Global arthropod beta-diversity is spatially and temporally structured by latitude.

Global biodiversity gradients are generally expected to reflect greater species replacement closer to the equator. However, empirical validation of global biodiversity gradients largely relies on vertebrates, plants, and other less diverse taxa. Here we assess the temporal and spatial dynamics of global arthropod biodiversity dynamics using a beta-diversity framework. Sampling includes 129 sampling sites whereby malaise traps are deployed to monitor temporal changes in arthropod communities. Overall, we encountered more than 150,000 unique barcode index numbers (BINs) (i.e. species proxies). We assess between site differences in community diversity using beta-diversity and the partitioned components of species replacement and richness difference. Global total beta-diversity (dissimilarity) increases with decreasing latitude, greater spatial distance and greater temporal distance. Species replacement and richness difference patterns vary across biogeographic regions. Our findings support long-standing, general expectations of global biodiversity patterns. However, we also show that the underlying processes driving patterns may be regionally linked.

ddRAD Sequencing and DNA Barcoding.

Double-digest restriction site-associated DNA sequencing is a library preparation protocol that enables capturing variable sites across the genome including single-nucleotide polymorphisms (SNPs). These SNPs can be utilized to gain evolutionary insights into patterns observed in DNA barcodes, to infer population structure and phylogenies, to detect gene flow and introgression, and to perform species delimitation analyses. The protocol includes chemically shearing genomic DNA with restriction enzymes, unique tagging, size selection, and amplification of the resulting DNA fragments. Here we provide a detailed description of each step of the protocol, as well as information on essential equipment and common issues encountered during laboratory work.

Patterns of speciation in a parapatric pair of Saturnia moths as revealed by target capture.

The focus of this study has been to understand the evolutionary relationships and taxonomy of a widely distributed parapatric species pair of wild silk moths in Europe: Saturnia pavonia and Saturnia pavoniella (Lepidoptera: Saturniidae). To address species delimitation in these parapatric taxa, target enrichment and mtDNA sequencing was employed alongside phylogenetic, admixture, introgression, and species delimitation analyses. The dataset included individuals from both species close to and farther away from the contact zone as well as two hybrids generated in the lab. Nuclear markers strongly supported both S. pavonia and S. pavoniella as two distinct species, with hybrids forming a sister group to S. pavoniella. However, the Maximum Likelihood (ML) tree generated from mtDNA sequencing data presented a different picture, showing both taxa to be phylogenetically intermixed. This inconsistency is likely attributable to mitonuclear discordance, which can arise from biological factors (e.g., introgressive hybridization and/or incomplete lineage sorting). Our analyses indicate that past introgressions have taken place, but that there is no evidence to suggest an ongoing admixture between the two species, demonstrating that the taxa have reached full postzygotic reproductive isolation and hence represent two distinct biological species. Finally, we discuss our results from an evolutionary point of view taking into consideration the past climatic oscillations that have likely shaped the present dynamics between the two species. Overall, our study demonstrates the effectiveness of the target enrichment approach in resolving shallow phylogenetic relationships under complex evolutionary circumstances and that this approach is useful in establishing robust and well-informed taxonomic delimitations involving parapatric taxa.

Exploring and validating observations of non-local species in eDNA samples.

The development of DNA-based methods in recent decades has opened the door to numerous new lines of research in the biological sciences. While the speed and accuracy of DNA methodologies are clearly beneficial, the sensitivity of these methods has the adverse effect of increased susceptibility to false positives resulting from contamination in field or lab. Here, we present findings from a metabarcoding study on the diet of and food availability for five insectivorous birds, in which multiple lepidopteran species not known to occur locally were discovered. After describing the pattern of occurrences of these non-local species in the samples, we discuss various potential origins of these sequences. First, we assessed that the taxonomic assignments appeared reliable, and local occurrences of many of the species could be plausibly ruled out. Then, we looked into the possibilities of natural environmental contamination, judging it to be unlikely, albeit impossible to fully falsify. Finally, while dissimilar combinations of non-local species' occurrences across the samples did not initially suggest lab contamination, we found overlap with taxa and sequences handled in the same lab, which was undoubtedly not coincidental. Even so, not all exact sequences were accounted for in these locally conducted studies, nor was it clear if these and other sequences could remain detectable years later. Although the full explanation for the observations of non-local species remains inconclusive, these findings highlight the importance of critical examination of metabarcoding results, and showcase how species-level taxonomic assignments utilizing comprehensive reference libraries may be a tool in detecting potential contamination events, and false positives in general.

