Clinical Characteristics of Avoidable Patient Transfers for Suspected Pediatric Appendicitis

INTRODUCTION

Pediatric surgical care is becoming increasingly regionalized, often resulting in limited access. Interfacility transfers pose a significant financial and emotional burden to when they are potentially avoidable. Of transferred patients, we sought to identify clinical factors associated with avoidable transfers in pediatric patients with suspected appendicitis.

METHODS

We performed a single-center retrospective study at an academic tertiary referral children's hospital in an urban setting. We included children who underwent interfacility transfer to our center with a transfer diagnosis of appendicitis from July 1, 2021 to June 30, 2023. Encounters were designated as either an appropriate transfer (underwent appendectomy) or an avoidable transfer (did not undergo appendectomy). Encounters treated nonoperatively for complicated appendicitis were excluded. Bivariate analysis was performed using Mann-Whitney test and chi-square tests.

RESULTS

A total of 444 patients were included: 71.2% were classified as appropriate transfers and 28.8% as avoidable transfers. Patients with avoidable transfer were younger compared to those in the appropriate transfer cohort (median age 9 y, interquartile range: 7-13 versus 11 y, interquartile range: 8-14; P < 0.001). Avoidable transfers less frequently presented with the typical symptoms of fever, migratory abdominal pain, anorexia, and nausea/emesis (P = 0.005). Avoidable transfers also reported shorter symptom duration (P = 0.040) with lower median white blood cell count (P < 0.001), neutrophil percentage (P < 0.001), and C-reactive protein levels (P < 0.003). Avoidable transfers more frequently underwent repeat imaging upon arrival (42.9% versus 12.7%, P < 0.001).

CONCLUSIONS

These findings highlight the importance of clinical history in children with suspected appendicitis. Younger patients without typical symptoms of appendicitis, those with a shorter duration of symptoms, and lower serum inflammatory markers may benefit from close observation without transfer.

A Standardized Post-gastrostomy Feeding Protocol for Pediatric Patients Reduces Time to Postoperative Goal Feeding Volume

BACKGROUND

Gastrostomy creation is a common pediatric surgical procedure, but the time to initiation of feeds and to goal feeding volumes postoperatively varies greatly. Delays in reaching goal feeding volumes promote malnutrition and may prolong hospital length of stay. We hypothesized that implementing an accelerated, standardized post-gastrostomy feeding protocol would allow patients to reach goal feeding volumes sooner, without increasing postoperative complications.

METHODS

We conducted a retrospective cohort study of children who underwent gastrostomy tube placement between 1/1/2022 and 11/30/2023. The feeding protocol was implemented on 11/16/2022, with patients separated into pre- and post-protocol cohorts. Abstracted data included comorbidities, time to initiation of enteral feeds, time to goal feeding volume, and postoperative complications.

RESULTS

322 patients were included: 166 pre-protocol and 156 post-protocol. The post-protocol cohort had a greater proportion of patients with gastrointestinal and/or cardiac comorbidities (P < .001). Through the protocol, postoperative enteral feeds were initiated significantly faster (5.4 hrs [IQR 43-7.7] vs 7.0 hrs [IQR 5.6-14.3]; P < .001). The post-protocol cohort also achieved goal feeding volumes sooner (12.8 hrs [IQR 9.1-25.3] vs 26.3 hrs [IQR 21.6-38.9]; P < .001). Postoperative complication rates did not differ between cohorts. Sub-analysis of children with complex cardiac conditions also demonstrated faster time to goal nutrition without an associated increase in postoperative events.

DISCUSSION

These findings demonstrate that our accelerated post-gastrostomy feeding protocol was effective in achieving goal enteral nutrition earlier without increasing postoperative adverse outcomes. This protocol may be used by other centers to safely expedite time to goal enteral feeds in children postoperatively.

Evaluation of Postoperative Outcomes After Enterostomy Closure in Low Body Weight Infants: A Multi-Center Retrospective Analysis

BACKGROUND

The minimum weight for enterostomy closure (EC) in infants remains debated with the current acceptable cut-off of >2 kg. As enterostomy-related complications or high enterostomy output (>30cc/kg/d) may prohibit a premature infant from reaching 2 kg, additional data is needed to evaluate the safety of EC in infants <2 kg. The objective of this study was to evaluate postoperative outcomes in low body weight (<2 kg) infants undergoing EC compared to larger infants.

METHODS

We performed a multi-center retrospective analysis from 1/1/2012-12/31/2022 of all infants (age <1 year) who were <4 kg at time of EC. Primary outcomes included postoperative complications and 30-day mortality. Non-parametric analysis was performed using the Kruskal-Wallis one-way analysis of variance and chi-square tests. Univariable logistic regression was performed to identify factors associated with postoperative complications.

RESULTS

Of 92 infants, 15 infants (16.3%) underwent EC at <2 kg, 16 (17.4%) at 2-2.49 kg, 31 (33.7%) at 2.5-2.99 kg, and 30 (32.6%) at ≥3 kg. Infants <2 kg at time of EC exhibited higher rates of hyperbilirubinemia (P = .030), neurologic comorbidities (P = .030), and high enterostomy output (P = .041). There was no difference in postoperative complications (P = .460) or 30-day mortality (P = .460) between the <2 kg group and larger weight groups. Low body weight was not associated with an increased risk for developing a postoperative complication (OR: 1.001, 95% CI: 1.001-1.001; P = .032).

CONCLUSION

Our findings suggest that EC in infants <2 kg may be safe with comparable postoperative outcomes to larger weight infants. Thus, the timing of EC should be based on the infant's physiologic status, in contrast to a predetermined minimum weight cut-off.

Differential RNA Expression Between Metastatic and Primary Neuroblastoma Cells

INTRODUCTION

Neuroblastoma (NB) is the most common extra-cranial malignancy in children. Poor survival in high-risk NB is attributed to recurrent metastatic disease. To better study metastatic disease, we used a novel mouse model to investigate differential gene expression between primary tumor cells and metastatic cells. We hypothesized that metastatic NB cells have a different gene expression profile from primary tumor cells and cultured cells.

METHODS

Using three human NB cell lines (NGP, CHLA255, and SH-SY5Y), orthotopic xenografts were established in immunodeficient nod/scid gamma mice via subcapsular renal injection. Mice were sacrificed and NB cells were isolated from the primary tumor and from sites of metastasis (bone marrow, liver). RNA sequencing, gene set analysis, and pathway analysis were performed to identify differentially expressed genes and molecular pathways in the metastatic cells compared to primary tumor cells.

