Automated identification of aquatic insects: A case study using deep learning and computer vision techniques

Deep learning techniques have recently found application in biodiversity research. Mayflies (Ephemeroptera), stoneflies (Plecoptera) and caddisflies (Trichoptera), often abbreviated as EPT, are frequently used for freshwater biomonitoring due to their large numbers and sensitivity to environmental changes. However, the morphological identification of EPT species is a challenging but fundamental task. Morphological identification of these freshwater insects is therefore not only extremely time-consuming and costly, but also often leads to misjudgments or generates datasets with low taxonomic resolution. Here, we investigated the application of deep learning to increase the efficiency and taxonomic resolution of biomonitoring programs. Our database contains 90 EPT taxa (genus or species level), with the number of images per category ranging from 21 to 300 (16,650 in total). Upon completion of training, a CNN (Convolutional Neural Network) model was created, capable of automatically classifying these taxa into their appropriate taxonomic categories with an accuracy of 98.7 %. Our model achieved a perfect classification rate of 100 % for 68 of the taxa in our dataset. We achieved noteworthy classification accuracy with morphologically closely related taxa within the training data (e.g., species of the genus Baetis, Hydropsyche, Perla). Gradient-weighted Class Activation Mapping (Grad-CAM) visualized the morphological features responsible for the classification of the treated species in the CNN models. Within Ephemeroptera, the head was the most important feature, while the thorax and abdomen were equally important for the classification of Plecoptera taxa. For the order Trichoptera, the head and thorax were almost equally important. Our database is recognized as the most extensive aquatic insect database, notably distinguished by its wealth of included categories (taxa). Our approach can help solve long-standing challenges in biodiversity research and address pressing issues in monitoring programs by saving time in sample identification.

Four decades of region- and species-specific trends in lowland stream Ephemeroptera abundance

Lowland stream ecosystems are under threat from climate change, industrialization, urbanization, and intensive agriculture. Since the 1980s, improvements in water quality have led to an increase in lowland stream biodiversity. Despite restoration efforts, however, further recovery is often hampered by the presence of region-specific (combinations of) stressors, and species-specific stressor responses. Identification of these stressors may not be achieved by the analysis of abundance data over large areas for entire communities or species assemblages. Therefore, our study introduces an alternative in-depth approach, selecting Ephemeroptera as a model organism group and analyzing 41 years of species abundance data across distinct geographical regions. Our findings revealed that 15 Ephemeroptera species had already disappeared before 1985, emphasizing the importance of evaluating an extended historical period when analyzing biodiversity trends. While biodiversity was generally characterized by an initial recovery that stagnated over time, the analysis of the past 41 years of Ephemeroptera abundance data revealed strong differences in species' abundance trends between periods, regions, and species. Certain species were likely to have benefitted from local restoration measures in specific geographical regions, while others may have declined due to the presence of region-specific stressors. Our approach underscores the importance of studying the development of region- and species-specific stream biodiversity trends over time to aid the selection of the appropriate restoration measures to recover lowland stream biodiversity.

Detailed DNA barcoding of mayflies in a small European country proved how far we are from having comprehensive barcode reference libraries

Mayflies (Ephemeroptera) are among the crucial water and habitat quality bioindicators. However, despite their intensive long-term use in various studies, more reliable mayfly DNA barcode data have been produced in a negligible number of countries, and only ~40% of European species had been barcoded with less than 50% of families covered. Despite being carried out in a small area, our study presents the second-most species-rich DNA reference library of mayflies from Europe and the first comprehensive view from an important biodiversity hotspot such as the Western Carpathians. Within 1153 sequences, 76 morphologically determined species were recorded and added to the Barcode of Life Data System (BOLD) database. All obtained sequences were assigned to 97 BINs, 11 of which were unique and three represented species never barcoded before. Sequences of 16 species with high intraspecific variability were divided into 40 BINs, confirming the presence of cryptic lineages. Due to the low interspecific divergence and the non-existing barcoding gap, sequences of six species were assigned to three shared BINs. Delimitation analyses resulted in 79 and 107 putative species respectively. Bayesian and maximum-likelihood phylogenies confirmed the monophyly of almost all species and complexes of cryptic taxa and proved that DNA barcoding distinguishes almost all studied mayfly species. We have shown that it is still sufficient to thoroughly investigate the fauna of a small but geographically important area to enrich global databases greatly. In particular, the insights gained here transcend the local context and may have broader implications for advancing barcoding efforts.

The genome sequence of the Northern Summer Mayfly, Siphlonurus alternatus (Say, 1824)

We present a genome assembly from an individual male Siphlonurus alternatus (the Northern Summer Mayfly; Arthropoda; Insecta; Ephemeroptera; Siphlonuridae). The genome sequence is 455.8 megabases in span. Most of the assembly is scaffolded into 11 chromosomal pseudomolecules, including the X sex chromosome. The mitochondrial genome has also been assembled and is 19.36 kilobases in length.

The genome sequence of the Large Brook Dun, Ecdyonurus torrentis (Kimmins, 1942)

We present a genome assembly from an individual female Ecdyonurus torrentis (the Large Brook Dun; Arthropoda; Insecta; Ephemeroptera; Heptageniidae). The genome sequence is 503.2 megabases in span. Most of the assembly is scaffolded into 11 chromosomal pseudomolecules, including the X sex chromosome. The mitochondrial genome has also been assembled and is 15.69 kilobases in length.

Altitudinal and seasonal distribution of benthic macroinvertebrates in River Tons - a tributary of Yamuna River, Uttarakhand, India

The main tributary of the Yamuna, the Tons River, exhibits altitudinal changes in its macroinvertebrate community's diversity, abundance, and composition. Between May 2019 and April 2021, the study was conducted in the upper section of the river. A total of 48 numbers of taxa from 34 families and ten orders were recorded during the investigation. At this elevation of 1150 to 1287 m, the two most predominant orders are Ephemeroptera (32.9%) and Trichoptera (29.5%). During the premonsoon season, they had the lowest macroinvertebrate density (250-290 individuals/m2), and the post-monsoon season had the highest density (600-640 individuals/m2). During the post-monsoon season, the maximum larval forms (60%) of various insect orders were predominant. The findings indicated that lower altitudes (1150-1232 m) have higher macroinvertebrate abundance than higher ones. The diversity of dominance is shallow at site-I (0.0738) and strong at the site-IV during the premonsoon season (0.03837). Taxa richness, as measured by the Margalef index (D), peaked in the spring season (January to March) at 6.9 and reached its lowest point (5.74) in the premonsoon season (April to May). Only 16 taxa were discovered in site-I and site-II, but 39 taxa were discovered at low altitudes (site-IV, 1100 m) (1277-1287 m). The Tons River contains a total of 12 and 13 genera, respectively, that belong to the orders Ephemeroptera and Trichoptera, according to qualitative study of the macroinvertebrates. The current study supports the use of macroinvertebrates as bioindicator species for monitoring biodiversity and assessing the health of ecosystems.

Characterizing Hox genes in mayflies (Ephemeroptera), with Hexagenia limbata as a new mayfly model

BACKGROUND

Hox genes are key regulators of appendage development in the insect body plan. The body plan of mayfly (Ephemeroptera) nymphs differs due to the presence of abdominal appendages called gills. Despite mayflies' phylogenetic position in Paleoptera and novel morphology amongst insects, little is known of their developmental genetics, such as the appendage-regulating Hox genes. To address this issue we present an annotated, early instar transcriptome and embryonic expression profiles for Antennapedia, Ultrabithorax, and Abdominal A proteins in the mayfly Hexagenia limbata, identify putative Hox protein sequences in the mayflies H. limbata, Cloeon dipterum, and Ephemera danica, and describe the genomic organization of the Hox gene cluster in E. danica.