Hydric effects on thermal tolerances influence climate vulnerability in a high-latitude beetle.

Species' thermal tolerances are used to estimate climate vulnerability, but few studies consider the role of the hydric environment in shaping thermal tolerances. As environments become hotter and drier, organisms often respond by limiting water loss to lower the risk of desiccation; however, reducing water loss may produce trade-offs that lower thermal tolerances if respiration becomes inhibited. Here, we measured the sensitivity of water loss rate and critical thermal maximum (CTmax ) to precipitation in nature and laboratory experiments that exposed click beetles (Coleoptera: Elateridae) to acute- and long-term humidity treatments. We also took advantage of their unique clicking behavior to characterize subcritical thermal tolerances. We found higher water loss rates in the dry acclimation treatment compared to the humid, and water loss rates were 3.2-fold higher for individuals that had experienced a recent precipitation event compared to individuals that had not. Acute humidity treatments did not affect CTmax , but precipitation indirectly affected CTmax through its effect on water loss rates. Contrary to our prediction, we found that CTmax was negatively associated with water loss rate, such that individuals with high water loss rate exhibited a lower CTmax . We then incorporated the observed variation of CTmax into a mechanistic niche model that coupled leaf and click beetle temperatures to predict climate vulnerability. The simulations indicated that indices of climate vulnerability can be sensitive to the effects of water loss physiology on thermal tolerances; moreover, exposure to temperatures above subcritical thermal thresholds is expected to increase by as much as 3.3-fold under future warming scenarios. The correlation between water loss rate and CTmax identifies the need to study thermal tolerances from a "whole-organism" perspective that considers relationships between physiological traits, and the population-level variation in CTmax driven by water loss rate complicates using this metric as a straightforward proxy of climate vulnerability.

Molecular phylogeny, divergence time, biogeography and trends in host plant usage in the agriculturally important tortricid tribe Grapholitini (Lepidoptera: Tortricidae: Olethreutinae).

The leaf-roller moth tribe Grapholitini comprises about 1200 described species and contains numerous notorious pests of fruits and seeds. The phylogeny of the tribe has been little studied using contemporary methods, and the monophyly of several genera remains questionable. In order to provide a more robust phylogenetic framework for the group, we conducted a multiple-gene phylogenetic analysis of 104 species representing 27 genera of Grapholitini and 29 outgroup species. Divergence time, ancestral area, and host plant usage were also inferred to explore evolutionary trends in the tribe. Our analyses indicate that Larisa and Corticivora, traditionally assigned to Grapholitini, are best excluded from the tribe. After removal of these two genera, the tribe is found to be monophyletic, represented by two major lineages-a Dichrorampha clade and a Cydia clade, the latter of which can be divided into seven generic groups. The genus Grapholita was found to be polyphyletic, comprising three different clades, and we propose three genera to accommodate these groups: Grapholita (sensu stricto), Aspila (formerly a subgenus of Grapholita) and Ephippiphora (formerly considered a synonym of Grapholita). We summarize each generic group, including related genera not included in our analysis, providing morphological, pheromone and food plant characters that support particular branches within the molecular hypotheses. Biogeographical analyses indicate that Grapholitini probably originated in the Nearctic, Afrotropical and Neotropical regions in the Lutetian of the middle Eocene (ca. 44.3 Ma). Our results also indicate that most groups in Grapholitini originated from Fabaceae-feeding monophagous or oligophagous ancestors, and that host plant shifts probably promoted species diversification within the tribe.

Genomic evidence for contrasting patterns of host-associated genetic differentiation across shared host-plant species in leaf- and bud-galling sawflies.

