A tenuis relationship: traditional taxonomy obscures systematics and biogeography of the ‘Acropora tenuis’ (Scleractinia: Acroporidae) species complex

Molecular phylogenetics has fundamentally altered our understanding of the taxonomy, systematics and biogeography of corals. Recently developed phylogenomic techniques have started to resolve species-level relationships in the diverse and ecologically important genus Acropora, providing a path to resolve the taxonomy of this notoriously problematic group. We used a targeted capture dataset (2032 loci) to investigate systematic relationships within an Acropora clade containing the putatively widespread species Acropora tenuis and its relatives. Using maximum likelihood phylogenies and genetic clustering of single nucleotide polymorphisms from specimens, including topotypes, collected across the Indo-Pacific, we show ≥ 11 distinct lineages in the clade, only four of which correspond to currently accepted species. Based on molecular, morphological and geographical evidence, we describe two new species; Acropora rongoi n. sp. and Acropora tenuissima n. sp. and remove five additional nominal species from synonymy. Systematic relationships revealed by our molecular phylogeny are incongruent with traditional morphological taxonomy and demonstrate that characters traditionally used to delineate species boundaries and infer evolutionary history are homoplasies. Furthermore, we show that species within this clade have much smaller geographical ranges and, consequently, population sizes than currently thought, a finding with profound implications for conservation and management of reef corals

Types, topotypes and vouchers are the key to progress in coral taxonomy: Comment on Wepfer et al. (2020)

[Extract] Wepfer et al. (2020) use a molecular phylogenomic approach to show that the species richness of the coral genus Galaxea (Scleractinia: Euphyllidae) is greater than currently accepted. The study is impressive in its geographical scale and provides further evidence that the currently-accepted taxonomy of the Scleractinia is flawed. However, with a broader conceptual framework and a closer attention to accepted taxonomic practices, the authors could have made much greater progress towards resolving the systematics of the genus Galaxea. In particular, the decision to work within the Veron (2000) taxonomic framework despite its known flaws along with a failure to target topotypes (defined here as specimens from the type locality that also match the type morphologically) and to retain voucher specimens for most of their material seriously limits the value of the research. To the credit of the authors, Wepfer et al. (2020) explicitly test the morphological species boundaries of Veron (2000) and find them largely incompatible with their molecular data. These results are not surprising given previous work on Galaxea fascicularis that Wepfer et al. (2020) highlight and are in line with numerous other recent papers that demonstrate that many “accepted” morpho-species concepts in scleractinian taxonomy are flawed (Kitahara et al., 2016). Thus, a clear priority now is to re-examine all the nominal species in a clade using an integrated framework where species boundaries and evolutionary relationships can be examined using multi-prong approaches that include molecules, morphology, and other lines of evidence. Good taxonomy is difficult and can be time-consuming, as the authors note, but it is much easier now than it used to be thanks to online resources such as the World Register of Marine Species (WoRMS), the Biodiversity Heritage Library, and the increasing availability of both type specimens and original descriptions in online digital data repositories. Given the current state of flux in scleractinian taxonomy, any study of coral systematics should include two key steps to allow for a robust, expandable examination of the taxonomy of the targeted group: (1) assemble the necessary taxonomic materials and (2) identify, collect, and incorporate topotype specimens

Spatial and temporal limits of coral-macroalgal competition: the negative impacts of macroalgal density, proximity, and history of contact

Tropical reefs are commonly transitioning from coral to macroalgal dominance, producing abrupt, and often lasting, shifts in community composition and ecosystem function. Although negative effects of macroalgae on corals are well documented, whether such effects vary with spatial scale or the density of macroalgae remains inadequately understood, as does the legacy of their impact on coral growth. Using adjacent coral-versus macroalgal-dominated areas, we tested effects of macroalgal competition on 2 common Indo-Pacific coral species. When corals were transplanted to areas of: (1) macroalgal dominance, (2) macroalgal dominance but with nearby macroalgae removed, or (3) coral dominance lacking macroalgae, coral growth was equivalently high in plots without macroalgae and low (62-90% less) in plots with macroalgae, regardless of location. In a separate experiment, we exposed corals to differing densities of the dominant macroalga Sargassum polycystum. Coral survivorship was high (>= 93% after 3 mo) and did not differ among treatments, whereas the growth of both coral species decreased as a function of Sargassum density. When Sargassum was removed after 3 mo, there was no legacy effect of macroalgal density on coral growth over the next 6 mo; however, there was no compensation for previously depressed growth. In sum, macroalgal impacts were density-dependent, and occurred only if macroalgae were in close contact, and coral growth was resilient to prior macroalgal contact. The temporal and spatial constraints of these interactions suggest that corals may be surprisingly resilient to periodic macroalgal competition, which could have important implications for ecosystem trajectories that lead to reef decline or recovery

