Divergent Processes Drive Parallel Evolution in Marine and Freshwater Fishes.

Evolutionary comparisons between major environmental divides, such as between marine and freshwater systems, can reveal the fundamental processes governing diversification dynamics. Although processes may differ due to the different scales of their biogeographic barriers, freshwater and marine environments nevertheless offer similar opportunities for diversification in benthic, demersal, and pelagic habitats. Here, we compare the evolutionary patterns and processes shaping teleost diversity in each of these three habitats and between marine and freshwater systems. Using specimens from the National Museum of Natural History, we developed a data set of linear measurements capturing body shape in 2266 freshwater and 3344 marine teleost species. With a novel comparative approach, we contrast the primary axis of morphological diversification in each habitat with the major axis defined by phylogenetic signal. By comparing angles between these axes, we find that fish in corresponding habitats have more similar primary axes of morphological diversity than would be expected by chance, but that different historical processes underlie these parallel patterns in freshwater and marine environments. Marine diversification is more strongly aligned with phylogenetic signal and shows a trend toward lineages occupying separate regions of morphospace. In contrast, ecological signal appears to be a strong driver of diversification in freshwater lineages through repeated morphological evolution in densely packed regions of morphospace. In spite of these divergent histories, our findings reveal that habitat has driven convergent patterns of evolutionary diversification on a global scale. [Benthic-pelagic axis; body shape; convergent evolution; morphological diversification; phylogenetic signal.].

Constraints on the Ecomorphological Convergence of Zooplanktivorous Butterflyfishes.

Whether distantly related organisms evolve similar strategies to meet the demands of a shared ecological niche depends on their evolutionary history and the nature of form-function relationships. In fishes, the visual identification and consumption of microscopic zooplankters, selective zooplanktivory, is a distinct type of foraging often associated with a suite of morphological specializations. Previous work has identified inconsistencies in the trajectory and magnitude of morphological change following transitions to selective zooplanktivory, alluding to the diversity and importance of ancestral effects. Here we investigate whether transitions to selective zooplanktivory have influenced the morphological evolution of marine butterflyfishes (family Chaetodontidae), a group of small-prey specialists well known for several types of high-precision benthivory. Using Bayesian ancestral state estimation, we inferred the recent evolution of zooplanktivory among benthivorous ancestors that hunted small invertebrates and browsed by picking or scraping coral polyps. Traits related to the capture of prey appear to be functionally versatile, with little morphological distinction between species with benthivorous and planktivorous foraging modes. In contrast, multiple traits related to prey detection or swimming performance are evolving toward novel, zooplanktivore-specific optima. Despite a relatively short evolutionary history, general morphological indistinctiveness, and evidence of constraint on the evolution of body size, convergent evolution has closed a near significant amount of the morphological distance between zooplanktivorous species. Overall, our findings describe the extent to which the functional demands associated with selective zooplanktivory have led to generalizable morphological features among butterflyfishes and highlight the importance of ancestral effects in shaping patterns of morphological convergence.

A evolução de estratégias similares para suprir as demandas de nichos ecológicos compartilhados em organismos pouco relacionados, depende da sua história evolutiva e da natureza das relações entre forma e função. Em peixes, a identificação visual e o consumo de zooplanctôn microscópico, a zooplanctivoria seletiva, é um tipo distinto de forrageamento frequentemente associado a um conjunto de especializações morfológicas. Estudos anteriores identificaram inconsistências na trajetória e magnitude das mudanças morfológicas que surgem a partir das transições para a zooplanctivoria seletiva, fazendo alusão à diversidade e importância dos efeitos ancestrais. Aqui investigamos se transições para a zooplanctivoria seletiva influenciaram a evolução morfológica dos peixes-borboleta marinhos (família Chaetodontidae), um grupo especialista em presas pequenas conhecido pelos muitos tipos de bentivoria de alta precisão. Utilizando uma estimativa ancestral bayesiana, inferimos a evolução recente da zooplanctivoria dentre os ancestrais bentívoros que caçavam pequenos invertebrados e alimentavam-se de pólipos de coral. Características relacionadas a captura de presa parecem ser funcionalmente versáteis com pouca distinção entre as espécies com modo de forrageamento bentívoro e planctívoro. Em contraste, várias características relacionadas a detecção da presa ou capacidade natatória estão evoluindo em direção a um novo ótimo, específico para a zooplanctivoria. Apesar da história evolutiva relativamente recente, uma morfologia geral comum, e evidência de uma restrição na evolução do tamanho corporal, a evolução convergente reduziu significativamente a distância morfológica entre as espécies zooplanctívoras. No geral, nossos resultados descrevem até que ponto as demandas funcionais associadas à zooplanctivoria seletiva levaram a características morfológicas generalizadas nos peixes-borboleta e destacam a importância dos efeitos ancestrais em moldar os padrões de convergência morfológica.