Resource specialization and ecological speciation arising through host-associated genetic differentiation (HAD) are frequently invoked as an explanation for the high diversity of plant-feeding insects and other organisms with a parasitic lifestyle. While genetic studies have demonstrated numerous examples of HAD in insect herbivores, the rarity of comparative studies means that we still lack an understanding of how deterministic HAD is, and whether patterns of host shifts can be predicted over evolutionary timescales. We applied genome-wide single nucleotide polymorphism and mitochondrial DNA sequence data obtained through genome resequencing to define species limits and to compare host-plant use in population samples of leaf- and bud-galling sawflies (Hymenoptera: Tenthredinidae: Nematinae) collected from seven shared willow (Salicaceae: Salix) host species. To infer the repeatability of long-term cophylogenetic patterns, we also contrasted the phylogenies of the two galler groups with each other as well as with the phylogeny of their Salix hosts estimated based on RADseq data. We found clear evidence for host specialization and HAD in both of the focal galler groups, but also that leaf gallers are more specialized to single host species compared with most bud gallers. In contrast to bud gallers, leaf gallers also exhibited statistically significant cophylogenetic signal with their Salix hosts. The observed discordant patterns of resource specialization and host shifts in two related galler groups that have radiated in parallel across a shared resource base indicate a lack of evolutionary repeatability in the focal system, and suggest that short- and long-term host use and ecological diversification in plant-feeding insects are dominated by stochasticity and/or lineage-specific effects.

Diversification linked to larval host plant in the butterfly Eumedonia eumedon.

It is widely accepted that the relationship between phytophagous insects and their host plants influences insect diversification. However, studies addressed at documenting host-associated genetic differentiation (HAD) and the mechanisms that drive reproductive isolation in host-associated lineages (or host races) are still scarce relative to insect diversity. To uncover further evidence on the HAD processes in Lepidoptera, we investigated the genetic structure of the geranium argus butterfly (Eumedonia eumedon) and tested for isolation by ecology (IBE) vs. isolation by distance (IBD). Genomic data revealed an array of host races (three of them in the same mountain range, the Cantabrian Mountains, northern Iberia) at apparently distinct levels of reproductive isolation. We found a pattern of IBE mediated by HAD at both local and European scales, in which genetic differentiation between populations and individuals correlated significantly with the taxonomic relatedness of the host plants. IBD was significant only when considered at the wider European scale. We hypothesize that, locally, HAD between Geranium-feeding populations was caused (at least partially) by allochrony, that is via adaptation of adult flight time to the flowering period of each host plant species. Nevertheless, the potential reproductive isolation between populations using Erodium and populations using Geranium cannot be explained by allochrony or IBD, and other mechanisms are expected to be at play.

New and little known Coleophora Hbner, 1822 species from Morocco. Part I. (Lepidoptera, Coleophoridae).

Altogether, 64 Coleophora (Lepidoptera: Coleophoridae) species from Morocco are reported, based on recent collecting expeditions. Twelve new species are described: C. retusa Tabell, sp. nov., C. afrofrischella Tabell, sp. nov., C. olei Tabell, sp. nov., C. carsteni Tabell, sp. nov., C. ifranensis Tabell & Kullberg, sp. nov., C. jaskai Tabell, sp. nov., C. submendica Tabell, sp. nov., C. adipella Tabell, sp. nov., C. antiatlasella Tabell, sp. nov., C. dikeratella Tabell & Kullberg, sp. nov., C. afrodianthi Tabell, sp. nov. and C. knudi Tabell, sp. nov. Of the previously described species, 20 are collected for the first time from Morocco, of which nine are also new to Africa. Adult males and females and their genitalia are illustrated. DNA barcodes of the presented species, if existing, are compared with those of all other Coleophoridae available on the BOLD database. Each of the barcoded new species has a unique BIN (Barcode Index Number). The female genitalia of C. arefactella Staudinger, 1859, C. stenidella Toll, 1952 and C. griseomixta Toll, 1960 are illustrated for the first time.

Palaearctic willow-catkin sawflies: a revision of the amentorum species group of Euura (Hymenoptera, Tenthredinidae).

