Friday, April 20, 2018

Weekend reads

Lots of work and distractions keep me from blogging these days. Hope to get back to old routine in the coming weeks. Meanwhile, some more papers to read:

New applications of DNA and RNA sequencing are expanding the field of biodiversity discovery and ecological monitoring, yet questions remain regarding precision and efficiency. Due to primer bias, the ability of metabarcoding to accurately depict biomass of different taxa from bulk communities remains unclear, while PCR-free whole mitochondrial genome (mitogenome) sequencing may provide a more reliable alternative. Here we used a set of documented mock communities comprising 13 species of freshwater macroinvertebrates of estimated individual biomass, to compare the detection efficiency of COI metabarcoding (3 different amplicons) and shotgun mitogenome sequencing. Additionally, we used individual COI barcoding and de novo mitochondrial genome sequencing, to provide reference sequences for OTU assignment and metagenome mapping (mitogenome-skimming) respectively. We found that even though both methods occasionally failed to recover very low abundance species, metabarcoding was less consistent, by failing to recover some species with higher abundances, probably due to primer bias. Shotgun sequencing results provided highly significant correlations between read number and biomass in all but one species. Conversely, the read-biomass relationships obtained from metabarcoding varied across amplicons. Specifically, we found significant relationships for 8 out of 13 (amplicons B1FR-450bp, FF130R-130bp) or 4 out of 13 (amplicon FFFR, 658bp) species. Combining the results of all three COI amplicons (multi-amplicon approach) improved the read-biomass correlations for some of the species. Overall, mitogenomic sequencing yielded more informative predictions of biomass content from bulk macroinvertebrate communities than metabarcoding. However, for large scale ecological studies, metabarcoding currently remains the most commonly used approach for diversity assessment.

BACKGROUND: DNA metabarcoding is used to generate species composition data for entire communities. However, sequencing errors in high-throughput sequencing instruments are fairly common, usually requiring reads to be clustered into operational taxonomic units (OTUs), losing information on intraspecific diversity in the process. While Cytochrome c oxidase subunit I (COI) haplotype information is limited in resolving intraspecific diversity it is nevertheless often useful e.g. in a phylogeographic context, helping to formulate hypotheses on taxon distribution and dispersal.
METHODS: This study combines sequence denoising strategies, normally applied in microbial research, with additional abundance-based filtering to extract haplotype information from freshwater macroinvertebrate metabarcoding datasets. This novel approach was added to the R package "JAMP" and can be applied to COI amplicon datasets. We tested our haplotyping method by sequencing (i) a single-species mock community composed of 31 individuals with 15 different haplotypes spanning three orders of magnitude in biomass and (ii) 18 monitoring samples each amplified with four different primer sets and two PCR replicates.
RESULTS: We detected all 15 haplotypes of the single specimens in the mock community with relaxed filtering and denoising settings. However, up to 480 additional unexpected haplotypes remained in both replicates. Rigorous filtering removes most unexpected haplotypes, but also can discard expected haplotypes mainly from the small specimens. In the monitoring samples, the different primer sets detected 177-200 OTUs, each containing an average of 2.40-3.30 haplotypes per OTU. The derived intraspecific diversity data showed population structures that were consistent between replicates and similar between primer pairs but resolution depended on the primer length. A closer look at abundant taxa in the dataset revealed various population genetic patterns, e.g. the stonefly Taeniopteryx nebulosa and the caddisfly Hydropsyche pellucidula showed a distinct north-south cline with respect to haplotype distribution, while the beetle Oulimnius tuberculatus and the isopod Asellus aquaticus displayed no clear population pattern but differed in genetic diversity.
DISCUSSION: We developed a strategy to infer intraspecific genetic diversity from bulk invertebrate metabarcoding data. It needs to be stressed that at this point this metabarcoding-informed haplotyping is not capable of capturing the full diversity present in such samples, due to variation in specimen size, primer bias and loss of sequence variants with low abundance. Nevertheless, for a high number of species intraspecific diversity was recovered, identifying potentially isolated populations and taxa for further more detailed phylogeographic investigation. While we are currently lacking large-scale metabarcoding datasets to fully take advantage of our new approach, metabarcoding-informed haplotyping holds great promise for biomonitoring efforts that not only seek information about species diversity but also underlying genetic diversity.

