Phylogenetic structure of body shape in a diverse inland ichthyofauna.

Body shape is a fundamental metric of animal diversity affecting critical behavioral and ecological dynamics and conservation status, yet previously available methods capture only a fraction of total body-shape variance. Here we use structure-from-motion (SFM) 3D photogrammetry to generate digital 3D models of adult fishes from the Lower Mississippi Basin, one of the most diverse temperate-zone freshwater faunas on Earth, and 3D geometric morphometrics to capture morphologically distinct shape variables, interpreting principal components as growth fields. The mean body shape in this fauna resembles plesiomorphic teleost fishes, and the major dimensions of body-shape disparity are similar to those of other fish faunas worldwide. Major patterns of body-shape disparity are structured by phylogeny, with nested clades occupying distinct portions of the morphospace, most of the morphospace occupied by multiple distinct clades, and one clade (Acanthomorpha) accounting for over half of the total body shape variance. In contrast to previous studies, variance in body depth (59.4%) structures overall body-shape disparity more than does length (31.1%), while width accounts for a non-trivial (9.5%) amount of the total body-shape disparity.

Accelerated body size evolution in upland environments is correlated with recent speciation in South American freshwater fishes.

Speciation rates vary greatly among taxa and regions and are shaped by both biotic and abiotic factors. However, the relative importance and interactions of these factors are not well understood. Here we investigate the potential drivers of speciation rates in South American freshwater fishes, the most diverse continental vertebrate fauna, by examining the roles of multiple biotic and abiotic factors. We integrate a dataset on species geographic distribution, phylogenetic, morphological, climatic, and habitat data. We find that Late Neogene-Quaternary speciation events are strongly associated with body-size evolution, particularly in lineages with small body sizes that inhabit higher elevations near the continental periphery. Conversely, the effects of temperature, area, and diversity-dependence, often thought to facilitate speciation, are negligible. By evaluating multiple factors simultaneously, we demonstrate that habitat characteristics associated with elevation, as well as body size evolution, correlate with rapid speciation in South American freshwater fishes. Our study emphasizes the importance of integrative approaches that consider the interplay of biotic and abiotic factors in generating macroecological patterns of species diversity.

Evolution of the Yangtze River and its biodiversity.

Documenting the origins of megadiverse (sub)tropical aquatic ecosystems is an important goal for studies of evolution and ecology. Nonetheless, the geological and ecological establishment of the modern Yangtze River remains poorly understood. Here, we reconstruct the geographic and ecological history of an endemic clade of East Asian fishes based on the mitochondrial phylogenomics analysis of Cyprinidae using 15 fossil calibrations. We estimate an ancestral condition of benthic spawning with demersal or adhesive eggs in southern East Asia before ∼23 Ma and a derived condition of riverine spawning with semibuoyant eggs in the Yangtze by ∼18 Ma. These results imply the formation of Yangtze riverine ecosystems around the Oligocene-Miocene boundary in response to plateau uplift and monsoon strengthening. Some of these cyprinids reverted to benthic spawning with adhesive eggs by ∼15 Ma, a time of rising to peak net diversification rates, indicating the formation of potamo-lacustrine ecosystems by the mid-Miocene during a strong East Asian summer monsoon. Our study provides increased spatiotemporal resolution for the co-evolutionary histories of the Yangtze River and its biodiversity and highlights biological evidence concerning the geomorphological dynamics of the Yangtze River.

Outcomes after concomitant arch replacement at the time of aortic root surgery.

