Historical influences dominate the population genetic structure of a sedentary marine fish,Atlantic wolffish (Anarhichas lupus), across the North Atlantic Ocean

Genetic variation was assessed in Atlantic wolffish, Anarhichas lupus, across the North Atlantic Ocean using microsatellite and amplified fragment length polymorphism (AFLP) markers. Despite unusual life history attributes such as large benthic eggs, large larvae, a limited pelagic stage and relatively sedentary adults, which suggest potential for strong population structure, range‐wide F_ST values were comparable to other marine fishes (≤0.035). Nevertheless, both significant genetic differentiation among regions and isolation by distance were observed, suggesting limited dispersal in this species. AFLP loci, evaluated on a subset of samples, revealed slightly higher F_ST values, but similar patterns of differentiation and isolation‐by‐distance estimates, compared to microsatellites. The genetic structure of Atlantic wolffish has likely been shaped by its post‐glacial history of recolonization, North Atlantic current patterns and continuity of habitat on continental shelves.     

Leaf‐litter breakdown in pasture and deciduous woodland streams: a comparison among three European regions

1. Human land‐use has altered catchments on a large scale in most parts of the world, with one of the most profound changes relevant for streams and rivers being the widespread clearance of woody riparian vegetation to make way for livestock grazing pasture. Increasingly, environmental legislation, such as the EU Water Framework Directive (EU WFD), calls for bioassessment tools that can detect such anthropogenic impacts on ecosystem functioning. 2. We conducted a large‐scale field experiment in 30 European streams to quantify leaf‐litter breakdown, a key ecosystem process, in streams whose riparian zones and catchments had been cleared for pasture compared with those in native deciduous woodland. The study encompassed a west–east gradient, from Ireland to Switzerland to Romania, with each of the three countries representing a distinct region. We used coarse‐mesh and fine‐mesh litter bags (10 and 0.5 mm, respectively) to assess total, microbial and, by difference, macroinvertebrate‐mediated breakdown. 3. Overall, total breakdown rates did not differ between land‐use categories, but in some regions macroinvertebrate‐mediated breakdown was higher in deciduous woodland streams, whereas microbial breakdown was higher in pasture streams. This result suggests that overall ecosystem functioning is maintained by compensatory increases in microbial activity in pasture streams. 4. We suggest that simple coefficients of breakdown rates on their own often might not be powerful enough as a bioassessment tool for detecting differences related to land‐use such as riparian vegetation removal. However, shifts in the relative contributions to breakdown by microbial decomposers versus invertebrate detritivores, as revealed by the ratios of their associated breakdown rate coefficients, showed clear responses to land‐use.     

The importance of water regimes operating at small spatial scales for the diversity and structure of wetland vegetation

1. In most cases, the most important determinant of wetland vegetation is the water regime. Although water regime is usually described and managed at the scale of whole wetlands, the patterning of vegetation is likely to be determined by water regimes that are experienced at much finer spatial scales. In this study, we assess the significance of internal heterogeneity in water regimes and the role that this heterogeneity plays in vegetation patterning. 2. The effects of water regime on wetland plant species richness and vegetation structure were studied at Dowd Morass, a 1500 ha, Ramsar‐listed wetland in south‐eastern Australia that is topographically heterogeneous. Data on plant variables and water depth were collected along 45 (50 m) transects throughout the wetland and related to water regimes assigned individually for each transect. Wetland plants were assigned to plant functional groups (PFG) that describe the response of plants to the presence or absence of water at different life stages. 3. The classification of water depth data indicated four distinct water regimes in the wetland that were differentiated primarily by the duration of the dry period. Representatives of all PFGs co‐existed over small spatial scales where topographical variation was present, and the richness and cover of understorey species declined as transects became more deeply and permanently flooded. Some PFGs (e.g. amphibious fluctuation tolerator‐low growing and amphibious fluctuation responder‐morphologically plastic) were eliminated by extended periods of flooding, which increased the cover but not richness of submerged plants. Species richness and foliage projective cover declined as water regimes shifted from shallow and frequently exposed conditions to regimes typified by deeper and longer inundation. Cover of the structurally dominant woody species was compromised by deeply flooded conditions but vegetative regeneration occurred despite high water levels. 4. Internal topographical variation generates mosaics of water regimes at fine spatial scales that allow plant species with different water regime requirements to co‐exist over small distances. Deep water and an absence of dry periods result in decreased cover of plants and an overall loss of species richness in the understorey. Water regimes are described that promote regeneration and cover of structurally dominant taxa and increased species richness in the understorey. The study demonstrates a strong association between vegetation and the diverse water regimes that exist within a single wetland, a pattern that will be useful for modelling the effects of modified water regimes on wetland vegetation.     

How do sucker‐footed bats hold on,and why do they roost head‐up?

