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Phenotypic adaptations can allow organisms to relax abiotic selection and facilitate their ecological success in challenging habitats, yet we have relatively little data for the prevalence of this phenomenon at macroecological scales. Using data on the relative abundance of coral reef wrasses and parrotfishes (f. Labridae) spread across three ocean basins and the Red Sea, we reveal the consistent global dominance of extreme wave-swept habitats by fishes in the genus Thalassoma, with abundances up to 15 times higher than any other labrid. A key locomotor modification-a winged pectoral fin that facilitates efficient underwater flight in high-flow environments-is likely to have underpinned this global success, as numerical dominance by Thalassoma was contingent upon the presence of high-intensity wave energy. The ecological success of the most abundant species also varied with species richness and the presence of congeneric competitors. While several fish taxa have independently evolved winged pectoral fins, Thalassoma appears to have combined efficient high-speed swimming (to relax abiotic selection) with trophic versatility (to maximize exploitation of rich resources) to exploit and dominate extreme coral reef habitats around the world.

The ability to sustain high swimming speeds is believed to be an important factor affecting resource acquisition in fishes. While we have gained insights into how fin morphology and motion influences swimming performance in coral reef fishes, the role of other traits, such as body shape, remains poorly understood. We explore the ability of two mechanistic models of the causal relationship between body fineness ratio and endurance swimming-performance to predict maximum prolonged-swimming speed (Umax ) among 84 fish species from the Great Barrier Reef, Australia. A drag model, based on semi-empirical data on the drag of rigid, submerged bodies of revolution, was applied to species that employ pectoral-fin propulsion with a rigid body at U max. An alternative model, based on the results of computer simulations of optimal shape in self-propelled undulating bodies, was applied to the species that swim by body-caudal-fin propulsion at Umax . For pectoral-fin swimmers, Umax increased with fineness, and the rate of increase decreased with fineness, as predicted by the drag model. While the mechanistic and statistical models of the relationship between fineness and Umax were very similar, the mechanistic (and statistical) model explained only a small fraction of the variance in Umax . For body-caudal-fin swimmers, we found a non-linear relationship between fineness and Umax , which was largely negative over most of the range of fineness. This pattern fails to support either predictions from the computational models or standard functional interpretations of body shape variation in fishes. Our results suggest that the widespread hypothesis that a more optimal fineness increases endurance-swimming performance via reduced drag should be limited to fishes that swim with rigid bodies.

Macroalgal-dominated reefs are a prominent component of tropical seascapes providing food and shelter for many species whilst subsidising secondary productivity in coastal ecosystems. Monitoring and managing macroalgae require an understanding of key processes that alter these assemblages, especially at the local scale. Here we consider how sediment depth/cover and abundance of the urchin Tripneustes gratilla influence variation in community composition and physical structure of macroalgal patches within the World Heritage listed Ningaloo Reef, Western Australia. Our study found high urchin densities in sites with lower sediment cover and depth and that sediments, urchin abundance, and seascape position explained 32% of the spatial variation in macroalgal community composition with a greater occurrence of Sargassopsis, Caulerpa, Sirophysalis and Hormophysa in the lagoon where sediment cover/depth was high. Canopy height and cover of canopy-forming macroalgae were also greater where sediments were high and urchin abundance low. Macroalgal genera with a strong and robust thallus were found in sediment depths up to 6 cm as opposed to those with softer, fragile thalli that were found in sediments < 2 cm. Our results demonstrate that high densities of urchins and mobile sediments can have profound effects on the composition and structure of tropical macroalgal assemblages. Changes to macroalgal community composition and physical structure will have flow-on effects for ecological processes such as productivity and habitat use which can alter the ecosystem goods and services macroalgal-dominated habitats provide., Author(s): Rosalie J. Harris [sup.1] , Shaun K. Wilson [sup.2] [sup.3] , Christopher J. Fulton [sup.1] Author Affiliations: (1) grid.1001.0, 0000 0001 2180 7477, Ecology & Evolution, Research School of [...]

