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.

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.

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.

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).

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.

Ecomorphological convergence in planktivorous surgeonfishes.

Morphological convergence plays a central role in the study of evolution. Often induced by shared ecological specialization, homoplasy hints at underlying selective pressures and adaptive constraints that deterministically shape the diversification of life. Although midwater zooplanktivory has arisen in adult surgeonfishes (family Acanthuridae) at least four independent times, it represents a clearly specialized state, requiring the capacity to swiftly swim in midwater locating and sucking small prey items. Whereas this diet has commonly been associated with specific functional adaptations in fishes, acanthurids present an interesting case study as all nonplanktivorous species feed by grazing on benthic algae and detritus, requiring a vastly different functional morphology that emphasizes biting behaviours. We examined the feeding morphology in 30 acanthurid species and, combined with a pre-existing phylogenetic tree, compared the fit of evolutionary models across two diet regimes: zooplanktivores and nonzooplanktivorous grazers. Accounting for phylogenetic relationships, the best-fitting model indicates that zooplanktivorous species are converging on a separate adaptive peak from their grazing relatives. Driving this bimodal landscape, zooplanktivorous acanthurids tend to develop a slender body, reduced facial features, smaller teeth and weakened jaw adductor muscles. However, despite these phenotypic changes, model fitting suggests that lineages have not yet reached the adaptive peak associated with plankton feeding even though some transitions appear to be over 10 million years old. These findings demonstrate that the selective demands of pelagic feeding promote repeated - albeit very gradual - ecomorphological convergence within surgeonfishes, while allowing local divergences between closely related species, contributing to the overall diversity of the clade.

How predation shaped fish: the impact of fin spines on body form evolution across teleosts.

It is well known that predators can induce morphological changes in some fish: individuals exposed to predation cues increase body depth and the length of spines. We hypothesize that these structures may evolve synergistically, as together, these traits will further enlarge the body dimensions of the fish that gape-limited predators must overcome. We therefore expect that the orientation of the spines will predict which body dimension increases in the presence of predators. Using phylogenetic comparative methods, we tested this prediction on the macroevolutionary scale across 347 teleost families, which display considerable variation in fin spines, body depth and width. Consistent with our predictions, we demonstrate that fin spines on the vertical plane (dorsal and anal fins) are associated with a deeper-bodied optimum. Lineages with spines on the horizontal plane (pectoral fins) are associated with a wider-bodied optimum. Optimal body dimensions across lineages without spines paralleling the body dimension match the allometric expectation. Additionally, lineages with longer spines have deeper and wider body dimensions. This evolutionary relationship between fin spines and body dimensions across teleosts reveals functional synergy between these two traits and a potential macroevolutionary signature of predation on the evolutionary dynamics of body shape.

Two waves of colonization straddling the K-Pg boundary formed the modern reef fish fauna.

Living reef fishes are one of the most diverse vertebrate assemblages on Earth. Despite its prominence and ecological importance, the origins and assembly of the reef fish fauna is poorly described. A patchy fossil record suggests that the major colonization of reef habitats must have occurred in the Late Cretaceous and early Palaeogene, with the earliest known modern fossil coral reef fish assemblage dated to 50 Ma. Using a phylogenetic approach, we analysed the early evolutionary dynamics of modern reef fishes. We find that reef lineages successively colonized reef habitats throughout the Late Cretaceous and early Palaeogene. Two waves of invasion were accompanied by increasing morphological convergence: one in the Late Cretaceous from 90 to 72 Ma and the other immediately following the end-Cretaceous mass extinction. The surge in reef invasions after the Cretaceous-Palaeogene boundary continued for 10 Myr, after which the pace of transitions to reef habitats slowed. Combined, these patterns match a classic niche-filling scenario: early transitions to reefs were made rapidly by morphologically distinct lineages and were followed by a decrease in the rate of invasions and eventual saturation of morphospace. Major alterations in reef composition, distribution and abundance, along with shifts in climate and oceanic currents, occurred during the Late Cretaceous and early Palaeogene interval. A causal mechanism between these changes and concurrent episodes of reef invasion remains obscure, but what is clear is that the broad framework of the modern reef fish fauna was in place within 10 Myr of the end-Cretaceous extinction.

rfishbase: exploring, manipulating and visualizing FishBase data from R.

This article introduces a package that provides interactive and programmatic access to the FishBase repository. This package allows interaction with data on over 30 000 fish species in the rich statistical computing environment, R. This direct, scriptable interface to FishBase data enables better discovery and integration essential for large-scale comparative analyses. This article provides several examples to illustrate how the package works, and how it can be integrated into phylogenetics packages such as ape and geiger.