RESULTS

There were 266 differentially expressed genes in metastatic tumor cells (bone marrow and liver combined) compared to primary tumor cells. The top upregulated gene was KCNK1 and the top downregulated genes were PDE7B and NEBL. Top upregulated pathways in the metastatic cells were involved in ion transport, cell signaling, and cell proliferation. Top downregulated pathways were involved in DNA synthesis, transcription, and cellular metabolism.

CONCLUSIONS

In metastatic NB cells, our study identified the upregulation of biologic processes involved in cell cycle regulation, cell proliferation, migration, and invasion. Ongoing studies aim to validate downstream translation of these genomic alterations, as well as target these pathways to more effectively suppress and inhibit recurrent metastatic disease in NB.

Precision Oncology in Pediatric Cancer Surgery

Pediatric precision oncology has provided a greater understanding of the wide range of molecular alterations in difficult-to-treat or rare tumors with the aims of increasing survival as well as decreasing toxicity and morbidity from current cytotoxic therapies. In this article, the authors discuss the current state of pediatric precision oncology which has increased access to novel targeted therapies while also providing a framework for clinical implementation in this unique population. The authors evaluate the targetable mutations currently under investigation-with a focus on pediatric solid tumors-and discuss the key surgical implications associated with novel targeted therapies.

Sex-based Disparities in the Management of Pediatric Gonadal Torsion

INTRODUCTION

In 2015, the U.S. News and World Report (USNWR) implemented a quality metric to expedite surgery for testicular torsion (TT), but not ovarian torsion (OT). This study examined OR timing among children with suspected TT and OT before and after this metric.

METHODS

A single-center retrospective cohort study of children (1-18yr) who underwent surgery for suspected gonadal torsion was performed. Time to OR (TTOR) from hospital presentation to surgery start was calculated. An interrupted time series analysis identified changes in TTOR for suspected TT versus OT after the 2015 USNWR quality metric.

RESULTS

Overall, 216 patients presented with TT and 120 with OT. Median TTOR for TT was 147 min (IQR:99-198) versus 462 min (IQR:308-606) for OT. Post-quality metric, children with TT experienced a 27.8 min decrease (95% CI:-51.7,-3.9, p = 0.05) in annual median TTOR. No significant decrease was observed for children with OT (p = 0.22). Children with history of a known ovarian mass (N = 62) experienced a shorter TTOR compared to those without (422 vs 499min; p = 0.04).

CONCLUSION

Implementation of a national quality metric for TT expedited surgical care for children with TT, but not children with OT. These findings highlight the need for equitable quality metrics for children presenting with suspected gonadal torsion.

LEVEL OF EVIDENCE

III.

TYPE OF STUDY

Retrospective Comparative Study, Observational Cohort Study.

Lessons Learned From the First-In-Human Compassionate Use of Connect-EA™ in Ten Patients With Esophageal Atresia

INTRODUCTION

Delayed primary repair of esophageal atresia in patients with high-risk physiologic and anatomic comorbidities remains a daunting challenge with an increased risk for peri-operative morbidity and mortality via conventional repair. The Connect-EA device facilitates the endoscopic creation of a secure esophageal anastomosis. This follow-up study reports our long-term outcomes with the novel esophageal magnetic compression anastomosis (EMCA) Connect-EA device for EA repair, as well as lessons learned from the ten first-in-human cases. We propose an algorithm to maximize the advantages of the device for EA repair.

METHODS

Under compassionate use approval, from June 2019 to December 2022, ten patients with prohibitive surgical or medical risk factors underwent attempted EMCA with this device. All patients underwent prior gastrostomy, tracheoesophageal fistula ligation (if necessary), and demonstrated pouch apposition prior to EMCA.

RESULTS

Successful device deployment and EMCA formation were achieved in nine patients (90%). Mean time to anastomosis formation was 8 days (range 5-14) and the device was retrieved endoscopically in five (56%) cases. At median follow-up of 22 months (range 4-45), seven patients (78%) are tolerating oral nutrition. Balloon dilations (median 4, range 1-11) were performed either prophylactically for radiographic asymptomatic anastomotic narrowing (n = 7, 78%) or to treat clinically-significant anastomotic narrowing (n = 2, 22%) with no ongoing dilations at 3-month follow up post-repair.

CONCLUSION

EMCA with the Connect-EA device is a safe and feasible minimally-invasive alterative for EA repair in high-risk surgical patients. Promising post-operative outcomes warrant further Phase I investigation.

LEVEL OF EVIDENCE

IV, Case series of novel operative technique without comparison group.

Evaluation of a Magnetic Compression Anastomosis for Jejunoileal Partial Diversion in Rhesus Macaques

PURPOSE

Metabolic surgery remains underutilized for treating type 2 diabetes, as less invasive alternative interventions with improved risk profiles are needed. We conducted a pilot study to evaluate the feasibility of a novel magnetic compression device to create a patent limited caliber side-to-side jejunoileal partial diversion in a nonhuman primate model.

MATERIALS AND METHODS

Using an established nonhuman primate model of diet-induced insulin resistance, a magnetic compression device was used to create a side-to-side jejunoileal anastomosis. Primary outcomes evaluated feasibility (e.g., device mating and anastomosis patency) and safety (e.g., device-related complications). Secondary outcomes evaluated the device's ability to produce metabolic changes associated with jejunoileal partial diversion (e.g., homeostatic model assessment of insulin resistance [HOMA-IR] and body weight).

RESULTS

Device mating, spontaneous detachment, and excretion occurred in all animals (n = 5). There were no device-related adverse events. Upon completion of the study, ex vivo anastomoses were widely patent with healthy mucosa and no evidence of stricture. At 6 weeks post-device placement, HOMA-IR improved to below baseline values (p < 0.05). Total weight also decreased in a linear fashion (R2 = 0.97) with total weight loss at 6 weeks post-device placement of 14.4% (p < 0.05).

CONCLUSION

The use of this novel magnetic compression device to create a limited caliber side-to-side jejunoileal anastomosis is safe and likely feasible in a nonhuman primate model. The observed glucoregulatory and metabolic effects of a partial jejunoileal bypass with this device warrant further investigation to validate the long-term glucometabolic impact of this approach.

Outcomes of pediatric pilonidal disease treatment: excision with off-midline flap reconstruction versus endoscopic pilonidal sinus treatment

PURPOSE

Pilonidal disease (PD) is marked by chronic inflammation and frequent recurrence which can decrease quality of life. However, debate remains regarding the optimal treatment for PD in the pediatric population. This study compares two recommended treatment approaches-excision with off-midline flap reconstruction (OMF: Bascom cleft lift flap, modified Limberg flap) and minimally invasive endoscopic pilonidal sinus treatment (EPSiT).