Background: Contemporary series of aortic arch replacement at the time of aortic root surgery are limited in number of patients and mostly address hemiarch replacement. We describe outcomes after aortic root and concomitant arch replacement, including total arch replacement. Methods: This single-institution retrospective review studied 1196 consecutive patients from May 2004 to September 2020 who underwent first-time aortic root replacement. Patients undergoing surgery for endocarditis were excluded (n = 68, 5.7%). Patients undergoing concomitant root and arch replacement were propensity matched with patients undergoing isolated root surgery based on indication, clinical and operative characteristics, demographics, medical history including connective tissue disorders, and urgency. Multivariable Cox proportional hazards and logistic regression modeling were used to assess the primary outcome of all-cause mortality and the secondary outcomes of prolonged ventilator use, postoperative blood transfusion, and debilitating stroke, adjusted for patient and operative characteristics. Results: Among the 1128 patients who underwent aortic root intervention during the study period, 471 (41.8%) underwent concomitant aortic arch replacement. Most underwent hemiarch replacement (n = 411, 87.4%); 59 patients (12.6%) underwent total arch replacement (with elephant trunk: n = 23, 4.9%; without elephant trunk: n = 36, 7.7%). The mean follow-up time was 4.6 years postprocedure. Operative mortality was 2.2%, and total mortality over the entire study period was 9.2%. Propensity matching generated 348 matches (295 concomitant hemiarch, 53 concomitant total arch). Concomitant hemiarch (hazard ratio, 1.00; 95% confidence interval, 0.54-1.86, P = .99) and total arch replacement (hazard ratio, 1.60, 95% confidence interval, 0.72-3.57, P = .24) were not significantly associated with increased mortality. Rates of stroke were not significantly different among each group: isolated root (n = 11/348, 3.7%), root + hemiarch (n = 17/295, 5.8%), and root + total arch (n = 3/53, 5.7%) replacement (P = .50), nor was the adjusted risk of stroke. Both concomitant arch interventions were associated with prolonged ventilator use and use of postoperative blood transfusions. Conclusions: Hemiarch and total arch replacement are safe to perform at the time of aortic root intervention, with no significant differences in survival or stroke rates, but increased ventilator and blood product use.

Landscape dynamics and diversification of the megadiverse South American freshwater fish fauna.

Landscape dynamics are widely thought to govern the tempo and mode of continental radiations, yet the effects of river network rearrangements on dispersal and lineage diversification remain poorly understood. We integrated an unprecedented occurrence dataset of 4,967 species with a newly compiled, time-calibrated phylogeny of South American freshwater fishes-the most species-rich continental vertebrate fauna on Earth-to track the evolutionary processes associated with hydrogeographic events over 100 Ma. Net lineage diversification was heterogeneous through time, across space, and among clades. Five abrupt shifts in net diversification rates occurred during the Paleogene and Miocene (between 30 and 7 Ma) in association with major landscape evolution events. Net diversification accelerated from the Miocene to the Recent (c. 20 to 0 Ma), with Western Amazonia having the highest rates of in situ diversification, which led to it being an important source of species dispersing to other regions. All regional biotic interchanges were associated with documented hydrogeographic events and the formation of biogeographic corridors, including the Early Miocene (c. 23 to 16 Ma) uplift of the Serra do Mar and Serra da Mantiqueira and the Late Miocene (c. 10 Ma) uplift of the Northern Andes and associated formation of the modern transcontinental Amazon River. The combination of high diversification rates and extensive biotic interchange associated with Western Amazonia yielded its extraordinary contemporary richness and phylogenetic endemism. Our results support the hypothesis that landscape dynamics, which shaped the history of drainage basin connections, strongly affected the assembly and diversification of basin-wide fish faunas.

Human impacts outpace natural processes in the Amazon.

Amazonian environments are being degraded by modern industrial and agricultural activities at a pace far above anything previously known, imperiling its vast biodiversity reserves and globally important ecosystem services. The most substantial threats come from regional deforestation, because of export market demands, and global climate change. The Amazon is currently perched to transition rapidly from a largely forested to a nonforested landscape. These changes are happening much too rapidly for Amazonian species, peoples, and ecosystems to respond adaptively. Policies to prevent the worst outcomes are known and must be enacted immediately. We now need political will and leadership to act on this information. To fail the Amazon is to fail the biosphere, and we fail to act at our peril.