Coral reefs promote the evolution of morphological diversity and ecological novelty in labrid fishes.

Although coral reefs are renowned biodiversity hotspots it is not known whether they also promote the evolution of exceptional ecomorphological diversity. We investigated this question by analysing a large functional morphological dataset of trophic characters within Labridae, a highly diverse group of fishes. Using an analysis that accounts for species relationships, the time available for diversification and model uncertainty we show that coral reef species have evolved functional morphological diversity twice as fast as non-reef species. In addition, coral reef species occupy 68.6% more trophic morphospace than non-reef species. Our results suggest that coral reef habitats promote the evolution of both trophic novelty and morphological diversity within fishes. Thus, the preservation of coral reefs is necessary, not only to safeguard current biological diversity but also to conserve the underlying mechanisms that can produce functional diversity in future.

Functional versatility supports coral reef biodiversity.

We explore the role of specialization in supporting species coexistence in high-diversity ecosystems. Using a novel ordination-based method to quantify specialist and generalist feeding structures and diets we examined the relationship between morphology and diet in 120 wrasses and parrotfishes from the Great Barrier Reef. We find that wrasses, despite their morphological diversity, exhibit weak links between morphology and diet and that specialist morphologies do not necessarily equate to specialized diets. The dominant pattern shows extensive overlap in morphology (functional morphospace occupation) among trophic groups; fish with a given morphology may have a number of feeding modes. Such trophic versatility may lay the foundation for both the origins and maintenance of high biodiversity on coral reefs.

Wave energy and swimming performance shape coral reef fish assemblages.

Physical factors often have an overriding influence on the distribution patterns of organisms, and can ultimately shape the long-term structure of communities. Although distribution patterns in sessile marine organisms have frequently been attributed to functional characteristics interacting with wave-induced water motion, similar evidence for mobile organisms is lacking. Links between fin morphology and swimming performance were examined in three diverse coral reef fish families from two major evolutionary lineages. Among-habitat variation in morphology and performance was directly compared with quantitative values of wave-induced water motion from seven coral reef habitats of different depth and wave exposure on the Great Barrier Reef. Fin morphology was strongly correlated with both field and experimental swimming speeds in all three families. The range of observed swimming speeds coincided closely with the magnitude of water velocities commonly found on coral reefs. Distribution patterns in all three families displayed highly congruent relationships between fin morphology and wave-induced water motion. Our findings indicate a general functional relationship between fin morphology and swimming performance in labriform-swimming fishes, and provide quantitative evidence that wave energy may directly influence the assemblage structure of coral reef fishes through interactions with morphology and swimming performance.

Evaluating the use of ram and suction during prey capture by cichlid fishes.

We characterized prey-capture strategies in seven species of cichlid fishes representing diverse trophic habits and anticipated feeding abilities. The species examined were Petenia splendida, Cichla ocellaris, Cichlasoma minckleyi, Astronotus ocellatus, Crenicichla geayi, Heros severus (formerly Cichlasoma severum) and Cyprichromis leptosoma. Three individuals per species were filmed with video at 500 Hz as they captured live adult Artemia sp. and Poecilia reticulata. For each feeding sequence, we measured the contribution of predator movement towards the prey (i.e. ram) and the movement of prey towards the predator due to suction. The use of ram differed significantly among prey types and predator species, varying as much as sixfold across predator species. High values of ram resulted in high attack velocities. Jaw protrusion contributed as much as 50% to overall ram values in some species, verifying its role in enhancing attack velocity. Suction distance did not vary significantly among species. Diversity in prey-capture behavior was therefore found to reflect differences among species in the strategy used to approach prey. Limited variation in the distance from which prey were sucked into the mouth is interpreted as the result of an expected exponential decline in water velocity with distance from the mouth of the suction-feeding predator. We propose that this relationship represents a major constraint on the distance over which suction feeding is effective for all aquatic-feeding predators.

Modulation of prey capture kinematics in the cheeklined wrasse Oxycheilinus digrammus (Teleostei: Labridae).

