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Enhancing metabarcoding efficiency and ecological insights through integrated taxonomy and DNA reference barcoding: A case study on beach meiofauna
No full textMolecular techniques like metabarcoding, while promising for exploring diversity of communities, are often impeded by the lack of reference DNA sequences available for taxonomic annotation. Our study explores the benefits of combining targeted DNA barcoding and morphological taxonomy to improve metabarcoding efficiency, using beach meiofauna as a case study. Beaches are globally important ecosystems and are inhabited by meiofauna, microscopic animals living in the interstitial space between the sand grains, which play a key role in coastal biodiversity and ecosystem dynamics. However, research on meiofauna faces challenges due to limited taxonomic expertise and sparse sampling. We generated 775 new cytochrome c oxidase I DNA barcodes from meiofauna specimens collected along the Netherlands' west coast and combined them with the NCBI GenBank database. We analysed alpha and beta diversity in 561 metabarcoding samples from 24 North Sea beaches, a region extensively studied for meiofauna, using both the enriched reference database and the NCBI database without the additional reference barcodes. Our results show a 2.5-fold increase in sequence annotation and a doubling of species-level Operational Taxonomic Units (OTUs) identification when annotating the metabarcoding data with the enhanced database. Additionally, our analyses revealed a bell-shaped curve of OTU richness across the intertidal zone, aligning more closely with morphological analysis patterns, and more defined community dissimilarity patterns between supralittoral and intertidal sites. Our research highlights the importance of expanding molecular reference databases and combining morphological taxonomy with molecular techniques for biodiversity assessments, ultimately improving our understanding of coastal ecosystems
“Something old, something new, something borrowed, and the oioxeny is true”: description of Plectanocotyle jeanloujustinei n. sp. (Polyopisthocotylea, Plectanocotylidae) from the MNHN Helminthology collection with novel molecular and morphological data for P. gurnardi (Van Beneden & Hesse, 1863) (sensu stricto) from Sweden
No full textNatural history museums worldwide house billions of apposite specimens, offering the potential for cost-free parasitological datasets. Herein, we provide novel morphological and molecular data (28S and cox1) for the polyopisthocotylean Plectanocotyle gurnardi sensu stricto from the type-host Eutrigla gurnardus from Sweden based on newly collected specimens from the Northeast Atlantic, and specimen from T. Odhner's collections at the Swedish Museum of Natural History (Stockholm, Sweden). The newly generated 28S sequences of P. gurnardi from E. gurnardus from the Northeast Atlantic were identical to those from the Western Mediterranean, and nested in a single clade, suggesting the presence of a single species. A 28S sequences of P. gurnardi sensu stricto from Sweden and those from the U.K. (type locality for P. caudata) were identical; we confirm that P. caudata and P. gurnardi are conspecific and formally synonymize them. A single 28S sequence of Plectanocotyle sp. from Chelidonichthys lastoviza off France differed from P. gurnardi from the Northeast Atlantic by 3–4 % and from P. gurnardi from France by 3%. Plectanocotyle sp. ex C. lastoviza off France is clearly not P. gurnardi, suggesting an oioxenic specificity of P. gurnardi to E gurnardus. Careful re-examination of Plectanocotyle cf. gurnardi from C. lastoviza from the Western Mediterranean from the Helminthology collection of Muséum national d'Histoire naturelle (Paris, France) revealed that it differs from all congeners by morphometry (size of clamps, of terminal lappet and its hamuli and uncinuli, and size of atrial spines). The cox1 divergences between P. cf. gurnardi and P. major, P. lastovizae, and P. gurnardi sensu stricto were 10–11 %, 10–11 % and 8 % respectively, falling within the interspecific variations range. Plectanocotyle from the Mediterranean is described as a new species, P. jeanloujustinei n. sp. We apprise nomenclature problems in Plectanocotyle and consider P. elliptica a species inquirenda
The Beginning of a Wilson Cycle in an Accretionary Orogen: The Mongol–Okhotsk Ocean Opened Assisted by a Devonian Mantle Plume
No full textThe opening of oceans within accretionary orogens is important for understanding the Wilson cycle. The Mongol–Okhotsk Ocean (MOO) began opening within the early Paleozoic accretionary collage of the Central Asian Orogenic Belt (CAOB), representing a world-class example to constrain the geodynamic history of ocean opening in accretionary orogens, but the kinematics and mechanisms associated to this process are highly debated. We report on a newly-discovered bimodal volcanic suite and associated volcanic-sediments that comprise part of the Altay-Sayan Rift System, which indicate a widespread Early Devonian extensional event within the CAOB. This extension regime is attributed to a Devonian mantle plume, which is thought to have impinged upon and weakened the lithosphere of the Early Paleozoic collage, and drove the opening of the MOO. Opening of the MOO suggests continent breakup in accretionary orogens tends to focus along intervening weak orogenic lithosphere between the rigid microcontinents.Research funders and strategic development areas (2 of 2): Chinese Academy of Sciences 10.13039/501100002367 National Natural Science Foundation of China10.13039/501100001809</p
Ophiolites in the Central Asian Orogenic Belt record Cambrian subduction initiation processes
