Tane H. Sinclair-Taylor

Fish mucous cocoons: the 'mosquito nets' of the sea

Mucus performs numerous protective functions in vertebrates, and in fishes may defend them against harmful organisms, although often the evidence is contradictory. The function of the mucous cocoons that many parrotfishes and wrasses sleep in, while long used as a classical example of antipredator behaviour, remains unresolved. Ectoparasitic gnathiid isopods (Gnathiidae), which feed on the blood of fish, are removed by cleaner fish during the day; however, it is unclear how parrotfish and wrasse avoid gnathiid attacks at night. To test the novel hypothesis that mucous cocoons protect against gnathiids, we exposed the coral reef parrotfish Chlorurus sordidus (Scaridae) with and without cocoons to gnathiids overnight and measured the energetic content of cocoons. Fish without mucous cocoons were attacked more by gnathiids than fish with cocoons. The energetic content of mucous cocoons was estimated as 2.5 per cent of the fishs daily energy budget fish. Therefore, mucous cocoons protected against attacks by gnathiids, acting like mosquito nets in humans, a function of cocoons and an efficient physiological adaptation for preventing parasite infestation that is not used by any other animal.

Larval fish dispersal in a coral-reef seascape

Larval dispersal is a critical yet enigmatic process in the persistence and productivity of marine metapopulations. Empirical data on larval dispersal remain scarce, hindering the use of spatial management tools in efforts to sustain ocean biodiversity and fisheries. Here we document dispersal among subpopulations of clownfish (Amphiprion percula) and butterflyfish (Chaetodon vagabundus) from eight sites across a large seascape (10,000 km2) in Papua New Guinea across 2 years. Dispersal of clownfish was consistent between years, with mean observed dispersal distances of 15 km and 10 km in 2009 and 2011, respectively. A Laplacian statistical distribution (the dispersal kernel) predicted a mean dispersal distance of 13–19 km, with 90% of settlement occurring within 31–43 km. Mean dispersal distances were considerably greater (43–64 km) for butterflyfish, with kernels declining only gradually from spawning locations. We demonstrate that dispersal can be measured on spatial scales sufficient to inform the design of and test the performance of marine reserve networks.

Hybridisation among groupers (genus Cephalopholis) at the eastern Indian Ocean suture zone: taxonomic and evolutionary implications

Hybridisation is a significant evolutionary process that until recently was considered rare in the marine environment. A suture zone in the eastern Indian Ocean is home to numerous hybridising sister species, providing an ideal opportunity to determine how hybridisation affects speciation and biodiversity in coral reef fishes. At this location, hybridisation between two grouper (Epinephelidae) species: Cephalopholis urodeta (Pacific Ocean) and C. nigripinnis (Indian Ocean) was investigated to determine the genetic basis of hybridisation and to compare the ecology and life history of hybrids and their parent species. This approach aimed to provide insights into the taxonomic and evolutionary consequences of hybridisation. Despite clear phenotypic differences, multiple molecular markers revealed hybrids, and their parent species were genetically homogenous within and (thousands of kilometres) outside of the hybrid zone. Hybrids were at least as fit as their parent species (in terms of growth, reproduction, and abundance) and were observed in a broad range of intermediate phenotypes. The two species appear to be interbreeding at Christmas Island due to inherent biological and ecological compatibilities, and the lack of genetic structure may be explained by three potential scenarios: (1) hybridisation and introgression; (2) discordance between morphology and genetics; and (3) incomplete lineage sorting. Further molecular analyses are necessary to discriminate these scenarios. Regardless of which applies, C. urodeta and C. nigripinnis are unlikely to evolve in reproductive isolation as they cohabit where they are common (Christmas Island) and will source congeneric mates where they are rare (Cocos Keeling Islands). Our results add to the growing body of evidence that hybridisation among coral reef fishes is a dynamic evolutionary factor.

Restricted grouper reproductive migrations support community-based management

Conservation commonly requires trade-offs between social and ecological goals. For tropical small-scale fisheries, spatial scales of socially appropriate management are generally small—the median no-take locally managed marine area (LMMA) area throughout the Pacific is less than 1 km2. This is of particular concern for large coral reef fishes, such as many species of grouper, which migrate to aggregations to spawn. Current data suggest that the catchment areas (i.e. total area from which individuals are drawn) of such aggregations are at spatial scales that preclude effective community-based management with no-take LMMAs. We used acoustic telemetry and tag-returns to examine reproductive migrations and catchment areas of the grouper Epinephelus fuscoguttatus at a spawning aggregation in Papua New Guinea. Protection of the resultant catchment area of approximately 16 km2 using a no-take LMMA is socially untenable here and throughout much of the Pacific region. However, we found that spawning migrations were skewed towards shorter distances. Consequently, expanding the current 0.2 km2 no-take LMMA to 1–2 km2 would protect approximately 30–50% of the spawning population throughout the non-spawning season. Contrasting with current knowledge, our results demonstrate that species with moderate reproductive migrations can be managed at scales congruous with spatially restricted management tools.

