Although much biological research depends upon species diagnoses, taxonomic expertise is collapsing. We are convinced that the sole prospect for a sustainable identification capability lies in the construction of systems that employ DNA sequences as taxon 'barcodes'. We establish that the mitochondrial gene cytochrome c oxidase I (COI) can serve as the core of a global bioidentification system for animals. First, we demonstrate that COI profiles, derived from the low-density sampling of higher taxonomic categories, ordinarily assign newly analysed taxa to the appropriate phylum or order. Second, we demonstrate that species-level assignments can be obtained by creating comprehensive COI profiles. A model COI profile, based upon the analysis of a single individual from each of 200 closely allied species of lepidopterans, was 100% successful in correctly identifying subsequent specimens. When fully developed, a COI identification system will provide a reliable, cost-effective and accessible solution to the current problem of species identification. Its assembly will also generate important new insights into the diversification of life and the rules of molecular evolution.

A short fragment of mt DNA from the cytochrome c oxidase 1 (CO1) region was used to provide the first CO1 barcodes for 37 species of Canadian mosquitoes (Diptera: Culicidae) from the provinces Ontario and New Brunswick. Sequence variation was analysed in a 617-bp fragment from the 5' end of the CO1 region. Sequences of each mosquito species formed barcode clusters with tight cohesion that were usually clearly distinct from those of allied species. CO1 sequence divergences were, on average, nearly 20 times higher for congeneric species than for members of a species; divergences between congeneric species averaged 10.4% (range 0.2-17.2%), whereas those for conspecific individuals averaged 0.5% (range 0.0-3.9%).

This paper reports the first tests of the suitability of the standardized mitochondrial cytochrome c oxidase subunit I (COI) barcoding system for the identification of Canadian deerflies and horseflies. Two additional mitochondrial molecular markers were used to determine whether unambiguous species recognition in tabanids can be achieved. Our 332 Canadian tabanid samples yielded 650 sequences from five genera and 42 species. Standard COI barcodes demonstrated a strong A + T bias (mean 68.1%), especially at third codon positions (mean 93.0%). Our preliminary test of this system showed that the standard COI barcode worked well for Canadian Tabanidae: the target DNA can be easily recovered from small amounts of insect tissue and aligned for all tabanid taxa. Each tabanid species possessed distinctive sets of COI haplotypes which discriminated well among species. Average conspecific Kimura two-parameter (K2P) divergence (0.49%) was 12 times lower than the average divergence within species. Both the neighbour-joining and the Bayesian methods produced trees with identical monophyletic species groups. Two species, Chrysops dawsoni Philip and Chrysops montanus Osten Sacken (Diptera: Tabanidae), showed relatively deep intraspecific sequence divergences (∼ 10 times the average) for all three mitochondrial gene regions analysed. We suggest provisional differentiation of Ch. montanus into two haplotypes, namely, Ch. montanus haplomorph 1 and Ch. montanus haplomorph 2, both defined by their molecular sequences and by newly discovered differences in structural features near their ocelli.

The value of using characters from multiple sources -chromosomes, ecology, gene sequences, and morphology -to evaluate the species status of closely related black flies is demonstrated for three European members of the Simulium vernum group: Simulium crenobium (Knoz, 1961), Simulium juxtacrenobium Bass & Brockhouse, 1990, and Simulium vernum s.s. Macquart, 1826. Simulium juxtacrenobium is a chromosomally, molecularly, and morphologically distinct species that diverged from S. crenobium and S. vernum s.s. about 2 Mya. It is specialized for intermittent streams, is univoltine, and is recorded for the first time from northern Europe, based on collections from Finland and Sweden, representing a range extension of about 1800 km. In contrast, S. crenobium, although confirmed as a distinct species, differs from S. vernum s.s. by only a few larval and chromosomal characters, and by a breeding habitat restricted to mountain spring brooks. Whereas all four character sets independently support the specific distinctness of S. juxtacrenobium and S. vernum s.s., multiple character sets are required to establish the specific validity of S. crenobium.

Prior allozyme studies have indicated that populations of the asexual ostracode, Cypridopsis vidua (Müller), show extraordinary clonal diversity. Based on a joint examination of allozyme variation and sequence divergence at the mitochondrial cytochrome c oxidase I (COI) gene, the present analysis provides new insights concerning the origins of this variation. The results establish that populations of C. vidua in one recently deglaciated region of North America are not only allozymically diverse, but also include several divergent mitochondrial DNA (mtDNA) lineages. The extent of sequence divergence among these lineages is so large as to suggest their diversification over the past 7–8 million years. The patterning of genetic divergence among co‐occurring clones makes it apparent that much of the mtDNA and allozyme diversity in local populations owes its origins to recurrent colonization events. However, in situ mutational diversification also appears to explain some variation. The mechanisms enabling the sustained coexistence of such a large array of closely allied genotypes remain unclear, but there is an apparent difference in equilibrium diversity between benthic and planktonic asexual organisms.