Biodiversity conservation and management requires surveillance that captures the full spectrum of taxa. Here, we showcase the potential for a portfolio of visual, extractive, and molecular methods for detecting previously hidden components of tropical fish biodiversity in an economically and culturally valuable marine site that spans a tropical‐temperate ecotone—the Ningaloo Coast World Heritage Area. With scale and practicality in mind, we demonstrate how environmental DNA (eDNA) methods deployed in a stratified sampling design can yield a more comprehensive monitoring program for species presence than current alternatives (e.g., extractive sampling via anesthetic). eDNA from filtered water samples detected up to six times as many cryptobenthic fish species per site than samples collected with anesthetic, indicating it is a potentially powerful tool for assessing biodiversity of tropical fishes. However, there were also species that were only found when using anesthetic and the contribution of cryptobenthic species to overall diversity of the fish assemblage was unexpectedly low, suggesting not all cryptobenthic fish species have been detected with eDNA. There were also distinct differences in cryptobenthic assemblages both among sites and sample depths (2–3 m) when using eDNA from filtered water, suggesting this technique may be able to identify fine scale spatial differences in cryptobenthic fish assemblage. eDNA collected from water detects the most cryptobenthic species and is therefore an efficient tool for rapidly assessing biodiversity, but extractive techniques may still be required for biological and monitoring studies, and when combined with eDNA sampling provides the most comprehensive assessment of cryptobenthic fishes. [ABSTRACT FROM AUTHOR]

Crustaceans are one of the most influential groups in aquatic trophic networks by providing a major connection between primary production and higher consumers. Although coral reefs support a high diversity and abundance of crustaceans and crustacean predators, their trophic interrelationships remain unclear. Using predator gut content analyses, we investigated trophic relationships between Crustacea and adult fishes of the family Labridae, which are one of the most abundant and diverse families of marine crustacean predators. Crustaceans were present within the guts of 93 % of the 30 wrasse genera investigated. We found a distinct division between micro- and macro-crustacean predators: wrasses 90 mm SL displayed a predominantly macro-Crustacea diet. Notably, micro-crustacean predators tended to specialise on certain crustacean taxa, whereas macro-crustacean predators consumed mostly brachyurans. Our findings highlight complex patterns of feeding diversity within crustacean predators that prompt a more nuanced approach to defining the role of crustacean-feeding fishes in coral reef trophodynamics. Electronic supplementary material The online version of this article (doi:10.1007/s00227-015-2710-0) contains supplementary material, which is available to authorized users., Author(s): Michael J. Kramer[sup.1] [sup.2] , Orpha Bellwood[sup.2] , Christopher J. Fulton[sup.3] , David R. Bellwood[sup.1] [sup.2] Author Affiliations: (1) Australian Research Council Centre of Excellence for Coral Reef Studies, [...]

Transgenerational marking enables mass-marking of larval fishes via transmission of enriched stable isotopes from mother to offspring, but potential impacts on the resultant progeny are poorly understood. We injected enriched stable isotopes ([sup.137]Ba and [sup.87]Sr) into female purple-spotted gudgeon, Mogurnda adspersa, to produce multiple batch markers and examined larval morphology at hatch as well as survival and growth to 31 days posthatch in marked and unmarked offspring. Transgenerational marking had minimal effects on larval growth and survival, whereas body depth at hatch was significantly reduced in marked larvae. A meta-analysis of transgenerational marking effects on larval morphology at hatch and growth rates across multiple fish species found a nonsignificant positive effect of enriched stable barium isotopes on larval morphology at hatch, but a significant negative effect on growth. There were no significant effects of strontium on morphology or growth. Meta-regression analysis revealed that larval size at hatch increased with the dose of injected stable barium isotopes, but this result should be interpreted cautiously. Because of high levels of between-study heterogeneity, we caution against assuming there are no effects of transgenerational marking on fish offspring; any such effects should be validated and incorporated into transgenerational marking studies of fish dispersal. Si la methode de marquage transgenerationnel permet le marquage d'un grand nombre de larves de poisson par la transmission d'isotopes stables enrichis de la mere a sa progeniture, ses impacts potentiels sur cette progeniture demeurent mal compris. Nous avons injecte des isotopes stables enrichis ([sup.137]Ba et [sup.87]Sr) dans une femelle de Mogurnda adspersa pour produire differents marqueurs de lot et avons examine la morphologie, la survie et la croissance de larves marquees et non marquees 31 jours apres leur eclosion. Si le marquage transgenerationnel a eu peu d'effets sur la croissance et la survie des larves, la profondeur du corps au moment de l'eclosion etait significativement plus faible pour les larves marquees. Une meta- analyse des effets du marquage transgenerationnel sur la morphologie des larves a l'eclosion et les taux de croissance pour differentes especes de poisson a revele un effet positif non significatif sur la morphologie des larves a l'eclosion, mais un effet negatif significatif sur la croissance, attribuable a l'enrichissement des isotopes stables de baryum. Aucun effet significatif du strontium sur la morphologie ou la croissance n'a ete decele. L'analyse de meta-regression a revele que la taille des larves a l'eclosion augmentait parallelement a la dose d'isotopes stables de baryum injectee, mais ce resultat devrait etre interprete avec prudence. En raison des degres eleves d'heterogeneite entre les etudes, il est recommande de ne pas presumer que le marquage transgenerationnel n'a aucun effet sur la progeniture de poisson, la presence de tels effets devant prealablement etre validee, puis incorporee dans les etudes sur la dispersion des poissons reposant sur le marquage transgenerationnel. [Traduit par la Redaction], Introduction Fish movement has often been studied using techniques that apply identifiable marks on individuals, such as visible external tags and radio-tags (Woodbury et al. 1956; Cooke et al. 2013). [...]

