Most soil and litter arthropods are unidentifable based on current DNA barcode reference libraries

We are far from knowing all species living on the planet.Understanding biodiversity is demanding and requires time and expertise.Most groups are understudied given problems of identifying and delimiting species.DNA barcoding emerged to overcome some of the difficulties in identi-fying species.Its limitations derive from incomplete taxonomic knowledge and the lack of comprehensive DNA barcode libraries for so many taxonomic groups.Here,we evaluate how useful barcoding is for identifying arthropods from highly diverse leaf litter communities in the south-ern Appalachian Mountains(USA).We used 3 reference databases and several automated classification methods on a data set including several arthropod groups.Acari,Araneae,Collembola,Coleoptera,Diptera,and Hymenoptera were well represented,showing different performances across methods and databases.Spiders performed the best,with correct identification rates to species and genus levels of~50%across data-bases.Springtails performed poorly,no barcodes were identified to species or genus.Other groups showed poor to mediocre performance,from around 3%(mites)to 20%(beetles)correctly identified barcodes to species,but also with some false identifications.In general,BOLD-based identification offered the best identification results but,in all cases except spiders,performance is poor,with less than a fifth of specimens correctly identified to genus or species.Our results indicate that the soil arthropod fauna is still insufficiently documented,with many species unrepresented in DNA barcode libraries.More effort toward integrative taxonomic characterization is needed to complete our reference libraries before we can rely on DNAbarcoding as a universally applicable identification method.

Mitochondrial phylogeography of the Iberian endemic frog Rana iberica,with implications for its conservation

Genetic characterization of species using phylogeographic approaches represents a basic reference to understand their evolutionary history as well as to identify conservation priorities to protect areas of particular interest regarding evolutionary potential.Even in well-studied regions such information is lacking for the majority of species,including many endemic species with reduced distribution ranges.We investigate the phylogeographic pattern of the Iberian frog Rana iberica,an endemic amphibian restricted to Central and North-Western Iberian Peninsula.Using mitochondrial sequences,we reconstruct the phylogeographic history of the species to test the effect of Quaternary climate changes on the evolutionary diversification of lineages,that is,the differentiation of mitochondrial lineages and the formation of genetic diversity melting pots,and integrate phylogeographic evidence for future conservation planning.Our results indicate the existence of 3 main mitochondrial lineages differentiated during the Upper Pleistocene.Both historical demographic analyses and climatic niche modeling show a strong effect of glacial climate changes,suggesting recurrent range contractions and expansions.Under such circumstances,differentiation took place most likely by isolation in allopatric interglacial refugia.Secondary lineage admixture in northern Portugal generated a broad mixed zone with highest nucleotide diversity.Given its particular evolutionary potential,its reduced distribution and eventual threats under current climate change scenario,conservation priorities should focus on the isolated lineage from Sierra de Guadalupe.

Limited long-distance dispersal success in a Western European fairy shrimp evidenced by nuclear and mitochondrial lineage structuring

Anostraca are known by their ability for long-distance dispersal,but the existence in several species of deep,geographically structured mtDNA lineages suggests their populations are subjected to allopatric differentiation,isolation,and prevalence of local scale dispersion.Tanymastix stagnalis is one of the most widespread species of Anostraca and previous studies revealed an unclear geographical pattern of mtDNA genetic diversity.Here,we analyze populations from the Iberian and Italian Peninsulas,Central Europe,and Scandinavia,with the aim to characterize the patterns of genetic diversity in a spatio-temporal framework using mtDNA and nuclear markers to test gene flow among close populations.For these aims we built a time-calibrated phylogeny and carried out Bayesian phylogeographic analyses using a continuous diffusion model.Our results indicated that T.stagnalis presents a deeply structured genetic diversity,including 7 ancient lineages,some of them even predating the Pleistocene.The Iberian Peninsula harbors high diversity of lineages,with strong isolation and recent absence of gene flow between populations.Dispersal at local scale seems to be the prevailing dispersal mode of T.stagnalis,which exhibits a pattern of isolation-bydistance in the Iberian Peninsula.We remark the vulnerability of most of these lineages,given the limited known geographic distribution of some of them,and the high risk of losing important evolutionary potential for the species.