Morphological support for a clade comprising two vermiform mite lineages: Eriophyoidea (Acariformes) and Nematalycidae (Acariformes)
Samuel J. Bolton, Philipp E. Chetverikov & Hans Klompen. 2017. Systematic and Applied Acarology 22(8):1096-1131.
A morphology-based parsimony analysis (50 taxa; 110 characters) focused on relationships among basal acariform mites places Eriophyoidea (formerly in Trombidiformes) within Nematalycidae (Sarcoptiformes). Although both taxa have worm-like bodies, this grouping is unexpected because it combines obligate plant inhabitants (Eriophyoidea) with obligate inhabitants of deep-soil or mineral regolith (Nematalycidae sensu stricto). The Eriophyoidea + Nematalycidae clade, which is strongly supported (Bremer =5; bootstrap =85%), retains moderately good support (Bremer=3; bootstrap=66%) when three ratio-based characters pertaining to body shape are excluded. A total of eleven unambiguous synapomorphies unite all or some of Nematalycidae with Eriophyoidea. These include an annulated opisthosoma, an unpaired vi seta on the prodorsum, fusion of the palp trochanter with the palp femur, and a large relative distance between the anus and the genitalia. Three of the four Triassic genera of eriophyoid-like mites were also included in our analysis. Although all four genera have been tentatively placed within a new superfamily, we found no support for the monophyly of this group. One other interesting result of the analysis is the placement of a “living fossil”, Proterorhagia oztotloica (Proterorhagiidae), as sister to the rest of Acariformes. However, support for this relationship is weak.
Triploidy in a sexually dimorphic passerine provides new evidence for the effect of the W chromosome on secondary sexual traits in birds
Crisley de Camargo, H. Lisle Gibbs, Mariellen C. Costa, Luís F. Silveira, Cláudia A. Rainho, Paulo E. M. Ribolla, Adriane P. Wasko, Mercival R. Francisco. 2017. J Avian Biol. Accepted Author Manuscript. doi:10.1111/jav.01504
In birds, there are two main models for the determination of sex: the Z Dosage model in which the number, or dose, of Z chromosomes determines sex, and the Dominant W model which argues that a specific gene in the W chromosome may influence Z gene expression and determine sex. The best evidence for W determination of sex comes from birds with 2 copies of the Z chromosome paired with a single W (e.g. ZZW) which are nonetheless females. Here, we expand the species where such a mechanism may operate by reporting a case of a triploid Neotropical passerine bird with sexually dimorphic plumage, the São Paulo marsh antwren Formicivora paludicola. Evidence from 17 autosomal unlinked microsatellite loci, and CHD1 sex-linked locus, indicate that this individual is a 3n ZZW triploid with intermediate plumage pattern. This example expands our knowledge of sex determination mechanisms in birds by demonstrating that both the W and the two Z chromosomes affect the expression of morphological secondary sexual traits in a non-galliform bird.
No Magic Number: an Examination of the Herd-Size Threshold in Pastoral Systems Using Agent-Based Modeling
Mark Moritz, Abigail Buffington, Andrew J. Yoak, Ian M. Hamilton, Rebecca Garabed. 2017. Human Ecology 45(4):525–532.
Pastoralists who depend on their herds for their livelihoods need a minimum number of animals to support their household. Due to the dynamics of herd growth, pastoralists may find themselves at times below that minimum number. Previous studies have shown that there is a herd-size threshold below which households are unlikely to escape poverty. We explore the concept of a herd-size threshold using an agent-based model to examine the role of scale and stochasticity in family herd dynamics. The model was parametrized with data from the literature. The results from the computer simulations show (1) that offtake rates significantly limit herd growth; and (2) that herd-size threshold is better understood as a range of probabilities. We discuss the methodological and conceptual advantages of using agent-based modeling to examine demographic dynamics, including the possibility of conducting multiple experiments in silico to examine the dynamics of herd growth.
