Extreme functional specialization of fertile leaves in a widespread fern species and its implications on the evolution of reproductive dimorphism.

Resource allocation theory posits that organisms distribute limited resources across functions to maximize their overall fitness. In plants, the allocation of resources among maintenance, reproduction, and growth influences short-term economics and long-term evolutionary processes, especially during resource scarcity. The evolution of specialized structures to divide labor between reproduction and growth can create a feedback loop where selection can act on individual organs, further increasing specializaton and  resource allocation. Ferns exhibit diverse reproductive strategies, including dimorphism, where leaves can either be sterile (only for photosynthesis) or fertile (for spore dispersal). This dimorphism is similar to processes in seed plants (e.g., the production of fertile flowers and sterile leaves), and presents an opportunity to investigate divergent resource allocation between reproductive and vegetative functions in specialized organs. Here, we conducted anatomical and hydraulic analyses on Onoclea sensibilis L., a widespread dimorphic fern species, to reveal significant structural and hydraulic divergences between fertile and sterile leaves. Fertile fronds invest less in hydraulic architecture, with nearly 1.5 times fewer water-conducting cells and a nearly 0.5 times less drought-resistant xylem compared to sterile fronds. This comes at the increased relative investment in structural support, which may help facilitate spore dispersal. These findings suggest that specialization in ferns-in the form of reproductive dimorphism-can enable independent selection pressures on each leaf type, potentially optimizing spore dispersal in fertile fronds and photosynthetic efficiency in sterile fronds. Overall, our study sheds light on the evolutionary implications of functional specialization and highlights the importance of reproductive strategies in shaping plant fitness and evolution.

Benefits for children with suspected cancer from routine whole-genome sequencing.

Clinical whole-genome sequencing (WGS) has been shown to deliver potential benefits to children with cancer and to alter treatment in high-risk patient groups. It remains unknown whether offering WGS to every child with suspected cancer can change patient management. We collected WGS variant calls and clinical and diagnostic information from 281 children (282 tumors) across two English units (n = 152 from a hematology center, n = 130 from a solid tumor center) where WGS had become a routine test. Our key finding was that variants uniquely attributable to WGS changed the management in ~7% (20 out of 282) of cases while providing additional disease-relevant findings, beyond standard-of-care molecular tests, in 108 instances for 83 (29%) cases. Furthermore, WGS faithfully reproduced every standard-of-care molecular test (n = 738) and revealed several previously unknown genomic features of childhood tumors. We show that WGS can be delivered as part of routine clinical care to children with suspected cancer and can change clinical management by delivering unexpected genomic insights. Our experience portrays WGS as a clinically impactful assay for routine practice, providing opportunities for assay consolidation and for delivery of molecularly informed patient care.

A cutaneous spindle cell neoplasm characterized by a COL3A1::PDGFRA fusion.

Cutaneous spindle cell neoplasms can be challenging to diagnose using routine histopathological techniques alone, and the growing repertoire of molecular studies can assist in diagnosis. We describe a cutaneous spindle cell neoplasm characterized by a COL3A1::PDGFRA rearrangement predicted to lead to constitutive activation of the PDGFRA kinase domain. The lesion shows some similarities to dermatofibrosarcoma protuberans and also benign and epithelioid fibrous histiocytomas but is distinct from these entities histopathologically and molecularly. This tumor is considered to represent an entity in the spectrum of PDGFR-driven cutaneous mesenchymal neoplasms.

Bottlebrush Networks: A Primer for Advanced Architectures.

Bottlebrush networks (BBNs) are an exciting new class of materials with interesting physical properties derived from their unique architecture. While great strides have been made in our fundamental understanding of bottlebrush polymers and networks, an interdisciplinary approach is necessary for the field to accelerate advancements. This review aims to act as a primer to BBN chemistry and physics for both new and current members of the community. In addition to providing an overview of contemporary BBN synthetic methods, we developed a workflow and desktop application (LengthScale), enabling bottlebrush physics to be more approachable. We conclude by addressing several topical issues and asking a series of pointed questions to stimulate conversation within the community.

Mesoporous Single Atom-Cluster Fe-N/C Oxygen Evolution Electrocatalysts Synthesized with Bottlebrush Block Copolymer-Templated Rapid Thermal Annealing.