Convergence is Only Skin Deep: Craniofacial Evolution in Electric Fishes from South America and Africa (Apteronotidae and Mormyridae).

Apteronotidae and Mormyridae are species-rich clades of weakly electric fishes from Neotropical and Afrotropical freshwaters, respectively, known for their high morphological disparity and often regarded as a classic example of convergent evolution. Here, we use CT-imaging and 3D geometric morphometrics to quantify disparity in craniofacial morphologies, and to test the hypothesis of convergent skull-shape evolution in a phylogenetic context. For this study, we examined 391 specimens representing 78 species of Apteronotidae and Mormyridae including 30 of 37 (81%) of all valid genera with the goal to sample most of the craniofacial disparity known in these clades. We found no overlap between Apteronotidae and Mormyridae in the skull-shape morphospace using PCA and a common landmark scheme, and therefore no instances of complete phenotypic convergence. Instead, we found multiple potential instances of incomplete convergence, and at least one parallel shift among electric fish clades. The greatest components of shape variance in both families are the same as observed for most vertebrate clades: heterocephaly (i.e., opposite changes in relative sizes of the snout and braincase regions of the skull), and heterorhynchy (i.e., dorsoventral changes in relative snout flexion and mouth position). Mormyrid species examined here exhibit less craniofacial disparity than do apteronotids, potentially due to constraints associated with a larger brain size, ecological constraints related to food-type availability. Patterns of craniofacial evolution in these two clades depict a complex story of phenotypic divergence and convergence in which certain superficial similarities of external morphology obscure deeper osteological and presumably developmental differences of skull form and function. Among apteronotid and mormyrid electric fishes, craniofacial convergence is only skin deep.

Single Lung Transplant Remains a Viable Option for Patients With Severe Secondary Pulmonary Hypertension.

BACKGROUND: Although double lung transplant is recommended in patients with severe secondary pulmonary hypertension (SPH), our institutional experiences suggest a role for single lung transplant in these patients. Here, we review our experience prioritizing single lung transplant in patients with SPH to minimize their surgical burden. METHODS: We conducted a retrospective review of our lung transplant database to identify patients with SPH who underwent single lung transplant. Patients were stratified as either mild SPH (mean pulmonary artery pressure 25-40 mm Hg) or severe SPH (mean pulmonary artery pressure >40 mm Hg). Singe lung recipients without PH transplanted over the same time were also examined. RESULTS: Between January 2017 and December 2019, 318 patients underwent single lung transplantation; 217 had mild SPH (68%), and 59 had severe SPH (18.5%). Forty-two patients without PH underwent single lung transplant. When the groups were compared, significantly higher pulmonary vascular resistance was noted in the severe SPH group, and obesity was noted in both the mild and severe SPH groups. Although the severe SPH group required more intraoperative cardiopulmonary support (37.3% versus 10.3% versus 4.7%, P < 0.05), there were no significant differences in most major postoperative parameters, including the duration of postoperative mechanical ventilation or the incidence of severe primary graft dysfunction. Survival 1 y posttransplant was not significantly different among the groups (93.2% versus 89.4% versus 92.9%, P = 0.58). CONCLUSIONS: Our experience supports the option of single lung transplantation with appropriate intraoperative mechanical circulatory support in patients with SPH. This strategy is worth pursuing, especially with ongoing donor lung shortages.

River network rearrangements promote speciation in lowland Amazonian birds.

Large Amazonian rivers impede dispersal for many species, but lowland river networks frequently rearrange, thereby altering the location and effectiveness of river barriers through time. These rearrangements may promote biotic diversification by facilitating episodic allopatry and secondary contact among populations. We sequenced genome-wide markers to evaluate the histories of divergence and introgression in six Amazonian avian species complexes. We first tested the assumption that rivers are barriers for these taxa and found that even relatively small rivers facilitate divergence. We then tested whether species diverged with gene flow and recovered reticulate histories for all species, including one potential case of hybrid speciation. Our results support the hypothesis that river rearrangements promote speciation and reveal that many rainforest taxa are micro-endemic, unrecognized, and thus threatened with imminent extinction. We propose that Amazonian hyper-diversity originates partly from fine-scale barrier displacement processes-including river dynamics-which allow small populations to differentiate and disperse into secondary contact.