Interfacial properties of avian stratum corneum monolayers investigated by Brewster angle microscopy and vibrational sum frequency generation
Ellen M. Adams, Alex M. Champagne, Joseph B. Williams, Heather C. Allen. 2017. Chemistry and Physics of Lipids. 208:1–9. https://doi.org/10.1016/j.chemphyslip.2017.08.002
The outermost layer of skin, the stratum corneum (SC), contains a complex mixture of lipids, which controls the rate of cutaneous water loss (CWL) in reptiles, mammals, and birds. However, the molecular structure of SC lipids and how molecular configurations influence CWL is poorly understood. Here, the organization and structure of SC lipids extracted from birds were investigated by means of Langmuir films. Properties of lipids from the SC of arid and semi-arid adapted larks, known to have a low CWL, were compared with lipids extracted from the SC of mesic lark species with higher CWL to gain insight into how structure impacts CWL. Film properties were probed with surface pressure-area isotherms, Brewster angle microscopy (BAM), and vibrational sum frequency generation (VSFG). Results indicate organization and ordering of SC lipids in the arid-adapted hoopoe lark was vastly different from all other species, forming a miscible, rigid monolayer, whereas monolayers from semi-arid and mesic species were immiscible and disordered. Probing of interfacial water structure reveals that film morphology determines organization of water molecules near the monolayer; monolayers with a porous morphology had an increased population of water molecules that are weakly hydrogen-bonded. In general, CWL appears related to the miscibility and ordering of lipid components within the SC, as well as the ability of these lipids to interact with water molecules. From a broader perspective, CWL in larks appears linked to both the SC lipid composition and the aridity of the species’ environment.
Bumble bee colony growth and reproduction on reclaimed surface coal mines
J. Lanterman, and K. Goodell. 2017. Restor Ecol. doi:10.1111/rec.12551
Reclamation of coal mine lands in the eastern United States creates pockets of grassland habitat in an otherwise predominantly forested region. These sites may represent an opportunity for pollinator conservation if they provide valuable foraging habitat for wild bees. To determine site characteristics that influence bee success on reclamation lands, we monitored growth and reproduction of 24 commercially reared bumble bee (Bombus impatiens) colonies placed on 12 former coal mines (aged 2 to 30+ years post-reclamation) in Ohio, U.S.A. Twenty colonies survived the duration of the experiment (May–August 2014). All colonies produced both new queens (mean 21.0 ± 37.0 SD) and males (36.5 ± 36.5), in proportion to overall colony size. Results of generalized linear models indicate that colony growth and reproduction increased with floral diversity and species turnover, and declined with site area and the proportion of forest in the surrounding landscape. The sex ratio of reproductive offspring was significantly more male-biased on sites with low flower diversity, underscoring the importance of floral diversity for meeting the higher resource demands of queen production. Floral resource composition and consistency were influenced by site age and surrounding landscape. Older sites had higher floral diversity and species turnover throughout the season than younger sites, and included high-quality native bee forage plants. We discuss the implications of this study for reclamation project managers seeking to promote bee reproduction and conservation.
Microcystin in Lake Erie fish: Risk to human health and relationship to cyanobacterial blooms
David M. Wituszynski, Chen lin Hub, Feng Zhang, Justin D. Chaffin, Jiyoung Lee, Stuart A. Ludsin, Jay F. Martin. 2017. Journal of Great Lakes Research. https://doi.org/10.1016/j.jglr.2017.08.006
Microcystin (MC) is a cyanobacteria-produced liver toxin that has been found in fish from Lake Erie, sometimes in excess of World Health Organization (WHO) guidelines for safe consumption. Even so, few studies have quantified MCs in Lake Erie fishes, and these studies have drawn different conclusions concerning the risk that fish consumption poses to public health. To address this gap in knowledge, we used Enzyme-Linked Immunosorbant Assay (ELISA) to evaluate the MC concentration in muscle tissue from three commonly harvested fish in Lake Erie: walleye (Sander vitreus, n = 29); yellow perch (Perca flavescens, n = 52); and white perch (Morone americana, n = 55), collected during summer 2013. Satellite remote sensing was used to compare MC concentrations in fish tissue to bloom conditions in Lake Erie at the time of harvest. We found a significant difference among mean MC concentrations in walleye (71 ng MC/g wet weight), white perch (37 ng MC/g), and yellow perch (8.1 ng MC/g). In addition, MC levels in white perch appeared to depend on local bloom conditions. While few of the fish collected contained MC in excess of WHO guidelines, our results indicate that more toxic blooms could increase MC in fish to levels that pose a greater risk to public health.