METHODS

Single-center retrospective evaluation of patients 1-21 years of age with PD who underwent either excision with OMF reconstruction or EPSiT between 10/1/2011 and 10/31/2021. Outcomes included were disease recurrence, reoperation, and wound complication rates. Comparisons were performed using Chi-square and Mann-Whitney U tests.

RESULTS

18 patients underwent excision/OMF reconstruction and 45 patients underwent EPSiT. The excision/OMF reconstruction cohort was predominantly male (44.4% vs 17.8% p = 0.028), with history of prior pilonidal infection (33.3% vs 6.7%; p = 0.006), and longer median operative time (60 min vs 17 min; p < 0.001). The excision/OMF reconstruction cohort had a higher rate of wound complications (22.2% vs 0%; p = 0.001), but lower rates of disease recurrence (5.6% vs 33.3%; p = 0.022) and reoperation (5.6% vs 31.1%; p = 0.031).

CONCLUSION

In pediatric patients with PD, excision with OMF reconstruction may decrease recurrence and reoperation rates with increased operative times and wound complication rates, compared to EPSiT.

Optimizing the Postoperative Management of Children Undergoing Resection of High-Risk Abdominal Neuroblastoma

BACKGROUND

Surgical resection is a mainstay of treatment in high-risk neuroblastoma (HR-NB), but there exists wide variability in perioperative management practices. The aim of this study was to evaluate two standardized adult perioperative enhanced recovery practices (ERPs) in pediatric patients undergoing open resection of abdominal HR-NB.

METHODS

All patients with abdominal HR-NB surgically resected at a free-standing children's hospital between 12/2010 and 7/2020 were retrospectively reviewed. Perioperative ERPs of interest included avoidance of routine nasogastric tube (NGT) use and the use of neuraxial anesthesia. Primary outcomes included time to enteral intake, urinary catheter use, opioid utilization, and length of stay (LOS).

RESULTS

Overall, 37 children, median age 33 months (IQR: 20-48 months), were identified. Avoidance of an NGT allowed for earlier feeding after surgery (P = .03). Neuraxial anesthesia use more frequently required an indwelling urinary catheter (P < .01) for a longer duration (P = .02), with no difference in total opioid utilization (P = .77) compared to patients without neuraxial anesthesia. Postoperative LOS was unaffected by avoidance of routine NGT use (P = .68) or use of neuraxial anesthesia (P = .89).

CONCLUSION

Children undergoing open resection of abdominal HR-NB initiated diet sooner when an NGT was not left postoperatively, and the need for a urinary catheter was significantly higher in patients who received neuraxial anesthesia. However, these two ERP components did not decrease postoperative LOS. To optimize the postoperative management of NB patients, postoperative NGTs should be avoided, while the benefit of neuraxial anesthesia is less clear as it necessitates the placement of a urinary catheter without decreasing opioid utilization.

Anti-CCL2 antibody combined with etoposide prolongs survival in a minimal residual disease mouse model of neuroblastoma

C-C motif chemokine ligand 2 (CCL2) is a monocyte chemoattractant that promotes metastatic disease and portends a poor prognosis in many cancers. To determine the potential of anti-CCL2 inhibition as a therapy for recurrent metastatic disease in neuroblastoma, a mouse model of minimal residual disease was utilized in which residual disease was treated with anti-CCL2 monoclonal antibody with etoposide. The effect of anti-CCL2 antibody on neuroblastoma cells was determined in vitro with cell proliferation, transwell migration, and 2-dimensional chemotaxis migration assays. The in vivo efficacy of anti-CCL2 antibody and etoposide against neuroblastoma was assessed following resection of primary tumors formed by two cell lines or a patient-derived xenograft (PDX) in immunodeficient NOD-scid gamma mice. In vitro, anti-CCL2 antibody did not affect cell proliferation but significantly inhibited neuroblastoma cell and monocyte migration towards an increasing CCL2 concentration gradient. Treatment of mice with anti-CCL2 antibody combined with etoposide significantly increased survival of mice after resection of primary tumors, compared to untreated mice.

Beyond the gut: spectrum of magnetic surgery devices

Since the 1970s, magnetic force has been used to augment modern surgical techniques with the aims of minimizing surgical trauma and optimizing minimally-invasive systems. The majority of current clinical applications for magnetic surgery are largely centered around gastrointestinal uses-such as gastrointestinal or bilioenteric anastomosis creation, stricturoplasty, sphincter augmentation, and the guidance of nasoenteric feeding tubes. However, as the field of magnetic surgery continues to advance, the development and clinical implementation of magnetic devices has expanded to treat a variety of non-gastrointestinal disorders including musculoskeletal (pectus excavatum, scoliosis), respiratory (obstructive sleep apnea), cardiovascular (coronary artery stenosis, end-stage renal disease), and genitourinary (stricture, nephrolithiasis) conditions. The purpose of this review is to discuss the current state of innovative magnetic surgical devices under clinical investigation or commercially available for the treatment of non-gastrointestinal disorders.

The Evolving Use of Magnets in Surgery: Biomedical Considerations and a Review of Their Current Applications

The novel use of magnetic force to optimize modern surgical techniques originated in the 1970s. Since then, magnets have been utilized as an adjunct or alternative to a wide array of existing surgical procedures, ranging from gastrointestinal to vascular surgery. As the use of magnets in surgery continues to grow, the body of knowledge on magnetic surgical devices from preclinical development to clinical implementation has expanded significantly; however, the current magnetic surgical devices can be organized based on their core function: serving as a guidance system, creating a new connection, recreating a physiologic function, or utilization of an internal–external paired magnet system. The purpose of this article is to discuss the biomedical considerations during magnetic device development and review the current surgical applications of magnetic devices.

Recovery After Thyroid and Parathyroid Surgery: How Do Our Patients Really Feel?

INTRODUCTION

Counseling on the immediate postoperative experience for outpatient procedures is largely based on anecdotal experience. We devised a short messaging service (SMS) survey using mobile phone text messages to evaluate real-time patient recovery following outpatient thyroid or parathyroid surgery.

MATERIALS AND METHODS

Daily automated SMS surveys were sent the evening of the operation until postoperative day 10. Pain, opioid use, voice quality, and energy levels were assessed. Impaired voice and energy was defined as a score < 2/3 of normal.