Is the Medium the Message? Functional Diversity Across Abiotic Gradients in Freshwater Electric Fishes.

Evolutionary transitions across abiotic gradients can occur among habitats at multiple spatial scales, and among taxa and biotas through a range of ecological and evolutionary time frames. Two diverse groups of electric fishes, Neotropical Gymnotiformes, and Afrotropical Mormyroidea, offer interesting examples of potentially convergent evolution in aspects of morphological, physiological, and life history traits. We examined biogeographical, morphological, and functional patterns across these two groups to assess the degree of convergence in association with abiotic environmental variables. While there are superficial similarities across the groups and continents, we found substantially more differences in terms of habitat occupancy, electric signal diversity, and morphological disparity. These differences likely correlate to differences in biogeographical histories across the Neotropics and Afrotropics, biotic factors associated with aquatic life and electric signals, and sampling issues plaguing both groups. Additional research and sampling are required to make further inferences about how electric fishes transition throughout diverse freshwater habitats across both microevolutionary and macroevolutionary scales.

Biogeography of curimatid fishes reveals multiple lowland-upland river transitions and differential diversification in the Neotropics (Teleostei, Curimatidae).

The Neotropics harbors a megadiverse ichthyofauna comprising over 6300 species with approximately 80% in just three taxonomic orders within the clade Characiphysi. This highly diverse group has evolved in tropical South America over tens to hundreds of millions of years influenced mostly by re-arrangements of river drainages in lowland and upland systems. In this study, we investigate patterns of spatial diversification in Neotropical freshwater fishes in the family Curimatidae, a species-rich clade of the order Characiformes. Specifically, we examined ancestral areas, dispersal events, and shifts in species richness using spatially explicit biogeographic and macroevolutionary models to determine whether lowlands-uplands serve as museums or cradles of diversification for curimatids. We used fossil information to estimate divergence times in BEAST, multiple time-stratified models of geographic range evolution in BioGeoBEARS, and alternative models of geographic state-dependent speciation and extinction in GeoHiSSE. Our results suggest that the most recent common ancestor of curimatids originated in the Late Cretaceous likely in lowland paleodrainages of northwestern South America. Dispersals from lowland to upland river basins of the Brazilian and Guiana shields occurred repeatedly across independently evolving lineages in the Cenozoic. Colonization of upland drainages was often coupled with increased rates of net diversification in species-rich genera such as Cyphocharax and Steindachnerina. Our findings demonstrate that colonization of novel aquatic environments at higher elevations is associated with an increased rate of diversification, although this pattern is clade-dependent and driven mostly by allopatric speciation. Curimatids reinforce an emerging perspective that Amazonian lowlands act as a museum by accumulating species along time, whereas the transitions to uplands stimulate higher net diversification rates and lineage diversification.

A Roadmap to Patient Engagement: Facioscapulohumeral Muscular Dystrophy and the ReSolve Clinical Trial.

We describe our efforts to overcome barriers to patient engagement in facioscapulohumeral muscular dystrophy (FSHD) and offer a roadmap that can be replicated in other rare neurologic disorders. We implemented an engagement plan during Clinical Trial Readiness to Solve Barriers to Drug Development for FSHD (ReSolve), an 18-month, multisite, observational study of individuals with FSHD. Elements of our engagement plan included conducting focus groups during protocol development, patient involvement on the ReSolve external advisory committee, creation of a patient advisory committee, and collaboration with patient advocacy groups. Patient feedback led to adaptations in the study protocol and to changes in recruitment and retention methods. Patient engagement ensures that the patient voice contributes to multiple aspects of trial design and implementation. Our engagement efforts exemplify how collaboration with patients and families can be accomplished in FSHD and the resultant roadmap process may be replicable in other rare neurologic diseases.

