechanisms of adaptation remain understudied. This special issue aims to communicate advances in evolutionary relationships and genomics, traits and genetic adaptation to changing environmental conditions, including hybridisation. Genetic diversity, distribution and the relevance of aquatic plant conservation are also addressed, specifically regarding vulnerable and endangered species in fragmented aquatic landscapes. Efforts on the integration of molecular genetics, landscape genetics, ecology, morphology, biogeography, and conservation biology improve our understanding of aquatic plant evolution, adaptation, ecosystem roles, and responses to environmental change. Further studies are needed in tropical and Southern Hemisphere regions. Additional research on recent molecular approaches, such as the use of environmental (eDNA) and sedimentary DNA (sedaDNA) is also required to shed light on the past and present aquatic plant biodiversity and invasions, and for monitoring purposes, given the bioindicator potential of aquatic plants.
The seagrasses of French Polynesia remain largely undocumented and unmapped, hindering a coherent understanding of their diversity, distribution and potential role in global carbon cycles. We present expanded data from nine sites across six islands and atolls including Bora Bora, Taha'a, Huahine, Moorea, Rangiroa and Fakarava, spanning a distance of more than 680 kilometres. At each location, replicate sites were scoped and new seagrass meadows described for Halophila decipiens and H. ovalis, including leaf morphometrics, seafloor covers (%) and dry weight (DW) biomass (g center dot m2). The study expands the documented observations of seagrass meadows to a total of 21 across French Polynesia including the first records for Taha'a and Fakarava. Novel data describing differences in leaf morphology of Halophila species and variation in seagrass meadow structure (covers ranging from 1.9% to 47.9%) are presented, along with observations of populations occurring within silty river mouth niches where meadows have not been previously reported within the region. Biomass estimates (ranging from 19.7 to 26 g center dot m2 DW) showed generally greater values in the volcanic Society Islands compared to the Tuamotu Archipelago, though this was modulated by the distribution of species. Our observations expand the documented records of Polynesian seagrass ecosystems and provide new ecological detail for Halophila species across a broad range of Pacific island environments.
Seagrass beds are important coastal ecosystems that provide valuable ecosystem services; however, they are increasingly threatened by climate change and human activities. We compared the fine-scale genetic structure of two tropical seagrass species, Enhalus acoroides and Cymodocea rotundata, which differ in their reproductive strategies, using 45 & times; 45 m plots with grid points at 5-m intervals. In addition, we compared the genetic structure between healthy and disturbed sites to better understand the mechanisms of population maintenance under different environmental conditions. Using high-resolution microsatellite markers, we conducted population genetic analyses of 732 samples of E. acoroides from nine plots and 621 samples of C. rotundata from eight plots in Bolinao (disturbed), as well as 665 samples of C. rotundata from eight plots in Laguindingan (undisturbed), Philippines. We detected higher clonal diversity and stronger genetic structure among plots in C. rotundata than in E. acoroides. Interestingly, multilocus genotypes of C. rotundata were shared between plots separated by up to approximately 3.58 km. We infer that C. rotundata populations have been maintained primarily through asexual reproduction, such as rhizome elongation and fragmentation. Furthermore, in C. rotundata, clonal diversity was higher and kinship was stronger at the disturbed site. Our findings indicate that C. rotundata is more vulnerable in highly disturbed areas and requires conservation and restoration efforts. Moreover, our results highlight the necessity of multiple sampling plots within a site to adequately estimate spatial genetic structure for conservation genetic studies of seagrasses.
Thalia, a representative aquatic genus within Marantaceae, provides a useful system for investigating secondary aquatic adaptation in Zingiberales, yet mitogenomic data for this lineage have remained unavailable. Here, we assembled and annotated the first mitogenome of T. dealbata using PacBio long-read sequencing data. The mitogenome is 485,505bp in length and comprises three circular molecules, forming a compact multipartite structure relative to terrestrial Zingiberales species. A total of 35 mitochondrial protein-coding genes (mt-PCGs) were identified, and the reduced abundance of repetitive sequences likely contributes to mitogenome compaction. Transcriptome-based analyses revealed 97 RNA editing sites across 35 mt-PCGs, substantially fewer than in terrestrial relatives. However, atp6 and nad7 harbored the highest numbers of editing sites, with conserved nonsynonymous edits in nad7 potentially involved in fine-tuning mitochondrial respiration under aquatic conditions. Most mt-PCGs were subject to strong purifying selection, whereas rps19 exhibited a weak signal of positive selection, potentially reflecting fine-scale modulation of mitochondrial protein synthesis during secondary aquatic adaptation. Phylogenomic analyses based on mt-PCGs robustly resolved T. dealbata as sister to Zingiberaceae within Zingiberales, whereas plastid-based analyses showed minor topological incongruence among closely related lineages, potentially reflecting differences in evolutionary rates or organellar inheritance histories.Overall, this study provides the first mitogenomic resource for Marantaceae and lays a valuable foundation for understanding mitogenome evolution and secondary aquatic adaptation in Zingiberales.
