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Pairwise contrasts of (a) pectoral fin aspect-ratio (AR), (b) routine swimming speed and (c) maximum prolonged speed among Acanthochromis polyacanthus occupying different continental shelf positions (inner-, mid-and outer-shelf) on the northern Great Barrier Reef
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While morphological variation across geographical clines has been well documented, it is often unclear whether such changes enhance individual performance to local environments. We examined whether the damselfish Acanthochromis polyacanthus display functional changes in swimming phenotype across a 40-km
cline in wave-driven water motion on the Grea...
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... In many taxa, the primary function of pectoral fins is for propulsion (Blake 1981;Webb 1994), and labriform locomotion is the most studied form of paired median fin-based propulsion (Montgomery and Macdonald 1984;Walker and Westneat 2002a,b;Fulton et al. 2017). The morphology of pectoral fins in this swimming mode has been shown to correlate with wave exposure gradients, with a higher aspect ratio usually seen in fishes that inhabit more exposed, wave-swept habitats, where they are associated with higher swimming speeds (Bellwood et al. 2002;Fulton et al. 2005Fulton et al. , 2013. The pectoral fins of benthicassociated fishes are often characterised as having low lift but relatively high drag, which is offset by increasing friction such as with extensive pectoral fins capable of grasping the substratum and/or creation of negative lift through changes in fin morphology, fin position and behaviour (Webb 1994;Binning and Roche 2015). ...
The study of phenotypic variation at the level of populations and species is central to understanding the processes that lead to evolutionary diversification. Triplefin fishes (Tripterygiidae) are a diverse and ecologically important family on New Zealand rocky reefs. This assemblage provides an opportunity to explore phenotype-environment relationships and the mechanisms responsible for the ecological speciation that is thought to have driven diversification in this clade. To test these relationships, we used two main approaches. Firstly, we used a geometric morphometric approach, and secondly, we used controlled rearing experiments in aquaria to examine the mechanism behind this phenotypic variation. The results showed that wild populations of the habitat generalist Forsterygion lapillum differed in body and fin morphology across a gradient in wave exposure in a region with extensive gene flow. Results of the tank experiments demonstrated that new recruits of F. lapillum from the same location that were raised in distinct water movement environments became morphologically distinct, whereas new recruits of F. lapillum from distinct water movement environments that were raised in identical conditions did not. The reciprocal rearing experiments, in conjunction with the morphological variation shown in wild individuals across the exposure gradient, indicate that plasticity is predominantly responsible for the phenotypic variation seen in F. lapillum populations in the Hauraki Gulf, New Zealand.
... For example, Piñeros et al. (2015) showed that individuals from the damselfish Abudefduf saxatilis, living in an environment with high planktonic biomass, have a more upward-oriented mouth compared with other individuals living with low planktonic biomass. Such morphological variation related to diet or habitat is even detected at spatial scales below 100 m and across coastal gradients (Fulton et al., 2013;Binning et al., 2014;Binning & Roche, 2015). To the best of our knowledge, no previous study has compared trophic and morphological traits among populations of coral reef fishes at both small and large spatial scales. ...
... Our work provides further evidence that, beyond colour variation (e.g. Bernardi et al., 2002;Schultz et al., 2007), the morphology of coral reef fishes varies among sites showing different environmental conditions (present study;Frédérich et al., 2012b;Fulton et al., 2013;Binning et al., 2014;Binning & Roche, 2015;Piñeros et al., 2015). ...
