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.     

Satellite-marked waterfowl reveal migratory connection between H5N1 outbreak areas in China and Mongolia

The role of wild birds in the spread of highly pathogenic avian influenza H5N1 has been greatly debated and remains an unresolved question. However, analyses to determine involvement of wild birds have been hindered by the lack of basic information on their movements in central Asia. Thus, we initiated a programme to document migrations of waterfowl in Asian flyways to inform hypotheses of H5N1 transmission. As part of this work, we studied migration of waterfowl from Qinghai Lake, China, site of the 2005 H5N1 outbreak in wild birds. We examined the null hypothesis that no direct migratory connection existed between Qinghai Lake and H5N1 outbreak areas in central Mongolia, as suggested by some H5N1 phylogeny studies. We captured individuals in 2007 from two of the species that died in the Qinghai Lake outbreaks and marked them with GPS satellite transmitters: Bar-headed Geese Anser indicus ( n  =   14) and Ruddy Shelduck Tadorna ferruginea ( n  =   11). Three of 25 marked birds (one Goose and two Shelducks) migrated to breeding grounds near H5N1 outbreak areas in Mongolia. Our results describe a previously unknown migratory link between the two regions and offer new critical information on migratory movements in the region.     

Impact of protein concentrate coproducts on net land requirement for European biofuel production

A methodology is proposed for calculating the net land area requirement for European biofuels, accounting for the substitution impact of animal feed protein coproducts such as dried distillers grains and solubles (DDGS) and rape meal. For example, when bioethanol is produced from cereal grain starch, grain protein is preserved in the DDGS coproduct. Each tonne of wheat DDGS has the potential to replace 0.59 tonnes of soy meal and 0.39 tonnes of cereals in EU animal feed, and the land area required for soy and cereal feed production offsets much of the land requirement for wheat bioethanol feedstock. While the land area needed for bioethanol from feed wheat in North West Europe is 0.40 ha t^?1, the net requirement after accounting for coproducts is just 0.03ha t^?1 of bioethanol produced, 6% of the gross land requirement. Calculated in this way, the net land area required to produce biofuel from EU cereal, rapeseed and sugar beet crops is much lower than the gross land requirement, and from cereal and sugar beet crops is less than the land requirement of biofuel from oil palm and sugar cane.     

Impacts of an anomalously warm year on soil nitrogen availability in experimentally manipulated intact tallgrass prairie ecosystems

Global climate change can potentially increase the frequency of climate anomalies. Anomalously warm years may cause an increase in soil nitrogen (N) availability by stimulating N mineralization. To date, most studies addressing the effects of ecosystem warming have been conducted in relatively cold ecosystems and few studies have addressed impacts of interannual as opposed to continuous, multiyear warming. In this study, 12 intact soil monoliths were excavated from a tallgrass prairie site near Purcell, Oklahoma, USA and divided among four large flux chambers (EcoCELLs). During the first year, all four EcoCELLs were subjected to Oklahoma air temperatures and precipitation. During the second year, air temperature in two EcoCELLs was increased by 4 °C throughout the year resulting in an increase in soil temperature of 2.3 °C at 7.5 cm depth. During the third and fourth years, temperatures in the warmed EcoCELL returned back to 'normal' conditions. During the warming year, vegetation N content was not significantly affected by the warming treatment suggesting no change in N availability. Other N availability indicators (soil solution chemistry, leaching, and N adsorption by ion exchange resins) did not show any effect of warming. Soil solution, leaching, and ion exchange resins showed a large pulse of NH₄⁺ at the start of the study most likely due to disturbance caused by monolith excavation and transport but these effects were short-lived and had disappeared before the treatment started. The lack of a clear warming effect may be explained by a reduction in soil moisture in the warming treatments compared with the controls offsetting a potential stimulation of N mineralization in response to increased temperatures. As a result, effects of an anomalously warm year on N availability in warmer ecosystems may be small compared with colder ecosystems but are likely to depend on soil moisture status.     

Nestling colouration is adjusted to parent visual performance in altricial birds

Hitherto, most of the investigation on the perceptual efficacy of begging signals has dwelled on how patterns of nestling colouration adjust to predominant nest luminosity. However, visual sensitivity of birds varies across species, which raises the question of whether colouration of traits involved in begging displays is adjusted to parent visual capacities. Here, by comparing nestling colouration and visual sensitivity across 22 altricial bird species, we provide a first test of this hypothesis. Firstly, we assessed differences in performance of typical UV‐tuned and violet‐tuned bird eyes when looking at the nestling traits under the light regimes prevailing at their nests. Secondly, while controlling for common ancestry in a comparative approach, we explored variation in colouration of nestlings in relation to parent visual system. The colour discrimination model indicated a general higher performance of the ultraviolet over the violet eye at detecting gape and body skin traits in either open‐ or hole‐nest light conditions. Gape colouration was associated with parental visual system as the nestlings of UVS species displayed more yellow and less pure ultraviolet mouths than the nestlings of VS species. Thus, our results agree with an adaptive parent–offspring communication scenario where the nestlings’ colours tuned the perception capacities of their parents.     