Extreme flood events can scour riverbeds and significantly reduce submerged aquatic macrophyte extent in river systems. In regulated systems, large dams disrupt longitudinal connectivity and may constrain post-flood recovery by limiting hydrochorous propagule transport. In 2011, the Brisbane River in south-eastern Queensland Australia experienced a major flood that severely reduced macrophyte abundance across the whole river system. Macrophyte recovery has been slow downstream of a major dam, Wivenhoe Dam, which has not yet recovered to historical abundances. To understand how the dam affects macrophyte recovery downstream following flood events, we quantified hydrochory and the sediment seed banks upstream and downstream of the dam. Propagule drift was measured monthly over 12 months using drift nets at two upstream and two downstream sites, while sediment seed banks were sampled seasonally at three sites both upstream and downstream. The most upstream site yielded an average of 1.15 +/- 1 propagules per two-hour sampling period, declining to 0.58 +/- 0.23 at the second most upstream site, with no propagules captured downstream of the dam. Seed bank germination found only two species, native macrophytes Vallisneria nana and Myriophyllum verrucosum, emerging from all upstream samples and no germination from downstream sediment samples. These results indicate that Wivenhoe Dam disrupts hydrochorous dispersal and contributes to limited propagule availability downstream, delaying macrophyte recovery after flood disturbance. Overall, we suggest active restoration strategies are necessary to mitigate the impacts of floods and dams to support macrophyte regeneration post-flood events.
Aquatic macrophytes of the genus Salvinia (Salviniaceae) are able to form extensive plant mats on the surface of water bodies, causing different negative impacts on the local biota. Submerged macrophytes are particularly susceptible to the uncontrolled growth of Salvinia spp., which limits light penetration; however, the effects of the high growth of these weeds on other forms of aquatic macrophyte life are still poorly known. Here, we present a previously unrecognized potential impact of Salvinia auriculata on emergent and amphibious macrophytes. We observed mats of S. auriculata acting as foraging platforms for leaf-cutting ants Atta laevigata in ponds in southeastern Brazil. Herbivory by A. laevigata utilizing S. auriculata mats reduced the length and fresh biomass of the emergent macrophyte Eleocharis interstincta (Cyperaceae). Our results indicate that S. auriculata mats may facilitate herbivory on aquatic macrophytes, potentially affecting their performance and spatial distribution through an indirect interaction, an effect previously unknown.
Alismatid monocots, comprising the aquatic orders Alismatales and Potamogetonales, exhibit a wide array of growth forms and reproductive strategies. Over the past ten years, there have been substantial advances in taxon sampling and DNA sequencing technology that have enabled a reappraisal of phylogenetic relationships and morphological evolution in this diverse group. We evaluated taxonomic, phylogenetic, and morphological evidence from across the diversity of alismatids, to determine the current state of understanding and to identify areas where further research would be beneficial. Nearly all alismatid genera and the majority of species are represented by nuclear and plastid data, with a relatively smaller proportion having mitochondrial data reported. After constructing phylogenies using representative DNA sequence data from available nuclear, plastid, and mitochondrial gene regions, we explored the diversity and evolution of pollination systems that include water-surface and underwater strategies. Phylogenetic reconstructions support at least three independent derivations of underwater pollination (hypohydrophily) in both freshwater and marine lineages.
The reproductive biology of threatened plant species is a critical determinant of their persistence, yet remains poorly understood for many aquatic taxa. We investigated the sexual reproduction of two aquatic Utricularia species, U. gibba and the sterile hybrid U. & times; neglecta, in natural Portuguese freshwater populations. Field observations and experimental assays assessed floral traits, reproductive systems, flower-insect interactions, and sexual fitness across four U. gibba populations and seven U. & times; neglecta populations. Both species share bilabiate yellow flowers with nectariferous spurs, indicative of adaptation to insect pollination, yet they exhibit contrasting reproductive strategies. U. gibba shows a mixed mating system with delayed selfing and facultative outcrossing, pollination-induced floral senescence, and occasional cross-pollination by cryptic, unidentified insects, ensuring reproductive assurance while maintaining genetic diversity. Nectar production, flower size, and display traits were strongly associated with pollinator-mediated pollen transfer in U. gibba, suggesting potential selection on floral traits. In contrast, U. & times; neglecta exhibits larger flowers, higher nectar production, and a thigmonastic stigma, which mediates interactions with pollinators; however, experimental pollinations confirm functional male sterility, preventing sexual reproduction and forcing exclusive reliance on vegetative propagation. These divergent strategies translate into contrasting conservation vulnerabilities, highlighting the need to integrate floral morphology, reproductive functionality, and pollinator dynamics to develop effective, speciesspecific conservation strategies for threatened aquatic plants.
Chara hispida L. is a widely distributed charophyte species belonging to the subsection Hartmania, where species discrimination mainly relies on quantitative characters rather than qualitative ones. To obtain data on morphological and physiological response to environmental variation, laboratory incubations were conducted that mimicked the broad range of temperature and irradiance conditions under which the species thrives. In general, reduced irradiation as well as high temperatures promoted elongation, and other morphological characters exhibited high variability. Photosynthetic efficiency increased under moderate temperatures and low light but decreased under chilling or high-light conditions. Protective mechanisms, such as non-photochemical quenching and adjustments in pigment composition were observed, although their capacity was limited at very low temperatures. Overall, Chara hispida exhibits morphological and physiological plasticity, enabling survival across a wide range of light and temperature conditions.