El hecho de que organismos con parentesco lejano evolucionen estrategias similares para satisfacer las demandas de un nicho ecológico compartido depende de su historia evolutiva y de la naturaleza de la relación forma-función. En peces, la identificación visual y el consumo de plancton microscópico, la zooplanctivoría selectiva, es un tipo específico de alimentación usualmente asociado a un conjunto de especializaciones morfológicas. Estudios previos han identificado inconsistencias en la trayectoria y magnitud de cambios morfológicos tras transiciones hacia zooplanctivoría selectiva, aludiendo a la diversidad e importancia de efectos ancestrales. Aquí investigamos si las transiciones a zooplanctivoría selectiva han influido en la evolución morfológica de los peces mariposa marinos (familia Chaetodontidae), un grupo especializado en presas pequeñas conocido por varios tipos de alimentación de alta precisión en el bentos. Usando una estimación de estado ancestral Bayesiana, inferimos la evolución reciente de la zooplanctivoría entre ancestros bentívoros que cazaron pequeños invertebrados y se alimentaron de pólipos de coral. Los rasgos relacionados con la captura de presas parecen ser versátiles funcionalmente con escasa distinción morfológica entre especies con modos de alimentación bentívoros y planctívoros. En cambio, múltiples rasgos relacionados con la detección de presas o con la capacidad natatoria están evolucionando hacia un nuevo óptimo específico para zooplanctivoría. A pesar de una historia evolutiva relativamente corta, una morfología general común, y evidencia de restricción en la evolución del tamaño de los peces, una evolución convergente ha reducido la distancia morfológica entre especies zooplanctívoras de forma casi significativa. En conclusión, nuestros hallazgos describen hasta qué punto las demandas funcionales asociadas con la zooplanctivoría selectiva han desembocado en rasgos morfológicos generalizados en peces mariposa y destacan la importancia de los efectos ancestrales en la creación de patrones de morfología convergente.

Body shape diversification along the benthic-pelagic axis in marine fishes.

Colonization of novel habitats can result in marked phenotypic responses to the new environment that include changes in body shape and opportunities for further morphological diversification. Fishes have repeatedly transitioned along the benthic-pelagic axis, with varying degrees of association with the substrate. Previous work focusing on individual lineages shows that these transitions are accompanied by highly predictable changes in body form. Here, we generalize expectations drawn from this literature to study the effects of habitat on body shape diversification across 3344 marine teleost fishes. We compare rates and patterns of evolution in eight linear measurements of body shape among fishes that live in pelagic, demersal and benthic habitats. While average body shape differs between habitats, these differences are subtle compared with the high diversity of shapes found within each habitat. Benthic living increases the rate of body shape evolution and has led to numerous lineages evolving extreme body shapes, including both exceptionally wide bodies and highly elongate, eel-like forms. By contrast, we find that benthic living is associated with the slowest diversification of structures associated with feeding. Though we find that habitat can serve as an impetus for predictable trait changes, we also highlight the diversity of responses in marine teleosts to opportunities presented by major habitats.

Colour dimorphism in labrid fishes as an adaptation to life on coral reefs.

Conspicuous coloration displayed by animals that express sexual colour dimorphism is generally explained as an adaptation to sexual selection, yet the interactions and relative effects of selective forces influencing colour dimorphism are largely unknown. Qualitatively, colour dimorphism appears more pronounced in marine fishes that live on coral reefs where traits associated with strong sexual selection are purportedly more common. Using phylogenetic comparative analysis, we show that wrasses and parrotfishes exclusive to coral reefs are the most colour dimorphic, but surprisingly, the effect of habitat is not influenced by traits associated with strong sexual selection. Rather, habitat-specific selective forces, including clear water and structural refuge, promote the evolution of pronounced colour dimorphism that manifests colours less likely to be displayed in other habitats. Our results demonstrate that environmental context ultimately determines the evolution of conspicuous coloration in colour-dimorphic labrid fishes, despite other influential selective forces.

A CURE for a Major Challenge in Phenomics: A Practical Guide to Implementing a Quantitative Specimen-Based Undergraduate Research Experience.