The Euura amentorum species group is Holarctic, and in Europe it is most species-rich in the North. Their larvae develop entirely within the female catkins of Salix species: some species bore in the central stalk, whereas others live outside this and feed mainly on the developing seeds. Eight Palaearctic species are treated here as valid, and a key to these is provided. Males of five species are known. Two new species are described from northern Europe: Euura pohjola sp. n. and E. ursaminor sp. n. First records of E. itelmena (Malaise, 1931) from the West Palaearctic are presented. We propose seven new synonymies: Pontopristia montana Lindqvist, 1961 (junior secondary homonym in Euura) with Euura freyja (Liston, Taeger & Blank, 2009); Pontopristia brevilabris Malaise, 1921, Amauronematus fennicus Lindqvist, 1944, Pontopristia boreoalpina Lindqvist, 1961, Pontopristia punctulata Lindqvist, 1961, and Amauronematus pyrenaeus Lacourt, 1995 with Euura microphyes (Frster, 1854); and Pteronidea holmgreni Lindqvist, 1968 with Nematus umbratus Thomson, 1871. Lectotypes are designated for: Amauronematus fennicus Lindqvist, 1944, Nematus amentorum Frster, 1854, Nematus suavis Ruthe, 1859, Pontopristia brevilabris Malaise, 1921, Pontopristia itelmena Malaise, 1931, Pontopristia kamtchatica Malaise, 1931, Pontopristia lapponica Malaise, 1921, Pontopristia latiserra Malaise, 1921, Pontopristia romani Malaise, 1921, and Pristiphora amentorum var. nigripleuris Enslin, 1916. Many new host plant associations are recorded.

Linking large-scale genetic structure of three Argynnini butterfly species to geography and environment.

Understanding which factors and processes are associated with genetic differentiation within and among species remains a major goal in evolutionary biology. To explore differences and similarities in genetic structure and its association with geographical and climatic factors in sympatric sister species, we conducted a large-scale (>32° latitude and >36° longitude) comparative phylogeographical study on three Argynnini butterfly species (Speyeria aglaja, Fabriciana adippe and F. niobe) that have similar life histories, but differ in ecological generalism and dispersal abilities. Analyses of nuclear (ddRAD-sequencing derived SNP markers) and mitochondrial (COI sequences) data revealed differences between species in genetic structure and how genetic differentiation was associated with climatic factors (temperature, solar radiation, precipitation, wind speed). Geographical proximity accounted for much of the variation in nuclear and mitochondrial structure and evolutionary relationships in F. adippe and F. niobe, but only explained the pattern observed in the nuclear data in S. aglaja, for which mitonuclear discordance was documented. In all species, Iberian and Balkan individuals formed genetic clusters, suggesting isolation in glacial refugia and limited postglacial expansion. Solar radiation and precipitation were associated with the genetic structure on a regional scale in all species, but the specific combinations of environmental and geographical factors linked to variation within species were unique, pointing to species-specific responses to common environments. Our findings show that the species share similar colonization histories, and that the same ecological factors, such as niche breadth and dispersal capacity, covary with genetic differentiation within these species to some extent, thereby highlighting the importance of comparative phylogeographical studies in sympatric sister species.

Integrative taxonomy reveals overlooked cryptic diversity in the conifer feeding Batrachedrapinicolella (Zeller, 1839) (Lepidoptera, Batrachedridae).

During efforts to generate DNA barcodes for all European Lepidoptera, Batrachedrapinicolella (Zeller, 1839) was found to comprise two genetically distinct clusters. Morphological investigation and results from two nuclear markers and ddRAD sequencing furthermore support the existence of two distinct taxa which we treat as two separate species, B.pinicolella and B.confusella sp. nov. A lectotype for B.pinicolella is designated. Available data indicate that the biology of both species also differs, with Piceaabies (L.) Karsten as a proved host-plant for B.pinicolella and Pinussylvestris L. for B.confusella sp. nov. Both species are mainly distributed on the European continent with B.pinicolella occurring in boreal parts of North and Central Europe and introduced to Canada, reflecting a boreo-montane distribution pattern. Batrachedraconfusella sp. nov. is more widely distributed in temperate Northern and Central Europe.

Changes in Biomass and Diversity of Soil Macrofauna along a Climatic Gradient in European Boreal Forests.

