Estimation of Species Identification Error: Implications for Raptor Migration Counts and Trend Estimation

Abstract: One of the primary assumptions associated with many wildlife and population trend studies is that target species are correctly identified. This assumption may not always be valid, particularly for species similar in appearance to co-occurring species. We examined size overlap and identification error rates among Cooper's (Accipiter cooperii) and sharp-shinned (A. striatus) hawks specific to a raptor migration count station along the Pacific Coast of North America. Illustrating the difficulty of distinguishing between these 2 species, we found overlap in 7 metrics among species-sex groups and in 2 metrics between species, and a principal components analysis revealed a continuum of discrete clusters for each species-sex combination in morphospace. Among juvenile hawks (n = 940), we found the greatest misidentification rate for male Cooper's hawks (23% of the 156 males were identified as sharp-shinned), lesser error rates for female Cooper's (8%, n = 339) and female sharp-shinned (6%, n = 246), and the lowest misidentification rate for male sharp-shinned hawks (0%, n = 199). We observed a similar pattern of misidentification among adult hawks (n = 48). We attempted to use conditional probabilities (identification rates) from calibration data to calculate the true number of adult and juvenile Cooper's hawks and sharp-shinned hawks. Discrepancies between total number of observed accipiters and estimated number using calibration data suggest that daily observer misclassification rates are higher than misclassification rates estimated from calibration data and prevent correction of the raw data. Our results illustrate the importance of testing for and quantifying observer error in species identification in wildlife census and population trend studies particularly when target species may be easily confused with other nontarget species.     

Making the cryptic visible – resolving the species complex of Aphodius fimetarius (Linnaeus) and Aphodius pedellus (de Geer) (Coleoptera: Scarabaeidae) by three complementary methods

Species in cryptic complexes are, per definition, difficult to identify using morphological characters. One such complex was recently detected in the dung beetle Aphodius fimetarius (Linnaeus) sensu lato, an abundant dung beetle with a wide distribution. While the two component taxa, Aphodius fimetarius sensu stricto and Aphodius pedellus (De Geer) exhibit distinctly different karyotypes, the validity of subtle morphological characters proposed to distinguish between them has been debated. Given the variability and minor interspecific differences in external characters, the large‐scale distribution of respective taxa has remained unknown, as have potential differences in ecology and habits. In this study, we ask how A. fimetarius and A. pedellus can best be distinguished, whether the use of different types of characters (karyotypes, DNA sequences and morphological traits) results in consistent species identification, where these species occur and whether they exhibit ecological differences. In total, we inspected a material of 4401 individuals from across the globe, of which 183 were examined for both mtDNA sequences and morphology, 154 for both morphology and karyotype, and 9 (including the recently proposed neotype of Aphodius fimetarius) for all three types of characters. As a marker gene, we sequenced a 590 bp region of the cytochrome c oxidase I gene for 183 individuals. Overall, DNA sequences offered a clear‐cut distinction between taxa: sequences of A. fimetarius and A. pedellus differed by an average pairwise distance of 8.2%, whereas variation within species was only 0.9% for A. fimetarius and 0.5% for A. pedellus. Morphological and chromosomal characters offered species identifications consistent with that of molecular characters: karyotypes identified as A. pedellus consistently fell within one of the molecular clades, whereas karyotypes identified as A. fimetarius fell within the other clade. Likewise, the majority of individuals identified by morphological characters were assigned to the same species by sequence‐based characters. Both taxa thus defined were found to be Holarctic in distribution, with major sympatry within Central and Southern Europe and mixed patterns of sympatry within the US. Northern areas of Europe, Asia and North America are dominated by A. pedellus alone. Within A. pedellus, patterns of sequence diversity were indicative of a recent population expansion. In the western US, the phenology of a population of A. fimetarius was observed to significantly differ from that of a sympatric population of A. pedellus, thereby revealing an ecological difference between the two cryptic taxa. Overall, we conclude that all types of characters offered a consistent classification of the two species. Thus, the laborious karyotyping techniques used to originally establish the presence of two cryptic taxa can now be substituted by characters more easily applied to large ecological samples. Using this approach of integrative taxonomy, we were able to establish the global distribution and species‐specific ecology of these ecologically important cryptic taxa. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:4033473E-8BF7-40F4-852D-916E4F858593 .     

Barriers to the recovery of aquatic insect communities in urban streams

1. Worldwide, increasing numbers of stream restoration projects are being initiated to rehabilitate waterways modified by urbanisation. However, many of these projects have limited success in restoring stream communities. Prompted by this, we investigated previously unrecognised barriers to aquatic insect colonisation in urban streams. 2. To investigate whether the availability of suitable substrata for oviposition limited the longitudinal distribution of caddisflies, large boulders were added to the upstream reaches of one stream. Prior to the addition, more egg masses were observed downstream and this longitudinal pattern persisted subsequently. 3. Malaise trapping revealed that adult caddisfly diversity and abundance was greater downstream than upstream. Furthermore, in a previous study the authors found larval caddisflies reflected the longitudinal distribution of adults. 4. The only obvious potential obstructions between reaches were roads beneath which the stream flowed through culverted crossings. Malaise trapping was used to examine the effect of road culverts and bridges on caddisfly dispersal. Numbers of caddisflies caught declined upstream and about 2.5 × more individuals were taken in traps immediately below than above five culverts. 4. Bridges, which had a more open structure than culverts, had no significant effect on the size of catches made above and below them. 5. Road culverts could act as partial barriers to upstream flight, with consequences for larval recruitment in urban streams. We recommend that urban planners and designers of restoration projects consider possible synergistic effects of poor oviposition habitat and barriers to aquatic insect dispersal, which may be critical for the colonisation of urban headwater streams and for the maintenance of stream insect populations.     

