A re-analysis of the data in Sharkey et al.'s (2021) minimalist revision reveals that BINs do not deserve names, but BOLD Systems needs a stronger commitment to open science

Halting biodiversity decline is one of the most critical challenges for humanity, but monitoring biodiversity is hampered by taxonomic impediments. One impediment is the large number of undescribed species (here called "dark taxon impediment") whereas another is caused by the large number of superficial species descriptions, that can only be resolved by consulting type specimens ("superficial description impediment"). Recently, Sharkey et al. (2021) proposed to address the dark taxon impediment for Costa Rican braconid wasps by describing 403 species based on COI barcode clusters ("BINs") computed by BOLD Systems. More than 99% of the BINs (387 of 390) were converted into species by assigning binominal names (e.g. BIN "BOLD:ACM9419" becomes Bracon federicomatarritai) and adding a minimal diagnosis (consisting only of a consensus barcode for most species). We here show that many of Sharkey et al.'s species are unstable when the underlying data are analyzed using different species delimitation algorithms. Add the insufficiently informative diagnoses, and many of these species will become the next "superficial description impediment" for braconid taxonomy because they will have to be tested and redescribed after obtaining sufficient evidence for confidently delimiting species. We furthermore show that Sharkey et al.'s approach of using consensus barcodes as diagnoses is not functional because it cannot be applied consistently. Lastly, we reiterate that COI alone is not suitable for delimiting and describing species, and voice concerns over Sharkey et al.'s uncritical use of BINs because they are calculated by a proprietary algorithm (RESL) that uses a mixture of public and private data. We urge authors, reviewers and editors to maintain high standards in taxonomy by only publishing new species that are rigorously delimited with open-access tools and supported by publicly available evidence.

Comparative reproductive dormancy differentiation in European black scavenger flies (Diptera: Sepsidae)

Seasonality is a key environmental factor that regularly promotes life history adaptation. Insects invading cold-temperate climates need to overwinter in a dormant state. We compared the role of temperature and photoperiod in dormancy induction in the laboratory, as well as winter survival and reproduction in the field and the laboratory, of 5 widespread European dung fly species (Diptera: Sepsidae) to investigate their extent of ecological differentiation and thermal adaptation. Unexpectedly, cold temperature is the primary environmental factor inducing winter dormancy, with short photoperiod playing an additional role mainly in species common at high altitudes and latitudes (Sepsis cynipsea, neocynipsea, fulgens), but not in those species also thriving in southern Europe (thoracica, punctum). All species hibernate as adults rather than juveniles. S. thoracica had very low adult winter survivorship under both (benign) laboratory and (harsh) field conditions, suggesting flexible quiescence rather than genetically fixed winter diapause, restricting their distribution towards the pole. All other species appear well suited for surviving cold, Nordic winters. Females born early in the season reproduce before winter while late-born females reproduce after winter, fulgens transitioning earliest before winter and thoracica and punctum latest; a bet-hedging strategy of reproduction during both seasons occurs rarely but is possible physiologically. Fertility patterns indicate that females can store sperm over winter. Winter dormancy induction mechanisms of European sepsids are congruent with their geographic distribution, co-defining their thermal niches. Flexible adult winter quiescence appears the easiest route for insects spreading towards the poles to evolve the necessary overwinter survival.

Does thermal plasticity align with local adaptation? An interspecific comparison of wing morphology in sepsid flies

Although genetic and plastic responses are sometimes considered as unrelated processes, their phenotypic effects may often align because genetic adaptation is expected to mirror phenotypic plasticity if adaptive, but run counter to it when maladaptive. Because the magnitude and direction of this alignment has further consequences for both the tempo and mode of adaptation, they are relevant for predicting an organisms' reaction to environmental change. To better understand the interplay between phenotypic plasticity and genetic change in mediating adaptive phenotypic variation to climate variability, we here quantified genetic latitudinal variation and thermal plasticity in wing loading and wing shape in two closely related and widespread sepsid flies. Common garden rearing of 16 geographical populations reared across multiple temperatures revealed that wing loading decreases with latitude in both species. This pattern could be driven by selection for increased dispersal capacity in the cold. However, although allometry, sexual dimorphism, thermal plasticity and latitudinal differentiation in wing shape all show similar patterns in the two species, the relationship between the plastic and genetic responses differed between them. Although latitudinal differentiation (south to north) mirrored thermal plasticity (hot to cold) in Sepsis punctum, there was no relationship in Sepsis fulgens. While this suggests that thermal plasticity may have helped to mediate local adaptation in S. punctum, it also demonstrates that genetic wing shape differentiation and its relation to thermal plasticity may be complex and idiosyncratic, even among ecologically similar and closely related species. Hence, genetic responses can, but do not necessarily, align with phenotypic plasticity induced by changing environmental selection pressures.

Whitefly predation and extensive mesonotum color polymorphism in an Acletoxenus population from Singapore (Diptera, Drosophilidae)

Acletoxenus is a small genus of Drosophilidae with only four described species that are closely associated with whiteflies (adults and larvae). Here, the first video recordings of larvae feeding on whiteflies (Aleurotrachelus trachoides) are presented. Typical morphological adaptations for predation by schizophoran larvae are also described: the larval pseudocephalon lacks a facial mask and the cephaloskeleton is devoid of cibarial ridges that could be used for saprophagy via filtration. Despite being a predator, Acletoxenus is unlikely to be a good candidate for biological control of whiteflies because the life cycle is fairly long (24 days), lab cultures could not be established, and the puparia have high parasitization rates by a pteromalid wasp (Pachyneuron leucopiscida). Unfortunately, a confident identification of the Singapore Acletoxenus population to species was not possible because species identification and description in the genus overemphasize coloration characters of the mesonotum which are shown to be unsuitable because the Singapore population has flies with coloration patterns matching three of the four described species. Based on morphology and DNA sequences, the population from Singapore is tentatively assigned to Acletoxenus indicus or a closely related species.

New species and new records of Manota Williston from Colombia, Brazilian Amazonia, and Costa Rica (Diptera, Mycetophilidae)

The following five species are described as new: Manotaclavasp. n. (Colombia), Manotamultilobatasp. n. (Colombia), Manotaperplexasp. n. (Costa Rica), Manotasetilobatasp. n. (Colombia) and Manotasubaristatasp. n. (Colombia). In addition, new records for the following 11 species are presented: Manotaacuminata Jaschhof & Hippa, 2005 (Costa Rica), Manotaarenalensis Jaschhof & Hippa, 2005 (Costa Rica), Manotacorcovado Jaschhof & Hippa, 2005 (Costa Rica), Manotacostaricensis Jaschhof & Hippa, 2005 (Costa Rica), Manotadiversiseta Jaschhof & Hippa, 2005 (Colombia, Brazilian Amazonia, Costa Rica), Manotaminutula Hippa, Kurina & Sääksjärvi, 2017 (Brazilian Amazonia), Manotamultisetosa Jaschhof & Hippa, 2005 (Costa Rica), Manotaparva Jaschhof & Hippa, 2005 (Colombia, Costa Rica), Manotapisinna Hippa & Kurina, 2013 (Brazilian Amazonia), Manotaspinosa Jaschhof & Hippa, 2005 (Colombia) and Manotasquamulata Jaschhof & Hippa, 2005 (Costa Rica). Distribution patterns include (1) species known only locally in Costa Rica or Colombia, (2) distributions connecting Central America to west Andes lowlands, and (3) north-west Neotropical components, extending from Central America to Brazilian Amazonia. The possible biogeographical and taxonomical context of Manota species with a widespread distribution is considered.