Perennial grassland dynamics on fertile plains: Is coexistence mediated by disturbance?

Abstract The response of grasslands to disturbance varies with the nature of the disturbance and the productivity of the landscape. In highly productive grasslands, competitive exclusion often results in decreased species richness and grazing may allow more species to coexist. Once widespread, grasslands dominated by Dichanthium sericeum (Queensland bluegrass) and Astrebla spp. (Mitchell grass) occur on fertile plains but have been reduced in extent by cultivation. We tested the effects of exclusion of livestock grazing on these grasslands by comparing the floristic composition of sites in a nature reserve with an adjacent stock reserve. In addition, sites that had been cultivated within the nature reserve were compared with those where grazing but no cultivation had occurred. To partition the effects of temporal variation from spatial variation we sampled sites in three different years (1998, 2002 and 2004). Some 194 taxa were recorded at the nature reserve and surrounding stock routes. Sampling time, the occurrence of past cultivation and livestock grazing all influenced species composition. Species richness varied greatly between sampling periods relating to highly variable rainfall and water availability on heavy clay soils. Native species richness was significantly lower at previously cultivated sites (13–22 years after cultivation), but was not significantly influenced by grazing exclusion. After 8 years it appears that reintroducing disturbance in the form of livestock grazing is not necessary to maintain plant species richness in the reserve. The highly variable climate (e.g. droughts) probably plays an important role in the coexistence of species by negating competitive exclusion and allowing interstitial species to persist.     

Niche variation and the maintenance of variation in body size in a burying beetle

1. In burying beetles (Nicrophorinae), body size is known to provide both a fecundity advantage (in females) and successful resource defence (in males and females). Despite this, considerable variation in body sizes is observed in natural populations. 2. A possible explanation for the maintenance of this variation, even with intra‐ and inter‐specific resource competition, is that individuals might assort according to body size on different‐sized breeding resources. 3. We tested prediction that ‘bigger is always better’, in the wild and in the laboratory, by experimentally manipulating combinations of available breeding‐resource size (mouse carcasses) and competitor's body size in Nicrophorus vespilloides (Herbst 1783). 4. In the field, large female beetles deserted small carcasses, without breeding, more often than they did larger carcasses, but small females used carcasses indiscriminately with respect to size. In the laboratory, large beetles reared larger broods (with more offspring) on larger carcasses than small beetles, but on small carcasses small beetles had a reproductive advantage over large ones. Offspring size covaried with carcass size independently of parental body size. 5. The present combined results suggest breeding resource value depends on an individual's body size, and variation in body size is environmentally induced: maintained by differences in available carcass sizes. This produces a mechanism by which individual specialisation leads to an increase in niche variation via body size in these beetles.     

TELECARE,REMOTE MONITORING AND CARE

Telecare is often regarded as a win/win solution to the growing problem of meeting the care needs of an ageing population. In this paper we call attention to some of the ways in which telecare is not a win/win solution but rather aggravates many of the long‐standing ethical tensions that surround the care of the elderly. It may reduce the call on carers' time and energy by automating some aspects of care, particularly daily monitoring. This can release carers for other caring activities. On the other hand, remote and impersonal monitoring seems to fall short of providing care. Monitoring may be used to help elderly users retain independence. But it may also increase the amount of information which flows from users to carers, which can result in a form of function‐creep that actually undermines independence.     

CO2 uptake patterns depend on water current velocity and shoot morphology in submerged stream macrophytes

1. The influence of current velocity on the pattern of photosynthetic CO₂ uptake in three species of submerged stream macrophytes was described by analysing the grain density in autoradiographs of leaves exposed to ¹⁴CO₂. 2. In Elodea canadensis, the CO₂ uptake was approximately two‐fold higher near the leaf periphery compared with the midrib section at high current velocity, whereas at low current velocity the area of relatively high CO₂ uptake expanded from the leaf periphery towards the midrib and basal sections of the leaves. 3. In Potamogeton crispus and Callitriche stagnalis the CO₂ uptake was uniform throughout the leaves at low current velocity, whereas at high current velocity the CO₂ uptake appeared to increase randomly in some areas of the leaves. 4. The relationship between the photosynthetic CO₂ uptake pattern and the dynamics of flow surrounding submerged shoots at low and high current velocity is discussed in relation to shoot morphology. In E. canadensis, thick diffusive boundary layers may develop between leaves because of screening effects at high current velocity. Increased diffusion path for CO₂ may contribute to inhibitory effects on photosynthesis in this species.     

