Monitoring communities of fish is important for the management and sustainability of fisheries and marine ecosystems. Baited remote underwater video systems (BRUVs) are among the most effective ...nondestructive techniques for sampling bony fishes and elasmobranchs (sharks, rays, and skates). However, BRUVs sample visually conspicuous biota; hence, some taxa are undersampled or not recorded at all. We compared the diversity of fishes characterized using BRUVs with diversity detected via environmental DNA (eDNA) metabarcoding. We sampled seawater and captured BRUVs imagery at 48 locales that included reef and seagrass beds inside and outside a marine reserve (Jurien Bay in Western Australia). Eighty‐two fish genera from 13 orders were detected, and the community of fishes described using eDNA and BRUVs combined yielded >30% more generic richness than when either method was used alone. Rather than detecting a homogenous genetic signature, the eDNA assemblages mirrored the BRUVs’ spatial explicitness; differentiation of taxa between seagrass and reef was clear despite the relatively small geographical scale of the study site (∼35 km2). Taxa that were not sampled by one approach, due to limitations and biases intrinsic to the method, were often detected with the other. Therefore, using BRUVs and eDNA in concert provides a more holistic view of vertebrate marine communities across habitats. Both methods are noninvasive, which enhances their potential for widespread implementation in the surveillance of marine ecosystems.
Uso Combinado del Metacódigo de Barras de eDNA y Videograbaciones para la Evaluación de la Biodiversidad de Peces
Resumen
El monitoreo de comunidades de peces es importante para el manejo y sustentabilidad de las pesquerías y los ecosistemas marinos. Los sistemas remotos de video submarino con carnada (SRVSC) están entre las técnicas no destructivas más efectivas para el muestreo de peces óseos y elasmobranquios (tiburones, mantarrayas y rayas). Sin embargo, los SRVSC muestrean biota que es conspicua visiblemente; entonces, algunos taxones están mal muestreados o simplemente no se registran en los muestreos. Comparamos la diversidad de peces caracterizada usando SRVSC con la diversidad detectada por medio del metacódigo de barras de ADN ambiental (eDNA, en inglés). Muestreamos el agua de mar y capturamos imágenes con SRVSC en 48 localidades que incluyeron el arrecife y los pastos marinos dentro y fuera de una reserva marina (Bahía Jurien en el oeste de Australia). Se detectaron 83 géneros de peces de 13 órdenes, y la comunidad de peces descrita con el uso combinado del eDNA y el SRVSC produjo >30% riqueza más genérica que cuando cualquiera de los dos métodos se usó individualmente. En lugar de detectar una firma genética homogénea, los ensamblados de eDNA reflejaron la claridad espacial del SRVSC; la diferenciación de los taxones entre los pastos marinos y el arrecife fue clara a pesar la escala geográfica relativamente pequeña del sitio de estudio (∼35 km2). Los taxones que no fueron muestreados por uno de los métodos, por causa de limitaciones y sesgos intrínsecos al método, casi siempre fueron detectados usando el otro método. Por lo tanto, el uso de SRVSC y el eDNA en concreto proporciona una visión más holística de las comunidades marinas de vertebrados en todos los hábitats. Ambos métodos son no invasivos, lo que incrementa su potencial para ser una implementación de uso amplio en la vigilancia de los ecosistemas marinos.
Article impact statement: Use of video and environmental genomics in conservation will greatly improve capacity to effectively monitor fish biodiversity.
Selection is a central process in nature. Although our understanding of the strength and form of selection has increased, a general understanding of the temporal dynamics of selection in nature is ...lacking. Here, we assembled a database of temporal replicates of selection from studies of wild populations to synthesize what we do (and do not) know about the temporal dynamics of selection. Our database contains 5519 estimates of selection from 89 studies, including estimates of both direct and indirect selection as well as linear and nonlinear selection. Morphological traits and studies focused on vertebrates were well-represented, with other traits and taxonomic groups less well-represented. Overall, three major features characterize the temporal dynamics of selection. First, the strength of selection often varies considerably from year to year, although random sampling error of selection coefficients may impose bias in estimates of the magnitude of such variation. Second, changes in the direction of selection are frequent. Third, changes in the form of selection are likely common, but harder to quantify. Although few studies have identified causal mechanisms underlying temporal variation in the strength, direction and form of selection, variation in environmental conditions driven by climatic fluctuations appear to be common and important.