RESULTS

Transcriptomic sequencing of early instar H. limbata nymphs yielded a high-quality assembly of 83,795 contigs, of which 22,975 were annotated against Folsomia candida, Nilaparvata lugens, Zootermopsis nevadensis and UniRef90 protein databases. Homeodomain protein phylogeny and peptide annotations identified coding sequences for eight of the ten canonical Hox genes (excluding zerknüllt/Hox3 and fushi tarazu) in H. limbata and C. dipterum, and all ten in E. danica. Mayfly Hox protein sequences and embryonic expression patterns of Antp, Ubx, and Abd-A appear highly conserved with those seen in other non-holometabolan insects. Similarly, the genomic organization of the Hox cluster in E. danica resembles that seen in most insects.

CONCLUSIONS

We present evidence that mayfly Hox peptide sequences and the embryonic expression patterns for Antp, Ubx, and Abd-A are extensively conserved with other insects, as is organization of the mayfly Hox gene cluster. The protein data suggest mayfly Antp, Ubx, and Abd-A play appendage promoting and repressing roles during embryogenesis in the thorax and abdomen, respectively, as in other insects. The identified expression of eight Hox genes, including Ubx and abd-A, in early instar nymphs further indicates a post-embryonic role, possibly in gill development. These data provide a basis for H. limbata as a complementary Ephemeridae model to the growing repertoire of mayfly model species and molecular techniques.

Seasonal modifications of longitudinal distribution patterns within a stream: Interspecific interactions in the niche overlap zones of two Ephemera mayflies

Niche differentiation between closely related species leads to differentiation of their habitats. Segregation based on slight differences in environmental factors, that is niche differentiation on the microhabitat scale, allows more species to inhabit a certain geographic space. Therefore, such fine scale niche differentiation is an important factor in the support of species diversity. In addition, niche differentiation on the microhabitat scale and/or the differentiation of breeding seasons can be considered typical mechanisms that facilitate multispecies' co-existence. In this study, sister species (Commonly, Ephemera japonica inhabit at upstream region and Ephemera strigata inhabit at middle stream region), which often coexist in the upper to middle reaches of river systems of the Japanese Islands, were targeted and the following aspects were investigated. First, differences in habitat preference and interspecific differences in flow distribution patterns on a geographically fine scale were tracked in detail. Subsequently, the temporal transitions of their distribution patterns were investigated in detail and seasonal changes were investigated. Finally, we thoroughly investigated the disappearance of nymphs of each species from the river due to emergence affected the distribution of each species (by conducting daily emergence surveys). Combining results of these multiple studies also suggested that there may be spatiotemporal interspecial interaction between these two species within/around their overlapping regions. Traditionally, the longitudinal distribution pattern of these two Ephemera mayflies has been thought to be established based on a difference in habitat preferences, but this study revealed that the interspecific interaction between the two species also plays an important role. This study provides new insights into species diversity and distribution pattern formation in river-dwelling species.

Towards Insect-Friendly Road Lighting-A Transdisciplinary Multi-Stakeholder Approach Involving Citizen Scientists

Simple Summary

Road lighting is a service provided at night, mainly to ensure the secure and safe passage of humans. However, lighting at night can have adverse effects on insects or ecosystems, which are not yet considered in planning. Here, we introduce a comprehensive approach for the design and implementation of a novel insect-friendly road luminaire. The lighting design provides an optimized radiation geometry that avoids emissions at the trajectory height of insects, reduces the attraction of insects and the fragmentation of their habitats, and at the same time provides adequate night-time illumination in residential areas. The effects of the new design on insect behavior and night sky brightness will be evaluated two years before and two years after the change of the road luminaires and additionally in a direct comparison, as some luminaires of the old design will remain as controls. Citizen scientists are involved in the identification of insects and the measurement of night sky brightness. A broad public engagement program also highlights discussions about the competing interests of different stakeholders in lighting design, explicitly including the effects of illumination on insect fauna and biodiversity.

Abstract

(1) The project “Tatort Streetlight” implements an insect-friendly road light design in a four year before–after, control–impact (BACI) approach involving citizen scientists. It will broaden the stakeholder interests from solely anthropogenic perspectives to include the welfare of insects and ecosystems. Motivated by the detrimental impacts of road lighting systems on insects, the project aims to find solutions to reduce the insect attraction and habitat fragmentation resulting from roadway illumination. (2) The citizen science approach invites stakeholders to take part and join forces for the development of a sustainable and environmentally friendly road lighting solution. Here, we describe the project strategy, stakeholder participation and motivation, and how the effects of the alternative road luminaire and lighting design can be evaluated. (3) The study compares the changes in (a) insect behavior, (b) night sky brightness, and (c) stakeholder participation and awareness. For this purpose, different experimental areas and stakeholders in four communities in Germany are identified. (4) The project transfers knowledge of adverse effects of improperly managed road illumination and interacts with various stakeholders to develop a new road lighting system that will consider the well-being of street users, local residents, and insects.

Baetid abundances are a rapid indicator of thermal stress and riparian zone intactness

Riparian zone vegetation plays an integral role in freshwater ecology, notably by buffering water temperatures, and in providing habitat for the adult stages of many aquatic species. We measured the contribution that riparian vegetation makes to temperature buffering, and how this affects the freshwater fauna, specifically using changes in abundances of baetid may flies for the Luvuvhu River catchment in South Africa. Water temperatures were compared for shaded versus un-shaded sites, and thermal stress between seasons was estimated using a cumulative probability model for the most widespread mayfly species, Dabulamanzia media. It is concluded that thermal stress due to losses in riparian shading could be detected using mayfly abundances in a regular monitoring programme.

The fauna of aquatic invertebrates in the river impacted by wastewaters from the pulp and paper industry (Komi Republic)

BACKGROUND

Invertebrates are important elements of aquatic ecosystems and play a crucial role in the transformation of matter and energy in continental water bodies. Communities of aquatic invertebrates are characterised by high sensitivity to pollution by nutrients and toxic substances and acidification of water bodies; they serve as good bioindicators of the quality of the aquatic environment and impacts on hydroecosystems. All hydrobionts participate in the processes of self-purification of water bodies.The presented dataset provides information on the aquatic invertebrate community of a large northern river. During 2018-2020, we collected data on changes in the quantitative indicators of the development of benthic and planktonic communities, as well as the species diversity of their fauna. The dataset combines information about the occurrence and abundance of benthic and planktonic invertebrates and summarises data of aquatic invertebrate species found in the Vychegda River in the zone of influence from the pulp and paper mill.

NEW INFORMATION

The presented dataset is part of a monitoring programme of the river ecosystems in the production area of Mondi Syktyvkar JSC (the European North-East of Russia, Komi Republic). The dataset describes the structure of benthic invertebrate and plankton communities in the Northern Dvina River Basin. The data on the finding and abundance of large taxa of aquatic invertebrates and species of some groups: Oligochaeta, Cladocera, Copepoda, Rotifera, Ephemeroptera, Plecoptera and Trichoptera are presented. In total, the resource includes 8720 findings of invertebrates, of which 6041 are for zoobenthos organisms and 2679 for zooplankton organisms.

