bluuebunny/crossref_metadata_2025 huggingface dataset:
Axillary basal cell carcinoma: additional 25 patients and considerations
Authors: Betti R. , Crosti C. , Moneghini L. , Crespi E. , Menni S.
Published: September 2010

Background  Axillary basal cell carcinoma represents a rarely described occurrence in world literature.

Objective  To report our 14 years’ experience of axillary basal cell carcinomas.

Methods  A review of Pathology department database is given.

Results  Twenty‐five further patients with axillary basal cell carcinomas of 7367 basal cell carcinomas diagnosed are reported. These represent a percentage of 0.33%.The average age of patients was 64.96 years, not significantly different from the average age of patients with overall basal cell carcinomas. No patient had had previous radiant or immunosuppressive treatment or axillary sunburn. No patient had basal cell naevus syndrome. The subtypes involved were superficial and nodular. No patient of 17 patients followed up had recurrences or metastasis after 5 years of follow‐up.

Conclusion  Axillary Basal cell carcinomas are rare. No particular predisposing or risk factor is recorded. They do not seem to be significantly more aggressive than other basal cell carcinomas.
The effects of territorial behaviour on the stability and dispersion of Tawny owl (Strix aluco) populations
Authors: Hirons G. J. M.
Published: September 2010

The effect of territorial behaviour on the density and stability of Tawny owl (Strix aluco (L.)) populations was studied in three habitats during 1971–74: deciduous woodland (Wytham, near Oxford), mixed farmland (south Warwickshire) and conifer plantations (Dumfries). Territory size was determined by plotting the position of territorial challenges (hoots) of males; these were individually recognizable.

In all three areas, pairs of owls maintained contiguous territories which changed little in size and configuration from year to year. In Wytham, this was in spite of wide fluctuations in the abundance of rodent prey. Territory size was most variable on farmland (17–74 ha) where it was inversely correlated with the area of closed woodland contained within territories. The mean size of territories was significantly smaller in the deciduous woodland (18.2 ha) than the coniferous woodland (46.1 ha) or farmland (37.4 ha). This variation was probably ultimately related to the availability of prey in different habitats.

In Wytham, the annual rate of disappearance of territory‐holding males was around 15% and, except after a poor breeding season, birds which disappeared or were removed from their territories were replaced rapidly. Territory boundaries remained the same after replacement and the number and spatial configuration of territories (around 30) was similar to that found 14 years earlier. There is some evidence that individual pairs would be able to raise more young if they could defend larger territories than is possible at the current population size.

Recoveries of birds ringed nationally indicate that owls survive less well without territories, and that young suffer heavy mortality in their first autumn. The proportion of young recovered was highest in years when many were ringed. Examination of 276 corpses (mostly road casualties) suggests that many young starve soon after becoming independent.

These observations support the idea that the stability of Tawny owl populations results from the territorial behaviour of residents acting to produce subsequent mortality among birds unable to establish their own territories. This regulation probably applies over wide areas and a variety of habitats.
Opercular regeneration in Pomatoceros lamarckii Quatrefages (Polychaeta: Serpulidae). Differentiation of the operculum and deposition of the calcareous opercular plate
Authors: Bubel A. , Thorp C. H. , Fenn Ruth H. , Livingstone D.
Published: September 2010

Following opercular amputation, stages in opercular regeneration in Pomatoceros lamarckii have been described by light, transmission and scanning electron microscopy. Two to three days after amputation, the rudimentary opercular filament is invested with a delicate cuticle composed of an outer filamentous layer and an inner thicker component composed of orthogonally‐arranged layers of small fibril bundles. The opercular plate is uncalcified and composed of two major components, an outer, thin, electron‐dense layer and an inner, thicker component which structurally resembles that of the opercular filament cuticle. Between five and eight days, opercular plate calcification is initiated as needle‐like crystallites. The structural organization of the organic components of the opercular plate show changes which are related to the onset of calcification. From 13–17 days, the opercular plate becomes heavily calcified and is composed of highly‐ordered, prism‐like crystals. X‐ray diffraction shows these crystals to be aragonite. The structure of the cuticle remains unchanged except that the orthogonally‐arranged fibril bundles aggregate into thicker fibres. Amino acid analysis of the regenerated cuticle and organic components of the opercular plate show that they differ from one another and from the normal cuticle and opercular plate. During opercular regeneration, the differentiation of the cuticle and opercular plate‐secreting cells are described and the mechanisms of cuticle and calcareous opercular plate secretion are discussed.
Initiation of flight in the unrestrained fly, Drosophila melanogaster
Authors: Trimarchi J. R. , Schneiderman A. M.
Published: September 2010