Documenting phenotypic variation among populations is crucial for our understanding of micro-evolutionary processes. To date, the quantification of trophic and morphological variation among populations of coral reef fish at multiple geographical scales remains limited. This study aimed to quantify diet and body shape variation among four populations of the damselfish Dascyllus abudafur living in different environmental conditions from the central Red Sea and from Madagascar. Stomach content analyses showed that one adaptive response of D. abudafur inhabiting turbid waters is a trophic shift from almost exclusive zooplanktivory to a diet consisting of planktonic and benthic prey. Our morphometric data reveal differences in cephalic profile and body shape among populations, in agreement with this variation in trophic strategy. Isotopic diversity and body shape disparity vary among populations and we thus demonstrate that coral reef fish populations are not equal in terms of phenotypic diversity among sites and regions. Finally, our comparative analysis reveals that the main axes of body shape variation among populations are shared at both small (Red Sea sites) and large (Madagascar and Red Sea sites) spatial scales. This study raises new questions about the factors governing the direction of response to selection in this fish species.
... Wave-driven flow regimes are particularly prevalent on fringing and barrier reefs, reducing wave energy before it reaches the coastline (Moberg and Folke, 1999). Contending with wave stress is potentially an energetically expensive endeavor for fishes, and those that are behaviorally, morphologically or physiologically adapted to minimize energy expenditure will have a selective advantage in occupying areas of increased water flows (Fulton et al., 2013b). The intensity of wave exposure has been identified as an important factor affecting reef fish distributions, with correlations with fish morphology and swimming performance Fulton, 2010;Webb et al., 2010;Fulton et al., 2017). ...
... Coral reef fishes display a great diversity of body and fin shapes, and also swimming gaits, or patterns of fin use for swimming (Price et al., 2011;Fulton et al., 2013b;Pink and Fulton, 2014). Swimming mode in fishes can be divided into two broad functional groups: body-caudal fin (BCF) swimming, using lateral undulations of the body and caudal fin, and median-paired fin (MPF) swimming, involving movements of one or more median (dorsal and anal) or paired ( pectoral) fins, while the body is held rigid (Webb, 1998). ...
Oxygen consumption rates were measured for coral reef fishes during swimming in a bidirectional, oscillatory pattern to simulate station-holding in wave-induced, shallow water flows. For all species examined, increases in wave intensity, as simulated by increases in frequency and amplitude of oscillation, yielded increased metabolic rates and net costs of swimming (NCOS; swimming metabolic rate minus standard metabolic rate). Comparing species with different swimming modes, the caudal-fin swimming Kuhlia spp. (Kuhliidae) and simultaneous pectoral-caudal fin swimming Amphiprion ocellaris (Pomacentridae) turned around to face the direction of swimming most of the time, while the median-paired fin (MPF) swimmers, the pectoral -fin swimming Ctenochaetus strigosus (Acanthuridae) and dorsal-anal fin swimming Sufflamen bursa (Balistidae), more frequently swam in reverse for one half of the oscillation to avoid turning. Contrary to expectations, the body-caudal fin (BCF) swimming Kuhlia spp. had the lowest overall NCOS in the oscillatory swimming regime compared with the MPF swimmers. However, when examining the effect of increasing frequency of oscillation at similar average velocities, the Kuhlia spp. showed a 24% increase in NCOS with a 50% increase in direction changes and accelerations. The two strict MPF swimmers had lower increases on average, suggestive of reduced added costs with increasing frequency of direction changes with this swimming mode. Further studies are needed on the costs of unsteady swimming to determine if these differences can explain the observed prevalence of fishes using the MPF, pectoral-fin swimming mode in reef habitats exposed to high, wave-surge induced water flows.
http://jeb.biologists.org/content/jexbio/early/2019/01/17/jeb.191791.full.pdf
... A fundamental concept in evolutionary biology is species phenotypic variation in response to divergences of biological and abiotic conditions or genetic flow interchange (Khan et al., 2013;Theis et al., 2014). These biotic and abiotic conditions exert strong pressures on organisms, being a mechanism for phenotypic variations that may favour their performance under local conditions (Franssen et al., 2013;Fulton et al., 2013;Culumber & Tobler, 2016). Thus, adaptation to a particular habitat may lead to specialization when reproductive isolation accumulates as a by-product of adaptive divergence, or when different mutations occur in geographically separate populations (Rundle & Nosil, 2005;Khan et al., 2013). ...