Comparative phylogeography of the ocean planet Bowen, Brian W.; Gaither, Michelle R.; DiBattista, Joseph D. ...
Proceedings of the National Academy of Sciences - PNAS,
07/2016, Volume:
113, Issue:
29
Journal Article
Peer reviewed
Open access
Understanding how geography, oceanography, and climate have ultimately shaped marine biodiversity requires aligning the distributions of genetic diversity across multiple taxa. Here, we examine ...phylogeographic partitions in the sea against a backdrop of biogeographic provinces defined by taxonomy, endemism, and species composition. The taxonomic identities used to define biogeographic provinces are routinely accompanied by diagnostic genetic differences between sister species, indicating interspecific concordance between biogeography and phylogeography. In cases where individual species are distributed across two or more biogeographic provinces, shifts in genotype frequencies often align with biogeographic boundaries, providing intraspecific concordance between biogeography and phylogeography. Here, we provide examples of comparative phylogeography from (i) tropical seas that host the highest marine biodiversity, (ii) temperate seas with high productivity but volatile coastlines, (iii) migratory marine fauna, and (iv) plankton that are the most abundant eukaryotes on earth. Tropical and temperate zones both show impacts of glacial cycles, the former primarily through changing sea levels, and the latter through coastal habitat disruption. The general concordance between biogeography and phylogeography indicates that the population-level genetic divergences observed between provinces are a starting point for macroevolutionary divergences between species. However, isolation between provinces does not account for all marine biodiversity; the remainder arises through alternative pathways, such as ecological speciation and parapatric (semiisolated) divergences within provinces and biodiversity hotspots.
Environmental DNA (eDNA) metabarcoding, a technique for retrieving multispecies DNA from environmental samples, can detect a diverse array of marine species from filtered seawater samples. There is a ...growing potential to integrate eDNA alongside existing monitoring methods in order to establish or improve the assessment of species diversity. Remote island reefs are increasingly vulnerable to climate‐related threats and as such there is a pressing need for cost‐effective whole‐ecosystem surveying to baseline biodiversity, study assemblage changes and ultimately develop sustainable management plans. We investigated the utility of eDNA metabarcoding as a high‐resolution, multitrophic biomonitoring tool at the Cocos (Keeling) Islands, Australia (CKI)—a remote tropical coral reef atoll situated within the eastern Indian Ocean. Metabarcoding assays targeting the mitochondrial 16S rRNA and CO1 genes, as well as the 18S rRNA nuclear gene, were applied to 252 surface seawater samples collected from 42 sites within a 140 km2 area. Our assays successfully detected a wide range of bony fish and elasmobranchs (244 taxa), crustaceans (88), molluscs (37) and echinoderms (7). Assemblage composition varied significantly between sites, reflecting habitat partitioning across the island ecosystem and demonstrating the localisation of eDNA signals, despite extensive tidal and oceanic movements. In addition, we document putative new occurrence records for 46 taxa and compare the efficiency of our eDNA approach to visual survey techniques at CKI. Our study demonstrates the utility of a multimarker metabarcoding approach in capturing multitrophic biodiversity across an entire coral reef atoll and sets an important baseline for ongoing monitoring and management.