Using high speed cinematography and videography, we determined that unrestrained Drosophila melanogaster can initiate flight in two different ways, which we have designated Type 1 and Type 2 flight initiation. Type 1 behaviour is executed when the fly initiates flight ‘voluntarily’. Type 2 behaviour is executed in response to a visual stimulus and is presumably an escape response. During both types of flight initiation, the fly pushes off from the substratum using only the mesothoracic legs. The mesothoracic legs extend at the coxo‐trochanteric, femoro‐tibial and tibio‐metatarsal joints. Although the movements of the legs are similar during both Type 1 and Type 2 flight initiation, the movements of the wings are different. Prior to the onset of leg extension, during Type 1 flight initiation, the wings are raised and rotated from their resting position to a preflight position dorsal to the thorax. The wings are held in this upright position for several milliseconds and then rapidly depressed during leg extension. Prior to Type 2 flight initiation, by contrast, the wings are not raised and rotated, nor are the wings depressed during leg extension. Thus Type 1 flight initiation involves simultaneous leg extension and wing depression, whereas Type 2 flight initiation involves only leg extension.
Costs of breeding status in the European badger, Meles meles
Authors: Woodroffe Rosie , Macdonald D. W.
Published: September 2010

Compared with other mammals, reproduction is expected to be particularly costly for European badgers (Meles meles L.) since both the gestation and mating periods occur in the winter when the animals are inactive and feed little. This paper assesses the costs of breeding status in both male and female badgers, in terms of body condition, ectoparasite load, haematology and mortality. By the end of the lactation period (May), breeding females had suffered a marked loss in body condition, although there was no such cost associated with gestation. However, females regained the weight that they had lost by the autumn following lactation. Lactating two‐year‐olds experienced a higher age‐specific mortality than those that did not breed, but there was no difference among older females. No costs of breeding status could be detected among males at the end of the spring mating period. However, breeding males sustained testicular activity later into the summer than non‐breeders, and by the autumn they had acquired more bite wounds and become anaemic. This suggests that there was a physiological cost associated with extended testicular activity in breeding males.
Evaporative water loss in two sympatric species of vespertilionid bat, Plecotus auritus and Myotis daubentoni: relation to foraging mode and implications for roost site selection
Authors: Webb P. I. , Speakman J. R. , Racey P. A.
Published: September 2010

Simultaneous measures of oxygen consumption and evaporative water loss (EWL) were made in two species of temperate‐zone vespertilionid bat (Plecotus auritus and Myotis daubentoni; mean body mass 9.12 and 10.12g, respectively) at ambient temperatures (Ta) of 5, 15 and 25°C and variable vapour pressure deficit. EWL was directly dependent on vapour pressure deficit and oxygen consumption and inversely dependent on Ta. EWL was significantly greater in P. auritus than in M. daubentoni. A model for EWL in P. auritus under a variety of environmental conditions (5–25°C and 20–80% relative humidity) suggested that EWL from bats in shallow summer torpor will be lowest at low Ta, and that, except at low (> 50%) relative humidity, EWL from euthermic bats will be lowest at high Ta. At low relative humidity (< 20%), resting bats could lose over 30% of body mass per day (24 h) through evaporation. At high Ta (> 25°C), EWL from euthermic bats could be over 65% lower at high (> 80%) compared to low (< 20%) relative humidity. In bats in shallow summer torpor at low (5°C) Ta the equivalent saving was > 96%. At low relative humidity predicted EWL from bats in shallow summer torpor was 34 to 81% of that from euthermic bats, and at low Ta and high relative humidity was only 2%. In the wild, M. daubentoni has freer access to drinking water than does P. auritus and yet EWL at rest was higher in the latter species. We suggest that post‐prandial dumping of urinary water by M. daubentoni leads to a limit in the amount of body water available to this species to cover evaporative losses once within the day roost, which in turn has led to an adaptation of physiology towards the minimization of EWL when at rest.
Epidermal fine structure of the toe tips of Sphaerodactylus cinereus (Reptilia, Gekkonidae)
Authors: Röll Beate
Published: September 2010

This paper deals with epidermal structures of the sphaerodactyline gecko Sphaerodactylus cinereus: adhesive pads, cutaneous sensilla and intraepidermal axon terminals.

The adhesive pad is restricted to a single terminal scale and bears approximately 6,000 setae. The setae are complex, hair‐like structures which branch and sub‐branch up to five times. The terminal ends are shaped like inverted cones. They provide the friction which enables the gecko to walk even on vertical glass‐plates.

Cutaneous sensilla of supposed mechanoreceptive function are found in groups of three or four at the anterior free edge of all dorsal and distal scales of the digit. The sensillum consists of a circular platelet in an epidermal depression bordered by an annular furrow and two or three bristles in a central position.

Discoid axon terminals in the digital scales are located between relatively stiff structures: the corneous layers of the epidermis and a layer of tonofibrillar bundles. The axon terminals are hypothesized to be sensitive to the internal pressure depending on hyperextension of the toe.
Factors influencing home range and activity of wild boar (Sus scrofa) in a Mediterranean coastal area
Authors: Massei G. , Genov P. V. , Staines B. W. , Gorman M. L.
Published: September 2010

This paper analyses the temporal variation in the size of home range and activity of adult wild boar (Sus scrofa L.). Eighteen boar were radiotracked between 1991 and 1993 in the Maremma Natural Park (Central Italy). Variations of home‐range size and activity were related to sex, winter food availability and population density. The hypotheses that home‐range size was inversely related to food availability and population density, and that the amount of activity was directly related to population density and inversely related to food abundance, were tested. The size of the acorn crop was used as a measure of winter resource level. No differences were found in the size of ranges, core area, and activity between males and females. In 1991–92 home‐range size was larger than in 1992–93; conversely, activity increased from 1991–92 to 1992–93. Winter food availability was high in 1991–92 and low in the following year. Population density increased greatly in spring 1992 but crashed in spring and summer 1993, when a high mortality of wild boar occurred due to starvation.