Phenotypic differentiation among fish populations may be used for management of distinct stocks and helps in conserving biodiversity. We compared morphometric and meristic characters of the anchovy Anchoa januaria from shallow semi-closed bays between the south-eastern (Tropical, 23°S) and southern (Subtropical, 25°S) Brazilian coast. We hypothesized that differences between habitats and environmental conditions result in morphological divergence between conspecific populations. Fish size did not differ significantly between the two areas. Significant differences in the meristic and morphological characters were detected for individuals between the two areas, with specimens from the Subtropical region having significant larger head height, pectoral fin length and eye diameter compared with those from the Tropical region. Conversely, specimens from the Tropical region had significantly larger maxillary length, mouth length and body height than those from the Subtropical region. The number of rays for the dorsal and pectoral fins were higher for the specimens from the Subtropical region, whereas for the anal fin was higher for individuals from the Tropical region. Different morphological groups between the two regions were depicted by principal component analysis and discriminant function analysis, which suggest that morphological divergence is occurring. Local environmental influences and the lack of genetic interchange are likely to be the causes of such divergence. This is facilitated by the low tolerance of this species to marine waters that prevents connectivity between these stocks/populations.
... Across the GBR distinct gradients in faunal assemblages exist, with a general increase in abundance and diversity further from shore (Cheal et al., 2012;Emslie et al., 2017;Wismer et al., 2009). These ecological gradients follow distinct gradients in abiotic conditions such as hydrodynamic exposure gradients (Bellwood and Wainwright, 2001;Crossman et al., 2001;Fulton et al., 2013) and terrestrial influences on sediment loads and water quality (Fabricius et al., 2014;Tebbett et al., 2017). How sea urchin and triggerfish distributions conform to these previous patterns is unclear. ...
Urchins are ubiquitous components of coral reefs ecosystems, with significant roles in bioerosion and herbivory. By controlling urchin densities, triggerfishes have been identified as keystone predators. However, the functional linkages between urchins and triggerfishes, in terms of distributional patterns and concomitant effects on ecosystem processes, are not well understood, especially in relatively unexploited systems. To address this we censused urchins and triggerfishes on two cross-shelf surveys on the Great Barrier Reef (GBR) at the same times and locations. We also evaluated the role of urchins in bioerosion. Although urchin abundance and triggerfish biomass varied by 80% and nearly 900% across sites, respectively, this variability was driven primarily by shelf position with no evidence of top-down control on urchins by triggerfishes. Low urchin abundances meant urchins only played a minor role in bioerosion. We highlight the potential variability in functional links, and contributions to ecosystem processes, among regions.
... The study analysed morphological variations using a combination of geometric and traditional morphometric methods and revealed some subtle but important divergences among wild D. rerio populations. Divergence in morphological characteristics can result from competitive pressure from co-existing species as well as a response to differing environmentbiotic (Agrawal 2001) or abiotic (Fulton et al. 2013) factors within habitats (West-Eberhard 1989). These phenotypic variations can result from a combination of genetic and plastic influences (Levins 1968;West-Eberhard 2003;Sharpe et al. 2008). ...
Studies on morphological differences among populations from different ecological regions help towards understanding diversification of traits and is a fundamental step in adaptive radiation and ultimately, speciation. This study investigates the occurrence of variations in morphological traits among wild populations of zebrafish (Danio rerio) from India that inhabit a variety of habitat and ecological regimes. Geometric morphometric methods and traditional morphometric analysis were used to quantify the extent of differences in morphological traits between four populations of wild D. rerio from still-water (stagnant) (Kalibazaar, in West Bengal) and slow -medium flowing (Asan, Kaushalya and Seripetkalwa in Uttarakhand, Haryana and Andhra Pradesh respectively) habitats within India. Multivariate analyses showed significant effect of populations on morphology, post-hoc paired comparisons between populations show differences in body size as well as shape across these populations. Relative warps analyses on the landmarks selected for body shape showed higher loadings for caudal peduncle, head and eye regions. Population-wise scatterplots along relative warp1 (RW1)- relative warp4 (RW4) axes revealed Asan population cluster expands beyond the other population clusters along the RW1- RW2 axes, while the Kalibazaar cluster spreads out from the others along the RW3-RW4 axes. Multiple regression models to predict relation between shape and ecological attributes indicate the strongest role of dissolved oxygen, stream velocity and abundance of predators in explaining variations in morphology across these populations. This is significant as a first study utilising the tools of morphometric analyses in Danio rerio and indicating the role of multiple (biotic and abiotic) selective forces in shaping phenotypic variations in morphology.