Individuals of most bat species hang head‐down by their toenails from rough surfaces, but Madagascar's endemic sucker‐footed bat (Myzopoda aurita) clings head‐up to smooth leaves using specialized pads on its wrists and ankles. We investigated the adhesive performance of 28 individuals and found that attachment performance on brass was not affected by the presence or absence of a seal around the pad–surface interface. Furthermore, on smooth acrylic, the wrist pads were more than nine‐fold weaker when lifted perpendicular to the surface than when pulled parallel to it. The unimportance of a seal and the difference in strength in those directions on a smooth surface are characteristic of wet adhesion, but not of suction. Thus, despite its name, the sucker‐footed bat appears to adhere using wet adhesion. We observed that when wrist pads were pushed anteriorly, they unpeeled easily from the surface because of deformation of the pads. This most likely permits rapid detachment during crawling, but would also cause passive detachment if bats roosted head‐down. This provides an ecomorphological explanation to the head‐up roosting behaviour of these unique bats. The results obtained in the present study thus link morphology, behaviour, and roosting ecology for an enigmatic Malagasy endemic. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 233–240.     

Morphology of pollen and orbicules in some Dioscorea species and its systematic implications

Pollen and orbicule morphology of 35 Dioscorea L. species is described based on observations with light microscopy, and scanning and transmission electron microscopy. Pollen and orbicule characters are critically evaluated and discussed in the context of existing hypotheses of systematic relationships within the genus. Pollen is mostly bisulcate (sometimes monosulcate) with a perforate, microreticulate or striate sexine. Our results indicate that pollen data may be significant at sectional rank. The close relationship between sections Asterotricha and Enantiophyllum proposed by Burkill and Ayensu is supported by pollen morphology as all species investigated share bisulcate, perforate pollen with small perforations and a high perforation density. Macromorphological differences between the two compound-leaved sections Botryosicyos and Lasiophyton are also supported by pollen morphology; pollens of these two sections have very different perforation patterns. Orbicules in Dioscorea are mostly spherical and possess a smooth or spinulose surface. The latter is often correlated with a striate sexine.     

Procrustean analysis of fluctuating asymmetry in the bulb mite Rhizoglyphus robini Claparede (Astigmata: Acaridae)

We studied fluctuating asymmetry (FA) in two generations of the bulb mite Rhizoglyphus robini . We used Procrustes analyses, which allow the comparison of dimensionless shapes of body sides. We found little (<4%) directional asymmetry in either sex. Of the two morphs occurring in this species, fighters, which possess a thickened third pair of legs, exhibited higher FA than did scramblers, the morph with unmodified legs; this may reflect the costliness of the fighter developmental pathway. There was a negative relationship between FA and female fecundity, but the regression slope of mid-offspring on mid-parent FA was not significantly greater than zero. We propose that heritability estimates can be biased downwards if highly asymmetric individuals produce fewer viable offspring. However, we found no significant association between parental FA and the proportion of viable embryos in their broods. Furthermore, we hypothesized that parental FA might indicate the presence of largely recessive mutations deleterious to developmental homeostasis that would cause increased embryo mortality under inbreeding. However, we found no significant association between FA of parents that were mated to their full sibs and the proportion of viable embryos in their inbred progeny.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 499–505.     

Reconciling landscape and local views of aquatic communities: lessons from Michigan trout streams

1. Rapidly advancing geographical information systems (GIS) technologies are forcing a careful evaluation of the roles and biases of landscape and traditional site-based perspectives on assessments of aquatic communities. Viewing the world at very different scales can lead to seeming contradictions about the nature of specific ecological systems. In the case of Michigan trout streams, landscape analyses suggest a predictable community shaped by large-scale patterns in hydrology and geology. Most site-based studies, however, suggest these communities are highly variable in structure over time, and are strongly shaped by site-specific physical and biological dynamics. As the real world is comprised of processes operating both at local and landscape scales, an analytical framework for integrating these paradigms is desirable.
2. Decomposition of variances by factorial ANOVA into time, space and time–space interaction terms can provide a conceptual and analytical model for integrating processes operating at landscape and local scales. Using this approach, long-term data sets were examined for three insects and two fishes common in Michigan trout streams. Each taxon had a unique variance structure, and the observed variance structure was highly dependent upon sample size.
3. Both spatially extensive designs with little sampling over time (typical of many GIS studies) and temporally extensive designs with little or no spatial sampling (typical of population and community studies), are biased in terms of their view of the relative importance of local and landscape factors. The necessary, but in many cases costly, solution is to develop and analyse data sets that are both spatially and temporally extensive.     

Estimating abundance of introduced Chinese muntjac Muntiacus reevesi and native roe deer Capreolus capreolus using portable thermal imaging equipment

• 1 Managing the conservation impacts of deer requires knowledge of their numbers. However, estimating densities in forested areas is problematic, with pellet‐group‐based methods subject to error and uncertainty in estimating defecation and decay rates in addition to sampling variance. Use of thermal imaging equipment allows direct census by distance sampling.
• 2 Densities of introduced Chinese muntjac Muntiacus reevesi and native roe deer Capreolus capreolus were estimated in 12.8 km² of conifer forest in eastern England by thermal imaging distance transects. Estimated density of introduced muntjac (±95% confidence intervals [CI]: 20 ± 8 km⁻²) exceeded that of native roe deer (16 ± 6 km⁻²); 95% CI of c. 40% were achieved in 10 days of fieldwork.
• 3 Density estimates were not sensitive to the number of width bands applied during analysis. Detectability functions differed, with narrower effective strip widths (ESW) for muntjac (74 m) than roe deer (123 m). Thus, it is important to discriminate between species when censusing mixed assemblages. Detectability and ESW also differed among plantation growth stages. Stratification by habitat may therefore improve accuracy of density estimates but would require additional survey effort.