Comparison of measured and EF5-r-derived N2O fluxes from a spring-fed river

There is considerable uncertainty in the estimates of indirect N₂O emissions as defined by the Intergovernmental Panel on Climate Change's (IPCC) methodology. Direct measurements of N₂O yields and fluxes in aquatic river environments are sparse and more data are required to determine the role that rivers play in the global N₂O budget. The objectives of this research were to measure the N₂O fluxes from a spring‐fed river, relate these fluxes to the dissolved N₂O concentrations and NO₃‐N loading of the river, and to try to define the indirect emission factor (EF5‐r) for the river. Gas bubble ebullition was observed at the river source with bubbles containing 7.9 μL N₂O L^?1. River NO₃‐N and dissolved N₂O concentrations ranged from 2.5 to 5.3 mg L^?1 and 0.4 to 1.9 μg N₂O‐N L^?1, respectively, with N₂O saturation reaching 404%. Floating headspace chambers were used to sample N₂O fluxes. N₂O‐N fluxes were significantly related to dissolved N₂O‐N concentrations (r²=0.31) but not to NO₃‐N concentrations. The N₂O‐N fluxes ranged from 38 to 501 μg m^?2 h^?1, averaging 171 μg m^?2 h^?1 (±SD 85) overall. The measured N₂O‐N fluxes equated to an EF5‐r of only 6.6% of that calculated using the IPCC methodology, and this itself was considered to be an overestimate because of the degassing of antecedent dissolved N₂O present in the groundwater that fed the river.     

Floristic changes in the British Isles: comparison of techniques for assessing changes in frequency of plants with time

Botanical recording data are often used to assess changes in the frequencies of plant species over time, but are subject to marked variations in recording activity. We compare and evaluate some general methods that can be used to detect changes in species' frequencies taking into account the recording variations. Models for 15 species that have been studied in detail previously were compared using the numbers of individual records, sites, hectads, or vice-counties at different time scales (year, decade, moving averages, and pre-/post- specific dates), with or without correction for recording variation. The best methods had a correction for the amount of recording over time, summarized records by decade or moving average, and used an extrapolation between first and last records for sites or hectads. Increasing the geographical and temporal scales can decrease the influence of recording variations, but leads to a loss of sensitivity and under-estimates the true extent of change. The choice between sites and hectads will depend on the detail of the records available; cruder data sets should use the latter.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 152 , 279–301.     

The relationship between geographic area and the latitudinal gradient in species richness in New World birds

One hypothesis for the latitudinal gradient in species richness observed in most animal taxa is that the richness of a region is determined by its geographic area. However, the relationship between geographic area and species richness across regions is generally weak. It has been suggested that this is because species from the tropics spill out of this region of high richness, artificially inflating the richness of other regions. This generates the interesting prediction that the area and richness of extra-tropical regions should be more strongly correlated if tropical species are excluded. We test this prediction using the avifauna of the New World. We find that there is indeed a relationship between the land area and species richness of a region once tropical species are excluded. This relationship is independent of the latitude and productivity of regions. Both latitude and productivity can explain variance in richness unexplained by land area. There is no relationship between land area and species richness if tropical species are not excluded from the analysis, suggesting that tropical species do indeed mask the relationship between richness and area. We conclude that our results generally support the geographic area hypothesis, although tests of its other predictions and on other land masses are required.     

Utilization of 4 Sugars Known to Occur in Activated Sludge by Aspidisca cicada (Ciliata, Hypotrichida); Effect on Division Rate

SYNOPSIS. Indiviluals of the hypotrich Aspidisca cicada (Müller) were separated from activated sludge and grown clonally. Lactose and sucrose increased its division rate; D-glucose and arabinose were inhibitory. All 4 sugars stimulated growth of the bacteria associated with A. cicada. Spectrophotometric detection of acid production showed that A. cicada utilized lactose and sucrose markedly, glucose only slightly, and arabinose not at all. The increased fission rate in the presence of lactose and sucrose is probably caused directly by these sugars providing a carbon source, and indirectly by increasing the supply of food bacteria. Retardation of growth of A. cicada in the presence of glucose or arabinose perhaps results from these sugars somehow making the food bacteria unavailable to A. cicada. Sugars found in activated sludge may inhibit or stimulate growth in populations of A. cicada , frequently one of the dominant Protozoa in activated sludge.     

Two‐step vegetation response to enhanced precipitation in Northeast Brazil during Heinrich event 1

High resolution palynological and geochemical data of sediment core GeoB 3910‐2 (located offshore Northeast Brazil) spanning the period between 19 600 and 14 500 calibrated year bp (19.6–14.5 ka) show a land‐cover change in the catchment area of local rivers in two steps related to changes in precipitation associated with Heinrich Event 1 (H1 stadial). At the end of the last glacial maximum, the landscape in semi‐arid Northeast Brazil was dominated by a very dry type of caatinga vegetation, mainly composed of grasslands with some herbs and shrubs. After 18 ka, considerably more humid conditions are suggested by changes in the vegetation and by C_org and C/N data indicative of fluvial erosion. The caatinga became wetter and along lakes and rivers, sedges and gallery forest expanded. The most humid period was recorded between 16.5 and 15 ka, when humid gallery (and floodplain) forest and even small patches of mountainous Atlantic rain forest occurred together with dry forest, the latter being considered as a rather lush type of caatinga vegetation. During this humid phase erosion decreased as less lithogenic material and more organic terrestrial material were deposited on the continental slope of northern Brazil. After 15 ka arid conditions returned. During the humid second phase of the H1 stadial, a rich variety of landscapes existed in Northeast Brazil and during the drier periods small pockets of forest could probably survive in favorable spots, which would have increased the resilience of the forest to climate change.     