Current electrocatalysts for oxygen evolution reaction (OER) are either expensive (such as IrO2, RuO2) or/and exhibit high overpotential as well as sluggish kinetics. This article reports mesoporous earth-abundant iron (Fe)-nitrogen (N) doped carbon electrocatalysts with iron clusters and closely surrounding Fe-N4 active sites. Unique to this work is that the mechanically stable mesoporous carbon-matrix structure (79 nm in pore size) with well-dispersed nitrogen-coordinated Fe single atom-cluster is synthesized via rapid thermal annealing (RTA) within only minutes using a self-assembled bottlebrush block copolymer (BBCP) melamine-formaldehyde resin composite template. The resulting porous structure and domain size can be tuned with the degree of polymerization of the BBCP backbone, which increases the electrochemically active surface area and improves electron transfer and mass transport for an effective OER process. The optimized electrocatalyst shows a required potential of 1.48 V (versus RHE) to obtain the current density of 10 mA/cm2 in 1 M KOH aqueous electrolyte and a small Tafel slope of 55 mV/decade at a given overpotential of 250 mV, which is significantly lower than recently reported earth-abundant electrocatalysts. Importantly, the Fe single-atom nitrogen coordination environment facilitates the surface reconstruction into a highly active oxyhydroxide under OER conditions, as revealed by X-ray photoelectron spectroscopy and in situ Raman spectroscopy, while the atomic clusters boost the single atoms reactive sites to prevent demetalation during the OER process. Density functional theory (DFT) calculations support that the iron nitrogen environment and reconstructed oxyhydroxides are electrocatalytically active sites as the kinetics barrier is largely reduced. This work has opened a new avenue for simple, rapid synthesis of inexpensive, earth-abundant, tailorable, mechanically stable, mesoporous carbon-coordinated single-atom electrocatalysts that can be used for renewable energy production.

Large-Area Fabrication of Porous Graphene Networks on Carbon Fabric via Millisecond Photothermal Processing of Polyaniline for Supercapacitors.

Supercapacitors demonstrate promising potential for flexible, multi-functional energy storage devices; however, their widespread adoption is confronted by fabrication challenges. To access a combination of desirable device qualities such as flexibility, lightweight, structural stability, and enhanced electrochemical performance, carbon fiber (CF) can be utilized as a current collector, alongside graphene as an electrochemically active material. Yet achieving a cost-effective, large-scale graphene production, particularly on CF, remains challenging. Here, a rapid (<1 min) photothermal approach is developed for the large-scale production of graphene directly onto CF, utilizing polyaniline (PANI) as a polymer precursor. The in situ electropolymerization of PANI on CF facilitates its rapid synthesis on large areas, followed by conversion into graphene networks, enabling the binder-free fabrication of supercapacitor devices. These devices exhibit an areal capacitance of 180 mF cm-2 (at 2 mA cm-2 in 1 m H2SO4), an order of magnitude higher than other fabric-based devices. Moreover, the devised photothermal strategy allows for one-step preparation of supercapacitor devices on areas exceeding 100 cm-2, yielding an absolute areal capacitance of 4.5 F. The proportional increase in capacitance with device area facilitates scaling and indicates the commercial viability of this approach for low-cost, energy-efficient, and high-throughput production of lightweight, high-performance graphene-based multi-functional supercapacitor devices.

Factors predictive of hospital length of stay in patients with an index episode of acute necrotizing pancreatitis.

INTRODUCTION: Acute necrotizing pancreatitis (ANP) complicates 15 % of acute pancreatitis cases and is associated with prolonged length of stay (LOS). There are limited studies exploring potential predictors. METHODS: We carried out a retrospective study of all consecutive patients presenting to a large referral healthcare system with ANP. Patients younger than 18 years of age, without confirmed glandular necrosis and with in-hospital mortality were excluded. Poisson regression was carried out to identify potential predictors of prolonged hospital stay. RESULTS: One hundred and sixty-two patients hospitalized between December 2016 and June 2020 were included. The median LOS was 12 days (range: 1-155 days). On multivariate analysis, organ dysfunction at presentation (Incidence rate ratio (IRR) 1.21, p = 0.01) or during admission (IRR 1.32, p = 0.001), Charlson Comorbidity Index scores (IRR 1.1 per CCI point, p < 0.001), known chronic pancreatitis (IRR 1.19, p = 0.03), concurrent (non-pancreas related) infections (IRR 1.13, p = 0.04), need for enteral tube placement (IRR 3.42, p < 0.001) and in-hospital interventions (IRR 1.48-2.85 depending on intervention, p < 0.001) were associated with increased LOS. For patients in the cohort to whom this applied, delayed hospital transfers (IRR 1.02, p < 0.001) and delayed start of enteral feeds (IRR 1.01, p = 0.017) contributed to increased overall LOS. CONCLUSION: We demonstrate that multiple factors including delayed transfers to hospitals with pancreaticobiliary expertise lead to increased length of hospitalization. We suggest various strategies that can be considered to target those gaps and may have a favorable effect on LOS.