While phylogeographic structure has been examined in many North American vertebrate species, insects have received much less attention despite their central ecological roles. The moth genus Malacosoma (Hübner, 1820), is an important group of forestry pests responsible for large-scale defoliation across much of the Nearctic and Palearctic. The present study uses sequence variation in the mitochondrial cytochrome c oxidase 1 (COI) gene to examine the population genetic structure of the three widespread Malacosoma species (M. americana, M. californica, and M. disstria). Populations of all three species showed highest diversity in the south, suggesting that modern populations derived from southern refugia with loss of variation as these lineages dispersed northwards. However, despite similar life histories and dispersal abilities, the extent of regional variation varied among the taxa. M. americana, a species restricted to eastern North America, showed much less genetic structure than the western M. californica or the widespread M. disstria. The regional differentiation in the latter reflects the likely derivation of modern lineages from several refugia, as well as taxonomic uncertainty in M. californica. In these respects, the three species of Malacosoma share phylogeographic patterns similar to those detected in vertebrates which are characterised by greater phylogeographic breaks in the western half of the continent and limited structure in the east.

Sea turtles are distributed in tropical and subtropical seas worldwide. They play several ecological roles and are considered important indicators of the health of marine ecosystems. Studying epibiotic diatoms living on turtle shells suggestively has great potential in the study of turtle behavior because diatoms are always there. However, diatom identification at the species level is time consuming, requires well-trained specialists, and there is a high probability of finding new taxa growing on turtle shells, which makes identification tricky. An alternative approach based on DNA barcoding and high throughput sequencing (HTS), metabarcoding, has been developed in recent years to identify species at the community level by using a DNA reference library. The suitabilities of morphological and molecular approaches were compared. Diatom assemblages were sampled from seven juvenile green turtles (Chelonia mydas) from Mayotte Island, France. The structures of the epibiotic diatom assemblages differed between both approaches. This resulted in different clustering of the turtles based on their diatom communities. Metabarcoding allowed better discrimination between turtles based on their epibiotic diatom assemblages and put into evidence the presence of a cryptic diatom diversity. Microscopy, for its part, provided more ecological information of sea turtles based on historical bibliographical data and the abundances of ecological guilds of the diatom species present in the samples. This study shows the complementary nature of these two methods for studying turtle behavior.

BACKGROUND: Advancements in portable scientific instruments provide promising avenues to expedite field work in order to understand the diverse array of organisms that inhabit our planet. Here, we tested the feasibility for in situ molecular analyses of endemic fauna using a portable laboratory fitting within a single backpack in one of the world's most imperiled biodiversity hotspots, the Ecuadorian Chocó rainforest. We used portable equipment, including the MinION nanopore sequencer (Oxford Nanopore Technologies) and the miniPCR (miniPCR), to perform DNA extraction, polymerase chain reaction amplification, and real-time DNA barcoding of reptile specimens in the field.
FINDINGS: We demonstrate that nanopore sequencing can be implemented in a remote tropical forest to quickly and accurately identify species using DNA barcoding, as we generated consensus sequences for species resolution with an accuracy of >99% in less than 24 hours after collecting specimens. The flexibility of our mobile laboratory further allowed us to generate sequence information at the Universidad Tecnológica Indoamérica in Quito for rare, endangered, and undescribed species. This includes the recently rediscovered Jambato toad, which was thought to be extinct for 28 years. Sequences generated on the MinION required as few as 30 reads to achieve high accuracy relative to Sanger sequencing, and with further multiplexing of samples, nanopore sequencing can become a cost-effective approach for rapid and portable DNA barcoding.
CONCLUSIONS: Overall, we establish how mobile laboratories and nanopore sequencing can help to accelerate species identification in remote areas to aid in conservation efforts and be applied to research facilities in developing countries. This opens up possibilities for biodiversity studies by promoting local research capacity building, teaching nonspecialists and students about the environment, tackling wildlife crime, and promoting conservation via research-focused ecotourism.