The decrease in home‐range size during the food shortage was explained as a possible strategy adopted by wild boar to cope with starvation. The difference in home‐range size and amount of activity found between the first and the second year of study were probably influenced by differences in population density, although the individual effects of food availability and population density were not clearly separable.
Inter‐island variation in the diet of female northern fur seals (Callorhinus ursinus) in the Bering Sea
Authors: Antonelis G. A. , Sinclair E. H. , Ream R. R. , Robson B. W.
Published: September 2010

The diet of adult female northern fur seals (Callorhinus ursinus) is examined through the analysis of faecal material collected during the summer breeding season at three breeding locations in the Bering Sea: St. Paul Island (1988, 1990) and St. George Island (1988, 1990) of the Pribilof Islands Group (USA), and Medny Island (1990) of the Commander Islands Group (Russia). Prey consumption varies annually and accordingly with the physical and biological environment surrounding each island. Juvenile walleye pollock (Theragra chalcogramma) is the most common prey of northern fur seals from St. Paul Island; the island is surrounded by a broad neritic environment with widely separated frontal zones and is the greatest distance from the continental shelf‐edge. Gonatid squid (Gonatopsis borealis/Berryteuthis magister and Gonatus madokail Gonatus middendorffi) were the most common prey of northern fur seals from Medny Island; the island is surrounded by a compressed neritic environment and is adjacent to the continental shelf‐edge and the oceanic marine environment. A combination of walleye pollock and gonatid squid is consumed by northern fur seals from St. George Island; the island has a surrounding oceanographic environment intermediate between the other two islands.

Variability in predation on walleye pollock is consistent with fishery information concerning the relative abundance and availability of walleye pollock around St. George and St. Paul Islands. The abundance and availability of these prey resources during the summer breeding season are key factors which influence the health and growth of the northern fur seal populations in the Bering Sea.
Movement patterns of river crabs (Decapoda, Potamoidea) in the field: predictable and unpredicatable components
Authors: Barbaresi S. , Gherardi F. , Vannini M.
Published: September 2010

Radio‐telemetry was used to investigate locomotor activity rhythms in a field population of the freshwater crab Potamon fluviatile. Fourteen adult specimens were radio‐tracked almost continuously over a 13‐day period along a hill stream in Tuscany, Italy. A rough nychthemeral movement pattern was found in some animals of both sexes. None of the crabs showed a constant activity on different days, nor did they follow any periodical pattern. Although average displacement amounted to about 5m/d, activity was concentrated over several days at a time, followed randomly by periods of almost total inactivity. On average, only about 3/4 of radio‐tagged crabs were active every day and only a small fraction active at the same time. The crabs spent about 60% (females) or 70% (males) of their time out of the water, but there was no regular pattern in land‐water preference. The random high variation in locomotor activity on different days seems to be a constant pattern in all decapods that have been studied so far, using individual marking techniques.
The relative efficiency of two commercial live‐traps for small mammals
Authors: Lambin Xavier , MacKinnon James
Published: September 2010

Data obtained from live‐trapping a population of field voles, Microtus agrestis, over a seven‐month period was used to compare the trapping efficiencies of the Longworth and the Ugglan Mouse Special traps. The Ugglan Mouse Special is a cheaper alternative that is widely used in Scandinavia. Biases in the sex or age of captured animals were the same for both types of trap and the total numbers of captures were similar. There was no evidence that individual animals were more likely to be captured in the same type of trap at each capture session. We conclude that the Ugglan Mouse Special trap is a practical alternative to the Longworth trap for studies of small mammals by capture‐mark‐recapture techniques.
Geophagy in birds of Crater Mountain Wildlife Management Area, Papua New Guinea
Authors: Symes C. T. , Hughes J. C. , Mack A. L. , Marsden S. J.
Published: September 2010