Radiation-induced angiosarcoma of the breast: retrospective analysis at a regional treatment centre.

BACKGROUND: Radiation-induced angiosarcoma (RIA) is an uncommon but morbid complication after radiotherapy for breast cancer. METHODS: Retrospective analysis of breast RIA patients at Cambridge University Hospital (CUH), a regional treatment centre in the East of England. RESULTS: 22 patients were identified between 2010 and 2022. Median age of diagnosis was 65 years (range 41-78). Median time from breast radiotherapy to RIA diagnosis was 6.5 years (range 2.4-16.0)-this interval has decreased over the last 24 years (r2 = 0.6601). 9% had metastasis at presentation. All patients underwent surgery (55% at CUH, 45% at local hospitals). 27% received peri-operative pegylated liposomal doxorubicin in the first-line setting. 62% relapsed following their primary curative-intent treatments after a median of 28 months. Metastases occurred in 36%, the commonest sites being lung (100%) and lymph node (50%). 2-year and 5-year overall survival (OS) rates for all patients were 73% and 60%, respectively. No correlation between progression-free survival (PFS) and OS was found with tumour size, margin, peri-operative chemotherapy, and whether surgery was performed at CUH. Patients with multifocal disease on their breasts had shorter PFS following surgery compared to single-lesion disease (median 10 vs 65 months; HR = 4.359 [95% CI 1.342-14.16]; P = 0.0143). Patients aged > 72 years had a median OS of 45 months vs 102 months for those ≤ 72 years (HR = 7.129 [95% CI 1.646-30.88]; P = 0.0086). CONCLUSION: RIA has high rates of recurrence and mortality and appears to be occurring sooner after breast radiotherapy. Further studies on its pathogenesis and effective treatment are warranted.

Silicone elastomers and the Persson-Brener adhesion model.

Many modern anti-icing and anti-fouling coatings rely on soft, low surface energy elastomeric materials such as polydimethylsiloxane for their functionality. While the low surface energy is desirable for reducing adhesion, very little work considers the larger contribution to adhesive failure caused by the viscoelastic nature of elastomers. Here we examine several different siloxane elastomers using a JKR adhesion test, which was operated over a range of different speeds and temperatures. Additionally, we characterize the dynamic mechanical modulus over a large range of frequencies for each material. We note that surface energies of the materials are all similar, but variation in adhesion strength is clear in the data. The variation at low speeds is related to elastomer architecture but the speed dependence itself is independent of architecture. Qualitative correlations are noted between the JKR adhesion measurements and the dynamic moduli. Finally, an attempt is made to directly compare moduli and adhesion through the recent Persson-Brener model. Approximations of the model are shown to be inaccurate. The full model is found to be accurate at low speeds, although it fails to precisely capture higher speed behaviour.

Corrigendum: LetsTalkShots: personalized vaccine risk communication.

[This corrects the article DOI: 10.3389/fpubh.2023.1195751.].

Zooplankton-phytoplankton biomass and diversity relationships in the Great Lakes.

Quantifying the relationship between phytoplankton and zooplankton may offer insight into zooplankton sensitivity to shifting phytoplankton assemblages and the potential impacts of producer-consumer decoupling on the rest of the food web. We analyzed 18 years (2001-2018) of paired phytoplankton and zooplankton samples collected as part of the United States Environmental Protection Agency (U.S. EPA) Great Lakes Biology Monitoring Program to examine both the long-term and seasonal relationships between zooplankton and phytoplankton across all five Laurentian Great Lakes. We also analyzed effects of phytoplankton diversity on zooplankton biomass, diversity, and predator-prey (zooplanktivore/grazer) ratios. Across the Great Lakes, there was a weak positive correlation between total algal biovolume and zooplankton biomass in both spring and summer. The relationship was weaker and not consistently positive within individual lakes. These trends were consistent over time, providing no evidence of increasing decoupling over the study period. Zooplankton biomass was weakly negatively correlated with algal diversity across lakes, whereas zooplankton diversity was unaffected. These relationships did not change when we considered only the edible phytoplankton fraction, possibly due to the high correlation between total and edible phytoplankton biovolume in most of these lakes. Lack of strong coupling between these producer and consumer assemblages may be related to lagging responses by the consumers, top-down effects from higher-level consumers, or other confounding factors. These results underscore the difficulty in predicting higher trophic level responses, including zooplankton, from changes in phytoplankton assemblages.

