Detection and characterisation of the biopollutant Xenostrobus securis (Lamarck 1819) Asturian population from DNA Barcoding and eBarcoding

DNA efficiently contributes to detect and understand marine invasions. In 2014 the potential biological pollutant pygmy mussel (Xenostrobus securis)was observed for the first time in the Avilés estuary (Asturias, Bay of Biscay). The goal of this study was to assess the stage of invasion, based on demographic and genetic (DNA Barcoding) characteristics, and to develop a molecular tool for surveying the species in environmental DNA. A total of 130 individuals were analysed for the DNA Barcode cytochrome oxidase I gene in order to determine genetic diversity, population structure, expansion trends, and to inferring introduction hits. Reproductionwas evidenced by bimodal size distributions of 1597 mussels. High population genetic variation and genetically distinct clades might suggest multiple introductions from several source populations. Finally, species-specific primers were developed within the DNA barcode for PCR amplification from water samples in order to enabling rapid detection of the species in initial expansion stages

Accounting for kin sampling reveals genetic connectivity in Tasmanian and New Zealand school sharks, Galeorhinus galeus

Ecology and Evolution published by John Wiley & Sons Ltd. Fishing represents a major problem for conservation of chondrichthyans, with a quarter of all species being overexploited. School sharks, Galeorhinus galeus, are targeted by commercial fisheries in Australia and New Zealand. The Australian stock has been depleted to below 20% of its virgin biomass, and the species is recorded as Conservation Dependent within Australia. Individuals are known to move between both countries, but it is disputed whether the stocks are reproductively linked. Accurate and unbiased determination of stock and population connectivity is crucial to inform effective management. In this study, we assess the genetic composition and population connectivity between Australian and New Zealand school sharks using genome-wide SNPs, while accounting for non-random kin sampling. Between 2009 and 2013, 88 neonate and juvenile individuals from Tasmanian and New Zealand nurseries were collected and genotyped. Neutral loci were analyzed to detect fine-scale signals of reproductive connectivity. Seven full-sibling groups were identified and removed for unbiased analysis. Based on 6,587 neutral SNPs, pairwise genetic differentiation from Tasmanian and New Zealand neonates was non-significant (F ST = 0.0003, CI₉₅ = [−0.0002, 0.0009], p = 0.1163; D est  = 0.0006 ± 0.0002). This pattern was supported by clustering results. In conclusion, we show a significant effect of non-random sampling of kin and identify fine-scale reproductive connectivity between Australian and New Zealand school sharks

Papua New Guinea: a potential refuge for threatened Indo–Pacific river sharks and sawfishes

The conservation of threatened elasmobranchs in tropical regions is challenging due to high local reliance on aquatic and marine resources. Due primarily to fishing pressure, river sharks (Glyphis) and sawfishes (Pristidae) have experienced large population declines in the Indo-Pacific. Papua New Guinea (PNG) may offer a refuge for these species, as human population density is low, and river shark and sawfish populations are thought to persist. However, few data are available on these species in PNG, and risk posed by small-scale fishers is poorly understood. This study observed elasmobranch catches in small-scale fisheries in riverine and coastal environments in the East Sepik (northern region), Gulf, and Western Provinces (southern region) of PNG. Surveys were conducted over a period of weeks to months in each region, during the dry season across seven field trips from 2017 to 2020. We observed a total of 783 elasmobranchs encompassing 38 species from 10 families. River sharks made up 29.4% of observations in the southern region, while sawfishes made up 14.8 and 20.3% in the northern and southern regions, respectively. River sharks were commonly caught by small-scale fishers in lower riverine environments in southern PNG, while sawfishes were generally less common and mainly observed through dried rostra. The primary threat to river shark and sawfish populations is their capture by small-scale fishers targeting teleosts for swim bladder. Persisting populations of river sharks and sawfishes indicate that PNG is the second known nation with viable populations of multiple species in the Indo-Pacific. However, populations are declining or at high risk of decline, and fisheries management and conservation are required to realize the potential of PNG as a long-term refuge