Evidence for wing development in the Late Palaeozoic Palaeodictyoptera revisited

The numerous fossil specimens described as consecutive series of different larval stages of two species, Tchirkovaea guttata and Paimbia fenestrata (Palaeodictyoptera: Tchirkovaeidae), were reinvestigated with emphasis on comparing the development and growth of their wings with that of the wings of a recent mayfly, Cloeon dipterum. This unique fossil material was for a long time considered as undisputed evidence for an unusual type of wing development in Palaeozoic insects. The original idea was that the larvae of Palaeodictyopterida had wings, which were articulated and fully movable in their early stages of postembryonic development and that these gradually enlarging wings changed their position from longitudinal to perpendicular to the body axis. Moreover, the development of wings was supposed to include two or more subimaginal instars, implying that the fully winged instars moulted several times during their postembryonic development. The results of the present study revealed that there is no evidence that this series of nymphal, subimaginal and imaginal wings provide support for the original idea of wing development in Palaeozoic insects. On the contrary, our results indicate, that the supposed palaeodictyopteran larval wings are in fact wing pads with a wing developing inside the cuticular sheath as in recent hemimetabolous insects. Moreover, this study newly reinterpreted the wing pad base of Parathesoneura carpenteri and confirmed the presence of nygma like structures on wings and wing pads of palaeodictyopteran Tchirkovaeidae.

The influence of the environment in the incorporation of copper and cadmium in scraper insects

In regions with intense agricultural activity, increases in heavy metal concentrations in aquatic environments are common. Among the metals associated with agricultural activities, copper (Cu) and cadmium (Cd) have been found to directly affect aquatic trophic structures due to the ease of incorporation by primary producers and consuming organisms. Aquatic insects are predominantly found in streams, and their presence is determined by environmental characteristics and food availability. In this study, we seek to understand how the incorporation of Cu and Cd by scraper insects relates to their environment and food sources. We collected water, sediment, biofilm and scraper insect samples in streams with different intensities of agricultural activities in the drainage areas. The intensity of agricultural activities in the catchment area positively influenced the Cu and Cd concentrations in organisms and other aquatic compartments. The metals were readily incorporated by the biofilms. Although the functional characteristics are important to understand the functioning of ecosystems, in this study, we found that the physiological characteristics can be determinants in the concentrations of metals in aquatic insects.

Comparative Mitogenomic Analysis of Heptageniid Mayflies (Insecta: Ephemeroptera): Conserved Intergenic Spacer and tRNA Gene Duplication

Large intergenic spacers and tRNA gene duplications have been reported in several insect groups, although little is known about mitogenomes of mayflies. Here, we determined complete mitogenomes of ten heptageniid species and systemically analyzed their mitogenomic features. Both a conserved intergenic spacer (IGS) and trnM duplication were detected in those mitogenomes. The IGS, which was observed in heptageniids, could be further folded into a stable stem-loop structure. The tRNA gene duplication was found in almost all analyzed mitogenomes, and a unique gene block trnI-trnM-trnQ-trnM-ND2 was also discovered. Our analysis demonstrates that the heptageniid gene arrangement pattern can be explained by the tandem duplication-random loss (TDRL) model. Phylogenetic analyses using both Bayesian inference (BI) and maximum likelihood (ML) methods based on the nucleotide and amino acid sequence data recovered the genus Epeorus as monophyletic with strong support. Our results provide a better understanding of mitogenomic evolution in Heptageniidae, as well as novel molecular markers for species identification of mayflies.

Mayfly response to different stress types in small and mid-sized lowland rivers

Freshwater ecosystems are endangered worldwide by various human pressures, resulting in dramatic habitat and species loss. Many aquatic invertebrates respond to disturbances in their habitat, and mayflies are among the most sensitive ones. Therefore, we investigated mayfly response to anthropogenic disturbances at 46 study sites encompassing slightly to heavily modified small and mid-sized lowland streams and rivers. Mayfly nymphs were sampled between April and September 2016 using a benthos hand net. A total of 21 species was recorded, with Cloeondipterum (Linnaeus, 1761) being the most frequently recorded one. Nevertheless, the taxa richness was rather low per site, i.e., between zero and nine. Assemblage structure had a high share of lower reaches and lentic (potamic and littoral) elements, and detritivores (gatherers/collectors and active filter feeders). This indicates that hydromorphological alterations lead to assemblage “potamisation” in small and mid-sized rivers. More mayfly species were related to higher oxygen concentration and lower water temperature, abundance of aquatic vegetation and total organic carbon. Additionally, the assemblage diversity and abundance were negatively associated with increasing intensive agriculture area at the catchment scale. This study confirms mayfly bio-indicative properties, i.e., their sensitivity to alterations of their habitat and pollution, but also provides new data related to mayfly response to the impacted environment. Those data can be used for management and protection activities of lowland rivers and their biota according to the requirements of the European Water Framework Directive.

Novel gene rearrangement pattern in the mitochondrial genomes of Torleya mikhaili and Cincticostella fusca (Ephemeroptera: Ephemerellidae)

The mayfly family Ephemerellidae (Insecta: Ephemeroptera) is distributed around the world and has very high species diversity. However, its evolution pattern of mitogenome and phylogenetic relationships within Ephemeroptera remain unclear. In this study, the complete mitochondrial genomes (mitogenomes) of Torleya mikhaili (15,042 bp) and Cincticostella fusca (15,135 bp) were firstly determined and analyzed. Two ephemerellid mitogenomes shared similar gene organization with 37 typical genes as well as a putative control region. Compared with other reported mitogenomes of mayflies, the unique gene order (I'-CR-Q-M) was found in these two mitogenomes. Although the observed rearrangement pattern is novel within ephemeropteran mitogenomes, it could be explained presumably by the mechanisms of tandem duplication-random loss and recombination. The phylogenetic analyses using both Bayesian inference (BI) and maximum likelihood (ML) methods based on four nucleotide datasets placed three ephemerellid species together. Furthermore, the phylogenetic relationships of the three genera were recovered as ((Ephemerella + Cincticostella) + Torleya).

Complex and nonlinear climate-driven changes in freshwater insect communities over 42 years

The ongoing biodiversity crisis becomes evident in the widely observed decline in abundance and diversity of species, profound changes in community structure, and shifts in species' phenology. Insects are among the most affected groups, with documented decreases in abundance up to 76% in the last 25-30 years in some terrestrial ecosystems. Identifying the underlying drivers is a major obstacle as most ecosystems are affected by multiple stressors simultaneously and in situ measurements of environmental variables are often missing. In our study, we investigated a headwater stream belonging to the most common stream type in Germany located in a nature reserve with no major anthropogenic impacts except climate change. We used the most comprehensive quantitative long-term data set on aquatic insects available, which includes weekly measurements of species-level insect abundance, daily water temperature and stream discharge as well as measurements of additional physicochemical variables for a 42-year period (1969-2010). Overall, water temperature increased by 1.88 °C and discharge patterns changed significantly. These changes were accompanied by an 81.6% decline in insect abundance, but an increase in richness (+8.5%), Shannon diversity (+22.7%), evenness (+22.4%), and interannual turnover (+34%). Moreover, the community's trophic structure and phenology changed: the duration of emergence increased by 15.2 days, whereas the peak of emergence moved 13.4 days earlier. Additionally, we observed short-term fluctuations (<5 years) in almost all metrics as well as complex and nonlinear responses of the community toward climate change that would have been missed by simply using snapshot data or shorter time series. Our results indicate that climate change has already altered biotic communities severely even in protected areas, where no other interacting stressors (pollution, habitat fragmentation, etc.) are present. This is a striking example of the scientific value of comprehensive long-term data in capturing the complex responses of communities toward climate change.

