Diversification rates within four conspicuous coral reef fish families (Labridae, Chaetodontidae, Pomacentridae and Apogonidae) were estimated using Bayesian inference. Lineage through time plots ...revealed a possible late Eocene/early Oligocene cryptic extinction event coinciding with the collapse of the ancestral Tethyan/Arabian hotspot. Rates of diversification analysis revealed elevated cladogenesis in all families in the Oligocene/Miocene. Throughout the Miocene, lineages with a high percentage of coral reef–associated taxa display significantly higher net diversification rates than expected. The development of a complex mosaic of reef habitats in the Indo‐Australian Archipelago (IAA) during the Oligocene/Miocene appears to have been a significant driver of cladogenesis. Patterns of diversification suggest that coral reefs acted as a refuge from high extinction, as reef taxa are able to sustain diversification at high extinction rates. The IAA appears to support both cladogenesis and survival in associated lineages, laying the foundation for the recent IAA marine biodiversity hotspot.
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•Monophyly of New World Halichoeres including Oxyjulis and Saggitalarva.•Atlantic Ocean is the ancestral area.•Five of 25 speciation events occurred across Isthmus of ...Panama.•Trans-Isthmian speciation events range in age from 20.8 to 4.8 Ma.•Three speciation events across the Orinoco/Amazon outflow.
The New World Halichoeres comprises about 30 small to medium sized wrasse species that are prominent members of reef communities throughout the tropical Western Atlantic and Eastern Pacific. We conducted a phylogenetic analysis of this group and related lineages using new and previously published sequence data. We estimated divergence times, evaluated the monophyly of this group, their relationship to other labrids, as well as the time-course and geography of speciation. These analyses show that all members of New World Halichoeres form a monophyletic group that includes Oxyjulis and Sagittalarva. New World Halichoeres is one of numerous labrid groups that appear to have radiated rapidly about 32 Ma and form a large polytomy within the julidine wrasses. We reconstruct the tropical Western Atlantic to be the ancestral area of New World Halichoeres, with four invasions of the Eastern Pacific and one reversal from East Pacific to Western Atlantic. These five speciation events were spread across the history of the group, with none corresponding closely to the time of the closure of the Isthmus of Panama. Three speciation events within the Atlantic occurred across the Orinoco-Amazon outflow and within the Pacific, five involve splits between lineages that occupy coastal reef systems and offshore islands. Of eight sister species pairs, seven show complete allopatry and one is fully sympatric.
Fishes that feed from live corals (corallivores) are a conspicuous component of healthy coral reef environments. However, knowledge of the occurrence and ecological significance of this feeding mode ...is fragmentary. Historically, very few fish were considered capable of feeding from live coral, and those few that did were considered ecologically insignificant. More recently, the role of corallivores has been re‐evaluated; published records document 128 corallivorous fish species from 11 different families, with 69 of these belonging to the family Chaetodontidae. Other families, including the Labridae, Tetraodontidae, Balistidae, Monacanthidae, Pomacentridae and Scaridae, all have between seven and ten coral‐feeding species. One‐third of coral‐feeding fishes feed almost exclusively on corals, with more than 80% of their diet based on coral. Corallivorous fish show distinct prey preferences and consume only a small subset of available corals, usually the genera Acropora, Pocillopora and Porites. This selective predation by corallivores can limit abundance and distribution of preferred corals. Chronic predation by corallivores may also exacerbate effects of coral disturbance (e.g. climate‐induced coral bleaching), impeding reef recovery and causing further coral loss. Conversely, the cover of preferred corals can be a primary determinant of corallivore abundance and physiological condition. Owing to this close association, obligate corallivores invariably decline in response to loss of coral cover. Increased knowledge of the number of corallivores and their diets suggest that this feeding mode is more important to coral reef food webs than traditionally thought.