Numerous New Guinea birds, mostly psittaciforms and columbiforms, have been recorded feeding on soil. This study documents geophagy in the Crater Mountain Wildlife Management Area (CMWMA) in the Eastern Highlands of Papua New Guinea. We present the first documented case of geophagy in the palm cockatoo Probosciger aterrimus and in up to 11 other species. Soil from the site where geophagy by palm cockatoos was recorded was highly weathered and acidic, with a mixture of kaolin, gibbsite, goethite and illite in the clay fraction. Analyses may support the hypothesis that soil is ingested to counterbalance the effects of toxic compounds in fruit. We suggest that the accessibility of the site (an exposed bank), rather than the nature of the soil itself, prompted its use by birds. At another site, a blue‐coloured soil on which cassowaries fed was rich in vivianite (an iron phosphate) and contained an iron‐rich smectite, and some kaolin and mica in the clay fraction. Why cassowaries feed on this particular soil is unclear, but they may obtain trace elements from it, or take advantage of its high iron or phosphorus content. Obtaining other elements, in particular calcium and sodium, may also be important. Alternatively, there may simply be an attraction to its blue colour, which also attracted the interest of local people and folklore. Birds were also reported to drink salt water within the CMWMA. Taken together, there may be quite different reasons for ingestion of minerals/soils among as many as 23 bird species from five families.
Influence of fawning on the spatial behaviour and habitat selection of female fallow deer (Dama dama) during late pregnancy and early lactation
Authors: Ciuti S. , Bongi P. , Vassale S. , Apollonio M.
Published: September 2010

Home‐range sizes and habitat selection among calving and non‐calving female fallow deer Dama dama were analysed during the last months of pregnancy and following parturition. The study was carried out in central Italy using radio‐tracking techniques. It was based on data collected on 23 adult females (calving n=15, non‐calving n=8) from March 2003 to August 2003. Seasonal and bimonthly home‐range analyses showed marked differential spatial behaviour between calving and non‐calving females only when fawns were present. These were born during June, and the summer and July–August home ranges of calving females were significantly lower than those recorded for non‐calving ones. Although differences between spatial use of calving and non‐calving females became significant only after the birth of fawns, habitat choices were significantly different from late pregnancy, when females had already reached parturition sites. Therefore, whereas during March–April calving and non‐calving females showed similar habitat choices, from May, habitat selection proved to be significantly different between the two classes of females. In particular, major differences were detected in the use of marshes and meadows. That female fallow deer adopt anti‐predator tactics during the calving season was shown by their higher use of marshes, the habitat that offers the greatest cover and provides good concealment for fawns. Calving females avoided meadows, because these are open areas without any concealment for fawns; however they were selected by non‐calving females as a function of their high productivity, as shown by analysis of the grass quality of the study site. The use of sub‐optimal habitats by calving females because of the presence of fawns confirmed the findings of previous studies. These showed that ungulate mothers may move to poorer but safer habitats, compromising their energy intakes, to reduce the predation risk to their neonates.
Differences in foraging behaviour between Pipistrellus pipistrellus (Schreber, 1774) and Pipistrellus pygmaeus (Leach, 1825)
Authors: Davidson‐Watts I. , Jones G.
Published: September 2010

From 2001 to 2003 we radio tracked 23 Pipistrellus pipistrellus and 23 Pipistrellus pygmaeus to investigate whether there are any differences in foraging behaviour between the two cryptic species during the summer, and to consider whether any differences between these species are important for their conservation planning. There were significant differences between the two species in relation to flying time, mean maximum distances travelled from the roost, numbers of foraging bouts made and span of home ranges. The results suggest that P. pipistrellus makes more flights to a greater number of foraging locations (and possibly) feeding habitats than P. pygmaeus, although these foraging areas are likely to be closer to the roosts. This behaviour is particularly marked during lactation. In contrast, P. pygmaeus spends less time flying, makes fewer foraging bouts but travels further distances, suggesting that this species is selecting specific foraging habitats. These differences in foraging behaviour support the hypothesis that these species occupy different ecological niches, and conservation planners should be aware of these differences when considering the requirements of pipistrelles in the UK.
Predator threat, copulation effort and immunity in male rats (Rattus norvegicus)
Authors: Hõrak P. , Tummeleht L. , Talvik H.
Published: September 2010

Parental investment theory predicts that organisms should increase their current reproductive investments when they perceive a threat to future reproduction. In such a situation, animals are expected to pay the cost of reproduction by committing a terminal reproductive effort (TRE). We aimed to induce a TRE in male Wistar rats by exposing experimental animals to predator (cat) odour, while the control group was exposed to the odour of rabbit. As response variables, we measured the parameters of male copulatory activity (copulation effort) and resistance to the experimental infection with a neurotropic nematode, Toxocara canis. Contrary to our expectations, control animals received a greater average number of ejaculations in ad libitum copulation trials than predator‐exposed animals. Other parameters of copulatory activity (intromission and ejaculation latencies, numbers of mounts and intromissions, ejaculation efficiency, duration of post‐ejaculatory interval) did not differ between treatment groups. Exposure to predator odour resulted in growth retardation and immune suppression as revealed by the elevated urinary corticosterone levels and higher parasite counts in brain and muscle tissues as compared with control animals. We failed to detect any immunological cost of increased copulatory activity as no significant correlations between measures of copulatory activity and immune parameters could be found. Individual mount number correlated positively with urine creatinine concentration (an index of muscular activity), suggesting that this aspect of male copulatory behaviour is energetically most demanding. Our experiment thus failed to support the hypotheses that exposure to predator odour increases copulatory activity in male rats and that intense copulatory activity leads to immune suppression. The hypothesis that predator odour exposure leads to immune suppression and reduced infection resistance was supported.
Divergent juvenile growth and development mediated by food limitation and foraging in the water strider Aquarius remigis (Heteroptera: Gerridae)
Authors: Blanckenhorn W. U.
Published: September 2010