Aquatic Insects Are Dramatically Underrepresented in Genomic Research

Aquatic insects comprise 10% of all insect diversity, can be found on every continent except Antarctica, and are key components of freshwater ecosystems. However, aquatic insect genome biology lags dramatically behind that of terrestrial insects. If genomic effort was spread evenly, one aquatic insect genome would be sequenced for every ~9 terrestrial insect genomes. Instead, ~24 terrestrial insect genomes have been sequenced for every aquatic insect genome. This discrepancy is even more dramatic if the quality of genomic resources is considered; for instance, while no aquatic insect genome has been assembled to the chromosome level, 29 terrestrial insect genomes spanning four orders have. We argue that a lack of aquatic insect genomes is not due to any underlying difficulty (e.g., small body sizes or unusually large genomes), yet it is severely hampering aquatic insect research at both fundamental and applied scales. By expanding the availability of aquatic insect genomes, we will gain key insight into insect diversification and empower future research for a globally important taxonomic group.

Declines in an abundant aquatic insect, the burrowing mayfly, across major North American waterways

Seasonal animal movement among disparate habitats is a fundamental mechanism by which energy, nutrients, and biomass are transported across ecotones. A dramatic example of such exchange is the annual emergence of mayfly swarms from freshwater benthic habitats, but their characterization at macroscales has remained impossible. We analyzed radar observations of mayfly emergence flights to quantify long-term changes in annual biomass transport along the Upper Mississippi River and Western Lake Erie Basin. A single emergence event can produce 87.9 billion mayflies, releasing 3,078.6 tons of biomass into the airspace over several hours, but in recent years, production across both waterways has declined by over 50%. As a primary prey source in aquatic and terrestrial ecosystems, these declines will impact higher trophic levels and environmental nutrient cycling.

The mitochondrial genome of Caenis sp. (Ephemeroptera: Caenidae) from Fujian and the phylogeny of Caenidae within Ephemeroptera

The phylogenetic relationship of Caenidae remains hotly debated within the Ephemeroptera. We sequenced the complete mitochondrial genome of Caenis sp. (Ephemeroptera: Caenidae) to discuss the phylogenetic relationships among the Caenidae. The mitochondrial genome of Caenis sp. collected from Jian’ou, Fujian province, China is a circular molecule of 15,392 bp in length containing 37 genes (13 protein-coding genes, 22 tRNAs, and two rRNAs), which showed the typical insect mitochondrial gene arrangement. In BI and ML phylogenetic trees using 23 species from 13 families, the monophyly of the families Caenidae, Heptageniidae, Isonychiidae, and Vietnamellidae was strongly supported. The clade of Caenidae is a sister clade to the clade of Teloganodidae and Baetidae.

The First Establishment of "Hand-Pairing" Cross-Breeding Method for the Most Ancestral Wing Acquired Insect Group

Insects are the most diverse organisms in the world and have been in existence since ca. 480 Ma; given this, they can provide profound insights into evolution. Among them, the order Ephemeroptera is one of the most basal clades of winged insects. This makes Ephemeroptera a significant key taxon in understanding the macro-evolution or the insect groundplan. In the development of biological evolutionary studies of this taxon, it is important to establish a technique for cross-breeding. Furthermore, the establishment of these techniques also makes a great contribution in the fields of micro-evolution. In a non-model taxon, the mayfly, subcultivation in the laboratory has been thus far considered impossible. With the exception of some parthenogenetic strains, it is extremely difficult to mate these insects in artificial environments. In this study, we established a successful artificial mating technique, i.e., a "hand-pairing" based cross-breeding method for mayflies. Furthermore, we also succeeded in clearly verifying by a genotyping method that the offspring reproduced by hand-pairing were in fact derived from the actual male and female which were used for hand-pairing. We established a reproductive experimental technique for hand-pairing of Dipteromimus tipuliformis and verified this technique by means genotyping. This technique could allow the artificial control of fertilization timing, and result in offspring which can be verified as to their status by means of genotyping. This achievement will be extremely important in the future for both the macro- and micro-evolutionary studies of insects.

Establishment of the mayfly Cloeon dipterum as a new model system to investigate insect evolution

The great capability of insects to adapt to new environments promoted their extraordinary diversification, resulting in the group of Metazoa with the largest number of species distributed worldwide. To understand this enormous diversity, it is essential to investigate lineages that would allow the reconstruction of the early events in the evolution of insects. However, research on insect ecology, physiology, development and evolution has mostly focused on few well-established model species. The key phylogenetic position of mayflies within Paleoptera as the sister group of the rest of winged insects and life history traits of mayflies make them an essential order to understand insect evolution. Here, we describe the establishment of a continuous culture system of the mayfly Cloeon dipterum and a series of experimental protocols and omics resources that allow the study of its development and its great regenerative capability. Thus, the establishment of Cloeon as an experimental platform paves the way to understand genomic and morphogenetic events that occurred at the origin of winged insects.

Temperature affects acute mayfly responses to elevated salinity: implications for toxicity of road de-icing salts

Salinity in freshwater ecosystems has increased significantly at numerous locations throughout the world, and this increase often reflects the use or production of salts from road de-icing, mining/oil and gas drilling activities, or agricultural production. When related to de-icing salts, highest salinity often occurs in winter when water temperature is often low relative to mean annual temperature at a site. Our study examined acute (96 h) responses to elevated salinity (NaCl) concentrations at five to seven temperature treatments (5-25°C) for four mayfly species (Baetidae: Neocloeon triangulifer, Procloeon fragile; Heptageniidae: Maccaffertium modestum; Leptophlebiidae: Leptophlebia cupida) that are widely distributed across eastern North America. Based on acute LC50s at 20°C, P. fragile was most sensitive (LC50 = 767 mg l^-1, 1447 µS cm^-1), followed by N. triangulifer (2755 mg l^-1, 5104 µS cm^-1), M. modestum (2760 mg l^-1, 5118 µS cm^-1) and L. cupida (4588 mg l^-1, 8485 µS cm^-1). Acute LC50s decreased as temperature increased for all four species (n = 5-7, R ² = 0.65-0.88, p = 0.052-0.002). Thus, acute salt toxicity is strongly temperature dependent for the mayfly species we tested, which suggests that brief periods of elevated salinity during cold seasons or in colder locations may be ecologically less toxic than predicted by standard 20 or 25°C laboratory bioassays.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

Why are mayflies (Ephemeroptera) lost following small increases in salinity? Three conceptual osmophysiological hypotheses

The salinity of many freshwaters is increasing globally as a result of human activities. Associated with this increase in salinity are losses of Ephemeroptera (mayfly) abundance and richness. The salinity concentrations at which Ephemeroptera decline in nature are lower than their internal salinity or haemolymph osmolality. Many species also suffer substantial mortality in single species laboratory toxicity tests at salinities lower than their internal salinity. These findings are problematic as conventional osmoregulation theory suggests that freshwater animals should not experience stress where external osmolality is greater than haemolymph osmolality. Here I explore three hypotheses to explain salt sensitivity in Ephemeroptera. These conceptual hypotheses are based on the observations that as the external sodium ion (Na⁺) concentration increases so does the Na⁺ turnover rate (both uptake and elimination rates increase). Sulphate ([Formula: see text]) uptake in mayflies also increases with increasing external [Formula: see text] although, unlike Na⁺, its rate of increase decreases with increasing external [Formula: see text] The first hypothesis is premised on ion turnover being energetically costly. The first hypothesis proposes that individuals must devote a greater proportion of their energy to ion homeostasis at the expense of other uses including growth and development. Lethal levels of salinity presumably result from individuals not being able to devote enough energy to maintain ion homeostasis without critical loss of other vital functions. The second hypothesis is premised on the uptake of Na⁺ exchanged for (an outgoing) H⁺, leading to (localized) loss of pH regulation. The third hypothesis is premised on localized Na⁺ toxicity or poisoning with increased Na turnover as salinity increases. None of the proposed hypotheses is without potential problems, yet all are testable, and research effort should be focused at attempting to falsify them.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