RESULTS

One hundred fifty five patients were enrolled with an overall response rate of 81.6%. One hundred thirty three patients had an individual response rate > 50% and were included in the final analysis. Median patient age was 60 y with 102 females (76.7%). Seventy patients (52.6%) underwent parathyroidectomy and 66 (49.6%) thyroidectomy and 10 (7.5%) neck dissection. Forty eight patients (36.1%) did not use any opioids postoperatively. Independent risk factors for higher total pain scores included thyroidectomy and patients with preoperative opioid or tobacco use, while increased opioid use was associated with age < 60 y, body mass index > 30 kg/m², preoperative opioid or tobacco use, and history of anxiety or depression. Patients with loss of intraoperative recurrent laryngeal nerve signaling had a significantly worse overall voice score (54.65 versus 92.67, P < 0.001). Up to 10% of patients were still using opioids and/or reported impaired voice and energy levels beyond 1 wk postoperatively.

CONCLUSIONS

Real-time SMS survey is an effective and potentially valuable way to monitor patient recovery following surgery. A subset of patients reported impaired voice and energy and was still using opioids beyond 1 wk after thyroid and parathyroid surgery and these patients may benefit from closer follow-up and earlier intervention.

Chaenothecopsis (Mycocaliciales, Ascomycota) from exudates of endemic New Zealand Podocarpaceae

The order Mycocaliciales (Ascomycota) comprises fungal species with diverse, often highly specialized substrate ecologies. Particularly within the genus Chaenothecopsis, many species exclusively occur on fresh and solidified resins or other exudates of vascular plants. In New Zealand, the only previously known species growing on plant exudate is Chaenothecopsis schefflerae, found on several endemic angiosperms in the family Araliaceae. Here we describe three new species; Chaenothecopsis matai Rikkinen, Beimforde, Tuovila & A.R. Schmidt, C. nodosa Beimforde, Tuovila, Rikkinen & A.R. Schmidt, and C. novae-zelandiae Rikkinen, Beimforde, Tuovila & A.R. Schmidt, all growing on exudates of endemic New Zealand conifers of the Podocarpaceae family, particularly on Prumnopitys taxifolia. Phylogenetic analyses based on ribosomal DNA regions (ITS and LSU) grouped them into a distinct, monophyletic clade. This, as well as the restricted host range, suggests that all three taxa are endemic to New Zealand. Copious insect frass between the ascomata contain ascospores or show an early stage of ascomata development, indicating that the fungi are spread by insects. The three new species represent the first evidence of Chaenothecopsis from any Podocarpaceae species and the first from any gymnosperm exudates in New Zealand.

Overtransfusion of packed red blood cells during massive transfusion activation: a potential quality metric for trauma resuscitation

Objectives

The goal of this study was to explore the incidence of overtransfusion in trauma patients requiring massive transfusion protocol (MTP) activation and identify modifiable risk factors. We hypothesized that overtransfusion is common after MTP activation.

Methods

Patients admitted to a level I trauma center from July 2016 to December 2019 and who required MTP activation were selected. The primary outcome was overtransfusion, defined as a hemoglobin (Hg) ≥11 g/dL at 24 hours (±2 hours). A Cox regression model was used to identify independent risk factors for overtransfusion.

Results

140 patients met inclusion criteria. The median age was 39.0 years, with the majority (74.3%) being male. The median (IQR) Injury Severity Score (ISS) was 24.0 (58.0) and 38.4% had a penetrating mechanism. The median (IQR) admission Hg was 12.6 (11.7) g/dL. Overall, 71.4% of patients were overtransfused by the conclusion of MTP, 43.6% 24 hours later, and 29.5% at discharge. Overtransfusion did not correlate with the number of units of blood transfused nor with the duration of MTP. Overtransfused patients at 24 hours after the conclusion of MTP were significantly more likely to present with a penetrating injury (52.5% vs. 27.3%, p=0.003) and have a significantly lower ISS (median (IQR) 18.5 (44.0) vs. 26.0 (58.0), p=0.035.) In a Cox regression model, penetrating mechanism (adjusted HR (AHR): 2.93; adjusted p=0.004) and admission base excess (BE) (AHR: 1.15; adjusted p=0.001) were the only variables independently associated with overtransfusion.

Conclusions

Overtransfusion of trauma patients requiring MTP activation is highly common, leading to overutilization of a limited resource. Penetrating trauma and BE may be modifiable risk factors that can help limit overtransfusion. Overtransfusion should be tracked as a data point by blood banks and trauma centers and be further studied as a potential quality metric for the resuscitation of massively transfused trauma patients.

Level of evidence

III.

Pioneering polyploids: the impact of whole-genome duplication on biome shifting in New Zealand Coprosma (Rubiaceae) and Veronica (Plantaginaceae)

The role of whole-genome duplication (WGD) in facilitating shifts into novel biomes remains unknown. Focusing on two diverse woody plant groups in New Zealand, Coprosma (Rubiaceae) and Veronica (Plantaginaceae), we investigate how biome occupancy varies with ploidy level, and test the hypothesis that WGD increases the rate of biome shifting. Ploidy levels and biome occupancy (forest, open and alpine) were determined for indigenous species in both clades. The distribution of low-ploidy (Coprosma: 2x, Veronica: 6x) versus high-ploidy (Coprosma: 4-10x, Veronica: 12-18x) species across biomes was tested statistically. Estimation of the phylogenetic history of biome occupancy and WGD was performed using time-calibrated phylogenies and the R package BioGeoBEARS. Trait-dependent dispersal models were implemented to determine support for an increased rate of biome shifting among high-ploidy lineages. We find support for a greater than random portion of high-ploidy species occupying multiple biomes. We also find strong support for high-ploidy lineages showing a three- to eightfold increase in the rate of biome shifts. These results suggest that WGD promotes ecological expansion into new biomes.

Using target sequence capture to improve the phylogenetic resolution of a rapid radiation in New Zealand Veronica

PREMISE

Recent, rapid radiations present a challenge for phylogenetic reconstruction. Fast successive speciation events typically lead to low sequence divergence and poorly resolved relationships with standard phylogenetic markers. Target sequence capture of many independent nuclear loci has the potential to improve phylogenetic resolution for rapid radiations.

METHODS

Here we applied target sequence capture with 353 protein-coding genes (Angiosperms353 bait kit) to Veronica sect. Hebe (common name hebe) to determine its utility for improving the phylogenetic resolution of rapid radiations. Veronica section Hebe originated 5-10 million years ago in New Zealand, forming a monophyletic radiation of ca 130 extant species.

RESULTS

We obtained approximately 150 kbp of 353 protein-coding exons and an additional 200 kbp of flanking noncoding sequences for each of 77 hebe and two outgroup species. When comparing coding, noncoding, and combined data sets, we found that the latter provided the best overall phylogenetic resolution. While some deep nodes in the radiation remained unresolved, our phylogeny provided broad and often improved support for subclades identified by both morphology and standard markers in previous studies. Gene-tree discordance was nonetheless widespread, indicating that additional methods are needed to disentangle fully the history of the radiation.