Assessing the utility of eDNA as a tool to survey reef-fish communities in the Red Sea

Relatively small volumes of water may contain sufficient environmental DNA (eDNA) to detect target aquatic organisms via genetic sequencing. We therefore assessed the utility of eDNA to document the diversity of coral reef fishes in the central Red Sea. DNA from seawater samples was extracted, amplified using fish-specific 16S mitochondrial DNA primers, and sequenced using a metabarcoding workflow. DNA sequences were assigned to taxa using available genetic repositories or custom genetic databases generated from reference fishes. Our approach revealed a diversity of conspicuous, cryptobenthic, and commercially relevant reef fish at the genus level, with select genera in the family Labridae over-represented. Our approach, however, failed to capture a significant fraction of the fish fauna known to inhabit the Red Sea, which we attribute to limited spatial sampling, amplification stochasticity, and an apparent lack of sequencing depth. Given an increase in fish species descriptions, completeness of taxonomic checklists, and improvement in species-level assignment with custom genetic databases as shown here, we suggest that the Red Sea region may be ideal for further testing of the eDNA approach.

Spatial patterns of cryptobenthic coral-reef fishes in the Red Sea

AbstractSurveys to document coral-reef fish assemblages are often limited to visually conspicuous species, thus excluding a significant proportion of the biodiversity. Through standardized collections of cryptobenthic reef fishes in the central and southern Red Sea, a total of 238 species and operational taxonomic units (OTUs) from 35 families were collected. Abundance and species richness increased by 60 and 30%, respectively, from north to south, and fish community composition differed between the two regions and with proximity to shore in the central region. Models suggest regional influences in fish communities, with latitudinal patterns influenced by key coral groups (Acropora, Pocilloporidae) and variation in environmental parameters (chlorophyll a, sea surface temperature, salinity). This study illustrates the limited taxonomic resolution in this group and in this region, and the need to expand baseline data for this under-studied assemblage. To assist in advancing this initiative, we have produced a catalogue of specimens, archived photographs, and established a DNA sequence library based on cytochrome-c oxidase subunit-I barcodes for all OTUs.

Diagnostic nuclear markers for hybrid Nemos in Kimbe Bay, PNG-Amphiprion chrysopterus x Amphiprion sandaracinos hybrids

Hybridization among clownfish (genus Amphiprion) is common in the aquarium trade and has also been reported in natural environments. Putative hybrids between Amphiprion chrysopterus and Amphiprion sandaracinos have been identified in a previous genetic study. However, convenient diagnostic tools for hybrid detection for this case are still missing. During the present study, several potential nuclear markers were tested on both parental species and their hybrids collected from Kimbe Bay, Papua New Guinea. Two diagnostic nuclear markers were found that can confidently discriminate the parent species and their hybrids. A haploweb analysis based on those two diagnostic nuclear markers indicated that one backcrossed hybrid was misclassified as one of the purebred parent species. Identification results from these two diagnostic markers were supported by results from microsatellites, mitochondrial gene markers, and morphological traits analysis.

Ice ages and butterflyfishes: Phylogenomics elucidates the ecological and evolutionary history of reef fishes in an endemism hotspot

Abstract For tropical marine species, hotspots of endemism occur in peripheral areas furthest from the center of diversity, but the evolutionary processes that lead to their origin remain elusive. We test several hypotheses related to the evolution of peripheral endemics by sequencing ultraconserved element (UCE) loci to produce a genome‐scale phylogeny of 47 butterflyfish species (family Chaetodontidae) that includes all shallow water butterflyfish from the coastal waters of the Arabian Peninsula (i.e., Red Sea to Arabian Gulf) and their close relatives. Bayesian tree building methods produced a well‐resolved phylogeny that elucidated the origins of butterflyfishes in this hotspots of endemism. We show that UCEs, often used to resolve deep evolutionary relationships, represent an important tool to assess the mechanisms underlying recently diverged taxa. Our analyses indicate that unique environmental conditions in the coastal waters of the Arabian Peninsula probably contributed to the formation of endemic butterflyfishes. Older endemic species are also associated with narrow versus broad depth ranges, suggesting that adaptation to deeper coral reefs in this region occurred only recently (<1.75 Ma). Even though deep reef environments were drastically reduced during the extreme low sea level stands of glacial ages, shallow reefs persisted, and as such there was no evidence supporting mass extirpation of fauna in this region.

Breakdown in assortative mating leads to hybrid swarm in pygmy angelfishes

Hybridisation is widespread in coral reef taxa (Richards and Hobbs 2015); however, the processes leading to interbreeding are poorly understood. A breakdown in assortative mating is commonly implicated in hybridisation of reef fishes, and although mixed-species groups are often recorded, interbreeding is rarely observed (Hobbs and Salmond 2008). Interbreeding could occur unintentionally (accidental hybridisation), or through the deliberate actions of one (sneak spawning) or both parent species (disassortative mate choice). Molecular studies reveal a history of hybridisation among pygmy angelfishes (DiBattista et al. 2016). These fishes form discrete harems comprised of one large male and multiple smaller females. During field trips to Christmas Island (Indian Ocean) in September 2015, April 2016 and June 2017, we observed interbreeding between Centropyge flavissima, C. eibli and C. vrolikii. Wevisited 19mixed-species haremsandobserved themale courted and then sequentially spawned with each of the females in his harem (Fig. 1a; electronic supplementary material, ESM). Across the haremsweobservedeverymating combination involvingmales and females of each species and their hybrids (Fig. 1b: ESM). The mixed-species harems we observed have been stable (same location and harem members) for 1–6 yrs. Monitoring of six harems revealed interbreeding occurred on consecutive days and across multiple years. We conclude that members of the mixed-species harems repeatedly choose to interbreed with other species. Introgression identified in the genes of these three species (DiBattista et al. 2016) can be explained by the ongoing breakdown in assortative mating caused by disassortative mate choice. References