Venoarterial Extracorporeal Membrane Oxygenation in Massive Pulmonary Embolism-Related Cardiac Arrest: A Systematic Review.

OBJECTIVE: Management of patients experiencing massive pulmonary embolism-related cardiac arrest is controversial. Venoarterial extracorporeal membranous oxygenation has emerged as a potential therapeutic option for these patients. We performed a systematic review assessing survival and predictors of mortality in patients with massive PE-related cardiac arrest with venoarterial extracorporeal membranous oxygenation use. DATA SOURCES: A literature search was started on February 16, 2020, and completed on March 16, 2020, using PubMed, Embase, Cochrane Central, Cinahl, and Web of Science. STUDY SELECTION: We included all available literature that reported survival to discharge in patients managed with venoarterial extracorporeal membranous oxygenation for massive PE-related cardiac arrest. DATA EXTRACTION: We extracted patient characteristics, treatment details, and outcomes. DATA SYNTHESIS: About 301 patients were included in our systemic review from 77 selected articles (total screened, n = 1,115). About 183 out of 301 patients (61%) survived to discharge. Patients (n = 51) who received systemic thrombolysis prior to cannulation had similar survival compared with patients who did not (67% vs 61%, respectively; p = 0.48). There was no significant difference in risk of death if PE was the primary reason for admission or not (odds ratio, 1.62; p = 0.35) and if extracorporeal membranous oxygenation cannulation occurred in the emergency department versus other hospital locations (odds ratio, 2.52; p = 0.16). About 53 of 60 patients (88%) were neurologically intact at discharge or follow-up. Multivariate analysis demonstrated three-fold increase in the risk of death for patients greater than 65 years old (adjusted odds ratio, 3.08; p = 0.03) and six-fold increase if cannulation occurred during cardiopulmonary resuscitation (adjusted odds ratio, 5.67; p = 0.03). CONCLUSIONS: Venoarterial extracorporeal membranous oxygenation has an emerging role in the management of massive PE-related cardiac arrest with 61% survival. Systemic thrombolysis preceding venoarterial extracorporeal membranous oxygenation did not confer a statistically significant increase in risk of death, yet age greater than 65 and cannulation during cardiopulmonary resuscitation were associated with a three- and six-fold risks of death, respectively.

Scientists' warning to humanity on the freshwater biodiversity crisis.

Freshwater ecosystems provide irreplaceable services for both nature and society. The quality and quantity of freshwater affect biogeochemical processes and ecological dynamics that determine biodiversity, ecosystem productivity, and human health and welfare at local, regional and global scales. Freshwater ecosystems and their associated riparian habitats are amongst the most biologically diverse on Earth, and have inestimable economic, health, cultural, scientific and educational values. Yet human impacts to lakes, rivers, streams, wetlands and groundwater are dramatically reducing biodiversity and robbing critical natural resources and services from current and future generations. Freshwater biodiversity is declining rapidly on every continent and in every major river basin on Earth, and this degradation is occurring more rapidly than in terrestrial ecosystems. Currently, about one third of all global freshwater discharges pass through human agricultural, industrial or urban infrastructure. About one fifth of the Earth's arable land is now already equipped for irrigation, including all the most productive lands, and this proportion is projected to surpass one third by midcentury to feed the rapidly expanding populations of humans and commensal species, especially poultry and ruminant livestock. Less than one fifth of the world's preindustrial freshwater wetlands remain, and this proportion is projected to decline to under one tenth by midcentury, with imminent threats from water transfer megaprojects in Brazil and India, and coastal wetland drainage megaprojects in China. The Living Planet Index for freshwater vertebrate populations has declined to just one third that of 1970, and is projected to sink below one fifth by midcentury. A linear model of global economic expansion yields the chilling prediction that human utilization of critical freshwater resources will approach one half of the Earth's total capacity by midcentury. Although the magnitude and growth of the human freshwater footprint are greater than is generally understood by policy makers, the news media, or the general public, slowing and reversing dramatic losses of freshwater species and ecosystems is still possible. We recommend a set of urgent policy actions that promote clean water, conserve watershed services, and restore freshwater ecosystems and their vital services. Effective management of freshwater resources and ecosystems must be ranked amongst humanity's highest priorities.