Effective marine management requires comprehensive data on the status of marine biodiversity. However, efficient methods that can document biodiversity in our oceans are currently lacking. ...Environmental DNA (eDNA) sourced from seawater offers a new avenue for investigating the biota in marine ecosystems. Here, we investigated the potential of eDNA to inform on the breadth of biodiversity present in a tropical marine environment. Directly sequencing eDNA from seawater using a shotgun approach resulted in only 0.34% of 22.3 million reads assigning to eukaryotes, highlighting the inefficiency of this method for assessing eukaryotic diversity. In contrast, using 'tree of life' (ToL) metabarcoding and 20-fold fewer sequencing reads, we could detect 287 families across the major divisions of eukaryotes. Our data also show that the best performing 'universal' PCR assay recovered only 44% of the eukaryotes identified across all assays, highlighting the need for multiple metabarcoding assays to catalogue biodiversity. Lastly, focusing on the fish genus Lethrinus, we recovered intra- and inter-specific haplotypes from seawater samples, illustrating that eDNA can be used to explore diversity beyond taxon identifications. Given the sensitivity and low cost of eDNA metabarcoding we advocate this approach be rapidly integrated into biomonitoring programs.
Effective biomonitoring is critical for driving management outcomes that ensure long‐term sustainability of the marine environment. In recent years, environmental DNA (eDNA), coupled with ...metabarcoding methodologies, has emerged as a promising tool for generating biotic surveys of marine ecosystems, including those under anthropogenic pressure. However, more empirical data are needed on how to best implement eDNA field sampling approaches to maximize their utility for each specific application. The effect of the substrate chosen for eDNA sampling on the diversity of marine taxa detected by DNA metabarcoding has not yet been systematically analysed, despite aquatic systems being those most commonly targeted for eDNA studies. We investigated the effect of four commonly used eDNA substrates to explore taxonomic diversity: (a) surface water, (b) marine sediment, (c) settlement plates and (d) planktonic tows. With a focus on coastal ports, 332 eDNA samples from Australia (Indian and Southern oceans) and Kazakhstan (Caspian Sea) were collected and analysed by multi‐assay DNA metabarcoding. Across study locations, between 30% and 52% of eukaryotic families detected were unique to a particular substrate and <6% of families were found in all four substrates. Taxonomic composition varied significantly depending on the substrate sampled implying that the suitability (and bias) of an eDNA substrate will depend on the focal taxa. These findings demonstrate that single substrate eDNA metabarcoding likely underestimates the total eukaryotic diversity. Future eDNA experimental design should consider incorporating multiple substrates or select substrate(s) best suited to the specific detection of target taxa.
Loss of biodiversity from lower to upper trophic levels reduces overall productivity and stability of coastal ecosystems in our oceans, but rarely are these changes documented across both time and ...space. The characterisation of environmental DNA (eDNA) from sediment and seawater using metabarcoding offers a powerful molecular lens to observe marine biota and provides a series of 'snapshots' across a broad spectrum of eukaryotic organisms. Using these next-generation tools and downstream analytical innovations including machine learning sequence assignment algorithms and co-occurrence network analyses, we examined how anthropogenic pressures may have impacted marine biodiversity on subtropical coral reefs in Okinawa, Japan. Based on 18 S ribosomal RNA, but not ITS2 sequence data due to inconsistent amplification for this marker, as well as proxies for anthropogenic disturbance, we show that eukaryotic richness at the family level significantly increases with medium and high levels of disturbance. This change in richness coincides with compositional changes, a decrease in connectedness among taxa, an increase in fragmentation of taxon co-occurrence networks, and a shift in indicator taxa. Taken together, these findings demonstrate the ability of eDNA to act as a barometer of disturbance and provide an exemplar of how biotic networks and coral reefs may be impacted by anthropogenic activities.