Timing of ERCP after extracorporeal shock wave lithotripsy for large main pancreatic duct stones.

BACKGROUND AND AIMS: Extracorporeal shock wave lithotripsy (ESWL) is performed to fragment large main pancreatic duct (MPD) stones in symptomatic patients. Subsequent endoscopic retrograde cholangiopancreatography (ERCP) is often performed to clear the stone fragments. Edema of surrounding tissue after ESWL theoretically affects the ability to perform ERCP. However, the optimal timing of ERCP after ESWL is not clearly defined. The aim of this study is to determine the efficacy and safety of same-day ERCP after ESWL and to determine if the timing of ERCP after ESWL affects outcomes. METHODS: This is a retrospective study of consecutive patients from January, 2013 to September, 2019 who received ESWL for MPD stones at our center. Included patients received subsequent same-day ERCP under the same general anesthesia session or later session ERCP (1-30 days after ESWL). Demographics, anatomical findings, history, and outcomes were collected. Success was defined as complete or near complete (> 80%) stone fragmentation with clearance. RESULTS: 218 patients were treated with ESWL and subsequent ERCP. 133 (61.0%) received ERCP on the same day immediately after ESWL, while 85 (39.0%) returned for ERCP at a later day (median 3.0 days after ESWL). Baseline characteristics demonstrated patients who received same-day ERCP had a higher rate of pain at baseline (94.7% vs 87.1%, p = 0.045). Main outcomes demonstrated an overall successful MPD stone clearance rate of 90.4%, with similar rates between same-day ERCP and later session ERCP (91.7% vs 88.2%, p = 0.394). Additionally, successful cannulation at ERCP, adverse events, and post-procedure admission rates were similar. CONCLUSIONS: Delaying ERCP to allow peripancreatic tissue recovery after ESWL does not affect outcomes. Same-day ERCP after ESWL is safe and effective.

LetsTalkShots: personalized vaccine risk communication.

Introduction: Vaccine hesitancy is a global health threat undermining control of many vaccine-preventable diseases. Patient-level education has largely been ineffective in reducing vaccine concerns and increasing vaccine uptake. We built and evaluated a personalized vaccine risk communication website called LetsTalkShots in English, Spanish and French (Canadian) for vaccines across the lifespan. LetsTalkShots tailors lived experiences, credible sources and informational animations to disseminate the right message from the right messenger to the right person, applying a broad range of behavioral theories. Methods: We used mixed-methods research to test our animation and some aspects of credible sources and personal narratives. We conducted 67 discussion groups (n = 325 persons), stratified by race/ethnicity (African American, Hispanic, and White people) and population (e.g., parents, pregnant women, adolescents, younger adults, and older adults). Using a large Ipsos survey among English-speaking respondents (n = 2,272), we tested animations aligned with vaccine concerns and specific to population (e.g., parents of children, parents of adolescents, younger adults, older adults). Results: Discussion groups provided robust feedback specific to each animation as well as areas for improvements across animations. Most respondents indicated that the information presented was interesting (85.5%), clear (96.0%), helpful (87.0%), and trustworthy (82.2%). Discussion: Tailored vaccine risk communication can assist decision makers as they consider vaccination for themselves, their families, and their communities. LetsTalkShots presents a model for personalized communication in other areas of medicine and public health.

Adhesion and mechanical properties of poly(dimethylsiloxane) bottlebrush elastomers.

Poly(dimethylsiloxane) (PDMS) bottlebrush elastomers (BBEs) are attractive soft materials with well-controlled bulk mechanical properties. However, their surface and interfacial properties have not been studied in depth. We report a detailed study of the adhesion of PDMS BBEs to glass using a contact adhesion test to determine the critical energy release rates, Gc, as a function of interfacial separation velocity. For BBEs, Gc for initiating separation, G0, was found to be independent of the crosslink density. We hypothesize that the monomer chemistry of side chains plays a primary role in defining surface properties for this materials system. After crack initiation, BBEs showed a significantly lower Gc and less velocity dependence than linear chain networks. Scaling analysis attributes these properties to the faster dissipative relaxation mechanisms within the BBEs. These findings demonstrate that the adhesion properties of BBEs can be finely tuned through the monomer chemistry and side chain length for potential applications.

Reproductive phases coincide with changes in morphology and photosynthetic physiology in an endangered cycad species.