Diver-based Underwater Visual Censuses (UVCs), particularly transect-based surveys, are key tools in the study of coral reef fish ecology. These techniques, however, have inherent problems that make ...it difficult to collect accurate numerical data. One of these problems is the diver effect (defined as the reaction of fish to a diver). Although widely recognised, its effects have yet to be quantified and the extent of taxonomic variation remains to be determined. We therefore examined relative diver effects on a reef fish assemblage on the Great Barrier Reef. Using common UVC methods, the recorded abundance of seven reef fish groups were significantly affected by the ongoing presence of SCUBA divers. Overall, the diver effect resulted in a 52% decrease in the mean number of individuals recorded, with declines of up to 70% in individual families. Although the diver effect appears to be a significant problem, UVCs remain a useful approach for quantifying spatial and temporal variation in relative fish abundances, especially if using methods that minimise the exposure of fishes to divers. Fixed distance transects using tapes or lines deployed by a second diver (or GPS-calibrated timed swims) would appear to maximise fish counts and minimise diver effects.
Parrotfish play important ecological roles in coral reef and seagrass communities across the globe. Their dentition is a fascinating object of study from an anatomical, functional and evolutionary ...point of view. Several species maintained non‐interlocked dentition and browse on fleshy algae, while others evolved a characteristic beak‐like structure made of a mass of coalesced teeth that they use to scrape or excavate food off hard limestone substrates. While parrotfish use their highly specialized marginal teeth to procure their food, they can also develop a series of large fangs that protrude from the upper jaw, and more rarely from the lower jaw. These peculiar fangs do not participate in the marginal dentition and their function remains unclear. Here we describe the morphology of these fangs and their developmental relationship to the rest of the oral dentition in the marbled parrotfish (Leptoscarus vaigiensis), the star‐eye parrotfish (Calotomus carolinus), and the palenose parrotfish (Scarus psittacus). Through microtomographic and histological analyses, we show that some of these fangs display loosely folded plicidentine along their bases, a feature that has never been reported in parrotfish. Plicidentine is absent from the marginal teeth and is therefore exclusive to the fangs. Parrotfish fangs develop a particular type of simplexodont plicidentine with a pulpal infilling of alveolar bone at later stages of dental ontogeny. The occurrence of plicidentine and evidence of extensive tooth wear, and even breakage, lead us to conclude that the fangs undergo frequent mechanical stress, despite not being used to acquire food. This strong mechanical stress undergone by fangs could be linked either to forced contact with congeners or with the limestone substrate during feeding. Finally, we hypothesize that the presence of plicidentine in parrotfish is not derived from a labrid ancestor, but is probably a recently evolved trait in some parrotfish taxa, which may even have evolved convergently within this subfamily.
Some parrotfish display fangs that exhibit a particular type of simplexodont plicidentine with a pulpal infilling of alveolar bone at later stages of dental ontogeny. The extensive tooth wear and the breakage of certain fangs lead us to conclude that they undergo frequent mechanical stress, although they are not used to acquire food. This strong mechanical stress undergone by fangs could be linked either to forced contact with congeners or with the limestone substrate during feeding. We hypothesize that the presence of plicidentine in parrotfish is not derived from a labrid ancestor, but is probably a recently evolved trait in some parrotfish taxa, which may even have evolved convergently within this subfamily.
One of the expected effects of global change is increased variability in the abundance and distribution of living organisms, but information at the appropriate temporal and geographical scales is ...often lacking to observe these patterns. Here we use local knowledge as an alternative information source to study some emerging changes in Mediterranean fish diversity. A pilot study of thirty-two fishermen was conducted in 2009 from four Mediterranean locations along a south-north gradient. Semi-quantitative survey information on changes in species abundance was recorded by year and suggests that 59 fish species belonging to 35 families have experienced changes in their abundance. We distinguished species that increased from species that decreased or fluctuated. Multivariate analysis revealed significant differences between these three groups of species, as well as significant variation between the study locations. A trend for thermophilic taxa to increase was recorded at all the study locations. The Carangidae and the Sphyraenidae families typically were found to increase over time, while Scombridae and Clupeidae were generally identified as decreasing and Fistularidae and Scaridae appeared to fluctuate in abundance. Our initial findings strongly suggest the northward expansion of termophilic species whose occurrence in the northern Mediterranean has only been noted previously by occasional records in the scientific literature.