The measurement and analysis of phenotypes is often a rate-limiting step for many integrative organismal studies but engaging undergraduate researchers can help overcome this challenge. We present a practical guide to implementing a quantitative specimen-based Course-based Undergraduate Research Experience (CURE), which trains students to collect phenotypic data and mentors them through the entire scientific process using the data they help to collect. Direct access to specimens is not necessary to implement this undergraduate research experience, as recent efforts to digitize museum collections along with online image archives allow data extraction to take place in any classroom. We focus in particular on hypothesis development and quantitative skills, as they are essential for modern biological discovery but are rarely emphasized in traditional lecture-based classes. We have implemented this experience, focusing on collecting and analyzing body shape data across fishes, at two institutions with a total of 39 students. It has so far resulted in 14 talks and 4 posters presented by students at local symposia and 2 scientific papers in preparation with undergraduate co-authors. Moreover, the students had a positive experience that, according to their own assessment, improved their critical thinking and analytical skills as well as their knowledge of science and the scientific process.

La caractérisation et l'analyse de phénotypes peuvent imposer des contraintes temporelles importantes dans le cadre d'études intégratives sur la biologie des organismes. Une solution avantageuse pour pallier ce problème est de solliciter la participation d'étudiant(e)s-chercheur(e)s de premier cycle universitaire. Nous proposons un guide pratique afin de mettre en œuvre une expérience de recherche par cours pour des étudiant(e)s de premier cycle (CURE = Course-based Undergraduate Research Experience) fondée sur l'analyse quantitative de spécimens. Au cours de cette expérience, nous entraînons les étudiant(e)s à récolter des données phénotypiques qui sont ensuite utilisées afin de leur enseigner l'ensemble des étapes du processus scientifique. Considérant les efforts récents investis dans la digitalisation de collections muséales et la disponibilité de bases de données d'images en ligne, l'accès direct à des spécimens n'est pas fondamental à la complétion de cette expérience de recherche, les données nécessaires pouvant être extraites d'internet dans n'importe quelle salle de classe. Nous focalisons particulièrement sur l'élaboration d'hypothèses et le développement d'aptitudes en analyses quantitatives, puisque ces compétences sont essentielles aux découvertes contemporaines en sciences biologiques malgré qu'elles ne reçoivent généralement que peu d'emphase dans les formations traditionnelles dans le domaine. Nous avons réalisé cette expérience dans deux institutions universitaires avec un total de 39 étudiant(e)s afin de récolter et d'analyser des données morphologiques à travers l'ensemble des poissons. Jusqu'à présent, les résultats de ces analyses ont fait l'objet de 14 présentations orales ainsi que 4 affiches scientifiques dans des conférences régionales, et nos étudiant(e)s de premier cycle seront co-auteur(e)s de 2 articles scientifiques en cours de préparation. De plus, les étudiant(e)s ont apprécié cette expérience et ont affirmé avoir vu une amélioration dans leur capacité à exercer une pensée critique, dans leurs aptitudes analytiques, ainsi que dans leurs connaissances de la science et du processus scientifique.

Building a Body Shape Morphospace of Teleostean Fishes.

We present a dataset that quantifies body shape in three dimensions across the teleost phylogeny. Built by a team of researchers measuring easy-to-identify, functionally relevant traits on specimens at the Smithsonian National Museum of Natural History it contains data on 16,609 specimens from 6144 species across 394 families. Using phylogenetic comparative methods to analyze the dataset we describe the teleostean body shape morphospace and identify families with extraordinary rates of morphological evolution. Using log shape ratios, our preferred method of body-size correction, revealed that fish width is the primary axis of morphological evolution across teleosts, describing a continuum from narrow-bodied laterally compressed flatfishes to wide-bodied dorsoventrally flattened anglerfishes. Elongation is the secondary axis of morphological variation and occurs within the more narrow-bodied forms. This result highlights the importance of collecting shape on three dimensions when working across teleosts. Our analyses also uncovered the fastest rates of shape evolution within a clade formed by notothenioids and scorpaeniforms, which primarily thrive in cold waters and/or have benthic habits, along with freshwater elephantfishes, which as their name suggests, have a novel head and body shape. This unprecedented dataset of teleostean body shapes will enable the investigation of the factors that regulate shape diversification. Biomechanical principles, which relate body shape to performance and ecology, are one promising avenue for future research.

Extending the Geometric Approach for Studying Biomechanical Motions.