Flexible traits can be crucial in helping animals meet the challenges of a highly variable environment. We examined whether coral reef fishes systematically alter their swimming behaviour in response to temporal changes in hydrodynamic conditions. Exploiting site-based differences in wave energy impinging on reef habitats over calm and rough weather, we found many reef fishes changed their swimming behaviour alongside increases in wave-driven water motion. Most fishes tended to orient their bodies parallel to oncoming wave-driven flow and recruited additional stabilising fins during rough weather; such changes in swimming behaviour aid stability and minimise drag. However, not all species displayed such flexibility, with fishes possessing highly tapered pectoral fins and high levels of swimming performance continuing to successfully navigate reef habitats without significantly altering their swimming behaviour. We highlight how labile behaviours augment the morphology and performance of species to underpin their occupation of habitats subject to variable environmental conditions., Introduction Phenotype-environment interactions have received increasing attention due to concerns about how organisms may be affected by changing environmental conditions arising from climatic change. While organisms can respond to environmental [...]

We investigated how thermal stress may alter the locomotor phenotype of barramundi, Lates calcarifer, from genetically distinct northern (low latitude) and southern (high latitude) populations in tropical Australia. Following early growth and development under native (25 °C and 30 °C) and non-native (20 °C and 35 °C) temperatures, we observed distinct differences in the swimming performance of northern and southern individuals that were consistent with expectations based on local thermal adaptation. Southern population fish exhibited significantly faster swimming speeds (32.10 ± 0.33 [cm*s.sup.-1], mass-adjusted mean ± 95% confidence limit) than their northern counterparts (28.58 ± 0.64 [cm*s.sup.-1] under cold-stress (20 °C) conditions. Conversely, northern population fish performed significantly better (51.63 ± 2.1 [cm*s.sup.-1]) than their southern counterparts (44.18 ± 3.11 [cm*s.sup.-1]) under heat-stress (35 °C) conditions. We conclude that L. calcarifer display locomotor phenotypes thermally adapted to their local environment, with early growth under non-native temperatures leading to significantly reduced phenotypic fitness. Resume: Nous etudions de quelle maniere le stress thermique peut modifier le phenotype locomoteur du barramundi, Lates calcarifer, dans des populations genetiquement distinctes du nord (de basse latitude) et du sud (de haute latitude) d'Australie tropicale. Apres le debut de la croissance et du developpement a des temperatures de leur milieu d'origine (25 °C et 30 °C) ou non (20 °C et 35 °C), nous observons de nettes differences dans la performance de nage entre les individus du nord et du sud qui correspondent aux attentes basees sur l'adaptation thermique locale. Les populations du sud nt des vitesses de nage significativement plus elevees (32,10 ± 0,33 [cm*s.sup.-1], moyenne ajustee a la masse ± intervalles de confiance de 95 %) que les populations du nord (28,58 ± 0,64 [cm*s.sup.-1]) dans des conditions de stress au froid (20 °C). A l'inverse, les populations de poissons du nord performent significativement mieux (51,63 [+ or -] 2,1 [cm*s.sup.-1]) que celles du sud (44,18 ± 3,11 [cm*s.sup.-1]) dans des conditions de stress a la chaleur (35 °C). Nous concluons que L. calcarifer possede des phenotypes locomoteurs adaptes thermiquement a leur environnement local et qu'une croissance au debut de la vie a des temperatures autres que celles de son milieu d'origine mene a une reduction significative de la fitness phenotypique. [Traduit par la Redaction], Introduction Organisms can respond via changes in their morphology, physiology, or survivorship to the temperature regime of their native habitat. Ectothermic, or cold-blooded, organisms are particularly responsive to their home-range [...]