Cycadales is highly endangered and one of the oldest dioecious gymnosperm lineages, making their reproductive biology highly relevant to conservation efforts and our understanding of the impact of dioecy, yet cycad reproductive ecophysiology is poorly understood. We examined how the costs associated with reproduction may impact basic physiological variation in cycad species. Specifically, we measured traits related to functional morphology and photosynthetic physiology in sterile and fertile staminate plants ('males') of Zamia portoricensis. Light response curves showed that sterile plants had greater light-use efficiency and maximum photosynthetic capacity per area compared with fertile plants. However, fertile and sterile plants exhibited similar respiration rates. We found significantly more nitrogen in leaves of fertile individuals, but similar nitrogen isotope composition and no differences in carbon content between sterile and fertile individuals. Despite having lower leaf-level photosynthetic rates, fertile plants had greater canopy-level photosynthesis than sterile plants, which was achieved by increasing leaf number and total leaf area. Our data suggest that sterile individuals may have greater light demands relative to fertile individuals, and fertile individuals may have greater nitrogen demands, which may be critical for successful reproductive events in staminate plants of the endangered cycad, Z. portoricensis.

Functional traits and trait coordination change over the life of a leaf in a tropical fern species.

PREMISE: Plant ecological strategies are often defined by the integration of underlying traits related to resource acquisition, allocation, and growth. Correlations between key traits across diverse plants suggest that variation in plant ecological strategies is largely driven by a fast-slow continuum of plant economics. However, trait correlations may not be constant through the life of a leaf, and it is still poorly understood how trait function varies over time in long-lived leaves. METHODS: Here, we compared trait correlations related to resource acquisition and allocation across three different mature frond age cohorts in a tropical fern species, Saccoloma inaequale. RESULTS: Fronds exhibited high initial investments of nitrogen and carbon, but with declining return in photosynthetic capacity after the first year. In the youngest fronds, we found water-use efficiency to be significantly lower than in the oldest mature fronds due to increased transpiration rates. Our data suggest that middle-aged fronds are more efficient relative to younger, less water-use efficient fronds and that older fronds exhibit greater nitrogen investments without higher photosynthetic return. In addition, several trait correlations expected under the leaf economics spectrum (LES) do not hold within this species, and some trait correlations only appear in fronds of a specific developmental age. CONCLUSIONS: These findings contextualize the relationship between traits and leaf developmental age with those predicted to underlie plant ecological strategy and the LES and are among the first pieces of evidence for when relative physiological trait efficiency is maximized in a tropical fern species.

Large Area Millisecond Preparation of High-Quality, Few-Layer Graphene Films on Arbitrary Substrates via Xenon Flash Lamp Photothermal Pyrolysis and Their Application for High-Performance Micro-supercapacitors.

We report a method for fast, efficient, and scalable preparation of high-quality, large area, few-layer graphene films on arbitrary substrates via high-intensity pulsed xenon flash lamp photothermal pyrolysis of thin precursor films at ambient conditions in millisecond time frames. The precursors comprised poly(2,2-bis(3,4-dihydro-3-phenyl-1,3-benzoxazine)), and cyclized polyacrylonitrile and possess significant absorption cross section within the bandwidth of the emission spectrum of a xenon flash lamp. By localizing light absorption to the precursor films, the process enabled the preparation of few-layer graphene films on any substrate, including thermally sensitive substrates without the need for any catalytic substrate as in chemical vapor deposition-based approaches or conductive electrodes as in electrochemical method-based approaches. The extent of conversion of the precursor films to graphene was strongly dependent on pulse energy and the local temperature achieved due to photothermal effect, which were controlled via pulse power modulation; it also depended on structural properties of the precursor and to a lesser extent on the substrate. The cPAN showed a higher efficiency for conversion to graphene, as confirmed by Raman spectra (ID/IG ∼ 0.3), and sheet resistance of 0.1 Ω cm. To demonstrate the utility of the process, graphene film electrodes prepared photothermally on carbon fiber current collector were used for the fabrication of micro-supercapacitors with a very high areal supercapacitance of 3.5 mF/cm2. Subsequent deposition of manganese oxide onto the fabricated electrodes significantly increased the energy storage capability of the supercapacitor, yielding a device with exceptionally high capacitance of 80 F/g at 1 mA current, good rate capability, and long cycle life.

Utilization pattern of prophylactic measures for prevention of post-ERCP pancreatitis: a National Survey Study.