... Hydrodynamic forces and differences in reef morphology may also explain the differences between reefs in the same shelf position. Hydrodynamic energy decreases towards the coast [94], and although inner-shelf reefs are in the resuspension zone, they experience more consistent hydrodynamic forces, which may reduce differences in grain size distributions among individual reefs. Mid-and outer-shelf reefs are likely to be exposed to much more variable hydrodynamic environments [80,81] and this hydrodynamic variability can explain some of the variation in grain size distributions between individual reefs in the same shelf position. ...
Sediments are found in the epilithic algal matrix (EAM) of all coral reefs and play important roles in ecological processes. Although we have some understanding of patterns of EAM sediments across individual reefs, our knowledge of patterns across broader spatial scales is limited. We used an underwater vacuum sampler to quantify patterns in two of the most ecologically relevant factors of EAM sediments across the Great Barrier Reef: total load and grain size distribution. We compare these patterns with rates of sediment production and reworking by parrotfishes to gain insights into the potential contribution of parrotfishes to EAM sediments. Inner-shelf reef EAMs had the highest sediment loads with a mean of 864.1 g m⁻², compared to 126.8 g m⁻² and 287.4 g m⁻² on mid- and outer-shelf reefs, respectively. High sediment loads were expected on inner-shelf reefs due to their proximity to the mainland, however, terrigenous siliceous sediments only accounted for 13–24% of total mass. On inner-shelf reef crests parrotfishes would take three months to produce the equivalent mass of sediment found in the EAM. On the outer-shelf it would take just three days, suggesting that inner-shelf EAMs are characterised by low rates of sediment turnover. By contrast, on-reef sediment production by parrotfishes is high on outer-shelf crests. However, exposure to oceanic swells means that much of this production is likely to be lost. Hydrodynamic activity also appears to structure sediment patterns at within-reef scales, with coarser sediments (> 250 μm) typifying exposed reef crest EAMs, and finer sediments (< 250 μm) typifying sheltered back-reef EAMs. As both the load and grain size of EAM sediments mediate a number of important ecological processes on coral reefs, the observed sediment gradients are likely to play a key role in the structure and function of the associated coral reef communities.
... To examine how incident wave energy influenced the relative abundance of Thalassoma (the most abundant labrid genus) and all other genera, we quantified the abundance of all labrid fishes within shallow reef habitats (3 m depth) that are either sheltered (back reef) or directly exposed (crest) to incident trade wind-driven waves across a 40-km cline on the northern Great Barrier Reef (GBR), Australia (Fulton, Binning, Wainwright, & Bellwood, 2013b). Our GBR surveys comprised four replicate belt transects (timed swims as above) taken within each habitat zone (back, crest) of two reefs at each of three continental shelf positions (inner-, mid-and outer-shelf). ...
... Corresponding measures of maximum in situ habitat flow velocities were taken at the same GBR reefs, using three dynamometers (Bell & Denny, 1994) deployed simultaneously at 5 m depth within the reef back and crest habitats of the same six reefs, during an 8-day period when south-easterly winds gusted above 20 knots daily (Fulton et al., 2013b). We used a permutational multivariate analysis of variance (Anderson, Gorley, & Clarke, 2008) on a binomial deviance dissimilarity matrix (Anderson & Millar, 2004) constructed from the log 10 (x + 1)-transformed data to explore differences in the relative density of Thalassoma versus other genera with the fixed factors of continental shelf position and habitat zone (crest/back), and random reef replicates nested within shelf position. ...