The factors leading to variation in growth, development and body size are of central importance for the study of life histories. I investigated the effect of food limitation on patterns of growth and development in the water strider Aquarius remigis (Heteroptera: Gerridae). Groups of 10 juveniles were allowed to develop under field conditions at three different food levels. Food limitation prolonged juvenile development, reduced growth rates and led to smaller adult body size and weight, the most common life‐history response in ectotherms; it also increased the variance among individuals in these traits, demonstrating variance accumulation suggesting divergent growth. Evidence that this resulted from competition among individuals for limited food was equivocal. On the one hand, direct observation of foraging nymphs showed that larger instar individuals were more likely to obtain monopolizable prey items than expected by chance, independent of food level. On the other hand, there was only a trend for the variance in moulting dates to increase when striders were raised in groups as opposed to singly at various temperatures in a controlled laboratory experiment. When food limitation prolongs juvenile development, variance accumulation with age can result from food limitation per se, as well as from random or heritable variation in growth trajectories. Foraging competition may amplify this effect, but not necessarily so. Therefore, it must not be assumed that divergent growth is necessarily caused by food competition.
Movement patterns in the monogamous sleepy lizard (Tiliqua rugosa): effects of gender, drought, time of year and time of day
Authors: Kerr G. D. , Bull C. M.
Published: September 2010

To determine the effect of environment and behaviour on locomotor activity, we explored sex‐based differences in activity patterns before and after mating in the monogamous Australian sleepy lizard Tiliqua rugosa. We obtained continuous records of lizard step counts in the field for two 9‐month activity periods. Lizards moved infrequently in both periods and were active for an average 13.2 (se 0.8)% of the day (07:00–20:00 h). Both sexes significantly reduced activity during drought and outside the spring activity period. Drought in the 2002/2003 period resulted in little reproductive activity, with no sex difference in activity. In early spring of the following period, with normal rainfall and food, males on average took significantly more steps per day, moved significantly faster for longer and covered nearly twice the distance each day as females. Males moved significantly faster in the mornings. Daily activity of both sexes had a unimodal peak around midday in early spring, shifting to distinctly bimodal patterns later in spring and early summer. In the 2‐month pairing period before mating, when resource levels were high, the two sexes adopted different foraging strategies: males switched to a time maximization strategy, whereas females continued with an energy maximization strategy. After mating, females were significantly more active than males, with higher levels of activity in the afternoons. Males may be more active than females before mating because of multiple tasking in males, searching for extra pair matings, defence against rival males or as a signal of vigour by males to females.
A new species of shrew tenrec (Microgale jobihely) from northern Madagascar
Authors: Goodman S. M. , Raxworthy C. J. , Maminirina C. P. , Olson L. E.
Published: September 2010

A new species of shrew tenrec in the genus Microgale is described from a series of 12 specimens taken on the south‐western slopes of the Tsaratanana Massif in northern Madagascar and is named Microgale jobihely. This new species is distinguished from other named members of this endemic genus by a variety of mensural and discrete morphological characters. Phylogenetic analysis of the mitochondrial ND2 gene supports its recognition as a distinct species and suggests a sister relationship with the much more widespread Microgale cowani. Microgale jobihely appears to be the only member of this genus that is a very localized endemic, and a biogeographic scenario is presented to explain this observation. It is currently known from a small area of forest, outside of the protected areas system, that is faced with considerable anthropogenic pressure.
Using sparse survey data to investigate the declining abundance of British harbour seals
Authors: Lonergan M. , Duck C. D. , Thompson D. , Mackey B. L. , Cunningham L. , Boyd I. L.
Published: September 2010

This study presents an analysis of changes in the regional abundance of harbour seals Phoca vitulina based on repeated aerial surveys of haulouts, and demonstrates the use of sparse data to deliver advice about population status and management. Generalized linear models with negative binomial errors were used to represent these overdispersed data. The shape parameter of the negative binomial distribution was directly estimated from the data where this was possible. Information from time‐series of counts where there were few gaps in the data was used to improve the estimation of this parameter in areas where fewer surveys had been carried out. The results show that the number of harbour seals in eastern England has not increased since the end of the 2002 phocine distemper epidemic. There is also evidence of a general decline in most of the large harbour seal colonies around Britain. The populations in the Inner Hebrides were an exception, with numbers appearing to be stable or increasing. Between 2001 and 2006, the population in Orkney and Shetland declined by 40% (95% confidence interval: 30–50%), indicating harbour seals in these areas experienced substantially increased mortality or very low recruitment over this period. The widespread declines, ranging from Shetland to The Wash, suggest that the causes may have been present over a large part of the North Sea.
SEEDLINGS
Authors: FENNER M.
Published: September 2010