Latitudinal gradients allow insights into the factors that shape ecosystem structure and delimit ecosystem processes, particularly climate. We asked whether the biomass and diversity of soil macrofauna in boreal forests change systematically along a latitudinal gradient spanning from 60° N to 69° N. Invertebrates (3697 individuals) were extracted from 400 soil samples (20 × 20 cm, 30 cm depth) collected at ten sites in 2015-2016 and then weighed and identified. We discovered 265 species living in soil and on the soil surface; their average density was 0.486 g d·w·m-2. The species-level diversity decreased from low to high latitudes. The biomass of soil macrofauna showed no latitudinal changes in early summer but decreased towards the north in late summer. This variation among study sites was associated with the decrease in mean annual temperature by ca 5 °C and with variation in fine root biomass. The biomass of herbivores and fungivores decreased towards the north, whereas the biomass of detritivores and predators showed no significant latitudinal changes. This variation in latitudinal biomass patterns among the soil macrofauna feeding guilds suggests that these guilds may respond differently to climate change, with poorly understood consequences for ecosystem structure and functions.

Climate shapes the spatiotemporal variation in color morph diversity and composition across the distribution range of Chrysomela lapponica leaf beetle.

Color polymorphism offers rich opportunities for studying the eco-evolutionary mechanisms that drive the adaptations of local populations to heterogeneous and changing environments. We explored the color morph diversity and composition in a Chrysomela lapponica leaf beetle across its entire distribution range to test the hypothesis that environmental and climatic variables shape spatiotemporal variation in the phenotypic structure of a polymorphic species. We obtained information on 13 617 specimens of this beetle from museums, private collections, and websites. These specimens (collected from 1830-2020) originated from 959 localities spanning 33° latitude, 178° longitude, and 4200 m altitude. We classified the beetles into five color morphs and searched for environmental factors that could explain the variation in the level of polymorphism (quantified by the Shannon diversity index) and in the relative frequencies of individual color morphs. The highest level of polymorphism was found at high latitudes and altitudes. The color morphs differed in their climatic requirements; composition of colour morphs was independent of the geographic distance that separated populations but changed with collection year, longitude, mean July temperature and between-year temperature fluctuations. The proportion of melanic beetles, in line with the thermal melanism hypothesis, increased with increasing latitude and altitude and decreased with increasing climate seasonality. Melanic morph frequencies also declined during the past century, but only at high latitudes and altitudes where recent climate warming was especially strong. The observed patterns suggest that color polymorphism is especially advantageous for populations inhabiting unpredictable environments, presumably due to the different climatic requirements of coexisting color morphs.

Genomics Reveal Admixture and Unexpected Patterns of Diversity in a Parapatric Pair of Butterflies.

We studied the evolutionary relationship of two widely distributed parapatric butterfly species, Melitaea athalia and Melitaea celadussa, using the ddRAD sequencing approach, as well as genital morphology and mtDNA data. M. athalia was retrieved as paraphyletic with respect to M. celadussa. Several cases of mito-nuclear discordance and morpho-genetic mismatch were found in the contact zone. A strongly diverged and marginally sympatric clade of M. athalia from the Balkans was revealed. An in-depth analysis of genomic structure detected high levels of admixture between M. athalia and M. celadussa at the contact zone, though not reaching the Balkan clade. The demographic modelling of populations supported the intermediate genetic make-up of European M. athalia populations with regards to M. celadussa and the Balkan clade. However, the dissimilarity matrix of genotype data (PCoA) suggested the Balkan lineage having a genetic component that is unrelated to the athalia-celadussa group. Although narrowly sympatric, almost no signs of gene flow were found between the main M. athalia group and the Balkan clade. We propose two possible scenarios on the historical evolution of our model taxa and the role of the last glacial maximum in shaping their current distribution. Finally, we discuss the complexities regarding the taxonomic delimitation of parapatric taxa.

Response to Zamani et al. (2020): The omission of critical data in the pursuit of "revolutionary" methods to accelerate the description of species.

Here we respond to the criticisms leveled against a proposal that suggested an efficient solution to the taxonomic impediment. We clarify some of our objectives and demonstrate that many of the criticisms apply more to traditional approaches to taxonomy rather than to our minimalist approach.

Promiscuous specialists: Host specificity patterns among generalist louse flies.