The complete mitochondrial genome of Epeorus herklotsi (Ephemeroptera: Heptageniidae) from Longquan, Zhejiang, China and its phylogeny

The mitochondrial genome of Epeorus herklotsi (Ephemeroptera: Heptageniidae) from Longquan, Zhejiang province, China was a circular molecule of 15,499 bp in length, containing 13 protein-coding genes, two ribosomal RNAs, 23 transfer RNAs, and a control region. The A + T content of the overall base composition of H-strand is 65.7%. All of the 13 protein-coding genes were begun with ATN as start codon except ND5 using GTG. ATP6, ATP8, COI, COIII, ND1, ND2, ND4L, and ND6 genes were terminated with TAA as stop codon, Cyt b ended with TAG and the other three protein-coding genes end with an incomplete stop codon (TA or T). In BI phylogenetic trees, the monophyly of the families Caenidae, Heptageniidae, Isonychiidae and Viemamellidae, and the genus Epeorus were strongly supported. Epeorus is a sister clade to Parafronurus, then cluster with Paegniodes.

Clarifying the phylogenetic relationships and taxonomy of Stenonema, Stenacron and Maccaffertium, three common eastern North American mayfly genera

Stenonema, Stenacron, and Maccaffertium are three closely related genera of mayflies (Ephemeroptera:Heptageniidae) commonly found across North America. Due to their primarily aquatic life history and sensitivity to aquatic pollutants, these mayflies are often used as water quality indicators. However, there is little morphological variation within these genera, leading to difficulties in identification and rampant taxonomic confusion, limiting their utility as bioindicators. In an attempt to resolve the phylogenetic relationships of Stenonema, Stenacron, and Maccaffertium, and to clarify their higher-level classifications, we sequenced regions of two mitochondrial genes (cytochrome oxidase subunit 1 (cox1) and 16S ribosomal RNA (rrnl)) and two nuclear genes (Wingless (Wg) and histone H3) from 60 individuals representing most of the described species in these genera and included data from representatives of three heptageniid genera (Kageronia, Macdunnoa and Pseudiron) proposed in previous studies to be closely related to our focal taxa as well as two more distantly related heptageniid genera (Epeorus and Heptagenia) to root the phylogenies. Maximum likelihood and Bayesian analysis were conducted on single-gene and concatenated multi-gene data sets and species tree methods were utilized to resolve relationships. These analyses resolved Stenacron as a monophyletic group sister to a clade comprising Macdunnoa, Maccaffertium and Stenonema. Maccaffertium was found to be paraphyletic, with Stenonema femoratum resolved within Maccaffertium as sister to M. mexicanum. Many relationships remained unresolved or varied across analyses, making revision of the classification based on phylogenetic considerations challenging. To minimize confusion while naming clades and acknowledging uncertainty in our phylogenetic conclusions, we redefine Stenonema to include Maccaffertium and propose three subgenera-Stenonema, Maccaffertium and Lewisa- for key well-supported clades.

Jumping and the aerial behavior of aquatic mayfly larvae (Myobaetis ellenae, Baetidae)

Mayfly larvae generally are aquatic, but some madicolous taxa (i.e., living in thin water films) crawl over rocks within streams and waterfalls. When startled, these larvae can break the water film, jump, and enter an aerial phase of locomotion. Because mayfly larvae have been suggested as potential exemplars for the origin of insect wings as tracheal gills, and furthermore represent the most basal extant lineage of pterygotes, we analyzed jumping behavior and free-fall trajectories for one such species of mayfly (Myobaetis ellenae, Baetidae) in Costa Rica. Jumping was commonplace in this taxon, but was undirected and was characterized by body spinning at high angular velocities. No aerodynamic role for the tracheal gills was evident. By contrast, jumping by a sympatric species of bristletail (Meinertellus sp., Archaeognatha) consistently resulted in head-first and stable body postures during aerial translation. Although capable of intermittently jumping into the air, the mayfly larvae could neither control nor target their aerial behavior. By contrast, a stable body posture during jumps in adult bristletails, together with the demonstrated capacity for directed aerial descent in arboreal representatives of this order, support ancestrally terrestrial origins for insect flight within the behavioral context of either jumping or falling from heights.

The mitochondrial genome of Caenis sp. (Ephemeroptera: Caenidae) and the phylogeny of Ephemeroptera in Pterygota

The phylogenetic relationship between Ephemeroptera (mayflies) and Odonata (dragonflies and damselflies) remains hotly debated in the insect evolution community. We sequenced the complete mitochondrial genome of Caenis sp. (Ephemeroptera: Caenidae) to discuss the phylogenetic relationship of Palaeoptera. The mitochondrial genome of Caenis sp. is a circular molecule of 15,254 bp in length containing 37 genes (13 protein-coding genes, 22 tRNAs, and 2 rRNAs), which showed the typical insect mitochondrial gene arrangement. In BI and ML phylogenetic trees using 71 species of 12 orders, our results support the Ephemeroptera as the basal group of winged insects.

The complete mitochondrial genome of Isonychia kiangsinensis (Ephemeroptera: Isonychiidae)

The complete mitochondrial genome of Isonychia kiangsinensis is a circular molecule of 15,456 bp in length, containing 2 rRNA genes, 13 protein-coding genes, 22 tRNA genes, and a control region. The AT content of the overall base composition is 62.9%. The length of the control region for I. kiangsinensis is 745 bp with 68.6% AT content. In BI and ML phylogenetic trees, Isonychia kiangsinensis was a sister clade to I. ignota and Isonychiidae was shown to be the basal clade of Ephemeroptera excluding Siphluriscidae. The monophyly of the families Isonychiidae, Heptageniidae, Viemamellidae, and Baetidae and the genus Isonychia were well supported.

A biomechanical analysis of prognathous and orthognathous insect head capsules: evidence for a many-to-one mapping of form to function

Insect head shapes are remarkably variable, but the influences of these changes on biomechanical performance are unclear. Among 'basal' winged insects, such as dragonflies, mayflies, earwigs and stoneflies, some of the most prominent anatomical changes are the general mouthpart orientation, eye size and the connection of the endoskeleton to the head. Here, we assess these variations as well as differing ridge and sclerite configurations using modern engineering methods including multibody dynamics modelling and finite element analysis in order to quantify and compare the influence of anatomical changes on strain in particular head regions and the whole head. We show that a range of peculiar structures such as the genal/subgenal, epistomal and circumocular areas are consistently highly loaded in all species, despite drastically differing morphologies in species with forward-projecting (prognathous) and downward-projecting (orthognathous) mouthparts. Sensitivity analyses show that the presence of eyes has a negligible influence on head capsule strain if a circumocular ridge is present. In contrast, the connection of the dorsal endoskeletal arms to the head capsule especially affects overall head loading in species with downward-projecting mouthparts. Analysis of the relative strains between species for each head region reveals that concerted changes in head substructures such as the subgenal area, the endoskeleton and the epistomal area lead to a consistent relative loading for the whole head capsule and vulnerable structures such as the eyes. It appears that biting-chewing loads are managed by a system of strengthening ridges on the head capsule irrespective of the general mouthpart and head orientation. Concerted changes in ridge and endoskeleton configuration might allow for more radical anatomical changes such as the general mouthpart orientation, which could be an explanation for the variability of this trait among insects. In an evolutionary context, many-to-one mapping of strain patterns onto a relatively similar overall head loading indeed could have fostered the dynamic diversification processes seen in insects.