Summary

The factors which cause the death of seedlings were examined and an attempt was made to determine the selective forces to which they are subjected in the field. After briefly dealing with the difficulties of defining a seedling, I examine a few cases from the recent literature in which the causes of seedling mortality are identified and quantified either by monitoring populations under natural conditions or by manipulating the environment experimentally. The special vulnerability of the immediate post‐germination phase is illustrated and the consistent underestimation of seedling loss in many studies is suggested. Some interesting cases of the effects of neighbours on seedling mortality are examined and it is shown that nearest neighbours may affect a seedling's chance of being grazed. It is concluded that since the causes of seedling mortality‐are so varied and unpredictable in most habitats, individual plasticity may provide a better strategy for survival than highly specialized adaptations to specific mortality factors.
POPULATION DYNAMICS – THE INFLUENCE OF HERBIVORY
Authors: VERKAAR H. J.
Published: September 2010

Summary

Numbers in plant populations often vary widely and, as yet, only a few studies describe adequately how they are determined. The importance of abiotic factors in establishment as well as in determining the carrying capacity of the habitat has been widely recognized. It is also accepted that intraspecific competition for limiting resources may limit numbers in a density‐dependent way. In addition, both herbivores and pathogens may reduce numbers of plants through mechanisms which are either dependent or independent of population density.

Herbivory affects plants not only in the vegetative and reproductive phases but also in the pre‐dispersal and post‐dispersal phases of seeds. Because many studies on the population dynamics of plants have been confined to the former phases, the relative importance of herbivores is likely to have been underestimated for the latter. Furthermore, because herbivory often does not result in mortality but in reduced growth and seed production, its effects may be manifested only as reductions in the size of later generations. The effects of herbivory can therefore only be assessed properly if they are studied over several generations.

Examples are presented of plant populations in which numbers are determined by competition for limiting resources. However, other situations are recognized in which it is the activity of herbivores which appears to determine numbers. There is a continuing need for studies of population dynamics, but there is an urgent requirement for these studies to be related to a unifying conceptual base.
AN ARCHITECTURAL APPROACH TO THE COMPARATIVE ECOLOGY OF PLANT ROOT SYSTEMS
Authors: FITTER A. H.
Published: September 2010

Summary

Although plants devote a large proportion of their resources to roots, we have a poor understanding of the constraints under which root systems function. Roots are much less variable morphologically than leaves and it is likely that root systems rather than individual roots are the focus of natural selection. In other words, architecture is more important than morphology. Existing classifications of root systems, based on the developmental model, have failed to provide much insight into their functioning and an alternative, topological model is outlined, in which the link is the basic unit of classification. Other components of the architecture of root systems, including link lengths, branching angles and diameters, are considered and the ecological implications of variation in each is discussed.

Simulation models of transport and space exploration are discussed and it is shown that resource cost, transport efficiency and exploration efficiency cannot be simultaneously minimized and that optimum form may vary with the mobility of the resource. In general, a ‘herringbone’ structure seems to be the most efficient at exploration of space but the least transport‐efficient and the most expensive.
METAL TOLERANCE
Authors: BAKER A. J. M.
Published: September 2010

Summary

This paper highlights major developments in the field of heavy metal tolerance in plants over the last 15 years. Advances in experimental and theoretical aspects are considered. The value of both intra‐ and interspecific studies in assessing the ecological significance of adaptive strategies is stressed.
PHOTOSYNTHESIS AND CARBON ECONOMY OF PLANTS
Authors: OSMOND C. B.
Published: September 2010

Summary

The extent to which studies of photosynthesis and carbon economy are, or should be, at the forefront of comparative plant ecology is discussed from the points of view of carbon pathways, water‐use efficiency, irradiance and nutrients, especially nitrogen. The ways in which new integrative and reductionist techniques can be applied to photosynthesis in an ecological control are illustrated and their value assessed. The study of photosynthetic physiology of plants at the edges of their geographical range is urged as a means of understanding both their responses to stress and disturbance, and their competitive interactions.
VARIATION IN GENOMIC FORM IN PLANTS AND ITS ECOLOGICAL IMPLICATIONS
Authors: BENNETT MICHAEL D.
Published: September 2010