Arid Recovery – A comparison of reptile and small mammal populations inside and outside a large rabbit,cat and fox‐proof exclosure in arid South Australia

Australian arid zone mammal species within the Critical Weight Range (CWR) of 35 g–5.5 kg have suffered disproportionately in the global epidemic of contemporary faunal extinctions. CWR extinctions have been attributed largely to the effects of introduced or invasive mammals; however, the impact of these threatening processes on smaller mammals and reptiles is less clear. The change in small mammal and reptile assemblages after the removal of rabbits, cats and foxes was studied over a 6‐year period in a landscape‐scale exclosure in the Australian arid zone. Rodents, particularly Notomys alexis and Pseudomys bolami, increased to 15 times higher inside the feral‐proof Arid Recovery Reserve compared with outside sites, where rabbits, cats and foxes were still present. Predation by cats was thought to exert the greatest influence on rodent numbers owing to the maintenance of the disparity in rodent responses through dry years and the differences in dietary preferences between rabbits and P. bolami. The presence of introduced Mus domesticus or medium‐sized re‐introduced mammal species did not significantly affect resident small mammal or reptile abundance. Abundance of most dasyurids and small lizards did not change significantly after the removal of feral animals although reductions in gecko populations inside the reserve may be attributable to second order trophic interactions or subtle changes in vegetation structure and cover. This study suggests that populations of rodent species in northern South Australia below the CWR may also be significantly affected by introduced cats, foxes and/or rabbits and that a taxa specific model of Australian mammal decline may be more accurate than one based on body weight.     

Identification and functional characterization of effectors in expressed sequence tags from various life cycle stages of the potato cyst nematode Globodera pallida

In this article, we describe the analysis of over 9000 expressed sequence tags (ESTs) from cDNA libraries obtained from various life cycle stages of Globodera pallida . We have identified over 50 G. pallida effectors from this dataset using bioinformatics analysis, by screening clones in order to identify secreted proteins up-regulated after the onset of parasitism and using in situ hybridization to confirm the expression in pharyngeal gland cells. A substantial gene family encoding G. pallida SPRYSEC proteins has been identified. The expression of these genes is restricted to the dorsal pharyngeal gland cell. Different members of the SPRYSEC family of proteins from G. pallida show different subcellular localization patterns in plants, with some localized to the cytoplasm and others to the nucleus and nucleolus. Differences in subcellular localization may reflect diverse functional roles for each individual protein or, more likely, variety in the compartmentalization of plant proteins targeted by the nematode. Our data are therefore consistent with the suggestion that the SPRYSEC proteins suppress host defences, as suggested previously, and that they achieve this through interaction with a range of host targets.     

Impact of pre-harvest burning versus trash conservation on soil carbon and nitrogen stocks on a sugarcane plantation in the Brazilian Atlantic forest region

Owing to the increased demand for ethanol biofuel from sugar cane, the area planted to this crop in Brazil has increased from 4.8 to 9.5 Mha since 2000. At the same time there has been pressure from environmental groups and others to cease the pre-harvest burning of cane, and today over 40% of the crop is harvested without burning, thus conserving the trash on the soil surface. While most trash decomposes during the year, it is generally assumed that this transition from burning to trash conservation will have benefits for cane productivity and increase soil carbon stocks. To investigate the possible benefits of this change of practice an experiment was carried out in the state of Espírito Santo, south-eastern Brazil, to investigate the long-term effects of the practice of pre-harvested burning compared to trash conservation on soil fertility and soil C and N stocks. The results showed that over a 14-year period, trash conservation marginally decreased soil acidity and significantly increased soil C and N stocks in 0–10 cm depth interval. Although the trash conservation treatment accumulated 13 Mg C ha^?1 more than the burned treatment, this difference was not statistically different. However, the stocks of N to 100 cm depth were 900 kg ha^?1 higher under the trash conservation treatment and this difference was statistically significant. The ¹³C abundance data suggested that where trash was conserved, more soil C was derived from the sugar cane than from the original native vegetation.     

Low crowding threshold for induction of sexual reproduction and diapause in a Patagonian rotifer

1. This study investigates the basis and ecological significance of the extremely high propensity for mixis (sexual reproduction) observed in laboratory populations of Brachionus calyciflorus from a temporary pond in Patagonia. 2. Experiments with stem females hatched from resting eggs showed that these females were exclusively amictic but produced mictic daughters even at very low population densities. In six experiments, newly hatched stem females were cultured individually in different volumes (1.5, 12, 40 and 150 mL). The percentage of mictic daughters (mixis ratio) was high in the smaller volumes (e.g. 44–83% in 1.5 mL) and lower in the largest volume (6–21% in 150 mL). A regression analysis combining the data from these experiments showed a highly significant decrease in mixis ratio with volume and indicated that the lowest population density at which mixis still occurs (mixis threshold) would be 3.4 females L^?1 (95% CL 2.9–4.0 females L^?1). This value is considerably lower than mixis thresholds for other rotifers (25–250 females L^?1 for many species and 9000–477 000 females L^?1 for some Spanish Brachionus plicatilis). 3. In three additional experiments, stem females and their amictic daughters were cultured individually in 150 mL. The percentage of mictic daughters produced by these two generations of females was not significantly different, showing that the mixis response to crowding is not inhibited in the stem‐female generation. 4. Laboratory experiments showed that two common predators of the Patagonian B. calyciflorus (the calanoid copepod Parabroteas sarsi and the backswimmer Notonecta vereertbruggheni) each ate 60–70 B. calyciflorus predator^?1 per day and cleared all rotifers from c. 250 mL per day. Thus, a very low mixis threshold and high maximal mixis ratio may ensure production of some resting eggs soon after colonisation of the pond and before complete removal from the plankton. 5. Two laboratory experiments showed that resting eggs of the Patagonian B. calyciflorus hatched at variable rates (28 and 81%) after a brief diapause when kept in the conditions under which they were produced and oviposited (20–21 °C; L: D 16: 8). Early hatching of resting eggs from pond sediment may allow multiple periods of colonisation and resting egg production in a season. This may offset the fitness cost of limited population growth through female parthenogenesis in the face of unpredictable and abrupt risk of extinction because of predators.