Accounting for kin sampling reveals genetic connectivity in Tasmanian and New Zealand school sharks, Galeorhinus galeus

Ecology and Evolution published by John Wiley & Sons Ltd. Fishing represents a major problem for conservation of chondrichthyans, with a quarter of all species being overexploited. School sharks, Galeorhinus galeus, are targeted by commercial fisheries in Australia and New Zealand. The Australian stock has been depleted to below 20% of its virgin biomass, and the species is recorded as Conservation Dependent within Australia. Individuals are known to move between both countries, but it is disputed whether the stocks are reproductively linked. Accurate and unbiased determination of stock and population connectivity is crucial to inform effective management. In this study, we assess the genetic composition and population connectivity between Australian and New Zealand school sharks using genome-wide SNPs, while accounting for non-random kin sampling. Between 2009 and 2013, 88 neonate and juvenile individuals from Tasmanian and New Zealand nurseries were collected and genotyped. Neutral loci were analyzed to detect fine-scale signals of reproductive connectivity. Seven full-sibling groups were identified and removed for unbiased analysis. Based on 6,587 neutral SNPs, pairwise genetic differentiation from Tasmanian and New Zealand neonates was non-significant (F ST = 0.0003, CI₉₅ = [−0.0002, 0.0009], p = 0.1163; D est  = 0.0006 ± 0.0002). This pattern was supported by clustering results. In conclusion, we show a significant effect of non-random sampling of kin and identify fine-scale reproductive connectivity between Australian and New Zealand school sharks

Integrating complementary methods to improve diet analysis in fishery‐targeted species

Developing efficient, reliable, cost‐effective ways to identify diet is required to understand trophic ecology in complex ecosystems and improve food web models. A combination of techniques, each varying in their ability to provide robust, spatially and temporally explicit information can be applied to clarify diet data for ecological research. This study applied an integrative analysis of a fishery‐targeted species group—Plectropomus spp. in the central Great Barrier Reef, Australia, by comparing three diet‐identification approaches. Visual stomach content analysis provided poor identification with ~14% of stomachs sampled resulting in identification to family or lower. A molecular approach was successful with prey from ~80% of stomachs identified to genus or species, often with several unique prey in a stomach. Stable isotope mixing models utilizing experimentally derived assimilation data, identified similar prey as the molecular technique but at broader temporal scales, particularly when prior diet information was incorporated. Overall, Caesionidae and Pomacentridae were the most abundant prey families (>50% prey contribution) for all Plectropomus spp., highlighting the importance of planktivorous prey. Less abundant prey categories differed among species/color phases indicating possible niche segregation. This study is one of the first to demonstrate the extent of taxonomic resolution provided by molecular techniques, and, like other studies, illustrates that temporal investigations of dietary patterns are more accessible in combination with stable isotopes. The consumption of mainly planktivorous prey within this species group has important implications within coral reef food webs and provides cautionary information regarding the effects that changing resources could have in reef ecosystems

Integrating complementary methods to improve diet analysis in fishery-targeted species

Developing efficient, reliable, cost-effective ways to identify diet is required to understand trophic ecology in complex ecosystems and improve food web models. A combination of techniques, each varying in their ability to provide robust, spatially and temporally explicit information can be applied to clarify diet data for ecological research. This study applied an integrative analysis of a fishery-targeted species group—Plectropomus spp. in the central Great Barrier Reef, Australia, by comparing three diet-identification approaches. Visual stomach content analysis provided poor identification with ~14% of stomachs sampled resulting in identification to family or lower. A molecular approach was successful with prey from ~80% of stomachs identified to genus or species, often with several unique prey in a stomach. Stable isotope mixing models utilizing experimentally derived assimilation data, identified similar prey as the molecular technique but at broader temporal scales, particularly when prior diet information was incorporated. Overall, Caesionidae and Pomacentridae were the most abundant prey families (\u3e50% prey contribution) for all Plectropomus spp., highlighting the importance of planktivorous prey. Less abundant prey categories differed among species/color phases indicating possible niche segregation. This study is one of the first to demonstrate the extent of taxonomic resolution provided by molecular techniques, and, like other studies, illustrates that temporal investigations of dietary patterns are more accessible in combination with stable isotopes. The consumption of mainly planktivorous prey within this species group has important implications within coral reef food webs and provides cautionary information regarding the effects that changing resources could have in reef ecosystems