CONCLUSIONS

Phylogenomic target capture data sets both increase phylogenetic signal and deliver new insights into the complex evolutionary history of rapid radiations as compared with traditional markers. Improving methods to resolve remaining discordance among loci from target sequence capture is now important to facilitate the further study of rapid radiations.

The effect of single biome occupancy on the estimation of biome shifts and the detection of biome conservatism

Biome conservatism is often regarded as common in diversifying lineages, based on the detection of low biome shift rates or high phylogenetic signal. However, many studies testing biome conservatism utilise a single-biome-per-species approach, which may influence the detection of biome conservatism. Meta-analyses show that biome shift rates are significantly lower (less than a tenth), when single biome occupancy approaches are adopted. Using New Zealand plant lineages, estimated biome shifts were also significantly lower (14-67% fewer biome shifts) when analysed under the assumption of a single biome per species. Although a single biome approach consistently resulted in lower biome shifts, it detected fewer instances of biome conservatism. A third of clades (3 out of 9) changed status in biome conservatism tests between single and multiple biome occupancy approaches, with more instances of significant biome conservatism when using a multiple biome occupancy approach. A single biome approach may change the likelihood of finding biome conservatism because it assumes biome specialisation within species, falsely recognises some biome shift types and fails to include other biome shift types. Our results indicate that the degree of biome fidelity assumed has a strong influence on analyses assessing biome shift rates, and biome conservatism testing. We advocate analyses that allow species to occupy multiple biomes.

Polyploidy on Islands: Its Emergence and Importance for Diversification

Whole genome duplication or polyploidy is widespread among floras globally, but traditionally has been thought to have played a minor role in the evolution of island biodiversity, based on the low proportion of polyploid taxa present. We investigate five island systems (Juan Fernández, Galápagos, Canary Islands, Hawaiian Islands, and New Zealand) to test whether polyploidy (i) enhances or hinders diversification on islands and (ii) is an intrinsic feature of a lineage or an attribute that emerges in island environments. These island systems are diverse in their origins, geographic and latitudinal distributions, levels of plant species endemism (37% in the Galapagos to 88% in the Hawaiian Islands), and ploidy levels, and taken together are representative of islands more generally. We compiled data for vascular plants and summarized information for each genus on each island system, including the total number of species (native and endemic), generic endemicity, chromosome numbers, genome size, and ploidy levels. Dated phylogenies were used to infer lineage age, number of colonization events, and change in ploidy level relative to the non-island sister lineage. Using phylogenetic path analysis, we then tested how the diversification of endemic lineages varied with the direct and indirect effects of polyploidy (presence of polyploidy, time on island, polyploidization near colonization, colonizer pool size) and other lineage traits not associated with polyploidy (time on island, colonizer pool size, repeat colonization). Diploid and tetraploid were the most common ploidy levels across all islands, with the highest ploidy levels (>8x) recorded for the Canary Islands (12x) and New Zealand (20x). Overall, we found that endemic diversification of our focal island floras was shaped by polyploidy in many cases and certainly others still to be detected considering the lack of data in many lineages. Polyploid speciation on the islands was enhanced by a larger source of potential congeneric colonists and a change in ploidy level compared to overseas sister taxa.

NMR spectroscopy goes mobile: Using NMR as process analytical technology at the fume hood

Nuclear magnetic resonance (NMR) is potentially a very powerful process analytical technology (PAT) tool as it gives an atomic resolution picture of the reaction mixture without the need for chromatography. NMR is well suited for interrogating transient intermediates, providing kinetic information via NMR active nuclei, and most importantly provides universally quantitative information for all species in solution. This contrasts with commonly used PAT instruments, such as Raman or Flow-infrared (IR), which requires a separate calibration curve for every component of the reaction mixture. To date, the large footprint of high-field (≥400 MHz) NMR spectrometers and the immobility of superconducting magnets, coupled with strict requirements for the architecture for the room it is to be installed, have been a major obstacle to using this technology right next to fume hoods where chemists perform synthetic work. Here, we describe the use of a small, lightweight 60 MHz Benchtop NMR system (Nanalysis Pro-60) located on a mobile platform, that was used to monitor both small and intermediate scale Grignard formation and coupling reactions. We also show how low field NMR can provide a deceptively simple yes/no answer (for a system that would otherwise require laborious off-line testing) in the enrichment of one component versus another in a kilogram scale distillation. Benchtop NMR was also used to derive molecule specific information from Flow-IR, a technology found in most manufacturing sites, and compare the ease at which the concentrations of the reaction mixtures can be derived by NMR versus IR.

Reducing the arbitrary: fuzzy detection of microbial ecotones and ecosystems - focus on the pelagic environment

BACKGROUND

One of the central objectives of microbial ecology is to study the distribution of microbial communities and their association with their environments. Biogeographical studies have partitioned the oceans into provinces and regions, but the identification of their boundaries remains challenging, hindering our ability to study transition zones (i.e. ecotones) and microbial ecosystem heterogeneity. Fuzzy clustering is a promising method to do so, as it creates overlapping sets of clusters. The outputs of these analyses thus appear both structured (into clusters) and gradual (due to the overlaps), which aligns with the inherent continuity of the pelagic environment, and solves the issue of defining ecosystem boundaries.

RESULTS

We show the suitability of applying fuzzy clustering to address the patchiness of microbial ecosystems, integrating environmental (Sea Surface Temperature, Salinity) and bacterioplankton data (Operational Taxonomic Units (OTUs) based on 16S rRNA gene) collected during six cruises over 1.5 years from the subtropical frontal zone off New Zealand. The technique was able to precisely identify ecological heterogeneity, distinguishing both the patches and the transitions between them. In particular we show that the subtropical front is a distinct, albeit transient, microbial ecosystem. Each water mass harboured a specific microbial community, and the characteristics of their ecotones matched the characteristics of the environmental transitions, highlighting that environmental mixing lead to community mixing. Further explorations into the OTU community compositions revealed that, although only a small proportion of the OTUs explained community variance, their associations with given water mass were consistent through time.

CONCLUSION

We demonstrate recurrent associations between microbial communities and dynamic oceanic features. Fuzzy clusters can be applied to any ecosystem (terrestrial, human, marine, etc) to solve uncertainties regarding the position of microbial ecological boundaries and to refine the relation between the distribution of microorganisms and their environment.

Can we predict which species win when new habitat becomes available?