Al Wajh Bank in the northern Red Sea contains an extensive coral reef system that potentially supports a novel fish community. The large (1500km2) and shallow (< 40m depth) lagoon experiences greater ...temperature and salinity fluctuations, as well as higher turbidity, than most other Red Sea reefs. Since these conditions often influence coral community structure and introduce physiological challenges to its resident organisms, changes in reef-associated fishes are expected. We present critical baseline data on fish biodiversity and benthic composition for the Al Wajh Bank. Underwater visual census of conspicuous fishes and standardized collections of cryptobenthic fishes were combined to provide a comprehensive assessment of these fish communities. We documented 153 fish species and operational taxonomic units, including undescribed species, within 24 families on reefs largely dominated by hard coral and soft sediment (39% and 32% respectively). The families Pomacentridae and Gobiidae contributed the most towards fish diversity and abundance. Bray-Curtis dissimilarity distances among sampled sites suggest a distinctive fish community within the lagoon, and coefficients of variation for each species show high variation in their distribution across the lagoon. Species accumulation curves predict that additional sampling would document many more species throughout Al Wajh. Our findings provide the most extensive biodiversity survey of fishes from this region to date and record the condition of the reef prior to major coastal development planned to occur in the near future.
Aim
Environmental DNA (eDNA) metabarcoding has demonstrated its applicability as a highly sensitive biomonitoring tool across small spatial and temporal scales in marine ecosystems. However, it has ...rarely been tested across large spatial scales or biogeographical barriers. Here, we scale up marine eDNA metabarcoding, test its ability to detect a major marine biogeographic break and evaluate its use as a regional biomonitoring tool in Australia.
Location
North‐western Australia (NWA).
Methods
We applied metabarcoding assays targeting the mitochondrial 16S rRNA and CO1 genes to 284 surface seawater eDNA samples collected from 71 mid‐shelf, inshore, coastal and nearshore estuarine sites over 700 km of the NWA coastline.
Results
Metabarcoding detected a wide range of bony fish (404 taxa), elasmobranchs (44) and aquatic reptiles (5). We detected bioregional and depth differentiation within inshore bony fish communities. These findings support the presence of a marine biogeographic break, which is purported to occur in the vicinity of Cape Leveque, demarcating the border between the Kimberley and Canning bioregions. Inshore bony fish and elasmobranch communities, as well as coastal bony fish assemblages, were additionally found to differ between the South and North Kimberley regions suggesting previously unrecognized subregional differentiation amongst these taxa. The overall compositional data have been used to update distribution information for a number of endangered, elusive and data‐deficient taxa, including sawfish (family: Pristidae), northern river shark (Glyphis garricki) and wedgefish (genus: Rhynchobatus).
Main conclusions
eDNA metabarcoding demonstrated a high level of sensitivity that was able to discern fine‐scale patterns across the large‐scale, remote and oceanographically complex region of North‐western Australia. Importantly, this study highlights the potential of integrating broad‐scale eDNA metabarcoding alongside other baseline surveys and long‐term monitoring approaches, which are crucial for the sustainable management and conservation of marine biodiversity in this unique marine region.
Genetic variation is considered critical for allowing natural populations to adapt to their changing environment, and yet the effects of human disturbance on genetic variation in the wild are poorly ...understood. Different types of human disturbances may genetically impact natural populations in a predictable manner and so the aim of this study was to provide an overview of these changes using a quantitative literature review approach. I examined both allozyme and microsatellite estimates of genetic variation from peer-reviewed journals, using the mean number of alleles per locus and expected heterozygosity as standardized metrics. Populations within each study were categorized according to the type of human disturbance experienced (“hunting/harvest”, “habitat fragmentation”, or “pollution”), and taxon-specific, as well as time- and context-dependent disturbance effects were considered. I found that human disturbances are associated with weak, but consistent changes in neutral genetic variation within natural populations. The direction of change was dependent on the type of human disturbance experienced, with some forms of anthropogenic challenges consistently decreasing genetic variation from background patterns (e.g., habitat fragmentation), whereas others had no effect (e.g., hunting/harvest) or even slightly increased genetic variation (e.g., pollution). These same measures appeared sensitive to both the time of origin and duration of the disturbance as well. This suggests that the presence or absence, strength, type, as well as the spatial and temporal scale of human disturbance experienced may warrant careful consideration when conservation management plans are formulated for natural populations, with particular attention paid to the effects of habitat fragmentation.
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