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. K E Y W O R D S aspect ratio, ecomorphology, labriform, macroecology, specialization
... In contrast, riverine species have to live under harsher and more variable environmental conditions [13] and these could influence morphological plasticity of riverine fish species [14]. Morphological changes can be a result of adaptation to abiotic and biotic factors [15] There have been relationships between environmental and morphological characteristics among taxa of Barbus [16]. However, these relationships have been affected when a given morphological structure used for more than one function is subject to multiple selection or when adjacent structure perform different functions so that one structure influences a second character [16]. ...
Aim: To provide data on external morphology of Barbus altianalis from four major rivers in Lake Victoria watershed, determine whether there are significant morphometric differences between subpopulations from the rivers of the catchment area examined and to determine relationship between morphometric parameters and standard length (SL). Methods and Results: Morphometric analysis was carried out in the study. Based on 21 morphometric characters, Barbus altianalis populations from four Lake Victoria catchment rivers Nzoia, Yala, Nyando and Sondu-Miriu were morphologically characterised based on 21 morphometric parameters. Principal Component Analysis (PCA) showed separation of Rivers Yala from Nzoia, Nyando, and Sondu-Miriu populations. Factor loadings established that 11 characters were morphologically informative. PCA1 accounted for 43.25% of the variation while PCA2 accounted for 19.44% of the variation. Mann-Whitney U Test (α=0.05) indicated lack of significanct difference in morphological characteristics between Sondu-Miriu and Nyando, but significant intraspecific morphological difference between all the other pairs of rivers. All external parameters except 4 showed positive relationship with standard length (SL). Our results suggests presence of intra-specific morphometric variation between the four populations and corroborate findings based on mitochondrial DNA analysis. Conclusion: Morphological characterization reveal intra specific variation in Barbus altianalis in the Lake Victoria catchment and suggests the existence of river specific morphs, a possible adaptation to changes in the catchment. This could also provide evidence of long term existence of migratory as well as riverine sedentary populations of the species within Lake Victoria basin (LVB).
... It is also possible that the fish had adapted phenotypically to a high-flow environment, allowing them to exploit the area at all flows. Fulton et al. (2013) found that fin aspect ratio of a damsel fish was higher and that they swam faster on wave-exposed reefs compared to on sheltered reefs. The tidal flow could also have acted as an environmental filter, filtering away smaller, more vulnerable species. ...
Tidal currents are important features in reef environments with high tidal range Such current-influenced areas can be attractive for fish due to transport of nutrients and foo items. Biological sampling, however, is difficult in these environments and it remains poorl understood to what degree strong currents actually shape tropical and subtropical reef fish communities We used remote underwater video to investigate effects of flow velocity on fish acros the tidal cycle at a rocky reef in southern Mozambique. Fish were recorded during flow velocitie ranging from 0 to 1.44 m s-1. Current flow velocity had no significant effect on the benthic fis assemblage, while increasing flow velocity had a negative effect on pelagic fish abundance an influenced trophic group composition. Limits for tolerated flow velocity on the pelagic assemblag were species-specific, with the highest resistance for larger predatory fish using subcarangifor swimming. Flow velocity had significant positive effects on size of Caranx spp., showing tha smaller individuals had lower tolerance to flow than larger conspecifics. Planktivorous pomacentrid and monodactylids were very abundant in flows up to 0.5 m s?1, suggesting that the are functions as an important foraging ground for planktivorous fish up to this flow velocity, whil abundance of barracudas Sphyraena spp. was higher in moderate currents compared to slac water. For the benthic assemblage, benthic structures seemed to provide sufficient flow refuge fo fish throughout the tidal cycle, highlighting the importance of structural complexity for benthi fish in this environment. Fish assemblages on reefs subjected to strong tidal currents might therefor be sensitive to habitat modifications. The ecological importance of tidal currents should b considered in marine management.