Assessment of ecological status for the European Water Framework Directive (WFD) is based on "Biological Quality Elements" (BQEs), namely phytoplankton, benthic flora, benthic invertebrates and fish. Morphological identification of these organisms is a time-consuming and expensive procedure. Here, we assess the options for complementing and, perhaps, replacing morphological identification with procedures using eDNA, metabarcoding or similar approaches. We rate the applicability of DNA-based identification for the individual BQEs and water categories (rivers, lakes, transitional and coastal waters) against eleven criteria, summarised under the headlines representativeness (for example suitability of current sampling methods for DNA-based identification, errors from DNA-based species detection), sensitivity (for example capability to detect sensitive taxa, unassigned reads), precision of DNA-based identification (knowledge about uncertainty), comparability with conventional approaches (for example sensitivity of metrics to differences in DNA-based identification), cost effectiveness and environmental impact. Overall, suitability of DNA-based identification is particularly high for fish, as eDNA is a well-suited sampling approach which can replace expensive and potentially harmful methods such as gill-netting, trawling or electrofishing. Furthermore, there are attempts to replace absolute by relative abundance in metric calculations. For invertebrates and phytobenthos, the main challenges include the modification of indices and completing barcode libraries. For phytoplankton, the barcode libraries are even more problematic, due to the high taxonomic diversity in plankton samples. If current assessment concepts are kept, DNA-based identification is least appropriate for macrophytes (rivers, lakes) and angiosperms/macroalgae (transitional and coastal waters), which are surveyed rather than sampled. We discuss general implications of implementing DNA-based identification into standard ecological assessment, in particular considering any adaptations to the WFD that may be required to facilitate the transition to molecular data.

Consensus on the optimal high-throughput sequencing (HTS) approach to examine biodiversity in mixed terrestrial arthropod samples has not been reached. Metatranscriptomics could increase the proportion of taxonomically informative mitochondrial reads in HTS outputs but has not been investigated for terrestrial arthropod samples. We compared the efficiency of 16S rRNA metabarcoding, metagenomics and metatranscriptomics for detecting species in a mixed terrestrial arthropod sample (pooled DNA/RNA from 38 taxa). 16S rRNA metabarcoding and nuclear rRNA-depleted metatranscriptomics had the highest detection rate with 97% of input species detected. Based on cytochrome c oxidase I, metagenomics had the highest detection rate with 82% of input species detected, but metatranscriptomics produced a larger proportion of reads matching (Sanger) reference sequences. Metatranscriptomics with nuclear rRNA depletion may offer advantages over metabarcoding through reducing the number of spurious operational taxonomic units while retaining high detection rates, and offers natural enrichment of mitochondrial sequences which may enable increased species detection rates compared with metagenomics.

Freshwater metazoan biodiversity assessment using environmental DNA (eDNA) captured on filters offers new opportunities for water quality management. Filtering of water in the field is a logistical advantage compared to transport of water to the nearest lab, and thus, appropriate filter preservation becomes crucial for maximum DNA recovery. Here, the effect of four different filter preservation strategies, two filter types, and pre-filtration were evaluated by measuring metazoan diversity and community composition, using eDNA collected from a river and a lake ecosystem. The filters were preserved cold on ice, in ethanol, in lysis buffer and dry in silica gel. Our results show that filters preserved either dry or in lysis buffer give the most consistent community composition. In addition, mixed cellulose ester filters yield more consistent community composition than polyethersulfone filters, while the effect of pre-filtration remained ambiguous. Our study facilitates development of guidelines for aquatic community-level eDNA biomonitoring, and we advocate filtering in the field, using mixed cellulose ester filters and preserving the filters either dry or in lysis buffer.

Advances in DNA sequencing technology have revolutionised the field of molecular analysis of trophic interactions and it is now possible to recover counts of food DNA barcode sequences from a wide range of dietary samples. But what do these counts mean? To obtain an accurate estimate of the overall diet of a consumer should we work strictly with datasets summarising the frequency of occurrence of different food taxa, or is it possible to use the relative number of sequences? Both approaches are applied in the dietary metabarcoding literature, but occurrence data is often promoted as a more conservative and reliable option due to taxa-specific biases in recovery of sequences. Here, we point out that diet summaries based on occurrence data overestimate the importance of food consumed in small quantities (potentially including low-level contaminants) and are sensitive to the count threshold used to define an occurrence. Our simulations indicate that even with recovery biases incorporated, using relative read abundance (RRA) information can provide a more accurate view of population-level diet in many scenarios. The ideas presented here highlight the need to consider all sources of bias and to justify the methods used to interpret count data in dietary metabarcoding studies. We encourage researchers to continue to addressing methodological challenges, and acknowledge unanswered questions to help spur future investigations in this rapidly developing area of research.