Land cover change is a key component of anthropogenic global environmental change, contributing to changes in environmental conditions of habitats. Deforestation is globally the most widespread and anthropogenically driven land cover change leading to conversion from closed forest to open non-forest habitat. This study investigates the relative roles of geographic features, characteristics of species climatic niche and species traits in determining the ability of open-habitat plant species to take advantage of recently opened habitats. We use current occurrence records of 18 herbaceous, predominantly open-habitat species of the genus Acaena (Rosaceae) to determine their prevalence in recently opened habitat. We tested correlation of species prevalence in anthropogenically opened habitat with (i) geographic features of the spatial distribution of open habitat, (ii) characteristics of species climatic niche, and (iii) species traits related to dispersal. While primary open habitat (naturally open) was characterised by cold climates, secondary open habitat (naturally closed but anthropogenically opened) is characterised by warmer and wetter conditions. We found high levels of variation in the species prevalence in secondary open habitat indicating species differences in their ability to colonise newly opened habitat. For the species investigated, geographical features of habitat and climatic niche factors showed generally stronger relationships with species prevalence in secondary open habitat than functional traits. Therefore, for small herbaceous species, geographical features of habitat and environmental factors appear to be more important than species functional traits for facilitating expansion into secondary open habitats. Our results suggested that the land cover change might have triggered the shifts of factors controlling open-habitat plant distributions from the competition with forest trees to current environmental constraints.

The Pediatric Surgical Team: a Model for Increased Surgeon Index Case Exposure

BACKGROUND/PURPOSE

High surgical volume for both surgeons and hospital systems has been linked to improved outcomes for many surgical problems, yet case volumes per pediatric surgeon are diminishing nationally in complex pediatric surgery. We therefore sought to review our experience in a geographically isolated setting where a surgical team approach has been used to improve per-surgeon exposure to index pediatric surgical cases.

METHODS

As a surgical group, we incorporated a surgical team approach to complex pediatric surgical cases in 2010. We obtained institutional review board approval to review our pediatric surgeon index case volume experience. We then compared our surgeon experience to published surgical volumes for complex pediatric surgical cases.

RESULTS

A surgical team approach (2 or 3 board certified pediatric surgeons/urologists working as co-surgeons or assistant surgeon) was used in the majority of cases for tracheoesophageal fistula/esophageal atresia (77%), congenital pulmonary airway malformation (73.5%), cloaca (75%), anorectal malformation (43.6%) biliary atresia (77.8%), Hirschsprung's disease (51.9%), congenital diaphragmatic hernia (67.6%), robotic choledochal cyst (100%), and complex oncology (adrenal tumors, neuroblastoma, Wilms tumor and Hepatoblastoma surgery) (85-100%). Over the 5-year period, surgeon index case exposure for all index pediatric surgical cases was above the published national median for pediatric surgeons, except for in splenic operations when contrasted to published experience.

CONCLUSIONS

A surgical team approach to complex pediatric surgery may help maintain exposure to adequate index case volumes. This model may be useful for maintaining competence in geographically-isolated practice settings and low-volume pediatric hospitals that provide surgical care; the model has implications for systems development and workforce allocation within pediatric surgery.

LEVEL OF EVIDENCE

4.

Should a homeless person become a deceased organ donor?

Efforts to increase deceased donation have included the use of US Public Health Service (PHS) high-risk donors. The homeless have high rates of medical and substance abuse issues that are often unrecognized. This study investigates whether the homeless should become suitable organ donors. We retrospectively reviewed 193 brain-dead prospective donors from Hawaii's organ procurement organization (OPO; 2013-2018) and compared two groups: homeless (n = 13) and non-homeless (n = 180) prospective donors. The homeless prospective donors were older (48.0 vs 40.7 years, P = .009) and had more substance abuse (30.8% vs 10%, P = .046), methamphetamine use (53.8% vs 12.2%, P = .001), cocaine use (23.1% vs 3.9%, P = .022), and urine with amphetamines (54.5% vs 17.9%, P = .049). The homeless prospective donors trended toward more PHS high-risk designation (50% vs 19%, P = .062). There was no difference in medical history, gender/race, hepatitis serologies, authorization for donation, and organs procured/transplanted between prospective donors. We have provided evidence that the homeless should become prospective organ donors; however, they have more high-risk behaviors and often have limited information. Larger studies from OPOs are needed to better characterize organ donation and track disease transmission in this population.

Gametophyte niche differences among sympatric tree ferns

Forest community assembly is usually framed in terms of sporophyte dynamics; however, the recruitment and maintenance of fern populations, frequently influential in forest composition and structure, are initially determined by gametophytes. Sporophytes of three Cyathea tree fern species show habitat partitioning along gradients of phosphorus and light; we asked whether gametophyte niche differences parallel this pattern. To compare niche characteristics among taxa we compared growth rates to a size threshold (≥3 mm) of gametophytes under controlled conditions using a multi-factorial, multi-level (3 × 4) experiment, varying irradiance (5.4 ± 4.4; 59.1 ± 44.3; 107 ± 74.1 µmol m-2 s-1) and orthophosphate concentrations (5, 10, 20, 40 mg kg-1). Gametophytes of the pioneer species C. medullaris developed to the size threshold across a broad range of phosphate and irradiance treatments (more than 20% of gametophytes in ≥ 7 of the 12 treatments), peaking at 20 mg kg-1 P and 60 µmol m-2 s-1 irradiance. The growth rates of the forest understorey species C. dealbata and C. smithii also peaked at 60 µmol m-2 s-1 but varied across treatments, suggesting niche differentiation along irradiance and orthophosphate gradients. Our analysis suggests that gametophyte development is strategically aligned to the ecological habits of sporophytes and that forest community assembly is likely strongly influenced by the independent gametophyte life-stage.

Evolutionary priority effects persist in anthropogenically created habitats, but not through nonnative plant invasion

Evolutionary priority effects, where early-arriving lineages occupy niche space via diversification and preclude dominance of later arrivals, have been observed in alpine and forest communities. However, the potential for evolutionary priority effects to persist in an era of rapid global change remains unclear. Here, we use a natural experiment of historical disturbance in New Zealand to test whether anthropogenic changes in available habitat and nonnative invasion eliminate the role of evolutionary priority effects in community assembly. We also test whether evolutionary priority effects diminish with decreasing resource availability. Older plant clades, as estimated by clade crown age, were relatively more abundant in both primary and secondary grassland. Relative abundance in primary grassland decreased with clade stem age, but only weakly. However, for both clade age estimates, relative abundance decreased with age when nonnative biomass was high and soil moisture was low. Our data show that patterns in community structure consistent with evolutionary priority effects can occur in both primary and secondary grasslands, the latter created by anthropogenic disturbance. However, nonnative invasion may overwhelm the effect of immigration timing on community dominance, possibly as a result of high immigration rates and preadaptation to anthropogenically modified environments.