Revision of the Palaearctic species of the Helophorus minutus group (Coleoptera: Hydrophilidae), with chromosome analysis and hybridization experiments

Abstract. Investigation of the chromosomes has revealed a Helophorus species from Central and Eastern Europe, and West Siberia, here described as H.paraminutus sp.n., which often closely resembles minutus F., though some specimens are larger and resemble lapponicus Thomson. The chromosomes of paraminutus are clearly distinct from those of minutus but closely resemble those of lapponicus. In the laboratory first generation hybrids were obtained between minutus and paraminutus, lapponicus and paraminutus, and lapponicus and minutus, but in no case was it possible to breed from these hybrids. Thus there can be no doubt that these three species are distinct. Recognition of paraminutus as a distinct species, despite the fact that study of its morphology alone could suggest introgressive hybridization between lapponicus and minutus, requires the recognition of limbatus Motschulsky as a species separate from H. lapponicus and necessitates the revision of the Helophorus minutus group of species which, as here defined, includes minutus, paraminutus, hilaris Sharp, lapponicus, limbatus, mervensis Semenov, rinki Angus, fulgidicol-lis Motschulsky and asturiensis Kuwert. Types and synonymies are discussed, and a key to these species given. Two old, imperfectly known, names are discussed to clear them from the synonymy: granulans var. rufipennis Hubenthal is identified as brevipalpis Bedel, and a lectotype designated; H. griseus var. lateralis Dalla Torre is left as incertae sedis and is classed as a nomen oblitum.     

Tests of aryltin compounds as potato blight fungicides

Triphenyl(phenylthio)tin and triphenyl(p-chlorophenylthio)tin were as effective as fentin acetate in controlling potato blight (Phytophthora infestans) in laboratory tests on detached leaflets. Diphenyltin dichloride and bis(triphenyltin)sulphide were moderately effective. Dibenzyltin and some diphenyltin compounds were ineffective. A small change in the bioassay conditions, bringing them slightly closer to field conditions, increased the relative effectiveness of bis(triphenyltin)-sulphide, making it about one-quarter as effective as fentin acetate; however, the change did not increase the relative effectiveness of triphenyl(phenylthio)tin or dibutyltin diacetate.     

Separation of two species standing as Helophorus aquaticus (L.) (Coleoptera, Hydrophilidae) by banded chromosome analysis

Abstract. Methods are described for making chromosome preparations from developing embryos of Helophorus , for producing C- and G-banding, and for staining the nucleolus organizer with silver. These methods are used to compare the karyotypes of two species currently included in H.aquaticus (L.). It is shown that these species differ because of reciprocal translocations between some chromosomes, and that they would therefore be unable to produce fertile hybrids. Morphological differences in the male and female genitalia are described, and the range of aedeagal variation shown by each species is established by reference to chromosome preparations from testis. Reference to the relevant type specimens shows that the two species are H.aequalis Thomson and H.aquaticus (L.). The latter is not a British species. Differences in the egg cocoons and third instar larvae are described. The present distributions and Pleistocene histories of the two species are described.     

Low river flow alters the biomass and population structure of a riparian predatory invertebrate

1. Low flows in rivers are predicted to increase in extent and severity in many areas in the future, yet the consequent impacts of river drying on terrestrial communities via (i) changes to riparian microclimatic conditions and (ii) the identity and abundance of emerging aquatic insects available to riparian predators have not been quantified. 2. We investigated the influence of low river flow on a riparian fishing spider, Dolomedes aquaticus, in five New Zealand rivers containing permanently flowing and drying reaches and, in one river, along a longitudinal drying gradient. 3. The biomass of aquatic insects, potential prey for D. aquaticus, declined with low river flows while the abundance of potential terrestrial prey remained similar at all sites. In the replicate rivers, and along the longitudinal drying gradient, spider biomass was lower, and size classes were skewed towards more small and fewer large spiders, in drying sites. A desiccation experiment in the laboratory indicated high sensitivity of the spiders, with prey presence increasing spider survival. 4. Differences in the spatial distribution, biomass and population size structure of spiders were observed along the longitudinal drying gradient and disappeared within 16 days of the water returning to all sites. 5. In total, low river flow affected the biomass of D. aquaticus, as well as their size class structure and spatial distribution. This indicates that low river flows have the potential to affect adjacent terrestrial ecosystems.