Summary

The gross form of the nuclear genome varies greatly among plant species in both anatomy and genetic organization. Chromosome number (ft) ranges from 2 to over 600, and ploidy from 1 to over 20. The amount of DNA in the unreplicated haplophase genome (the 1C value) differs by more than 2500‐fold among angiosperms. Although it has been questioned since the 1930s whether such variation is of adaptive significance and whether it is related, perhaps causally, with environmental factors, no direct or causal links have yet been found. However, variation in DNA C‐value has far‐reaching biological consequences and can be of considerable adaptive and hence ecological significance. Strikingly precise interspecific relationships exist between DNA C‐value and many diverse phenotypic characters at the cellular level, and DNA can affect the phenotype in two ways, firstly by expression of its genie content and, secondly, by the biophysical effects of its mass and volume, the latter defined as nucleotypic effects. Nucleotypic variation in DNA C‐value sets absolute limits to both the minimum size and mass of the basic unit of plant anatomy (i.e. the cell) and the minumum time needed to produce a similar cell with newly synthesized organic molecules. Moreover, in complex multicellular vascular plants, such effects at successive cell cycles are additive, so that DNA C‐value influences many characters, including growth rate, seed weight, minimum generation time and type of life‐cycle. Thus, the nucleotype profoundly affects where, when and how plants grow. Selection for a particular genomic form acting on its spatial or temporal consequences may occur at various levels ranging from the cell to the whole organism and may operate throughout the life‐cycle or at just one stage. DNA C‐value is often indirectly related to environmental factors which determine time‐limited environments via selection acting on the temporal phenotypic consequences of nucleotypic variation. However, in the case of radio‐sensitivity, selection for a low DNA C‐value may act directly on the nucleotype itself, as the size of the nuclear DNA target directly affects the ability of the plant to survive.
THE ECOLOGICAL SIGNIFICANCE OF FRUCTAN IN A CONTEMPORARY FLORA
Authors: HENDRY GEORGE
Published: September 2010

Summary

From an extensive literature survey and from analytical data of 130 species from the Sheffield flora, the physiological and molecular attributes, and occurrence of fructan are considered. The exceptionally high concentrations of fructan in many native species and its exclusive vacuolar location are noted. In view of the contention that fructan may function in low temperature tolerance, estimates are given of their maximum vacuolar concentration. For most species examined, this is unlikely to make a significant contribution to low temperature tolerance under the field conditions of the Sheffield flora. The association of high concentrations in the shoots of several species with high nuclear 2C DNA values is recorded. It is this correlation which may be of significance to several early‐season growing species. By maintaining supplies of fructose and sucrose from vacuoles in tissue undergoing expansion at low temperatures (a feature associated with high DNA values), such species obviate the need for transport of carbohydrate over distance as in starch‐storing species. By shortening supply lines at critical cold periods, fructan‐rich species may have a considerable advantage over starch‐storing, small‐celled, transport‐dependent species. However, such an advantage is not commonly exploited by the contemporary Sheffield flora. It is suggested that the ecological significance of fructan may best be seen in floras of the past or in contemporary floras undergoing more severe environmental stresses.
GROWTH AND PARTITIONING
Authors: HUNT RODERICK , LLOYD PHILIP S.
Published: September 2010

Summary

Innate growth potential and innate patterns of allocation to different plant parts are both subject to physiological limitations. Yet the ways in which these attributes not only vary between species but also exhibit plasticity in response to environmental change are important determinants of ecological behaviour and contribute strands to Plant Strategy Theory. In this paper, we review the evidence for innate variation in growth potential and partitioning and consider the implications of this variation for the development of high‐level ecological syntheses.
INTERSPECIFIC VARIATION IN PLANT ANTI‐HERBIVORE PROPERTIES: THE ROLE OF HABITAT QUALITY AND RATE OF DISTURBANCE
Authors: COLEY PHYLLIS D.
Published: September 2010

Summary

General patterns of herbivory and plant defence are summarized for a range of tree species studied in a lowland rain forest of Panama. Species growing in comparable micro‐habitats differed by more than three orders of magnitude in the rates of herbivorous damage to mature leaves. Over 70% of this interspecific variation was statistically accounted for by differences in leaf characteristics. Species having tough, fibrous leaves with low nutritional value suffered little herbivory. Concentrations of immobile defences such as tannins and fibre were higher in species with long‐lived leaves. Among species, there was also a significant negative correlation between growth rate and defence, and a positive correlation between growth and herbivory. These results suggest that differences in defence among species are due to interspecific differences in intrinsic growth rates and not to differences in apparency.

Theories of plant defence based on interspecific differences in growth rate and apparency are combined in a single general model of plant defence. This model follows Grime's triangular classification of plant strategies and assumes that quality of habitat and rate of disturbance are both important determinants of plant defence. Predictions are made as to the types of defensive properties expected in stress‐tolerant, competitive and ruderal species.
Reconciling the incompatible: N2fixation And O2
Authors: Gallon J. R.
Published: September 2010

summary

N2fixation is an extremely O2‐sensitive process. N2‐fixing bacteria (diazotrophys) have therefore evolved a variety of strategies by which they maintain an active nitrogenase in the presence of atmospheric O2and, in some cases, of O2generated photosynthetically. In this review, the effects of O2on nitrogenase activity and synthesis are described, as are the mechanisms by which diazotrophs limit O2damage to nitrogenase. These mechanisms are classified as behavioural strategies, physical barriers or physiological and biochemical strategies. Individual diazotrophs frequently empoly a combination of these. In addition, the particular problems faced by the O2‐evolving cyanobacteria are discussed.