Reviewing the Genetic Evidence for Sex-Biased Dispersal In Elasmobranchs

Dispersal in many organisms is asymmetric by sex, a pattern that is often identified through the use of genetic tools. Sex-biased dispersal (SBD) is thought to derive from the varying fitness needs of females and males, as mediated by local ecology and life history. SBD is frequently reported in elasmobranchs (sharks, rays), long-lived fishes that often give live birth to well-developed young and are capable of dispersing thousands of kilometers. While many studies point to male-biased dispersal (MBD) being common, results are highly variable and no clear trends have yet emerged, even as the number of case studies has grown over the past decade. Here, we evaluated patterns in sampling regime, molecular marker type, and analysis method for every genetic structure study published to date that allowed for an assessment of SBD in elasmobranchs. We find that while some degree of MBD in elasmobranchs is likely, factors such as the pooling of life stages during data analysis and the inherent characteristics of different marker types, may lead to an overemphasis on male dispersal and potentially obscure genetic signals of female and male reproductive philopatry. The role of life history and biogeography in determining patterns of SBD in sharks and rays is also discussed

Dryad_T2

Stable isotope data from sampled coral trou

How does marker choice affect your diet analysis: comparing genetic markers and digestion levels for diet metabarcoding of tropical-reef piscivores

Tropical reefs are highly diverse ecosystems, and reliable biomonitoring, through diet metabarcoding, is needed to understand present and future trophic relationships in this changing habitat. Several studies have assessed the reliability and effectiveness of single molecular markers; however, a cross-marker validation has rarely been performed. This study identified crucial properties for 12S rDNA, 16S rDNA and COI metabarcoding in tropical-reef piscivores (Plectropomus spp.). In addition, three new versatile primer sets for 16S were designed in silico for metabarcoding of reef fish. Results showed that COI was overall better at recovering true diversity because of a well-supported database. Second, optimal 16S amplicon sizes ranged between 160 and 440 base pairs for full diversity recovery, with increased species detection for the 270-base pairs region. Finally, blocking of predator-specific COI sequences was not equally effective in all host species, potentially introducing bias when diet compositions are directly compared. In conclusion, this novel study showed that marker success for prey identification is highly dependent on the reference database, taxonomic scope, DNA quality, amplicon length and sequencing platform. Results suggest that COI, complemented with 16S, yields the best outcome for diet metabarcoding in reef piscivores. Findings in this paper are relevant to other piscivores and other metabarcoding applications

How does marker choice affect your diet analysis: comparing genetic markers and digestion levels for diet metabarcoding of tropical-reef piscivores

© 2019 CSIRO. Tropical reefs are highly diverse ecosystems, and reliable biomonitoring, through diet metabarcoding, is needed to understand present and future trophic relationships in this changing habitat. Several studies have assessed the reliability and effectiveness of single molecular markers; however, a cross-marker validation has rarely been performed. This study identified crucial properties for 12S rDNA, 16S rDNA and COI metabarcoding in tropical-reef piscivores (Plectropomus spp.). In addition, three new versatile primer sets for 16S were designed in silico for metabarcoding of reef fish. Results showed that COI was overall better at recovering true diversity because of a well-supported database. Second, optimal 16S amplicon sizes ranged between 160 and 440 base pairs for full diversity recovery, with increased species detection for the 270-base pairs region. Finally, blocking of predator-specific COI sequences was not equally effective in all host species, potentially introducing bias when diet compositions are directly compared. In conclusion, this novel study showed that marker success for prey identification is highly dependent on the reference database, taxonomic scope, DNA quality, amplicon length and sequencing platform. Results suggest that COI, complemented with 16S, yields the best outcome for diet metabarcoding in reef piscivores. Findings in this paper are relevant to other piscivores and other metabarcoding applications.status: publishe