Processing of ultrasound in a bush cricket's brain

The processing and categorization of conspecific and heterospecific acoustic signals is an important task of the central nervous system. In orthopteran species, carrier frequency (besides temporal cues) is one of the major discriminators. In the bush cricket species Ancistrura nigrovittata Brunner von Wattenwyl (Phaneropteridae, Barbitistini), ultrasound has potentially different meanings and may elicit vastly different behaviours depending on the context it is perceived in. In the present study, data are presented of the morphology and neuronal responses of three local brain neurones (LBNs) that respond best to ultrasound. All neurones show dense arborizations in the lateral protocerebrum, where ascending interneurones terminate. The LBN2 and LBN9 neurones are entirely restricted to one side of the brain, whereas LBN5 crosses the midline, thereby linking both hemispheres. The response maxima for LBN2 overlap closely with the peak carrier frequencies found in a species‐specific duet, which consists of sonic (16 kHz, male), as well as ultrasonic (24–28 kHz, female) sound. By contrast, LBN9 responds only to ultrasound in the range of the female reply, whereas the male song induces exceptionally long‐lasting inhibition. The LBN5 neurone shows strongest spike activity to a broad range of ultrasonic frequencies, as long as the pulse duration remains short. All three brain neurones respond to ultrasound in a unique way and may be involved in the shaping of different behavioural outcomes.     

Mismatches between breeding success and habitat preferences in Hen Harriers Circus cyaneus breeding in forested landscapes

During the past century, the upland breeding areas of Hen Harriers in Ireland have been extensively afforested. There is no evidence that this species avoids breeding in heavily forested landscapes and, indeed, young commercial forests in their second rotation are often selected as nest‐sites. However, Hen Harriers have coexisted with these forested areas for only a few decades and it is possible that such landscapes are suboptimal. We examined the relationship between breeding success and habitat using a dataset spanning three years and four study areas in the south and west of Ireland. We assessed whether nest success and fledged brood size were related to habitat type, both at the nest‐site and in the surrounding landscape. Neither measure of breeding productivity was related to total forest cover or to percentage cover of closed canopy forest in the landscape. However, in a subset of areas, high cover of second‐rotation pre‐thicket (young forests planted on land from which a first rotation has already been harvested) in the surrounding landscape was associated with low levels of breeding success. This may be due to factors related to predation, disturbance or prey availability. The fact that second‐rotation pre‐thicket is a preferred habitat for nesting in Ireland suggests that Hen Harriers may be making suboptimal decisions in the landscapes available to them.     

Heterozygosity–fitness correlations and associative overdominance: new detection method and proof of principle in the Iberian wild boar

Heterozygosity-fitness correlations (HFC) may result from a genome-wide process — inbreeding — or local effects within the genome. The majority of empirical studies reporting HFCs have attributed correlations to inbreeding depression. However, HFCs are unlikely to be caused by inbreeding depression because heterozygosity measured at a small number of neutral markers is unlikely to accurately capture a genome-wide pattern. Testing the strengths of localized effects caused by associative overdominance has proven challenging. In their current paper, Amos and Acevedo-Whitehouse present a novel test for local HFCs. Using stochastic simulations, they determine the conditions under which single-locus HFCs arise, before testing the strength of the correlation between the neutral marker and a linked gene under selection in their simulations. They used insights gained from simulation to statistically investigate the likely cause of correlations between heterozygosity and disease status using data on bovine tuberculosis infections in a wild boar population. They discover that a single microsatellite marker is an excellent predictor of tuberculosis progression in infected individuals. The results are relevant for wild boar management but, more generally, they demonstrate how single-locus HFCs could be used to identify coding loci under selection in free-living populations.     

Are avian eggshell colours effective intraspecific communication signals in the Muscicapoidea? A perceptual modelling approach

Diversity in the colour and appearance of avian eggshells has been proposed to serve a variety of visual functions, including crypsis from predation, mimicry and discrimination in facultative and obligate brood parasitism, and sexually selected intraspecific signalling of the extent of maternal investment in the egg. Here, we apply a photoreceptor noise-limited colour opponent model of avian perception to assess a necessary corollary of any intraspecific signalling hypothesis, namely that individual birds are able to discriminate between colours of eggs in different conspecific clutches. Clutches from 46 species in the superfamily Muscicapoidea were measured at the Natural History Museum collection in Tring, UK. The results demonstrate that, for these particular species, most eggs are predicted not to be easily discriminable from those in other conspecific clutches in terms of the shells' background coloration. These findings are of fundamental concern to any signalling hypothesis that looks to explain the evolution of avian-visible egg colour polymorphism through selection at the intraspecific level. Importantly, future studies should combine both the proximate mechanisms and the ultimate functions of trait variability when testing hypotheses of the variability in eggshell appearance.