BACKGROUND AND AIMS: Post-ERCP pancreatitis (PEP) is the most frequent adverse event of ERCP. Various prophylactic measures are endorsed by the American Society for Gastrointestinal Endoscopy and the European Society of Gastrointestinal Endoscopy to both lower the incidence of PEP and to decrease its severity. The extent to which these interventions are practiced throughout the United States is unclear. The aim of this study was to describe the utilization pattern of various PEP measures and determine factors that affect utilization of these measures. METHODS: A 27-question electronic survey was distributed using a cloud-based program (Qualtrics). The questions assessed ERCP training, practice setting, experience, practice patterns, and perceptions for PEP prophylaxis interventions. Endoscopists with practices based in the United States listed in the American Society for Gastrointestinal Endoscopy member directory received a survey invitation via e-mail. The invitation outlined the study and contained a link with instructions to complete the voluntary survey if they had an active ERCP practice. Data were de-identified for the purposes of analysis. RESULTS: Of survey respondents (N = 319), 46% reported therapeutic endoscopy fellowship training and 37% practiced in teaching programs. Annualized ERCP volume of >100 cases per year were reported by 47%, with pancreatic ERCP comprising ≤5% of procedure volume reported by the majority of respondents (61%). The majority of respondents used prophylactic pancreatic stent (PPS), and 54% reported frequent use during high-risk ERCP. The most common indications for PPS were difficult cannulation, to assist biliary access, and multiple pancreatic duct injections. Most respondents reported frequent use of indomethacin (89%). Of physicians who did not use PPS, use of indomethacin was the most common reason (80%). Variables associated with frequent use of PPS were ERCP fellowship training (P ≤ .001), practice at a teaching program (P ≤ .001), <10 years in practice (P = .005), higher procedure volume (P ≤ .001), and higher proportion of pancreatic cases (P ≤ .001). CONCLUSIONS: Physicians with higher annual ERCP volume, who teach at hospital-based ERCP practices, and who regularly perform pancreatic ERCP are more likely to use PPS. Therapeutic ERCP fellowship training and recent entry into practice were also associated with PPS utilization. Indomethacin use seems to be more frequent than PPS. Our findings suggest that indomethacin is supplanting PPS as the preferred method of PEP prophylaxis.

Identification of an Activating PDGFRA Deletion in a Novel Sinonasal Soft Tissue Neoplasm.

BACKGROUND: Spindle cell tumours in the sinonasal area are diagnostically challenging. We identified a neoplasm that defied histopathological classification using current criteria. METHODS: The case was subjected to histopathological, immunohistochemical and molecular analysis using a large small variant DNA panel. RESULTS: The tumour comprised cytologically bland epithelioid spindle cells with a rich vasculature, which lack expression of actin and other smooth muscle markers, CD34 and beta-catenin. An activating insertion/deletion in exon 12 of the PDGFRA gene was detected. This alteration has previously been described in gastrointestinal stromal tumours and inflammatory fibroid polyps of the GI tract, but the site, histological, and immunophenotypic features in this tumour are distinct. CONCLUSION: We describe a novel sinonasal spindle cell tumour characterised by an activating insertion/deletion in exon 12 of PDGFRA. The diagnosis of PDGFRA-activated sinonasal spindle cell tumour should be considered in difficult to classify mesenchymal lesions at this site.

A reduced role for water transport during the Cenozoic evolution of epiphytic Eupolypod ferns.

The Cretaceous-Cenozoic expansion of tropical forests created canopy space that was subsequently occupied by diverse epiphytic communities including Eupolypod ferns. Eupolypods proliferated in this more stressful niche, where lower competition enabled the adaptive radiation of thousands of species. Here, we examine whether xylem traits helped shape the Cenozoic radiation of Eupolypod ferns. We characterized the petiole xylem anatomy of 39 species belonging to the Eupolypod I and Eupolypod II clades occupying the epiphytic, hemiepiphytic, and terrestrial niche, and we assessed vulnerability to embolism in a subset of species. The transition to the canopy was associated with reduced xylem content and smaller tracheid diameters, but no differences were found in species vulnerability to embolism and pit membrane thickness. Phylogenetic analyses support selection for traits associated with reduced water transport in Eupolypod 1 species. We posit that in Eupolypod epiphytes, selection favored water retention via thicker leaves and lower stomatal density over higher rates of water transport. Consequently, lower leaf water loss was coupled with smaller quantities of xylem and narrower tracheid diameters. Traits associated with water conservation were evident in terrestrial Eupolypod 1 ferns and may have predisposed this clade toward radiation in the canopy.