The complete mitochondrial genome of Epeorus herklotsi (Ephemeroptera: Heptageniidae) and its phylogeny

The mitochondrial genome of Epeorus herklotsi (Ephemeroptera: Heptageniidae) is a circular molecule of 15,801 bp in length with a base composition of 32.7% A, 32.9% T, 21.5% C, 13.0% G, including extra tRNAMet gene. The IMQM tRNA cluster is found in E. herklotsi as well as Parafornuru youi and two species of Epeorus (KM244708, KJ493406), while the typical IQM tRNA cluster is found in Paegniodes cupulatus. In BI and ML phylogenetic trees, the monophyly of the families Heptageniidae, Baetidae, and Ephemerellidae are highly supported. E. herklotsi is a sister clade to Epeorus sp2. (KJ493406).

Application of Aquatic Insects (Ephemeroptera, Plecoptera And Trichoptera) In Water Quality Assessment of Malaysian Headwater

The Ephemeroptera, Plecoptera and Trichoptera (EPT) community structure and the specific sensitivity of certain EPT genera were found to be influenced by water parameters in the rivers of Gunung Jerai Forest Reserve (GJFR) in the north of peninsular Malaysia. The scores of EPT taxa richness of >10 in all rivers indicated all rivers’ habitats were non-impacted, having good water quality coinciding with Class I and Class II of Malaysian water quality index (WQI) classification of potable water. The abundance of EPT was very high in Teroi River (9,661 individuals) but diversity was lower (22 genera) than Tupah River which was highly diverse (28 genera) but lower in abundance (4,263 individuals). The lowest abundance and moderate diversity was recorded from Batu Hampar River (25 genera). Baetis spp. and Thalerosphyrus spp., Neoperla spp. and Cheumatopsyche spp. were the most common genera found. Classification for all rivers using EPT taxa Richness Index and WQI gave different category of water quality, respectively. The WQI classified Tupah and Batu Hampar rivers into Class II and Teroi River (Class I) was two classes above the classification of the EPT taxa Richness Index.

Larval aquatic insect responses to cadmium and zinc in experimental streams

To evaluate the risks of metal mixture effects to natural stream communities under ecologically relevant conditions, the authors conducted 30-d tests with benthic macroinvertebrates exposed to cadmium (Cd) and zinc (Zn) in experimental streams. The simultaneous exposures were with Cd and Zn singly and with Cd+Zn mixtures at environmentally relevant ratios. The tests produced concentration-response patterns that for individual taxa were interpreted in the same manner as classic single-species toxicity tests and for community metrics such as taxa richness and mayfly (Ephemeroptera) abundance were interpreted in the same manner as with stream survey data. Effect concentrations from the experimental stream exposures were usually 2 to 3 orders of magnitude lower than those from classic single-species tests. Relative to a response addition model, which assumes that the joint toxicity of the mixtures can be predicted from the product of their responses to individual toxicants, the Cd+Zn mixtures generally showed slightly less than additive toxicity. The authors applied a modeling approach called Tox to explore the mixture toxicity results and to relate the experimental stream results to field data. The approach predicts the accumulation of toxicants (hydrogen, Cd, and Zn) on organisms using a 2-pK_a bidentate model that defines interactions between dissolved cations and biological receptors (biotic ligands) and relates that accumulation through a logistic equation to biological response. The Tox modeling was able to predict Cd+Zn mixture responses from the single-metal exposures as well as responses from field data. The similarity of response patterns between the 30-d experimental stream tests and field data supports the environmental relevance of testing aquatic insects in experimental streams. Environ Toxicol Chem 2017;36:749-762. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

The mayfly nymph Austrophlebioides pusillus Harker defies common osmoregulatory assumptions

Osmoregulation is a key physiological function, critical for homeostasis. The basic physiological mechanisms of osmoregulation are thought to be well established. However, through a series of experiments exposing the freshwater mayfly nymph Austrophlebioides pusillus (Ephemeroptera) to increasing salinities, we present research that challenges the extent of current understanding of the relationship between osmoregulation and mortality. A. pusillus had modelled 96 h LC₁₀, LC₅₀ and LC₉₉ of 2.4, 4.8 and 10 g l^-1 added synthetic marine salt (SMS), respectively. They were strong osmoregulators. At aquarium water osmolality of 256 ± 3.12 mmol kg^-1 (±s.e.; equivalent to 10 g l^-1 added SMS), the haemolymph osmolality of A. pusillus was a much higher 401 ± 4.18 mmol kg^-1 (±s.e.). The osmoregulatory capacity of A. pusillus did not break down, even at the salinity corresponding to their LC₉₉, thus their mortality at this concentration is due to factors other than increased internal osmotic pressure. No freshwater invertebrate has been previously reported as suffering mortality from rises in salinity that are well below the iso-osmotic point. Recently, studies have reported reduced abundance/richness of Ephemeroptera with slightly elevated salinity. Given that salinization is an increasing global threat to freshwaters, there is an urgent need for studies into the osmophysiology of the Ephemeroptera to determine if their loss at locations with slightly elevated salinity is a direct result of external salinity or other, possibly physiological, causes.

An annotated catalogue of the mayfly fauna of Turkey (Insecta, Ephemeroptera)

The mayfly fauna of Turkey was reviewed including all hitherto known distribution records together with references and a few new records. Additionally, comments on taxonomy, identification and nomenclature are provided. Two species are new for the Turkish fauna: Ephemeraromantzovi Kluge, 1988 and Thraulusthraker Jacob, 1988. A list of taxa including their recorded distribution in Turkey (according to provinces) is provided in the annotated catalogue. The type locality is also given for each species originally described from Turkey. According to the literature and the new records, 157 mayfly taxa representing 33 genera and 14 families were described from Turkey. Among them, 24 species are considered endemic to Anatolia.

Molecular phylogeny and timing of diversification in Alpine Rhithrogena (Ephemeroptera: Heptageniidae)

Background

Larvae of the Holarctic mayfly genus Rhithrogena Eaton, 1881 (Ephemeroptera, Heptageniidae) are a diverse and abundant member of stream and river communities and are routinely used as bio-indicators of water quality. Rhithrogena is well diversified in the European Alps, with a number of locally endemic species, and several cryptic species have been recently detected. While several informal species groups are morphologically well defined, a lack of reliable characters for species identification considerably hampers their study. Their relationships, origin, timing of speciation and mechanisms promoting their diversification in the Alps are unknown.

Results

Here we present a species-level phylogeny of Rhithrogena in Europe using two mitochondrial and three nuclear gene regions. To improve sampling in a genus with many cryptic species, individuals were selected for analysis according to a recent DNA-based taxonomy rather than traditional nomenclature. A coalescent-based species tree and a reconstruction based on a supermatrix approach supported five of the species groups as monophyletic. A molecular clock, mapped on the most resolved phylogeny and calibrated using published mitochondrial evolution rates for insects, suggested an origin of Alpine Rhithrogena in the Oligocene/Miocene boundary. A diversification analysis that included simulation of missing species indicated a constant speciation rate over time, rather than any pronounced periods of rapid speciation. Ancestral state reconstructions provided evidence for downstream diversification in at least two species groups.