CONTENTSSummary571I.Introduction571II.N2fixation571III.O2toxicity574IV.Interrelations between O2and N2fixation577V.Strategies for limiting O2damage to nitrogenase581Acknowledgements601References602
Seedlings of black birch (Betula lentaL.) as foragers for nitrogen
Authors: Crabtree R. C. , Bazzaz F. A.
Published: September 2010

summary

Soil nitrogen environments are highly heterogeneous, containing microsites that differ in relative and absolute ammonium and nitrate contents. We investigated whether black birch (Betula lentaL.) seedlings can maximize growth by foraging preferentially for a particular form of nitrogen, and whether supply rate of N and ammonium: nitrate in a patch affects preferences. Seedlings were transplanted into 5 1 split pots with roots partitioned evenly, and assigned to 1 of 4 nitrogen form treatments: nitrate (NO3−) both sides, ammonium (NH4+) both sides, NH4NO3, ‘homogeneous choice, and NO3−one side/NH4+on the other, ‘patchy choice, crossed with two rates of nitrogen supply. Use of15N–labelled nitrate revealed the proportion of seedling N from nitrate. Seedlings offered a patchy choice did not significantly out–perform seedlings in homogeneous ammonium and nitrate treatments, whereas seedlings offered a homogeneous choice did out–perform homogeneous nitrate and patchy choice treatment plants. In choice treatments, approx. 35 % of seedling N came from a nitrate source. This selectivity was unaffected by rate of nitrogen application and ammonium: nitrate ratio. That patchy choice seedlings integrated patches to achieve this ammonium: nitrate uptake suggests that black birch has a preferred balance. The seedlings offered a homogeneous choice were significantly heavier than the seedlings offered a patchy choice, perhaps reflecting an additional cost of foraging for ammonium and nitrate separately.
Effects of nitrogen on the response of loblolly pine to water stress I. Photosynthesis and stomatal conductance
Authors: Green T. H. , Mitchell R. J.
Published: September 2010

summary

Photosynthetic and stomatal response of loblolly pine (Pinus taeda L.) to water stress were determined for seedlings grown under 4 different nitrogen levels. Photosynthetic rate of well–watered seedlings was linearly related to foliar N. There was no observed N effect on the relative reduction of photosynthesis due to water stress. N did not influence stomatal conductance before or during the water stress period. Therefore, instantaneous water use efficiency of well–watered seedlings was significantly increased with increased N. Significantly reduced internal CO2 concentration (Ci) associated with increased N in well–watered seedlings may be indicative of greater relative stomatal contribution to overall limitation of photosynthesis. Water stress caused an increase in Ci, the slope of the increase being related to N treatment. Stomatal conductance and photosynthesis correlated strongly within each N treatment, and increased N caused an increase in initial slope of the function. Therefore, stomatal control was uncoupled from photosynthetic capacity by N treatment in loblolly pine. These data fail to support the proposition that improved stomatal response to water stress can explain reported gains in water status of nitrogen–fertilized conifers in the field.
Nutrient status, water uptake and gas exchange for three desert succulents infected with mycorrhizal fungi
Authors: CUI Muyi , NOBEL Park S.
Published: September 2010

summary

Mycorrhizal infection and its consequences were assessed for Agave deserti Engelm., Ferocactus acanthodes (Lem.) Britton & Rose, and Opuntia ficus–indica (L.) Miller. For A. deserti and F. acanthodes in the field, mycorrhizal infection varied from 2 to 11%; the higher infection in May than in March 1991 was probably associated with improved soil water conditions. Using field–collected fungi, mycorrhizal infection for glasshouse–grown A. deserti, F. acanthodes and O. ficus–indica varied from 8 to 64%, with the highest infection occurring for lateral roots of A. deserti. Five months after inoculation, root P was significantly higher (P > 0—‐01) for inoculated A. deserti and shoot P and Zn were significantly higher (P < 002) for inoculated A. deserti and F. acanthodes compared with uninoculated plants. Root hydraulic conductivity (Lp) of lateral roots of A. deserti was 24% higher for inoculated than for uninoculated plants (P 01). The increase in Lp was caused by a higher radial conductivity, which could be due to increased root cell membrane permeability and more hyphal entry points. Daily net CO2 uptake was 19% higher for inoculated than uninoculated A. deserti. Mycorrhizal infection apparently enhances water and nutrient uptake in dry environments for these three desert succulents.
Mycorrhizas and drought resistance of Picea sitchensis (Bong.) Carr.
Authors: LEHTO TARJA
Published: September 2010

summary

Sitka spruce [Picea sitchensis (Bong.) Carr.] seedlings either mycorrhizal with Paxillus involutus (Batsch) Fr. or non–mycorrhizal were either subjected to drought or watered adequately. Stomatal conductance, net photosynthetic rate and water potential were higher in well–watered mycorrhizal plants than in non–mycorrhizal plants, and the effect of mycorrhizal infection on photosynthesis was interpreted as both a stomatal effect and an effect on the photosynthetic apparatus. During the drought treatment the mycorrhizal plants dried out their substrate sooner than the non–mycorrhizal plants, which were smaller, but their stomatal conductance, net photosynthetic rate and shoot water potential were similar to the non–mycorrhizal plants. A correlation between P concentration in the shoot and net photosynthetic rate was shown. The improved performance of the mycorrhizal seedlings was probably due to their better P and K nutrition and their more extensive root systems with mycelial strands.