Assessing extinction risk from geographic distribution data in Neotropical freshwater fishes

The IUCN Red List (RL) provides high-quality conservation assessments for individual species, yet the rate and scale of environmental deterioration globally challenges the conservation community to develop expedited methods for risk assessment. Here we compare threat assessments for 3,001 species of Neotropical freshwater fishes (NFF) in the IUCN-RL using readily accessible data types as proxies for extinction risk: geographic range, elevation, and species publication date. Furthermore, using geographic and taxonomic data alone, we generated preliminary conservation assessments for 2,334 NFF species currently awaiting IUCN assessment, identifying an additional 671 NFF species as potentially threatened. This number of potentially threatened species represents an increase of 59% over the number of species currently assigned to threat categories by the IUCN-RL. These results substantially expand the number of threatened NFF species from 422 currently on the IUCN RL to 1,093 species as threatened or potentially threatened, representing about 18% of all NFF species. Extinction risk is greater in species with smaller geographic ranges, which inhabit upland rivers, and which were described more recently. We propose the Central and Southern Andes, and Eastern Guiana Shield as priorities in the upcoming IUCN RL assessment of NFF species conservation risk.(AU)

A Lista Vermelha (IUCN) fornece avaliações precisas sobre status de conservação das espécies, porém a taxa e escala de deterioração ambiental desafia a comunidade conservacionista a desenvolver métodos rápidos para avaliações de riscos de extinção. Aqui, comparamos as avaliações da IUCN para 3.001 espécies de peixes dulcícolas neotropicais com dados facilmente acessíveis de risco de extinção: extensão de ocorrências, altitude e data de publicação das espécies. Além disso, usando apenas dados geográficos e taxonômicos, geramos avaliações preliminares de conservação para 2.334 espécies de peixes neotropicais aguardando avaliação da IUCN, e identificamos 671 espécies adicionais como potencialmente ameaçadas. Este número de espécies potencialmente ameaçadas representa um aumento de 59% em relação aquelas classificadas nas categorias de ameaça pela IUCN. Estes resultados expandem o número de espécies ameaçadas segundo a IUCN de 422 para 1.093 espécies ameaçadas ou potencialmente ameaçadas, representando cerca de 18% das espécies de peixes neotropicais. O risco de extinção é maior para espécies com distribuições geográficas restritas, que habitam rios de terras altas e que foram descritas mais recentemente. Sugerimos a região Central e Meridional do Andes e o Escudo das Guianas Orientais como prioridades para as próximas avaliações da IUCN sobre a conservação das espécies de peixes dulcícolas neotropicais.(AU)

Pulmonary vasculopathy in explanted lungs from patients with interstitial lung disease undergoing lung transplantation.