Laboratory tests confirmed a negative and variable response of the following four species to artificial UV radiation: Cypridopsis vidua, an ostracode; Chironomus riparius, a midge larvae; Hyalella azteca, an amphipod; and Daphnia magna, a daphnid. Severe damage occurred at UV-B irradiance ranging from 50 to 80% of incident summer values. Under constant exposure to UV and photosynthetically active radiation (PAR) the acute lethal response was recorded at 0.3, 0.8, 0.8 and 4.9 W m-2 UV-B for D. magna, H. azteca, C. riparius and C. vidua, respectively. Sublethal UV-B damage to invertebrates included impaired movement, partial paralysis, changes in pigmentation and altered water balance (bloating). A series of UV-B, UV-A and PAR treatments, applied separately and in combination, revealed a positive role for both UV-A and PAR in slowing down UV-B damage. Mean lethal concentration values of the species typically more tolerant to UV and PAR (Cypridopsis, Chironomus) decreased conspicuously when both UV-A and PAR were eliminated. For UV-B-sensitive species (Hyalella, Daphnia) these differences were notably smaller. We suggest that this gradation of sensitivity among the tested species demonstrates potential differences in repairing mechanisms which seem to work more efficiently for ostracodes and chironomids than for amphipods and daphnids. Manipulations with a cellulose acetate filter showed that lower range UV-B (280-290 nm), produced by FS-40 lamps, may cause excessive UV damage to invertebrates.

Accurate species identification is essential for cost-effective pest control strategies. We tested the utility of COI barcodes for identifying members of the black fly genus Cnephia Enderlein (Diptera: Simuliidae). Our efforts focus on four Nearctic Cnephia species-Cnephia dacotensis (Dyar & Shannon), Cnephia eremities Shewell, Cnephia ornithophilia (Davies, Peterson & Wood), and Cnephia pecuarum (Riley)--the latter two being current or potential targets of biological control programs. We also analyzed one Palearctic species, Cnephia pallipes (Fries). Although Cnephia adults can be identified anatomically to species, control programs target the larval stage, which is difficult or impossible to distinguish morphologically. By using neighbor-joining, maximum parsimony, and Bayesian methods, we found that COI barcodes successfully identified three Nearctic Cnephia species, but not C. pecuarum. The Palearctic C. pallipes was also successfully identified. Despite nonmonophyly of C. pecuarum, we show that data from COI barcoding, in combination with geographical and ecological information, can be used to distinguish all four Nearctic species. Finally, we discussed 1) possible reasons for paraphyly in C. pecuarum, 2) topological concordance to previously reported chromosomal dendrograms, and 3) evolution of diverse feeding strategies within the genus Cnephia.

Laboratory tests confirmed a negative and variable response of the following four species to artificial UV radiation: Cypridopsis vidua, an ostracode; Chironomus riparius, a midge larvae; Hyalella azteca, an amphipod; and Daphnia magna, a daphnid. Severe damage occurred at UV‐B irradiance ranging from 50 to 80% of incident summer values. Under constant exposure to UV and photosynthetically active radiation (PAR) the acute lethal response was recorded at 0.3, 0.8, 0.8 and 4.9 W m−2 UV‐B for D. magna, H. azteca, C. riparius and C. vidua, respectively. Sublethal UV‐B damage to invertebrates included impaired movement, partial paralysis, changes in pigmentation and altered water balance (bloating). A series of UV‐B, UV‐A and PAR treatments, applied separately and in combination, revealed a positive role for both UV‐A and PAR in slowing down UV‐B damage. Mean lethal concentration values of the species typically more tolerant to UV and PAR (Cypridopsis, Chironomus) decreased conspicuously when both UV‐A and PAR were eliminated. For UV‐B–sensitive species (Hyalella, Daphnia) these differences were notably smaller. We suggest that this gradation of sensitivity among the tested species demonstrates potential differences in repairing mechanisms which seem to work more efficiently for ostracodes and chironomids than for amphipods and daphnids. Manipulations with a cellulose acetate filter showed that lower range UV‐B (280–290 nm), produced by FS‐40 lamps, may cause excessive UV damage to invertebrates.