Contrasting bacterial communities in two indigenous Chionochloa (Poaceae) grassland soils in New Zealand

The cultivation of grasslands can modify both bacterial community structure and impact on nutrient cycling as well as the productivity and diversity of plant communities. In this study, two pristine New Zealand grassland sites dominated by indigenous tall tussocks (Chionochloa pallens or C. teretifolia) were examined to investigate the extent and predictability of variation of the bacterial community. The contribution of free-living bacteria to biological nitrogen fixation is predicted to be ecologically significant in these soils; therefore, the diazotrophic community was also examined. The C. teretifolia site had N-poor and poorly-drained peaty soils, and the C. pallens had N-rich and well-drained fertile soils. These soils also differ in the proportion of organic carbon (C), Olsen phosphorus (P) and soil pH. The nutrient-rich soils showed increased relative abundances of some copiotrophic bacterial taxa (including members of the Proteobacteria, Bacteroidetes and Firmicutes phyla). Other copiotrophs, Actinobacteria and the oliogotrophic Acidobacteria showed increased relative abundance in nutrient-poor soils. Greater diversity based on 16S rRNA gene sequences and the Tax4Fun prediction of enhanced spore formation associated with nutrient-rich soils could indicate increased resilience of the bacterial community. The two sites had distinct diazotrophic communities with higher diversity in C. teretifolia soils that had less available nitrate and ammonium, potentially indicating increased resilience of the diazotroph community at this site. The C. teretifolia soils had more 16S rRNA gene and nifH copies per g soil than the nutrient rich site. However, the proportion of the bacterial community that was diazotrophic was similar in the two soils. We suggest that edaphic and vegetation factors are contributing to major differences in the composition and diversity of total bacterial and diazotrophic communities at these sites. We predict the differences in the communities at the two sites will result in different responses to environmental change.

A national riparian restoration programme in New Zealand: Is it value for money?

National scale initiatives are being attempted in New Zealand (NZ) to meet important environmental goals following land-use intensification over recent decades. Riparian restoration to filter agricultural spillover effects is currently the most widely practised mitigation measure but few studies have investigated the cumulative value of these practices at a national level. We use an applied economic land use model the benefits (GHG emissions, N leaching, P loss, sedimentation and biodiversity gain) and relevant costs (fencing, alternative stock water supplies, restoration planting and opportunity costs) of restoring riparian margins (5-50 m) on all streams in NZ flowing through current primary sector land. Extensive sensitivity analysis reveals that depending on margin width and cost assumptions, riparian margin restoration generates net benefits of between NZ$1.7 billion - $5.2 billion/yr and benefit-cost ratios ranging between 1.4 and 22.4. This suggests that even when not monetising the increase in biodiversity or components of stream ecosystem health and other benefits from planting riparian strips, the benefits to climate and freshwater are significantly greater than the implementation costs of riparian restoration.

Evolutionary conservatism explains increasing relatedness of plant communities along a flooding gradient

Abiotic filters have been found either to increase or reduce evolutionary relatedness in plant communities, making it difficult to generalize responses of this major feature of biodiversity to future environmental change. Here, we hypothesized that the responses of phylogenetic structure to environmental change ultimately depend on how species have evolved traits for tolerating the resulting abiotic changes. Working within ephemeral wetlands, we tested whether species were increasingly related as flooding duration intensified. We also identified the mechanisms underlying increased relatedness by measuring root aerenchyma volume (RAV), a trait which promotes waterlogging tolerance. We found that species-specific responses to flooding explained most of the variation in occurrence for 63 vascular plant species across 5170 plots. For a subset of 22 species, we attributed these responses to variation in RAV. Large RAV specifically increased occurrence when flooding lasted for longer time periods, because large RAV reduced above-ground biomass loss. As large RAV was evolutionarily conserved within obligate wetland species, communities were more phylogenetically related as flooding increased. Our study shows how reconstructing the evolutionary history of traits that influence the responses of species to environmental change can help to predict future patterns in phylogenetic structure.

When do plant radiations influence community assembly? The importance of historical contingency in the race for niche space

Plant radiations are widespread but their influence on community assembly has rarely been investigated. Theory and some evidence suggest that radiations can allow lineages to monopolize niche space when founding species arrive early into new bioclimatic regions and exploit ecological opportunities. These early radiations may subsequently reduce niche availability and dampen diversification of later arrivals. We tested this hypothesis of time-dependent lineage diversification and community dominance using the alpine flora of New Zealand. We estimated ages of 16 genera from published phylogenies and determined their relative occurrence across climatic and physical gradients in the alpine zone. We used these data to reconstruct occupancy of environmental space through time, integrating palaeoclimatic and palaeogeological changes. Our analysis suggested that earlier-colonizing lineages encountered a greater availability of environmental space, which promoted greater species diversity and occupancy of niche space. Genera that occupied broader niches were subsequently more dominant in local communities. An earlier time of arrival also contributed to greater diversity independently of its influence in accessing niche space. We suggest that plant radiations influence community assembly when they arise early in the occupancy of environmental space, allowing them to exclude later-arriving colonists from ecological communities by niche preemption.

Reproductive niche conservatism in the isolated New Zealand flora over 23 million years

The temporal stability of plant reproductive features on islands has rarely been tested. Using flowers, fruits/cones and seeds from a well-dated (23 Ma) Miocene Lagerstätte in New Zealand, we show that across 23 families and 30 genera of forest angiosperms and conifers, reproductive features have remained constant for more than 20 Myr. Insect-, wind- and bird-pollinated flowers and wind- and bird-dispersed diaspores all indicate remarkable reproductive niche conservatism, despite widespread environmental and biotic change. In the past 10 Myr, declining temperatures and the absence of low-latitude refugia caused regional extinction of thermophiles, while orogenic processes steepened temperature, precipitation and nutrient gradients, limiting forest niches. Despite these changes, the palaeontological record provides empirical support for evidence from phylogeographical studies of strong niche conservatism within lineages and biomes.