DNA barcoding enhances the prospects for species-level identifications globally using a standardized and authenticated DNA-based approach. Reference libraries comprising validated DNA barcodes (COI) ...constitute robust datasets for testing query sequences, providing considerable utility to identify marine fish and other organisms. Here we test the feasibility of using DNA barcoding to assign species to tissue samples from fish collected in the central Mediterranean Sea, a major contributor to the European marine ichthyofaunal diversity.
A dataset of 1278 DNA barcodes, representing 218 marine fish species, was used to test the utility of DNA barcodes to assign species from query sequences. We tested query sequences against 1) a reference library of ranked DNA barcodes from the neighbouring North East Atlantic, and 2) the public databases BOLD and GenBank. In the first case, a reference library comprising DNA barcodes with reliability grades for 146 fish species was used as diagnostic dataset to screen 486 query DNA sequences from fish specimens collected in the central basin of the Mediterranean Sea. Of all query sequences suitable for comparisons 98% were unambiguously confirmed through complete match with reference DNA barcodes. In the second case, it was possible to assign species to 83% (BOLD-IDS) and 72% (GenBank) of the sequences from the Mediterranean. Relatively high intraspecific genetic distances were found in 7 species (2.2%-18.74%), most of them of high commercial relevance, suggesting possible cryptic species.
We emphasize the discriminatory power of COI barcodes and their application to cases requiring species level resolution starting from query sequences. Results highlight the value of public reference libraries of reliability grade-annotated DNA barcodes, to identify species from different geographical origins. The ability to assign species with high precision from DNA samples of disparate quality and origin has major utility in several fields, from fisheries and conservation programs to control of fish products authenticity.
A core eco‐evolutionary aim is to better understand the factors driving the diversification of functions in ecosystems. Using phylogenetic, trophic, and functional information, we tested whether ...trophic habits (i.e. feeding guilds) affect lineage and functional diversification in two major radiations of reef fishes. Our results from wrasses (Labridae) and damselfishes (Pomacentridae) do not fully support the ‘dead‐end’ hypothesis that specialisation leads to reduce speciation rates because the tempo of lineage diversification did not substantially vary among guilds in both fish families. Our findings also demonstrate a tight relationship between trophic habits and functional roles held by fish in reef ecosystems, which is not associated with a variation in the tempo of functional diversification among guilds. By illustrating the pivotal importance of the generalist feeding strategy during the evolutionary history of reef fishes, our study emphasises the role of this feeding guild as a reservoir for future diversity.
The ectoparasitic salmon louse (Lepeophtheirus salmonis) is a serious problem in salmon aquaculture (Salmo salar and rainbow trout Oncorhynchus mykiss). These parasitic copepods attach to fish and ...feed on their mucus and tissue, reducing feed conversion efficiency and causing sores, thereby increasing farming costs and reducing the value of the product. Many non-pharmaceutical approaches to controlling sea lice are being developed. One such is to use cleaner fish (in this case, wrasse) in co-culture with salmon to remove salmon lice. The objectives of this study were to assess the efficiency of wrasse as delousing agents and to compare the relative efficiency of wild vs. cultured individuals. Wrasse were extremely efficient in delousing salmon. At a ratio of 5% wrasse to salmon, the mean number of mobile lice life history stages on salmon was maintained at a level of less than one per fish. Intensively cultured wrasse were as efficient as wild wrasse at removing lice. The presence of wrasse did not affect the growth of salmon. This study demonstrates that wrasse, including intensively cultured ballan wrasse naïve of either salmon or salmon lice, can be introduced into sea cages on salmon farms and keep salmon lice loads at very low levels.
•The efficiency of wrasse as cleaner fish for delousing salmon was investigated•Both intensively cultured and wild wrasse were effective delousers•At a ratio of 5% wrasse:salmon, wrasse kept lice loads at very low levels
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