Whether it is swimming, walking, eating, or jumping, motions are a fundamental way in which organisms interact with their environment. Understanding how morphology contributes to motion is a primary focus of kinematic research and is necessary for gaining insights into the evolution of functional systems. However, an element that is largely missing from traditional analyses of motion is the spatial context in which they occur. We explore an application of geometric morphometrics (GM) for analyzing and comparing motions to evaluate the outputs of biomechanical linkage models. We focus on a common model for oral jaw mechanics of perciform fishes, the fourbar linkage, using GM to summarize motion as a trajectory of shape change. Two traits derived from trajectories capture the total kinesis generated by a linkage (trajectory length) and the kinematic asynchrony (KA) of its mobile components (trajectory nonlinearity). Oral jaw fourbar data from two subfamilies of Malagasy cichlids were used to generate form-function landscapes, describing broad features of kinematic diversity. Our results suggest that kinesis and KA have complex relationships with fourbar morphology, each displaying a pattern in which different shapes possess equivalent kinematic trait values, known as many-to-one mapping of form-to-function. Additionally, we highlight the observation that KA captures temporal differences in the activation of motion components, a feature of kinesis that has long been appreciated but was difficult to measure. The methods used here to study fourbar linkages can also be applied to more complex biomechanical models and broadly to motions of live organisms. We suggest that they provide a suitable alternative to traditional approaches for evaluating linkage function and kinematics.

Pectoral Dimorphism Is a Pervasive Feature of Skate Diversity and Offers Insight into their Evolution.

Mature skates (Batoidea: Rajoidei) display a unique form of sexual dimorphism in which males develop a concave anterior pectoral fin, giving them a bell-shaped appearance. Recent work has linked the male-specific transformation to differential skeletal development that is coincident with the rapid elongation of claspers, cartilage-supported intromittent organs. Still, little is known about the prevalence of pectoral dimorphism across skates or of interspecific variation in its expression. Here, we use various morphological approaches to broadly explore pectoral dimorphism in skates, with the goal of understanding its significance in their evolutionary history. We find that pectoral fin sexual dimorphism exists across skate diversity, positively identifying its presence in at least 131 species spanning 33 genera, approximately 40% of valid species. Further, we show that the nature of male-female shape change is largely consistent across species, but that it differs in its magnitude at a biologically meaningful scale. Finally, we use the pygmy skate Fenestraja plutonia as a case study to illustrate ontogenetic patterns in the development of pectoral fin dimorphism, additionally identifying sex-based differences in the pelvic girdle and jaw. Our work suggests that the diversity of pectoral dimorphism in skates is linked to comparative growth and maturation, and potentially to processes underlying reproductive and life history diversification within the group.

El Dimorfismo Pectoral es una Característica Generalizada de la Diversidad de Patines y Ofrece una Perspectiva de su Evolución Los patines (Batoidea: Rajoidei) muestran una forma única de dimorfismo sexual en el que los machos desarrollan una aleta pectoral anterior cóncava que les da una apariencia de campana. Estudios recientes han relacionado este dimorfismo en los machos con el desarrollo esquelético diferencial que coincide con la rápida elongación de los gonopterigios, órganos intromitentes soportados por cartílago. Sin embargo, poco se sabe acerca de la prevalencia del dimorfismo pectoral en patines o de la variación interespecífica en su expresión. En este estudio abordamos varios enfoques morfológicos para explorar ampliamente el dimorfismo pectoral en patines, con el objetivo de comprender su importancia en su historia evolutiva. Identificamos dimorfismo sexual en al menos 131 especies que abarcan 33 géneros, aproximadamente el 40% de las especies válidas. Además, mostramos que la naturaleza del cambio de forma masculino­femenino es en gran medida consistente en todas las especies, pero que difiere en su magnitud en una escala biológicamente significativa. Por último, utilizamos el patín pigmeo Fenestraja plutonia como estudio de caso para ilustrar los patrones ontogenéticos en el desarrollo del dimorfismo de la aleta pectoral, además de identificar dimorfismo sexual a nivel de cintura pélvica y mandíbula. Nuestro trabajo sugiere que la diversidad del dimorfismo pectoral en los patines está relacionada con el crecimiento y la maduración comparativos y, potencialmente, con los procesos subyacentes a la diversificación de la reproducción e historias de la vida dentro del grupo. Translated to Spanish by S. Hinojosa (hinojosa.silvia@gmail.com).