Stoma-free Survival After Rectal Cancer Resection With Anastomotic Leakage: Development and Validation of a Prediction Model in a Large International Cohort.

Objective:To develop and validate a prediction model (STOMA score) for 1-year stoma-free survival in patients with rectal cancer (RC) with anastomotic leakage (AL).Background:AL after RC resection often results in a permanent stoma.Methods:This international retrospective cohort study (TENTACLE-Rectum) encompassed 216 participating centres and included patients who developed AL after RC surgery between 2014 and 2018. Clinically relevant predictors for 1-year stoma-free survival were included in uni and multivariable logistic regression models. The STOMA score was developed and internally validated in a cohort of patients operated between 2014 and 2017, with subsequent temporal validation in a 2018 cohort. The discriminative power and calibration of the models' performance were evaluated.Results:This study included 2499 patients with AL, 1954 in the development cohort and 545 in the validation cohort. Baseline characteristics were comparable. One-year stoma-free survival was 45.0% in the development cohort and 43.7% in the validation cohort. The following predictors were included in the STOMA score: sex, age, American Society of Anestesiologist classification, body mass index, clinical M-disease, neoadjuvant therapy, abdominal and transanal approach, primary defunctioning stoma, multivisceral resection, clinical setting in which AL was diagnosed, postoperative day of AL diagnosis, abdominal contamination, anastomotic defect circumference, bowel wall ischemia, anastomotic fistula, retraction, and reactivation leakage. The STOMA score showed good discrimination and calibration (c-index: 0.71, 95% CI: 0.66-0.76).Conclusions:The STOMA score consists of 18 clinically relevant factors and estimates the individual risk for 1-year stoma-free survival in patients with AL after RC surgery, which may improve patient counseling and give guidance when analyzing the efficacy of different treatment strategies in future studies

Stoma-free survival after anastomotic leak following rectal cancer resection: worldwide cohort of 2470 patients

Background: The optimal treatment of anastomotic leak after rectal cancer resection is unclear. This worldwide cohort study aimed to provide an overview of four treatment strategies applied. Methods: Patients from 216 centres and 45 countries with anastomotic leak after rectal cancer resection between 2014 and 2018 were included. Treatment was categorized as salvage surgery, faecal diversion with passive or active (vacuum) drainage, and no primary/secondary faecal diversion. The primary outcome was 1-year stoma-free survival. In addition, passive and active drainage were compared using propensity score matching (2: 1). Results: Of 2470 evaluable patients, 388 (16.0 per cent) underwent salvage surgery, 1524 (62.0 per cent) passive drainage, 278 (11.0 per cent) active drainage, and 280 (11.0 per cent) had no faecal diversion. One-year stoma-free survival rates were 13.7, 48.3, 48.2, and 65.4 per cent respectively. Propensity score matching resulted in 556 patients with passive and 278 with active drainage. There was no statistically significant difference between these groups in 1-year stoma-free survival (OR 0.95, 95 per cent c.i. 0.66 to 1.33), with a risk difference of -1.1 (95 per cent c.i. -9.0 to 7.0) per cent. After active drainage, more patients required secondary salvage surgery (OR 2.32, 1.49 to 3.59), prolonged hospital admission (an additional 6 (95 per cent c.i. 2 to 10) days), and ICU admission (OR 1.41, 1.02 to 1.94). Mean duration of leak healing did not differ significantly (an additional 12 (-28 to 52) days). Conclusion: Primary salvage surgery or omission of faecal diversion likely correspond to the most severe and least severe leaks respectively. In patients with diverted leaks, stoma-free survival did not differ statistically between passive and active drainage, although the increased risk of secondary salvage surgery and ICU admission suggests residual confounding