Why are birds' eggs colourful? Eggshell pigments co‐vary with life‐history and nesting ecology among British breeding non‐passerine birds

The colourful appearance of bird eggshells has long fascinated biologists and considerable research effort has focused on the structure and biochemistry of the avian eggshell matrix. The presence of tetrapyrrole pigments was identified nearly a century ago. Surprisingly, how the concentrations of avian eggshell pigments vary among related species, and whether this variability is associated with either eggshell appearance and/or species life‐history traits, remains poorly understood. We quantified the concentrations of the two key eggshell pigments, protoporphyrin IX and biliverdin, from a diverse sample of eggshells stored at the Natural History Museum, Tring, UK. We explicitly tested how these two pigments are associated with physical measures of eggshell coloration and whether the pigment concentrations and colour diversity co‐vary with phylogenetic affiliations among species. We also tested a series of comparative hypotheses regarding the association between the concentrations of the two pigments and specific life‐history and breeding ecology traits. Across species, the average concentrations of protoporphyrin and biliverdin were positively correlated, and both strongly co‐varied with phylogenetic relatedness. Controlling for phylogeny, protoporphyrin concentration was associated with a higher likelihood of cavity nesting and ground nesting, whereas biliverdin concentration was associated with a higher likelihood of non‐cavity nesting habit and bi‐parental provisioning. Although unlikely to be explained by a single function, the breeding ecology and life history‐dependence of eggshell pigment concentrations in these comparative analyses implies that related species share pigment strategies, and that those strategies relate to broad adaptive roles in the evolution of variation in avian eggshell coloration and its underlying mechanisms. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 657–672.     

Chemosensory Behaviour of Strombidium purpureum, an Anaerobic Oligotrich with Endosymbiotic Purple Non-Sulphur Bacteria

ABSTRACT. Strombidium purpureum Kahl, is an anaerobic oligotrichous ciliate with endosymbiotic phototrophic bacteria. Like other anaerobic ciliates, S. purpureum reacts to O₂-pressure. In the light, the ciliates avoid even traces of O₂ (< 1% atmospheric saturation). In the dark, however, the ciliates accumulate in water with a pO₂ of 1–4% atmospheric saturation. Experiments show that ciliates which have accumulated in the dark under microaerophilic conditions react when the light is turned on, and their ability to escape is enhanced by steep O₂-gradients. The ciliates orient themselves in O₂-gradients by a series of phobic responses. They tumble whenever they swim towards a higher O₂-tension and thus they eventually all swim in the direction of lower pO₂. The ecological implications of such behaviour are discussed.     

Does reduction of the eggshell occur concurrently with or subsequent to the evolution of viviparity in phrynosomatid lizards?

Viviparity and placentation have evolved many times within squamate reptiles, but the sequence in which the attendant morphological modifications occur remains unclear. In particular, it is unknown whether a reduction of the egg shell occurs concurrently with longer periods of egg retention (i.e. increasingly advanced stages of embryogenesis at oviposition) or whether such thinning occurs after viviparity has evolved. To investigate this question, we evaluated the prediction that shell morphology and permeability vary systematically with the capacity to support embryonic development in utero (as judged by the maximum embryonic stage attainable in utero) in five species of oviparous sccloporine lizards and one lizard species in the sister genus Urosuarus. Despite major differences among species in the capacity to support embryogenesis, shell morphology (structure, thickness) and physiology (permeability to water vapour) did not vary as predicted. These results raise the intriguing possibility that other features associated with simple placentation (e.g. increased oviductal and chorioallantoic vascular density) evolve concurrently with longer periods of egg retention and viviparity and that shell thinning may occur subsequent to the evolution of viviparity, at least in sceloporine lizards.     

Rhacophyton from the Upper Devonian of West Virginia

A new species of Rhacophyton, R. ceratangium , is described from Upper Devonian rocks of West Virginia, U.S.A.; this is synonymous with R. incertum (Dawson) Krausel and Weyland but reasons are cited to indicate that the latter species name is not appropriate.
The collections include: stems up to 2 cm in diameter bearing bipinnate, non-laminate vegetative fronds; abundant well preserved fertile fronds that show clearly the distinctive morphology of their sterile and fertile pinnae; fragments of axes with woody tissues petrified.
The sporangia are particularly distinctive with their long slender tip; they dehisced longitudinally and contained several hundred spores; all available evidence indicates that the plant was homosporous. All petrified axes have a slender bar-shaped strand of primary wood swollen at either end and surrounded by strongly developed secondary wood consisting of scalariform tracheids and rays.
R. ceratangium is closely related to the Belgian R. zygopteroides Leelercq. A comparison with other Devonian and Carboniferous pteridophytes suggests that Rhacophyton is probably a primitive member of the Progymnospermopsida or immediately ancestral to that group.