No full textSubduction initiation remains elusive because no present example exists. Ophiolites formed over nascent subduction zones in the past provide the key to constraining the processes of subduction initiation. Here we document three Cambrian ophiolites with supra-subduction zone affinity, which likely reflect the inception of a plate-boundary scale subduction zone within the Paleo-Asian Ocean. Our findings, together with a compilation of Cambrian ophiolites in the Central Asian Orogenic Belt, indicate diachronous subduction initiation(s) along a > 6000 kilometer zone within the Paleo-Asian Ocean between 536 and 528 million years ago. The subduction initiation of the Paleo-Asian Ocean coincides with the closure of the Mirovoi Ocean following the collision of a series of microcontinents with the Siberian craton, likely representing a typical record of collision-induced subduction jump. Our observations and numerical modeling provide a new scenario that subduction initiations would locate at oceanic weak zones rather than passive margins of accreted microcontinents during collision-induced subduction process.Research funders: National Natural Science Foundation of China (grant Nos. 42272262 and 42172241), Strategic Priority Research Program of Chinese Academy of Sciences (grant No. XDB 41000000), the Second Tibetan Plateau Scientific Expedition and Research Program (Grant No. 2019QZKK0806), Ramón y Cajal Fellowship from the Spanish Ministry of Science and Innovation (Grant RYC2019-028244-I).</p
A common precursor for global hotspot lavas
No full textHotspot lavas exhibit chemical heterogeneity, much of which is ascribed to heterogeneous deep mantle sources that contain various components with distinct composition, origin and age. However, characterizing primary melt compositions and mantle heterogeneity directly is challenging. Here we investigate a global dataset of hotspot lavas to constrain the incompatible-element composition of their parental melts and sources. Trace-element ratios indicate that the compositional heterogeneity of global hotspot lavas is not primary, but reflects processes that hotspot melts undergo as they ascend to the surface. We find the parental melts of these lavas, as well as of kimberlites and basalts from large igneous provinces, to be uniform in their elemental, and radiogenic and noble-gas isotope, composition. We suggest that the parental melts to all of these lavas derive from a depleted and outgassed mantle reservoir that was replenished with incompatible element-enriched material during the Archaean. This interpretation explains the elemental, radiogenic and noble-gas isotope compositions of hotspot lavas without requiring a heterogeneous lower mantle or the long-term survival of undegassed relics from a primordial Earth.Research funders and strategic development areas: Gouvernement du Canada | Natural Sciences and Engineering Research Council of Canada10.13039/501100000038</p
Garnet growth in a geological blink of an eye
No full textMineral reactions determine the physical and rheological properties of rocks, but whether these reactions occur close to or far from equilibrium and whether they are continuous or pulsed is challenging to unravel. This introduces significant uncertainty in determining the thermomechanical properties and behavior of the crust and estimating the pressure and temperature conditions that rocks underwent during their tectonic history. Here, we employ elemental mapping and high-precision Lu-Hf chronology to investigate whether and to what extent garnet—one of the most important recorders of pressure, temperature, deformation, and time in the lithosphere—keeps up with tectonic processes. The analysis was done on a single 1.2-cm-sized garnet grain from a carbonate-rich mica schist from the Schneeberg Complex (Italy). Five compositionally distinct zones were identified and dated separately. The four inner zones, characterized by trace-elements oscillations, yielded identical ages with a weighted mean of 98.4 ± 0.1 Ma (2σ), whereas the outermost zone yielded 97.8 ± 0.3 Ma. During the first growth pulse, garnet grew at an average radial growth rate of at least 6.2 cm m.y.−1. Nucleation initiated out of equilibrium conditions and resulted in high fluid production that, in turn, boosted garnet growth, episodically limited by the rock’s elements transport permeabilities. This pulsed, ultrafast garnet growth must have occurred over a very limited pressure-temperature window. This example provides a rare glimpse into the discontinuous nature of mineral reactions in metamorphic rocks and highlights garnet as a unique recorder of the processes that occur when such rocks push toward equilibrium
Extinction risk of European bryophytes predicted by bioclimate and traits
No full textExtinction risk is not randomly distributed among species but depends on species traits, their relationship to climate and land use, and corresponding threats by global change. While knowledge of which factors influence extinction risk is increasingly available for some taxonomic groups, this is still largely lacking for bryophytes. Here, we used random forest models to study which biological and ecological traits and bioclimatic variables are important predictors for extinction risk in European bryophytes. We hypothesized that species with a high extinction risk have a short life span, low dispersal capacities, and are more likely specialists than generalists in terms of ecological traits and bioclimate. Overall, we found bioclimatic variables to be the most important predictors for extinction risk, most notably precipitation seasonality, and related ecological traits such as continentality and elevational range. Important biological traits were plant size, life strategy and sporophyte production. In general, species living at climatic extremes and/or those with a narrow environmental range are more likely to be threatened. In addition, small-sized species and/or species with low reproductive effort and/or larger spore size are more likely to be threatened. Our findings imply that climate change may become an important driver of bryophytes extinction risk and that biological and ecological traits will be most relevant for species in coping with future threats