Metabarcoding of lake sediments have been shown to reveal current and past biodiversity, but little is known about the degree to which taxa growing in the vegetation are represented in environmental DNA (eDNA) records. We analysed composition of lake and catchment vegetation and vascular plant eDNA at 11 lakes in northern Norway. Out of 489 records of taxa growing within 2 m from the lake shore, 17-49% (mean 31%) of the identifiable taxa recorded were detected with eDNA. Of the 217 eDNA records of 47 plant taxa in the 11 lakes, 73% and 12% matched taxa recorded in vegetation surveys within 2 m and up to about 50 m away from the lakeshore, respectively, whereas 16% were not recorded in the vegetation surveys of the same lake. The latter include taxa likely overlooked in the vegetation surveys or growing outside the survey area. The percentages detected were 61, 47, 25, and 15 for dominant, common, scattered, and rare taxa, respectively. Similar numbers for aquatic plants were 88, 88, 33 and 62%, respectively. Detection rate and taxonomic resolution varied among plant families and functional groups with good detection of e.g. Ericaceae, Roseaceae, deciduous trees, ferns, club mosses and aquatics. The representation of terrestrial taxa in eDNA depends on both their distance from the sampling site and their abundance and is sufficient for recording vegetation types. For aquatic vegetation, eDNA may be comparable with, or even superior to, in-lake vegetation surveys and may therefore be used as an tool for biomonitoring. For reconstruction of terrestrial vegetation, technical improvements and more intensive sampling is needed to detect a higher proportion of rare taxa although DNA of some taxa may never reach the lake sediments due to taphonomical constrains. Nevertheless, eDNA performs similar to conventional methods of pollen and macrofossil analyses and may therefore be an important tool for reconstruction of past vegetation.

Wednesday, March 28, 2018

Electric fish

Weakly electric fishes produce continuous wave-type electric organ discharges that are used for electrolocation and communication. Electrocommunication convergently evolved within the distantly related South American and African weakly electric fishes approximately 100 million years ago, enabling them to detect their environment and communicate with each other through the generation and sensation of electric signals. Most species use special muscle-derived electric organs to generate the necessary electric current. Members of the ghost knifefishes (family Apteronotidae)  have an electric organ derived from the axons of specialized spinal neurons (electromotorneurons). These eurons fire spontaneously and are the fastest-firing neurons known. Ghost knife fish discharge their electric organs in excess of 1 kHz. 

Today I came across a publication that looked into the evolution of these highly specialized organs. I must say I find this study very fascinating and very well executed. The colleagues show that a skeletal muscle–specific sodium channel gene duplicated in this lineage and, within approximately 2 million years, began expressing in the spinal cord, a novel site of expression for this isoform. Concurrently, amino acid replacements that cause a persistent sodium current accumulated in the regions of the channel underlying inactivation. Therefore, a novel adaptation allowing extreme neuronal firing arose from the duplication, change in expression, and rapid sequence evolution of a muscle-expressing sodium channel gene.

A must read ;-)


Friday, March 23, 2018

IPBES assessment reports

Biodiversity and nature's contributions to people sound, to many people, academic and far removed from our daily lives. Nothing could be further from the truth - they are the bedrock of our food, clean water and energy. They are at the heart not only of our survival, but of our cultures, identities and enjoyment of life. 
Sir Robert Watson, Chair of IPBES

Four peer-reviewed assessment reports by the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) focus on providing answers to key questions for different regions, including: why is biodiversity important, where are we making progress, what are the main threats and opportunities for biodiversity and how can we adjust our policies and institutions for a more sustainable future? 

The result of three years of work, the four regional assessments of biodiversity and ecosystem services cover the Americas, Asia and the Pacific, Africa, as well as Europe and Central Asia. In every region, with the exception of a number of positive examples where lessons can be learned, biodiversity and nature's capacity to contribute to people are being degraded, reduced and lost due to a number of common pressures - habitat stress; overexploitation and unsustainable use of natural resources; air, land and water pollution; increasing numbers and impact of invasive alien species and climate change, among others.

IPBES has today released the Summary for Policymakers of each of the four reports. The summaries present the key messages and policy options from each assessment, as approved by the IPBES Plenary. The complete reports (inclusive of all data) will be published later this year. 

As much as I appreciate and welcome such global studies that highlight humanity's negative impact on our planet resulting in a irrecoverable loss of life I am critical of meta-studies. It might sound paradox that I consider such a huge body of work not comprehensive enough but for realistic biodiversity estimates we need to dig deeper. Indirect measures and focus on key species is pragmatic given limited resources and already a lot of work for a lot of colleagues, but it likely shows only the tip of the iceberg. If you don't know how many species are out there let alone what they are doing (or in this context what ecosystem services they might provide) it is hard to quantify the true extent of loss of diversity. We might never know how many species have already disappeared and what cascading effects are already underway or waiting to happen. I am not saying reports like this one are futile, quite the contrary. Humanity needs to know where we are heading but I think some serious considerations of potential underestimates and adaptation of methodology are needed. I am not seeing  any inclusion of DNA-based methods in the reports but without the full reports one can't be 100% sure.