Conclusions

Our species-level analyses of five gene regions provide clearer definitions of species groups within European Rhithrogena. A constant speciation rate over time suggests that the paleoclimatic fluctuations, including the Pleistocene glaciations, did not significantly influence the tempo of diversification of Alpine species. A downstream diversification trend in the hybrida and alpestris species groups supports a previously proposed headwater origin hypothesis for aquatic insects.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-016-0758-1) contains supplementary material, which is available to authorized users.

DNA barcoding of mayflies (Insecta: Ephemeroptera) from South India

In this study, DNA barcodes were generated for 40 species belonging to 32 genera under 10 families of Ephemeroptera from South India. Nucleotide sequence divergences were calculated using the Kimura two-parameter distance model and a neighbour-joining analysis was performed to provide a graphic display of the patterns of divergence among the species. This study demonstrates that COI barcoding is effective in discriminating among the mayfly species of South India, and provides a reference library for their future molecular identification.

An updated list of type material of Ephemeroptera Hyatt & Arms, 1890, deposited at the Zoological Museum of Hamburg (ZMH)

The type specimens of Ephemeroptera (Insecta) housed at the Zoological Museum of Hamburg (ZMH) are compiled in this document. The current nomenclature of all species is given. In total, Ephemeroptera type material of ZMH encompasses 161 species. Fifty-one holotypes and five lectotypes are present. Forty-one species are represented by syntypes, 85 by paratypes and five by paralectotypes. Material of two species (Cinygma asiaticum Ulmer, 1924 and Pseudocloeon klapaleki Müller-Liebenau, 1982) is missing. The present catalogue is an updated version of Weidner (1964a).

Cryptic species diversity reveals biogeographic support for the 'mountain passes are higher in the tropics' hypothesis

The 'mountain passes are higher in the tropics' (MPHT) hypothesis posits that reduced climate variability at low latitudes should select for narrower thermal tolerances, lower dispersal and smaller elevational ranges compared with higher latitudes. These latitudinal differences could increase species richness at low latitudes, but that increase may be largely cryptic, because physiological and dispersal traits isolating populations might not correspond to morphological differences. Yet previous tests of the MPHT hypothesis have not addressed cryptic diversity. We use integrative taxonomy, combining morphology (6136 specimens) and DNA barcoding (1832 specimens) to compare the species richness, cryptic diversity and elevational ranges of mayflies (Ephemeroptera) in the Rocky Mountains (Colorado; approx. 40°N) and the Andes (Ecuador; approx. 0°). We find higher species richness and smaller elevational ranges in Ecuador than Colorado, but only after quantifying and accounting for cryptic diversity. The opposite pattern is found when comparing diversity based on morphology alone, underscoring the importance of uncovering cryptic species to understand global biodiversity patterns.

Mayflies, stoneflies, and caddisflies of streams and marshes of Indiana Dunes National Lakeshore, USA

United States National Parks have protected natural communities for one hundred years. Indiana Dunes National Lakeshore (INDU) is a park unit along the southern boundary of Lake Michigan in Indiana, USA. An inventory of 19 sites, consisting of a seep, 12 streams, four marshes, a bog, and a fen were examined for mayflies (Ephemeroptera), stoneflies (Plecoptera), and caddisflies (Trichoptera) (EPT taxa). Volunteers and authors collect 35 ultraviolet light traps during summer 2013 and supplementary benthic and adult sampling added species not attracted by lights or that were only present in colder months. Seventy-eight EPT species were recovered: 12 mayflies, two stoneflies, and 64 caddisflies. The EPT richness found at INDU was a low proportion of the number of species known from Indiana: caddisflies contributed only 32.7% of known state fauna, mayflies and stoneflies contributed 8.4% and 2.3%, respectively. Site EPT richness ranged from one for a seep to 34 for an 8 m-wide stream. Richness in streams generally increased with stream size. Seven new state records and rare species are reported. The number of EPT species at INDU is slightly larger than that found at Isle Royale National Park in 2013, and the community composition and evenness between orders were different.

Acute and chronic toxicity of neonicotinoids to nymphs of a mayfly species and some notes on seasonal differences

Mayfly nymphs are among the most sensitive taxa to neonicotinoids. The present study presents the acute and chronic toxicity of 3 neonicotinoids (imidacloprid, thiacloprid, and thiamethoxam) to a mayfly species (Cloeon dipterum) and some notes on the seasonality of the toxicity of imidacloprid to C. dipterum and 5 other invertebrate species. Imidacloprid and thiamethoxam showed equal acute and chronic toxicity to a winter generation of C. dipterum, whereas thiacloprid was approximately twice as toxic. The acute and chronic toxicity of imidacloprid was much higher for the C. dipterum summer generation than for the winter one. The acute toxicity differs by a factor of 20 for the 96-h 50% effective concentration (EC50) and by a factor of 5.4 for the chronic 28-d EC50. Temperature had only a slight effect on the sensitivity of C. dipterum to imidacloprid because we only found a factor of 1.7 difference in the 96-h EC50 between tests performed at 10 °C and 18 °C. The difference in sensitivity between summer and overwintering generations was also found for 3 other insect species. The results indicate that if the use and environmental fate of the 3 neonicotinoids are comparable, replacing imidacloprid by another neonicotinoid might not reduce the environmental impact on the mayfly nymph C. dipterum. The results also show the importance of reporting which generation is tested because sensitivity values of insects in the summer might be underestimated by the experiments performed with neonicotinoids and an overwintering population.

Ephemeroptera, Plecoptera, and Trichoptera on Isle Royale National Park, USA, compared to mainland species pool and size distribution

Extensive sampling for aquatic insects was conducted in the orders Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies) (EPT) of Isle Royale National Park (ISRO), Michigan, United States of America, during summer 2013. The island was ice covered until 8,000 to 10,000 years ago and is isolated by 22-70 km distance from the mainland. Two hypotheses were examined: that ISRO EPT richness would be much reduced from the mainland, and that the species colonizing ISRO would be of smaller size than mainland, adults presumably using updrafts to bridge the distance from mainland sources. Data sets were developed for known mainland EPT species and size for those species. The first hypothesis was confirmed with the mainland species pool consisting of 417 EPT, while ISRO is known to support 73 species. Richness of EPT is directly related to the number of specimens examined. Small streams supported five EPT species, while 15-25 species were found in larger streams. Lakeshores had intermediate diversity. The second hypothesis was substantiated for stoneflies, but not for mayflies or caddisflies. Stoneflies apparently are poorer fliers than either of the other two orders.

Croatian mayflies (Insecta, Ephemeroptera): species diversity and distribution patterns

Knowledge of the mayfly biodiversity in the Balkan Peninsula is still far from complete. Compared to the neighbouring countries, the mayfly fauna in Croatia is very poorly known. Situated at the crossroads of central and Mediterranean Europe and the Balkan Peninsula, Croatia is divided into two ecoregions: Dinaric western Balkan and Pannonian lowland. Mayflies were sampled between 2003 and 2013 at 171 sites, and a total of 66 species was recorded. Combined with the literature data, the Croatian mayfly fauna reached a total of 79 taxa. Of these, 29 species were recorded for the first time in Croatia while 15 species were not previously recorded in Dinaric western Balkan ecoregion. Based on the mayfly assemblage, sampling sites were first structured by ecoregion and then by habitat type. In comparison with the surrounding countries, the Croatian mayfly fauna is the most similar to the Hungarian and Bosnian fauna. Some morphologically interesting taxa such as Baetiscf.nubecularis Eaton, 1898 and Rhithrogena from the diaphana group were recorded. Ephemeracf.parnassiana Demoulin, 1958, the species previously recorded only from Greece, was also recorded.