Turf wars: experimental tests for alternative stable states in a two-phase coastal ecosystem

Alternative stable states have long been thought to exist in natural communities, but direct evidence for their presence and for the environmental switches that cause them has been scarce. Using a combination of greenhouse and field experiments, we investigated the environmental drivers associated with two distinctive herbaceous communities in coastal ecosystems in New Zealand. In a mosaic unrelated to micro-topography, a community dominated largely by native turf species (notably Leptinella dioica, Samolus repens, and Selliera radicans) alternates with vegetation comprising exotic (i.e., nonnative) pasture species (notably Agrostis stolonifera, Holcus lanatus, Lolium perenne, and Trifolium repens). The species of these two communities differ in functional characters related to leaf longevity and growth rate, and occupy soils of differing nitrogen levels. Both spatial and environmental factors influenced the species composition locally. Reciprocal transplants of soil, with and without associated vegetation, showed that a native turf community developed when sward or soil from either community was bounded by turf, and a pasture community developed when sward or soil from either community was surrounded by pasture. In artificial mixed communities in the greenhouse, turf was able to invade the pasture community where the vegetation was clipped to simulate grazing, and also where Trifolium was removed and/or salt spray was applied. The pasture community invaded the turf where Trifolium was present or nitrogen was added. These results were supported by trends in experimentally manipulated field plots, where the amount of turf cover increased when nitrogen was kept low and when salt spray was applied, whereas pasture cover increased in the absence of salt spray. Thus, persistence of the native turf community is dependent on grazing, both directly and via its effect on keeping nitrogen levels low by excluding the exotic, nitrogen-fixing Trifolium, and by exposing the vegetation to salt spray. If any of these factors change, there could be a state change to pasture dominance that might be resistant to reversion to turf. Managing such coastal herbaceous communities therefore requires an understanding of the environmental and species characteristics that maintain alternative states.

Increased nitrogen cycling facilitates native forest regeneration: potential for restoring extinct ecological processes?

Ecological processes often maintain the plant communities with which they have a long evolutionary association, and so their loss may favor invasions by nonnative species. We simulated the effects of fecal deposition and soil turnover by the extinct avian megafauna of New Zealand to test their influence on woody plant regeneration and nonnative plant invasion in a cool temperate rain forest. Hen manure increased soil available NO3-, leading to greater seedling regeneration relative to control plots. Although soil P was elevated within plots treated with hen manure, concentrations also increased within plots treated with liquid fertilizer, which did not have different seedling densities relative to controls. Simulated avian soil disturbance did not increase seedling densities, and none of the three treatments affected the proportion of woody seedlings that were nonnative. However, pretreatment variation in NO3- availability, which reflected longer-term rates of nitrogen cycling, reduced community invasibility. Our findings suggest that avian-derived nitrogen inputs increase the regeneration of native forests, raising the question of whether the functional role of extinct megaherbivores is absent in New Zealand.

Plant radiation history affects community assembly: evidence from the New Zealand alpine

The hypothesis that early plant radiations on islands dampen diversification and reduce habitat occupancy of later radiations via niche pre-emption has never, to our knowledge, been tested. We investigated clade-level dynamics in plant radiations in the alpine zone, New Zealand. Our aim was to determine whether radiations from older colonizations influenced diversification and community dominance of species from later colonizations within a common bioclimatic zone over the past ca 10 Myr. We used stem ages derived from the phylogenies of 17 genera represented in alpine plant communities in the Murchison Mountains, Fiordland, and assessed their presence and cover in 262 (5 × 5 m) vegetation plots. Our results show clear age-related community assembly effects, whereby congenerics from older colonizing genera co-occur more frequently and with greater cover per unit area than those from younger colonizing genera. However, we find no evidence of increased species richness with age of colonization in the alpine zone. The data support priority effects via niche pre-emption among plant radiations influencing community assembly.

Is New Zealand vegetation really 'problematic'? Dansereau's puzzles revisited

Over four decades ago, Pierre Dansereau, the noted North American ecologist, proposed six features of New Zealand vegetation as being problematic or unusual in a global context. We examine his propositions in the light of current ecological knowledge to determine whether or not these can still be considered unusual characteristics of New Zealand vegetation. (1) 'Climatic change is still progressing' resulting in disequilibrium between species' distributions and the present climate. New data and methods of analysis now available have removed the impression that Dansereau gained of imprecise zonation, unclear vegetation/climate relations and missing vegetation types. Communities cited as having regeneration failure can now be seen as even-aged stands that developed after major disturbance, although there are other, also non-climatic, explanations. However, the cause of the Westland 'Nothofagus gap' has become more, rather than less, controversial. (2) 'Continuity of community composition defies classification' and 'Very few New Zealand associations have faithful species' are correct observations, but perhaps equally true of vegetation elsewhere. Dansereau's assertion of low species richness in New Zealand is not supported by the comparative data available. (3) 'Lack of intolerant [i.e. mid-seral] trees …' is not evident with newer information. The order of species in succession, seen as unclear by Dansereau, has been determined by a range of approaches, largely confirming each other. (4) 'Discrepancies of form and function …' in divaricate shrubs and widespread heteroblasty are still controversial, with many more explanations. Several abiotic explanations have failed to stand up to investigation. Explanations in terms of herbivory have been well supported, although the extinction of the large avian herbivores makes certainty impossible. (5) 'Incidence of hybridization …' remains problematic. We do not know whether the incidence is unusually high, as Dansereau alleged, but the limited comparative data available suggest not. (6) The 'overwhelming … competing power of exotics' is strongly context dependent. They are prominent in many non-forest habitats. It seems that they are drivers of the vegetation change in some habitats, yet passengers after disturbance in others. Invasions can be slow, and may still be very incomplete in some ecosystem types. Whether exotics will eventually take over in most communities, or whether the native species will 'laugh them to scorn' as Cockayne suggested, only time will tell. In conclusion, some aspects of New Zealand's vegetation seem less unusual with increased knowledge, but others remain 'problems'.

Absence of mammals and the evolution of New Zealand grasses

Anthropogenic alteration of biotic distributions and disturbance regimes has dramatically changed the evolutionary context for the differentiation of species traits. Some of the most striking examples in recent centuries have been on islands where flightless birds, which evolved in the absence of mammalian carnivores, have been decimated following the widespread introduction of exotic predators. Until now, no equivalent case has been reported for plants. Here, we make use of robust analytical tools and an exceptionally well-sampled molecular phylogeny to show that a majority of New Zealand danthonioid grasses (Poaceae) may have adapted to the relaxed vertebrate herbivore pressure during the late Cenozoic through the development of a distinctive and unusual habit: abscission of old leaves. This feature occurs in only about 3 per cent of the world's roughly 11,000 grass species and has been empirically shown to increase plant productivity but to reduce protection against mammal grazing. This result suggests that release from a selective pressure can lead to species radiations. This seemingly anachronistic adaptation may represent an overlooked factor contributing to the severe decline in the geographical extent and species diversity of New Zealand's indigenous grasslands following the introduction of herbivorous terrestrial mammals in the 19th century.