Wednesday, March 21, 2018

From the inbox: Associate Professor / Professor of Biodiversity Genomics

Tenurable appointment - University of Western Australia - School of Biological Sciences

The School of Biological Sciences is a research-intensive school that prides itself in providing innovative, research-informed, teaching at both the undergraduate and postgraduate levels. The School has internationally recognised expertise in Computational Biology, Ecology and Conservation, Evolutionary Biology, Neuroscience and in Science Communication.

The School also hosts the Centre for Evolutionary Biology and the WA Biogeochemistry Centre and has strong links with other Schools in the Faculty of Science, in particular the School of Molecular Sciences and the UWA School of Agriculture and Environment, as well as the UWA Oceans Institute.

Applications are invited for the Associate Professor / Professor of Biodiversity Genomics in the School of Biological Sciences at The University of Western Australia. The position calls for  an outstanding academic in the field of Biodiversity Genomics who has made a significant contribution to high quality teaching and who is internationally recognised. 

For further information regarding the position please contact:

Professor Sarah Dunlop, Head of School, School of Biological Sciences on (08) 6488 2237 or .

This position is open to international applicants.

Our commitment to inclusion and diversity
UWA is committed to a diverse workforce. We celebrate inclusion and diversity and believe gender equity is fundamental to achieving our goal of being a top 50 university by 2050.

We have child friendly areas on campus, including childcare facilities. Flexible work arrangements, part-time hours and job sharing will all be considered.

UWA has been awarded Top Ten Employer for LGBTI – inclusion of the Australian Workplace Equity Index (AWEI -2016).
The University is also a proud member of the Athena SWAN/SAGE Pilot for Gender Equity.
To submit your application, please click on the "Go to application page" button on the university hiring page.

The ad comes with a very nice brochure.

Friday, March 16, 2018

Weekend reads

More to read for you in case you follow my recommendations. As stated before I am posting only a selection and all papers are chosen at least in part based on subjective criteria. So, here we go, my take on what I think you (and especially my students) should read ;-)

The biocide Bacillus thuringiensis var. israelensis (Bti) is widely applied for mosquito control in temporary wetlands of the German Upper Rhine Valley. Even though Bti is considered environmentally friendly, several studies have shown non-target effects on chironomids, a key food resource in wetland ecosystems. Chironomids have been proposed as important indicators for monitoring freshwater ecosystems, however, morphological determination is very challenging. In this study, we investigated the effectiveness of metabarcoding for chironomid diversity assessment and tested the retrieved chironomid operational taxonomic units (OTUs) for possible changes in relative abundance and species diversity in relation to mosquito control actions in four temporary wetlands. Three of these wetlands were, for the first year after 20 years of Bti treatment, partly left Bti-untreated in a split field design, and one wetland has never been treated with Bti. Our metabarcoding approach detected 54 chironomid OTUs across all study sites, of which almost 70% could be identified to species level comparisons against the BOLD database. We showed that metabarcoding increased chironomid species determination by 70%. However, we found only minor significant effects of Bti on the chironomid community composition, even though Bti reduced chironomid emergence by 65%. This could be due to a time lag of chironomid recolonization, since the study year was the first year of Bti intermittence after about 20 years of Bti application in the study area. Subsequent studies will have to address if and how the chironomid community composition will recover further in the now Bti-untreated temporary wetlands to assess effects of Bti.

The introduction of domesticated animals into new environments can lead to considerable ecological disruption, and it can be difficult to predict their impact on the new ecosystem. In this study, we use faecal metabarcoding to characterize the diets of three ruminant taxa in the rangelands of south-western New South Wales, Australia. Our study organisms included goats (Capra aegagrus hircus) and two breeds of sheep (Ovis aries): Merinos, which have been present in Australia for over two hundred years, and Dorpers, which were introduced in the 1990s. We used High-Throughput Sequencing methods to sequence the rbcL and ITS2 genes of plants in the faecal samples, and identified the samples using the GenBank and BOLD online databases, as well as a reference collection of sequences from plants collected in the study area. We found that the diets of all three taxa were dominated by the family Malvaceae, and that the Dorper diet was more diverse than the Merino diet at both the family and the species level. We conclude that Dorpers, like Merinos, are potentially a threat to some vulnerable species in the rangelands of New South Wales.

