Ant community composition and functional traits in new grassland strips within agricultural landscapes

1. Ongoing intensification and fragmentation of European agricultural landscapes dramatically reduce biodiversity and associated functions. Enhancing perennial noncrop areas holds great potential to support ecosystem services such as ant‐mediated pest control.
2. To study the potential of newly established grassland strips to enhance ant diversity and associated functions, we used hand collection data and predation experiments to investigate differences in (a) ant community composition and (b) biocontrol‐related functional traits, and (c) natural pest control across habitats in cereal fields, old grasslands, and new grassland transects of three years of age.
3. Ant species diversity was similar between new and old grasslands, but significantly higher in new grasslands than in surrounding cereal fields. Contrary, ant community composition of new grasslands was more similar to cereal fields and distinct from the species pool of old grasslands. The functional trait space covered by the ant communities showed the same distribution between old and new grasslands. Pest control did not differ significantly between habitat types and therefore could not be linked to the prevalence of functional ant traits related to biocontrol services in new grasslands.
4. Our findings not only show trends of convergence between old and new grasslands, but also indicate that enhancing ant diversity through new grasslands takes longer than three years to provide comparable biodiversity and functionality.
5. Synthesis and applications: Newly established grasslands can increase ant species richness and abundance and provide a consistent amount of biocontrol services in agroecosystems. However, three years after their establishment, new grasslands were still dominated by common agrobiont ant species and lacked habitat specialists present in old grasslands, which require a constant supply of food resources and long colony establishment times. New grasslands represent a promising measure for enhancing agricultural landscapes but must be preserved in the longer term to promote biodiversity and resilience of associated ecosystem services.

     

Points on the curve: An analysis of methods for assessing the shape of vertebrate claws

The form of amniote claws has been extensively investigated, often with inferences about ecological association being drawn from studies of their geometry. Various methods have been used to quantify differences in the geometry of claws, but rarely have the underlying assumptions of such methods been addressed. Here, we use one set of bird claws and apply six methods (five that have been previously used, and a new one) that are tasked with comparing their shape. In doing so, we compare the (1) ability of these methods to represent the shape of the claw; (2) validity of the assumptions made about underlying claw geometry; (3) their ability to be applied unambiguously; and (4) their ability to differentiate between predetermined functional clusters. We find that of the six methods considered only the geometric morphometric approach reveals differences in the shapes of bird claws. Our comparison shows that geometry‐based methods can provide a general estimate of the degree of curvature of claw arcs, but are unable to differentiate between shapes. Of all of the geometry‐based approaches, we conclude that the adjusted version of the Zani (2000) method is the most useful because it can be applied without ambiguity, and provides a reliable estimate of claw curvature. The three landmarks that define that method (tip and base of the claw arc, plus the intersection between said claw arc and a line drawn perpendicular from the midpoint of tip and claw base) do not all bear biological significance, but relatively clearly circumscribe the length‐to‐height ratio of the claw, which relates to its curvature. Overall, our comparisons reveal that the shape of avian claws does not differ significantly between climbing and perching birds, and that the utilization of preordained functional clusters in comparative data analysis can hinder the discovery of meaningful differences in claw shape. J. Morphol. 278:150–169, 2017. © 2016 Wiley Periodicals,Inc.     

Validation of density–elasticity relationships for finite element modeling of human pelvic bone by modal analysis

In total hip arthroplasty and particularly in revision surgery, computer assisted pre-operative prediction of the best possible anchorage strategy for implant fixation would be a great help to the surgeon. Computer simulation relies on validated numerical models. In the current study, three density–elasticity relationships (No. 1–3) from the literature for inhomogeneous material parameter assignment from CT data in automated finite element (FE) modeling of long bones were evaluated for their suitability for FE modeling of human pelvic bone. Numerical modal analysis was conducted on 10 FE models of hemipelvic bone specimens and compared to the gold standard provided by experimental modal analysis results from a previous in-vitro study on the same specimens. Overall, calculated resonance frequencies came out lower than measured values. Magnitude of mean relative deviation of numerical resonance frequencies with regard to measured values is lowest for the density–elasticity relationship No. 3 (−15.9%) and considerably higher for both density–elasticity relationships No. 1 (−41.1%) and No. 2 (−45.0%). Mean MAC values over all specimens amount to 77.8% (No. 1), 78.5% (No. 2), and 83.0% (No. 3). MAC results show, that mode shapes are only slightly influenced by material distribution. Calculated resonance frequencies are generally lower than measured values, which indicates, that numerical models lack stiffness. Even when using the best suited (No. 3) out of three investigated density–elasticity relationships, in FE modeling of pelvic bone a considerable underestimation of model stiffness has to be taken into account.     

The contribution of setal blades to effective swimming in the aquatic mite Limnochares americana (Acari: Prostigmata: Limnocharidae)

Two rows (anterior and posterior) of long fine setae inserted on the 3rd, 4th and 5th segments of the last two pairs of legs of L. americana form functional swimming blades. Each swimming setal is mounted in a mobile basal socket, and the structure of the setal base and socket configuration ensure that the blades will be passively erected during the leg's power stroke to provide increased thrust and collapsed during the recovery stroke to reduce water resistance. The erect swimming blades increase the effective area for thrust by approximately 500%, making it possible for the mite to lift itself off the bottom. The IVth legs contribute the greater proportion of the thrust developed during paddling, and the 4th segment (genu) bears the largest swimming blades on both legs.     

Neural Correlates of Body Integrity Dysphoria

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Taxonomic and functional homogenization of an endemic desert fish fauna

Aim The highly endemic fishes of the arid Southwest USA have been heavily impacted by human activities resulting in one of the most threatened fish faunas in the world. The aim of this study was to examine the patterns and drivers of taxonomic and functional beta diversity of freshwater fish in the Lower Colorado River Basin across the 20th century. Location Lower Colorado River Basin (LCRB). Methods The taxonomic and functional similarities of watersheds were quantified to identify patterns of biotic homogenization or differentiation over the period 1900–1999. Path analysis was used to identify the relative influence of dam density, urban land use, precipitation regimes and non‐native species richness on observed changes in fish faunal composition. Results The fish fauna of the LCRB has become increasingly homogenized, both taxonomically (1.1% based on β_sim index) and functionally (6.2% based on Bray–Curtis index), over the 20th century. The rate of homogenization varied substantially; range declines of native species initially caused taxonomic differentiation (?7.9% in the 1960s), followed by marginal homogenization (observed in the 1990s) in response to an influx of non‐native species introductions. By contrast, functional homogenization of the basin was evident considerably earlier (in the 1950s) because of the widespread introduction of non‐native species sharing similar suites of biological traits. Path analysis revealed that both taxonomic and functional homogenization were positively related to the direct and indirect (facilitation by dams and urbanization) effects of non‐native species richness. Main conclusions Our study simultaneously examines rates of change in multiple dimensions of the homogenization process. For the endemic fish fauna of the LCRB, we found that the processes of taxonomic and functional homogenization are highly dynamic over time, varying both in terms of the magnitude and rate of change over the 20th century.