Ectoparasites such as louse flies (Diptera: Hippoboscidae) have tendency for host specialization, which is driven by adaptation to host biology as well as competition avoidance between parasites of the same host. However, some louse fly species, especially in genera attacking birds, show wide range of suitable hosts. In the presented study, we have surveyed the current status of bird specific louse flies in Finland to provide comprehensive host association data to analyse the ecological requirements of the generalist species. A thorough sampling of 9342 birds, representing 134 species, recovered 576 specimens of louse flies, belonging to six species: Crataerina hirundinis, C. pallida, Ornithomya avicularia, O. chloropus, O. fringillina and Ornithophila metallica. Despite some overlapping hosts, the three Ornithomya species showed a notable pattern in their host preference, which was influenced not only by the host size but also by the habitat and host breeding strategy. We also provide DNA barcodes for ten Finnish species of Hippoboscidae, which can be used as a resource for species identification as well as metabarcoding studies in the future.

High resolution DNA barcode library for European butterflies reveals continental patterns of mitochondrial genetic diversity.

The study of global biodiversity will greatly benefit from access to comprehensive DNA barcode libraries at continental scale, but such datasets are still very rare. Here, we assemble the first high-resolution reference library for European butterflies that provides 97% taxon coverage (459 species) and 22,306 COI sequences. We estimate that we captured 62% of the total haplotype diversity and show that most species possess a few very common haplotypes and many rare ones. Specimens in the dataset have an average 95.3% probability of being correctly identified. Mitochondrial diversity displayed elevated haplotype richness in southern European refugia, establishing the generality of this key biogeographic pattern for an entire taxonomic group. Fifteen percent of the species are involved in barcode sharing, but two thirds of these cases may reflect the need for further taxonomic research. This dataset provides a unique resource for conservation and for studying evolutionary processes, cryptic species, phylogeography, and ecology.

Subspecies of Pleurota bicostella (Clerck, 1759) revisited and descriptions of nine new species in the P. bicostella species group (Lepidoptera: Gelechioidea: Oecophoridae: Pleurotinae).

The identities of five subspecies of Pleurota bicostella (Clerck, 1759) are studied, and each is raised from subspecies to species: P. andalusica Back, 1973, stat. nov.; P. aragonella Chrétien, 1925, stat. rev.; P. asiatica Back, 1973, stat. nov.; P. illucidella Chrétien, 1915, stat. rev.; P. lepigrei Lucas, 1937, stat. rev. Nine new Pleurota species which all belong to the P. bicostella species group are described: P. agadirensis Tabell, sp. nov.; P. aprilella Tabell, sp. n.; P. karsholti Tabell, sp. nov.; P. kullbergi Tabell, sp. nov.; P. monochroma Tabell, sp. nov.; P. murina Tabell, sp. nov.; P. paragallicella Tabell, sp. nov; P. phaeolepida Tabell, sp. nov., all from Morocco; and P. dalilae Tabell, sp. nov. from Tunisia. Adult males and females, and their genitalia are illustrated. DNA barcodes of the aforementioned species are compared with those of all other Pleurotinae available to us in the BOLD database. Each of the presented and barcoded species has a unique BIN (Barcode Index Number).

Relevance of ddRADseq method for species and population delimitation of closely related and widely distributed wolf spiders (Araneae, Lycosidae).

Although species delimitation is often controversial, emerging DNA-based and classical morphology-based methods are rarely compared using large-scale samplings, even less in the case of widely distributed species that have distant, allopatric populations. In the current study, we examined species boundaries within two wolf spider species of the genus Pardosa (Araneae, Lycosidae), P. riparia and P. palustris. Wolf spiders constitute an excellent model for testing the relevance of traditional vs. modern methods in species and population delimitation because several closely related species are distributed over cross-continental geographic ranges. Allopatric populations of the two Pardosa species were sampled across Europe to Far East Russia (latitudinal range > 150°) and several dozen individuals were studied using morphological characters (morphometry of three measures for both sexes, plus five in males only and two in females only), DNA barcoding (COI sequencing) and double-digest restriction site associated DNA sequencing (ddRADseq). The results obtained allow for changing the taxonomic status of two Far East Russian populations to subspecies and ddRADseq proved to be a powerful tool for taxonomic research despite scarce sampling and inherent subjectivity of species delimitation in allopatry. Overall, this study pleads for both multi-criteria and more population-based studies in taxonomy.