Effective ecosystem conservation and resource management require quantitative monitoring of biodiversity, including accurate descriptions of species composition and temporal variations of species abundance. Accordingly, quantitative monitoring of biodiversity has been performed for many ecosystems, but it is often time- and effort-consuming and costly. Recent studies have shown that environmental DNA (eDNA), which is released to the environment from macro-organisms living in a habitat, contains information about species identity and abundance. Thus, analysing eDNA would be a promising approach for more efficient biodiversity monitoring. In the present study, internal standard DNAs (i.e. known amounts of short DNA fragments from fish species that have never been observed in a sampling area) were added to eDNA samples, which were collected weekly from a coastal marine ecosystem in Maizuru Bay, Japan (from April 2015 to March 2016) and metabarcoding analysis was performed using Illumina MiSeq to simultaneously identify fish species and quantify fish eDNA copy numbers. A correction equation was obtained for each sample using the relationship between the number of sequence reads and the added amount of the standard DNAs and this equation was used to estimate the copy numbers from the sequence reads of non-standard fish eDNA. The calculated copy numbers showed significant positive correlations with those determined by quantitative PCR, suggesting that eDNA metabarcoding with standard DNA enabled useful quantification of eDNA. Furthermore, for samples that show a high level of PCR inhibition, this method might allow more accurate quantification than qPCR because the correction equations generated using internal standard DNAs would include the effect of PCR inhibition. A single run of Illumina MiSeq produced >70 quantitative fish eDNA time series in this study, showing that this method could contribute to more efficient and quantitative monitoring of biodiversity.

Freshwater metazoan biodiversity assessment using environmental DNA (eDNA) captured on filters offers new opportunities for water quality management. Filtering of water in the field is a logistical advantage compared to transport of water to the nearest lab, and thus, appropriate filter preservation becomes crucial for maximum DNA recovery. Here, the effect of four different filter preservation strategies, two filter types, and pre-filtration were evaluated by measuring metazoan diversity and community composition, using eDNA collected from a river and a lake ecosystem. The filters were preserved cold on ice, in ethanol, in lysis buffer and dry in silica gel. Our results show that filters preserved either dry or in lysis buffer give the most consistent community composition. In addition, mixed cellulose ester filters yield more consistent community composition than polyethersulfone filters, while the effect of pre-filtration remained ambiguous. Our study facilitates development of guidelines for aquatic community-level eDNA biomonitoring, and we advocate filtering in the field, using mixed cellulose ester filters and preserving the filters either dry or in lysis buffer.

We introduce a method for assigning names to CO1 metabarcode sequences with confidence scores in a rapid, high-throughput manner. We compiled nearly 1 million CO1 barcode sequences appropriate for classifying arthropods and chordates. Compared to our previous Insecta classifier, the current classifier has more than three times the taxonomic coverage, including outgroups, and is based on almost five times as many reference sequences. Unlike other popular rDNA metabarcoding markers, we show that classification performance is similar across the length of the CO1 barcoding region. We show that the RDP classifier can make taxonomic assignments about 19 times faster than the popular top BLAST hit method and reduce the false positive rate from nearly 100% to 34%. This is especially important in large-scale biodiversity and biomonitoring studies where datasets can become very large and the taxonomic assignment problem is not trivial. We also show that reference databases are becoming more representative of current species diversity but that gaps still exist. We suggest that it would benefit the field as a whole if all investigators involved in metabarocoding studies, through collaborations with taxonomic experts, also planned to barcode representatives of their local biota as a part of their projects.

Birds play unique functional roles in the maintenance of ecosystems, such as pollination and seed dispersal, and thus monitoring bird species diversity is a first step towards avoiding undesirable consequences of anthropogenic impacts on bird communities. In the present study, we hypothesized that birds, regardless of their main habitats, must have frequent contact with water and that tissues that contain their DNA that persists in the environment (environmental DNA; eDNA) could be used to detect the presence of avian species. To this end, we applied a set of universal PCR primers (MiBird, a modified version of fish/mammal universal primers) for metabarcoding avian eDNA. We confirmed the versatility of MiBird primers by performing in silico analyses and by amplifying DNAs extracted from bird tissues. Analyses of water samples from zoo cages of birds with known species composition suggested that the use of MiBird primers combined with Illumina MiSeq could successfully detect avian species from water samples. Additionally, analysis of water samples collected from a natural pond detected five avian species common to the sampling areas. The present findings suggest that avian eDNA metabarcoding would be a complementary detection/identification tool in cases where visual census of bird species is difficult.