BACKGROUND: Pulmonary hypertension (PH) causes increased morbidity and mortality in patients with interstitial lung diseases (ILD). Classification schemes, while well-characterised for the vasculopathy of idiopathic PH, have been applied, unchallenged, to ILD-related PH. We evaluated pulmonary arterial histopathology in explanted human lung tissue from patients who were transplanted for advanced fibrotic ILD. METHODS: Lung explants from 38 adult patients who underwent lung transplantation were included. Patients were divided into three groups: none, mild/moderate and severe PH by mean pulmonary artery pressure (mPAP) measured at pre lung transplantation right heart catheterisation (RHC). Grading of pulmonary vasculopathy according to Heath and Edwards scheme, and prelung transplantation evaluation data were compared between the groups. RESULTS: 38 patients with fibrotic ILDs were included, the majority (21) with idiopathic pulmonary fibrosis. Of the 38 patients, 18 had severe PH, 13 had mild/moderate PH and 7 had no PH by RHC. 16 of 38 patients had severe pulmonary arterial vasculopathy including vascular occlusion with intimal fibrosis and/or plexiform lesions. There were no correlations between mPAP and lung diffusion with the severity of pulmonary arterial pathological grade (Spearman's rho=0.14, p=0.34, rho=0.11, p=0.49, respectively). CONCLUSIONS: Patients with end stage ILD had severe pulmonary arterial vasculopathy in their explanted lungs irrespective of the presence and/or severity of PH as measured by RHC. These findings suggest that advanced pulmonary arterial vasculopathy is common in patients with advanced fibrotic ILD and may develop prior to the clinical detection of PH by RHC.

COVID-19 in lung transplant recipients.

Solid organ transplant recipients are considered at high risk for COVID-19 infection due to chronic immune suppression; little data currently exists on the manifestations and outcomes of COVID-19 infection in lung transplant recipients. Here we report 8 cases of COVID-19 identified in patients with a history of lung transplant. We describe the clinical course of disease as well as preexisting characteristics of these patients.

A redescription of deep-channel ghost knifefish, Sternarchogiton preto (Gymnotiformes: Apteronotidae), with assignment to a new genus

From a study of morphological and molecular datasets we determine that a species originally described as Sternarchogiton preto does not form a monophyletic group with the other valid species of Sternarchogiton including the type species, S. nattereri. Previously-published phylogenetic analyses indicate that this species is sister to a diverse clade comprised of six described apteronotid genera. We therefore place it into a new genus diagnosed by the presence of three cranial fontanels, first and second infraorbital bones independent (not fused), the absence of an ascending process on the endopterygoid, and dark brown to black pigments over the body surface and fins membranes. We additionally provide a redescription of this enigmatic species with an emphasis on its osteology, and provide the first documentation of secondary sexual dimorphism in this species.(AU)

RESUMO Através de um estudo com dados morfológicos e moleculares, nós propomos que a espécie originalmente descrita como Sternarchogiton preto não forma um grupo monofilético com outras espécies válidas de Sternarchogiton incluindo a espécie-tipo, S. nattereri. Análises filogenéticas anteriormente publicadas indicam que essa espécie é irmã de um clado diverso contendo seis gêneros descritos de Apteronotidae. Nós então a alocamos em um novo gênero diagnosticado pela presença de três fontanelas craniais, primeiro e segundo ossos infraorbitais independentes (não fusionados), ausência de um processo ascendente do endopterigoide e pigmentação marrom-escura à negra sobre a superfície do corpo e membranas das nadadeiras. Adicionalmente, nós realizamos a redescrição dessa enigmática espécie com ênfase na sua osteologia, e fazemos o primeiro registro de dimorfismo sexual secundário nessa espécie.(AU)

Using community phylogenetics to assess phylogenetic structure in the Fitzcarrald region of Western Amazonia

Here we explore the use of community phylogenetics as a tool to document patterns of biodiversity in the Fitzcarrald region, a remote area in Southwestern Amazonia. For these analyses, we subdivide the region into basin-wide assemblages encompassing the headwaters of four Amazonian tributaries (Urubamba, Yuruá, Purús and Las Piedras basins), and habitat types: river channels, terra firme (non-floodplain) streams, and floodplain lakes. We present a robust, well-documented collection of fishes from the region including 272 species collected from 132 field sites over 63 field days and four years, comprising the most extensive collection of fishes from this region to date. We conduct a preliminary community phylogenetic analysis based on this collection and recover results largely statistically indistinguishable from the random expectation, with only a few instances of phylogenetic structure. Based on these results, and of those published in other recent biogeographic studies, we conclude that the Fitzcarrald fish species pool accumulated over a period of several million years, plausibly as a result of dispersal from the larger species pool of Greater Amazonia.(AU)