The ability to modulate prey capture behaviors is of interest to organismal biologists as it suggests that predators can perceive features of the prey and select suitable behaviors from an available repertoire to successfully capture the item. Thus, behavior may be as important a trait as morphology in determining an organism's diet. Using high-speed video, we measured prey capture kinematics in three cheeklined wrasse, Oxycheilinus digrammus. We studied the effects of three experimental prey treatments: live fish, dead prawn suspended in the water column, and dead prawn pieces anchored to the substrate in a clip. Live prey elicited significantly more rapid strikes than dead prey suspended in the water column, and the head of the predator was expanded to significantly larger maxima. These changes in prey capture kinematics suggest the generation of more inertial suction. With greater expansion of the head, more water can be accelerated into the buccal cavity. The attached prey treatment elicited strikes as rapid as those on live prey. We suggest that the kinematics of rapid strikes on attached prey are indicative of attempts to use suction to detach the prey item. More rapid expansion of the buccal or mouth cavity should lead to higher velocities of water entering the mouth and therefore to enhanced suction. Further modulation in response to the attached prey item, such as clipping or wrenching behaviors, was not observed. J. Exp. Zool. 290:88-100, 2001.

Evolution and mechanics of long jaws in butterflyfishes (family Chaetodontidae).

We analyzed the functional morphology and evolution of the long jaws found in several butterflyfishes. We used a conservative reanalysis of an existing morphological dataset to generate a phylogeny that guided our selection of seven short- and long-jawed taxa in which to investigate the functional anatomy of the head and jaws: Chaetodon xanthurus, Prognathodes falcifer (formerly Chaetodon falcifer), Chelmon rostratus, Heniochus acuminatus, Johnrandallia nigrirostris, Forcipiger flavissimus, and F. longirostris. We used manipulations of fresh, preserved, and cleared and stained specimens to develop mechanical diagrams of how the jaws might be protruded or depressed. Species differed based on the number of joints within the suspensorium. We used high-speed video analysis of five of the seven species (C. xanthurus, Chel. rostratus, H. acuminatus, F. flavissimus, and F. longirostris) to test our predictions based on the mechanical diagrams: two suspensorial joints should facilitate purely anteriorly directed protrusion of the lower jaw, one joint should allow less anterior protrusion and result in more depression of the lower jaw, and no joints in the suspensorium should constrain the lower jaw to simple ventral rotation around the jaw joint, as seen in generalized perciform fishes. We found that the longest-jawed species, F. longirostris, was able to protrude its jaws in a predominantly anterior direction and further than any other species. This was achieved with little input from cranial elevation, the principal input for other known lower jaw protruders, and is hypothesized to be facilitated by separate modifications to the sternohyoideus mechanism and to the adductor arcus palatini muscle. In F. longirostris the adductor arcus palatini muscle has fibers oriented anteroposteriorly rather than medial-laterally, as seen in most other perciforms and in the other butterflyfish studied. These fibers are oriented such that they could rotate the ventral portion of the quadrate anteriorly, thus projecting the lower jaw anteriorly. The intermediate species lack modification of the adductor arcus palatini and do not protrude their jaws as far (in the case of F. flavissimus) or in a purely anterior fashion (in the case of Chel. rostratus). The short-jawed species both exhibit only ventral rotation of the lower jaw, despite the fact that H. acuminatus is closely related to Forcipiger.

Prey capture in long-jawed butterflyfishes (Chaetodontidae): the functional basis of novel feeding habits.

Several species of butterflyfishes (Chaetodontidae) possess extremely elongate jaws, and feed mostly by probing the benthos and biting off pieces of attached invertebrates. In contrast, Forcipiger longirostris, the longest-jawed chaetodontid, exhibits a novel pattern of prey use, feeding almost exclusively on small caridean shrimp, a mobile and highly elusive prey type that lives within the structure of coral reefs. We explored the functional basis of this novel pattern of prey use by comparing prey capture kinematics in this and four other butterflyfish species, including two other species that possess elongate jaws. High speed video recordings of feeding events on live adult brine shrimp were analyzed from individuals of five species: Forcipiger longirostris, F. flavissimus, Chelmon rostratus, Heniochus acuminatus, and Chaetodon xanthurus. We focused on a comparison among species of the relative contribution of "suction", measured as the amount of movement of the prey toward the predator's mouth, and "ram", measured as the distance moved by the predator toward the prey during the strike. All five species utilized a combination of suction and ram while feeding on brine shrimp. The contribution of suction did not differ significantly among species. However, F. longirostris exhibited a ram contribution to the strike that was more than twice that seen in any of the other species, permitting this species to initiate strikes from the greatest initial predator-prey distance. F. longirostris is known to possess a major structural novelty in the feeding mechanism that permits anterior movement of the entire jaw apparatus. The ability of this species to feed successfully on elusive prey appears to be related to exceptional jaw protrusion, resulting in greater use of ram during prey capture. This ability to protrude long, slender jaws toward the prey may allow it to move the jaws without detection within close enough proximity of the prey to then permit the effective use of suction. The use of extensive ram in this manner by small-mouthed fishes may be more widespread than previously thought.