Anthropogenic plastic pollution is a global problem. In the marine environment, one of its less studied effects is the transport of attached biota, which might lead to introductions of non-native species in new areas or aid in habitat expansions of invasive species. The goal of the present work was to assess if the material composition of beached anthropogenic litter is indicative of the rafting fauna in a coastal area and could thus be used as a simple and cost-efficient tool for risk assessment in the future. Beached anthropogenic litter and attached biota along the 200 km coastline of Asturias, central Bay of Biscay, Spain, were analysed. The macrobiotic community attached to fouled litter items was identified using genetic barcoding combined with visual taxonomic analysis, and compared between hard plastics, foams, other plastics and non-plastic items. On the other hand, the material composition of beached litter was analysed in a standardized area on each beach. From these two datasets, the expected frequency of several rafting taxa was calculated for the coastal area and compared to the actually observed frequencies. The results showed that plastics were the most abundant type of beached litter. Litter accumulation was likely driven by coastal sources (industry, ports) and river/sewage inputs and transported by near-shore currents. Rafting vectors were almost exclusively made up of plastics and could mainly be attributed to fishing activity and leisure/ household. We identified a variety of rafting biota, including species of goose barnacles, acorn barnacles, bivalves, gastropods, polychaetes and bryozoan, and hydrozoan colonies attached to stranded litter. Several of these species were non-native and invasive, such as the giant Pacific oyster (Crassostrea gigas) and the Australian barnacle (Austrominius modestus). The composition of attached fauna varied strongly between litter items of different materials. Plastics, except for foam, had a much more diverse attached community than non-plastic materials. The predicted frequency of several taxa attached to beached litter significantly correlated with the actually observed frequencies. Therefore we suggest that the composition of stranded litter on a beach or an area could allow for predictions about the corresponding attached biotic community, including invasive species.

Thursday, March 15, 2018

Saving endangered species with an app

An app developed with support from USAID is making wildlife protection officers more effective in their efforts to combat wildlife trafficking in Southeast Asia. WildScan, a mobile species identification and response app, is designed to help law enforcement officials respond to wildlife trafficking, an illicit trade estimated at $19 billion per year and run by organized criminal syndicates. WildScan is currently available for free on Android devices and available in English, Thai and Vietnamese. The app will soon be available in Bahasa Indonesia, Bahasa Malaysia and Khmer in addition to updated Android and new Apple iOS versions.

The app is a result of a collaborative partnership between academics, law enforcement, scientists and other wildlife specialists. USAID worked through its implementing partner, Freeland, under the USAID Asia’s Regional Response to Endangered Species Trafficking program.

Law enforcement agencies, as well as casual phone users, can now identify endangered species using high-resolution photos and the app allows them to report illegal collections of terrestrial, marine, and freshwater animals to the proper authorities. Wildscan not only includes clues to identify over 700 protected species but also offers primary care tips for injured animals.

Here is a video showcasing the app.

Thursday, March 8, 2018

Weekend reads

Another week, another pile of reading material. This time with some bioinformatics. Enjoy!

MOTIVATION:
In recent years, molecular species delimitation has become a routine approach for quantifying and classifying biodiversity. Barcoding methods are of particular importance in large-scale surveys as they promote fast species discovery and biodiversity estimates. Among those, distance-based methods are the most common choice as they scale well with large datasets; however, they are sensitive to similarity threshold parameters and they ignore evolutionary relationships. The recently introduced "Poisson Tree Processes" (PTP) method is a phylogeny-aware approach that does not rely on such thresholds. Yet, two weaknesses of PTP impact its accuracy and practicality when applied to large datasets; it does not account for divergent intraspecific variation and is slow for a large number of sequences.
RESULTS:
We introduce the multi-rate PTP (mPTP), an improved method that alleviates the theoretical and technical shortcomings of PTP. It incorporates different levels of intraspecific genetic diversity deriving from differences in either the evolutionary history or sampling of each species. Results on empirical data suggest that mPTP is superior to PTP and popular distance-based methods as it, consistently yields more accurate delimitations with respect to the taxonomy (i.e., identifies more taxonomic species, infers species numbers closer to the taxonomy). Moreover, mPTP does not require any similarity threshold as input. The novel dynamic programming algorithm attains a speedup of at least five orders of magnitude compared to PTP, allowing it to delimit species in large (meta-) barcoding data. In addition, Markov Chain Monte Carlo sampling provides a comprehensive evaluation of the inferred delimitation in just a few seconds for millions of steps, independently of tree size.
AVAILABILITY AND IMPLEMENTATION:
mPTP is implemented in C and is available for download at http://github.com/Pas-Kapli/mptp under the GNU Affero 3 license. A web-service is available at http://mptp.h-its.org.