Aquí exploramos el uso de la filogenética de comunidades como herramienta para documentar patrones de biodiversidad en la región de Fitzcarrald, un área remota en el suroeste de la Amazonía. Para estos análisis subdividimos la región en grupos de toda la cuenca que abarcan las cabeceras de cuatro tributarios del Amazonas (cuencas Urubamba, Yuruá, Purús y Las Piedras) y en los tipos de hábitat: canales fluviales, arroyos de tierra firme (sin planicie aluvial) y lagos de planicie aluvial. Presentamos una colección de peces robusta y bien documentada que incluye 272 especies, colectadas a lo largo de cuatro años y 63 días de campo, en 132 puntos de monitoreo. Convirtiéndose en la colección más extensa de peces de esta región hasta la fecha. Realizamos un análisis filogenético preliminar de la comunidad basado en esta recopilación y recuperamos resultados en gran medida estadísticamente indistinguibles de la expectativa aleatoria, con sólo unos pocos casos de estructura filogenética. Basándonos en estos resultados y los publicados en otros estudios biogeográficos recientes, concluimos que el grupo de especies de peces de Fitzcarrald acumulado durante un período de varios millones de años, se debe posiblemente al resultado de la dispersión del mayor grupo de especies de la Gran Amazonia.(AU)

Genetic differentiation through dispersal and isolation in two freshwater fish species from coastal basins of Northeastern Brazil

The coastal basins in Northeastern Brazil used in this study make up two different ecoregions for freshwater fishes (Amazonas estuary and coastal drainages, and Parnaiba) and two areas of endemism for Characiformes (Maranhão and Parnaíba), and exhibits a diversified yet poorly explored freshwater fish fauna. The population structure and biogeography of two migratory freshwater fish species that are commercially exploited from Maranhão and Parnaíba regions were herein analyzed. Molecular sequence data and statistical analyses were used to estimate haplotypes networks and lineage divergence times and correlated with hydrographic history of drainage and paleodrainages of the region. A total of 171 sequences was produced for both species, Schizodon dissimilis (coI, n = 70) and Prochilodus lacustris (D-loop, n = 101). All analyses identified the presence of three genetically delimited groups of S. dissimilis and six groups of P. lacustris. The lineage time analyses indicate diversification among these species within the past 1 million year. The results indicate the influence of geodispersal in the formation of the ichthyofauna in the studied area through headwater stream capture events and reticulated connections between the mouths of rivers along the coastal plain due to eustatic sea level fluctuations.(AU)

As bacias costeiras do nordeste do Brasil usadas neste estudo compõem duas ecorregiões diferentes para peixes de água doce (Estuário do Amazonas e drenagens costeiras e Parnaíba) e duas áreas de endemismo para Characiformes (Maranhão e Parnaíba), exibindo uma diversificada e ainda pouco explorada fauna de peixes de água doce. A estrutura populacional e biogeografia de duas espécies migradoras de peixes de água doce exploradas comercialmente nas regiões do Maranhão e Parnaíba foram analisadas. Dados de sequências moleculares e análises estatísticas foram utilizados para estimar redes de haplótipos e tempos de divergência entre linhagens, e foram correlacionados com a história hidrográfica das drenagens e paleodrenagens da região. Um total de 171 sequências foram geradas para ambas espécies, Schizodon dissimilis (coI, n = 70) e Prochilodus lacustris (D-loop, n = 101). Todas análises identificaram a presença de três grupos geneticamente delimitados para S. dissimilis e seis grupos para P. lacustris. A análise de tempo de divergência das linhagens indicou uma diversificação entre estas espécies nos últimos 1 Ma. Os resultados indicam influência da geodispersão na formação da ictiofauna do Maranhão, devido eventos de capturas de cabeceira e conexões reticuladas entre as fozes dos rios ao longo da planície costeira devido às flutuações eustáticas do nível do mar.(AU)