O Dimorfismo Peitoral é uma Característica Difusa da Diversidade do Skate e Oferece Informações sobre sua Evolução Rajídeos maduros (Batoidea: Rajoidei) exibem uma forma única de dimorfismo sexual em que os machos desenvolvem uma nadadeira peitoral anterior côncava, dando-lhes uma aparência em forma de sino. Trabalhos recentes correlacionam a forma específíca dos machos ao desenvolvimento diferencial do esqueleto, que coincide com o rápido alongamento dos clásperes, órgãos intromitantes cartilaginosos. Entretanto, pouco se sabe sobre a prevalência do dimorfismo peitoral em rajideos, ou sobre a variação interespecífica dessa expressão. Nesse trabalho utilizamos diversas abordagens morfológicas para explorar de forma ampla o dimorfismo peitoral dessas raias, com o objetivo de compreender sua significancia em relação à história evolutiva desse grupo. Descobrimos que o dimorfismo sexual da nadadeira peitoral existe entre de toda a diversidade dos rajídeos, observando sua presença em ao menos 131 espécies espalhadas por 33 gêneros, compreendendo aproximadamente 40% das espécies válidas. Além disso, mostramos que a natureza da mudança da forma entre machos e fêmeas é consistente entre as espécies, mas que diferem em sua magnitude em uma escala biologicamente significativa. Finalmente, usamos o rajideo pigmeu Fenestraja plutonia como um estudo de caso para ilustrar padrões ontogenéticos no desenvolvimento do dimorfismo da nadadeira peitoral, além de identificar diferenças baseadas no sexo na cintura pélvica e na mandíbula. Nosso trabalho sugere que a diversidade do dimorfismo peitoral em rajídeos está ligada ao crescimento e maturação comparativos e, potencialmente, aos processos subjacentes à diversificação reprodutiva e de história de vida dentro do grupo. Translated to Portuguese by J.P. Fontenelle (jp.fontenelle@mail.utoronto.ca).

An inductively coupled plasma mass spectrometry method for relative free copper determination and generation of a paediatric reference interval.

Background Diagnosis of Wilson's disease is currently performed using caeruloplasmin as a first-line screening test; however, this test has well-described limitations. Monitoring of known Wilson's disease patients often uses 24-h urine collection; however, this is inaccurate in children. Methods for directly measuring plasma free copper have been described, but no reference interval data exist for a paediatric population. Methods An inductively coupled plasma mass spectrometry method for measuring free copper was developed and validated, using ultracentrifugation. A paediatric reference interval was generated using 85 plasma samples from children attending outpatient clinics at University Hospital Southampton. Results Results showed no significant contamination of copper using the ultracentrifugation technique, and validation showed the method was accurate and precise with an analytical coefficient of variation between 5 and 7% depending on the concentration of free copper. Conclusions We describe the use and validation of an ultrafiltration inductively coupled plasma mass spectrometry method for plasma free copper with the first published paediatric reference interval. Free copper could provide much needed assistance for the monitoring of Wilson's disease in children and also for adults.

Phylogenomic analysis of a rapid radiation of misfit fishes (Syngnathiformes) using ultraconserved elements.

Phylogenetics is undergoing a revolution as large-scale molecular datasets reveal unexpected but repeatable rearrangements of clades that were previously thought to be disparate lineages. One of the most unusual clades of fishes that has been found using large-scale molecular datasets is an expanded Syngnathiformes including traditional long-snouted syngnathiform lineages (Aulostomidae, Centriscidae, Fistulariidae, Solenostomidae, Syngnathidae), as well as a diverse set of largely benthic-associated fishes (Callionymoidei, Dactylopteridae, Mullidae, Pegasidae) that were previously dispersed across three orders. The monophyly of this surprising clade of fishes has been upheld by recent studies utilizing both nuclear and mitogenomic data, but the relationships among major lineages within Syngnathiformes remain ambiguous; previous analyses have inconsistent topologies and are plagued by low support at deep divergences between the major lineages. In this study, we use a dataset of ultraconserved elements (UCEs) to conduct the first phylogenomic study of Syngnathiformes. UCEs have been effective markers for resolving deep phylogenetic relationships in fishes and, combined with increased taxon sampling, we expected UCEs to resolve problematic syngnathiform relationships. Overall, UCEs were effective at resolving relationships within Syngnathiformes at a range of evolutionary timescales. We find consistent support for the monophyly of traditional long-snouted syngnathiform lineages (Aulostomidae, Centriscidae, Fistulariidae, Solenostomidae, Syngnathidae), which better agrees with morphological hypotheses than previously published topologies from molecular data. This result was supported by all Bayesian and maximum likelihood analyses, was robust to differences in matrix completeness and potential sources of bias, and was highly supported in coalescent-based analyses in ASTRAL when matrices were filtered to contain the most phylogenetically informative loci. While Bayesian and maximum likelihood analyses found support for a benthic-associated clade (Callionymidae, Dactylopteridae, Mullidae, and Pegasidae) as sister to the long-snouted clade, this result was not replicated in the ASTRAL analyses. The base of our phylogeny is characterized by short internodes separating major syngnathiform lineages and is consistent with the hypothesis of an ancient rapid radiation at the base of Syngnathiformes. Syngnathiformes therefore present an exciting opportunity to study patterns of morphological variation and functional innovation arising from rapid but ancient radiation.