Phylogeny and biogeography of Asthenopodinae with a revision of Asthenopus, reinstatement of Asthenopodes, and the description of the new genera Hubbardipes and Priasthenopus (Ephemeroptera, Polymitarcyidae)

The Neotropical species of Asthenopodinae are revised in a formal phylogenetic context. The five known species of Asthenopus Eaton, 1871, together with other five new species were included in a cladistic analysis using morphological characters (continuous and discretes). Representatives of the Afro-Oriental group of the subfamily (Povilla Navás, 1912 and Languidipes Hubbard, 1984) were also included to test the monophyletic hypothesis traditionally accepted for the group. Additional taxa representing the other subfamilies of Polymitarcyidae were incorparated: Ephoron Williamson, 1802 (Polymitarcyinae) and Campsurus Eaton, 1868, Tortopus Needham & Murphy, 1924 and Tortopsis Molineri, 2010 (Campsurinae). A matrix of 17 taxa and 72 characters was analyzed under parsimony resulting in a single tree supporting the monophyly of the subfamily Asthenopodinae. Other results include the monophyly of the Afro-Oriental taxa (Povilla and Languidipes), the paraphyletic nature of Neotropical Asthenopodinae, and the recognition of four South American genera: Asthenopus (including Asthenopuscurtus (Hagen), 1861, Asthenopusangelae de Souza & Molineri, 2012, Asthenopusmagnus sp. n., Asthenopushubbardi sp. n., Asthenopusguarani sp. n.), Asthenopodes Ulmer, 1924, stat. n. (including Asthenopuspicteti Hubbard, 1975, stat. n., Asthenopodestraverae sp. n., Asthenopodeschumuco sp. n.), Priasthenopus gen. n. (including Priasthenopusgilliesi (Domínguez), 1988, comb. n.), and Hubbardipes gen. n. (including Hubbardipescrenulatus (Molineri et al.), 2011, comb. n.). Descriptions, diagnoses, illustrations and keys are presented for all Neotropical taxa of Asthenopodinae (adults of both sexes, eggs and nymphs). Additionally a key to the subfamilies and genera of Polymitarcyidae is included. A quantitative biogeographic analysis of vicariance is presented and discussed through the study of the "taxon history" of the group.

Ecology of ephemeroptera, plecoptera and trichoptera (insecta) in rivers of the gunung jerai forest reserve: diversity and distribution of functional feeding groups

A field study was performed to describe the functional feeding groups (FFGs) of Ephemeroptera, Plecoptera and Trichoptera (EPT) in the Tupah, Batu Hampar and Teroi Rivers in the Gunung Jerai Forest Reserve (GJFR), Kedah, Malaysia. Twenty-nine genera belonging to 19 families were identified. The EPTs were classified into five FFGs: collector-gatherers (CG), collector-filterers (CF), shredders (SH), scrapers (SC) and predators (P). In this study, CG and CF were the dominant groups inhabiting all three rivers. Ephemeroptera dominated these rivers due to their high abundance, and they were also the CG (90.6%). SC were the lowest in abundance among all groups. Based on the FFGs, the Teroi River was suitable for CG, whereas the Tupah and Batu Hampar Rivers were suitable for CG and CF. The distribution of FFGs differed among the rivers (CG, χ(2) = 23.6, p = 0.00; SH, χ(2) = 10.02, p = 0.007; P, χ(2) = 25.54, p = 0.00; CF, χ(2) = 21.95, p = 0.00; SC, χ(2) = 9.31, p = 0.01). These findings indicated that the FFGs found in rivers of the GJFR represent high river quality.

The complete mitochondrial genome of Paegniodes cupulatus (Ephemeroptera: Heptageniidae)

The complete mitochondrial genome of Paegniodes cupulatus (Ephemeroptera: Heptageniidae), which is sequenced for the first time here, is 15,715 bp in length, containing 13 protein-coding genes, 2 rRNAs, 22 tRNAs and a control region. The overall base composition of the genome is 33.1% for T, 20.7% for C, 32.5% for A and 13.7% for G, with an AT bias of 65.6%.

Discovery of an alien species of mayfly in South America (Ephemeroptera)

Despite its wide, almost worldwide distribution, the mayfly genus Cloeon Leach, 1815 (Ephemeroptera: Baetidae) is restricted in the Western hemisphere to North America, where a single species is reported. In the Neotropics, except for some species wrongly attributed to the genus in the past, there are no records of Cloeon. Recently, however, specimens of true Cloeon were collected along the coast of Espírito Santo, Southeastern Brazil. In order to verify the hypothesis that this species was recently introduced to Brazil, our aim was to identify the species based on morphological and molecular characters and to confirm the presence of true representatives of the genus in the Neotropics. Our results revealed that the specimens found in Brazil belong to the Afrotropical species C. smaeleni Lestage, 1924. The identity of the species, its distribution, along with its previous absence in regularly sampled sites, is a clear sign that the specimens of C. smaeleni found in Espírito Santo are introduced, well established, and that the colonization took place very recently.

Percentage of Impervious Surface Soil as Indicator of Urbanization Impacts in Neotropical Aquatic Insects

Several recent studies have shown a strong correlation between the area of impervious surface soil (IS) and the insect community structure from urban streams. This study assessed whether this relationship is observed in Neotropical streams. We examined if an increased IS reduces the diversity and simplifies the trophic structure of the community of Ephemeroptera, Plecoptera, and Trichoptera. An IS threshold was detected between 1.6 and 9.3%, in which there is a change in the community, both in taxonomic richness and trophic structure. Among the 27 genera identified, only 15 occurred in streams with IS > 9%, while 24 genera were registered in streams with IS < 2%. The trophic guilds of predators and shredders were not observed in streams with high IS, decreasing the number of guilds in these streams from 5 to 3, compared with the streams with low IS. Three hypotheses with cumulative effect have been proposed to explain such variations. Based on the IS threshold verified, the creation of a mosaic of land use, where some subbasins would be sacrificed and others would be preserved, was suggested as a mitigation measure for the impacts caused by urbanization in the Neotropical aquatic insects' fauna.

Aquatic Insects in Eastern Australia: A Window on Ecology and Evolution of Dispersal in Streams

Studies of connectivity of natural populations are often conducted at different timescales. Studies that focus on contemporary timescales ask questions about dispersal abilities and dispersal behavior of their study species. In contrast, studies conducted at historical timescales are usually more focused on evolutionary or biogeographic questions. In this paper we present a synthesis of connectivity studies that have addressed both these timescales in Australian Trichoptera and Ephemeroptera. We conclude that: (1) For both groups, the major mechanism of dispersal is by adult flight, with larval drift playing a very minor role and with unusual patterns of genetic structure at fine scales explained by the “patchy recruitment hypothesis”; (2) There is some evidence presented to suggest that at slightly larger spatial scales (∼100 km) caddisflies may be slightly more connected than mayflies; (3) Examinations of three species at historical timescales showed that, in southeast Queensland Australia, despite there being no significant glaciation during the Pleistocene, there are clear impacts of Pleistocene climate changes on their genetic structure; and (4) The use of mitochondrial DNA sequence data has uncovered a number of cryptic species complexes in both trichopterans and ephemeropterans. We conclude with a number of suggestions for further work.