OBJECTIVE:
The body of DNA sequence data lacking taxonomically informative sequence headers is rapidly growing in user and public databases (e.g. sequences lacking identification and contaminants). In the context of systematics studies, sorting such sequence data for taxonomic curation and/or molecular diversity characterization (e.g. crypticism) often requires the building of exploratory phylogenetic trees with reference taxa. The subsequent step of segregating DNA sequences of interest based on observed topological relationships can represent a challenging task, especially for large datasets.
RESULTS:
We have written TREE2FASTA, a Perl script that enables and expedites the sorting of FASTA-formatted sequence data from exploratory phylogenetic trees. TREE2FASTA takes advantage of the interactive, rapid point-and-click color selection and/or annotations of tree leaves in the popular Java tree-viewer FigTree to segregate groups of FASTA sequences of interest to separate files. TREE2FASTA allows for both simple and nested segregation designs to facilitate the simultaneous preparation of multiple data sets that may overlap in sequence content.

Biological soil crusts (BSCs) are amalgamations of autotrophic, heterotrophic and saprotrophic organisms. In the Polar Regions, these unique communities occupy essential ecological functions such as primary production, nitrogen fixation and ecosystem engineering. Here we present the first molecular survey of BSCs from the Arctic and Antarctica focused on both eukaryotes and prokaryotes as well as passive and active biodiversity. Considering sequence abundance, Bryophyta is among the most abundant taxa in all analyzed BSCs suggesting that they were in a late successional stage. In terms of algal and cyanobacterial biodiversity, the genera Chloromonas, Coccomyxa, Elliptochloris and Nostoc were identified in all samples regardless of origin confirming their ubiquitous distribution. For the first time, we found the chrysophyte Spumella to be common in polar BSCs as it was present in all analyzed samples. Co-occurrence analysis revealed the presence of sulfur metabolizing microbes indicating that BSCs also play an important role for the sulfur cycle. In general, phototrophs were most abundant within the BSCs but there was also a diverse community of heterotrophs and saprotrophs. Our results show that BSCs are unique microecosystems in polar environments with an unexpectedly high biodiversity.

eDNA metabarcoding represents a new tool for community biodiversity assessment in a broad range of aquatic and terrestrial habitats. However, much of the existing literature focuses on methodological development rather than testing of ecological hypotheses. Here, we use presence-absence data generated by eDNA metabarcoding of over 500 UK ponds to examine: 1) species associations between the great crested newt (Triturus cristatus) and other vertebrates, 2) determinants of great crested newt occurrence at the pondscape, and 3) determinants of vertebrate species richness at the pondscape. The great crested newt was significantly associated with nine vertebrate species. Occurrence in ponds was broadly reduced by more fish species, but enhanced by more waterfowl and other amphibian species. Abiotic determinants (including pond area, depth, and terrestrial habitat) were identified, which both corroborate and contradict existing literature on great crested newt ecology. Some of these abiotic factors (pond outflow) also determined species richness at the pondscape, but other factors were unique to great crested newt (pond area, depth, and ruderal habitat) or the wider biological community (pond density, macrophyte cover, terrestrial overhang, rough grass habitat, and overall terrestrial habitat quality) respectively. The great crested newt Habitat Suitability Index positively correlated with both eDNA-based great crested newt occupancy and vertebrate species richness. Our study is one of the first to use eDNA metabarcoding to test abiotic and biotic determinants of pond biodiversity. eDNA metabarcoding provided new insights at scales that were previously unattainable using established methods. This tool holds enormous potential for testing ecological hypotheses alongside biodiversity monitoring and pondscape management.

A method for the extraction of nucleic acids from a wide range of environmental samples was developed. This method consists of several modules, which can be individually modified to maximize yields in extractions of DNA and RNA or separations of DNA pools. Modules were designed based on elaborate tests, in which permutations of all nucleic acid extraction steps were compared. The final modular protocol is suitable for extractions from igneous rock, air, water, and sediments. Sediments range from high-biomass, organic rich coastal samples to samples from the most oligotrophic region of the world's oceans and the deepest borehole ever studied by scientific ocean drilling. Extraction yields of DNA and RNA are higher than with widely used commercial kits, indicating an advantage to optimizing extraction procedures to match specific sample characteristics. The ability to separate soluble extracellular DNA pools without cell lysis from intracellular and particle-complexed DNA pools may enable new insights into the cycling and preservation of DNA in environmental samples in the future. A general protocol is outlined, along with recommendations for optimizing this general protocol for specific sample types and research goals.