bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abundance, diversity and body size: patterns from a grassland arthropod community
Authors: Siemann EvaN. , Tilman David , Haarstad JohN. 
Published: March 2003

1.The empirical relationships among body size, species richness and number of individuals may give insight into the factors controlling species diversity and the relative abundances of species. To determine these relationships, we sampled the arthropods of grasslands and savannahs at Cedar Creek, MN using sweep nets (90 525 individuals of 1225 species) and pitfall traps (12 721 individuals of 92 species). Specimens were identified, enumerated and measured to determine body size.2.Both overall and within abundant taxonomic orders, species richness and numbers of individuals peaked at body sizes intermediate for each group. Evolution could create unimodal diversity patterns by random diversification around an ancestral body size or from size‐dependent fitness differences. Local processes such as competition or predation could also create unimodal diversity distributions.3.The average body size of a species depended significantly on its taxonomic order, but on contemporary trophic role only within the context of taxonomic order.4.Species richness (Si) within size classes was related to the number of individuals (Ii) asSi = Ii0·5. This relationship held across a 100 000‐fold range of body sizes. Within size classes, abundance distributions of size classes were all similar power functions. A general rule of resource division, together with similar minimum population sizes, is sufficient to generate the relationship between species richness and number of individuals.5.Smaller bodied species had slightly shallower abundance distributions and may, in general, persist at lower densities than larger species.6.Our results suggest there may be fewer undescribed small arthropod species than previously thought and that most undescribed species will be smaller than arthropods.
Annual variation in fat storage by a migrant warbler overwintering in the Indian tropics
Authors: Katti Madhusudan , Price Trevor 
Published: March 2003

1. We studied fat storage in a population of greenish leaf warblers (Phylloscopus trochiloides) in southern India over four winters (1993–97). This species breeds in temperate regions and overwinters in India from October to April. 2. Diurnal variation in fat scores was comparable to that seen among temperate wintering passerines. Seasonal variation was slight, except for premigratory fattening. There was significant annual variation: in drier winters, which were also winters of low food supplies, fat scores were higher. 3. Energy metabolized overnight is unlikely to vary across winters, and annual variation in fat scores is considered a response to uncertainty of food intake on a given day. Fat scores varied inversely with short‐term rainfall, which drives the abundance of arthropod prey. 4. Annual variation in fat scores was not accompanied by changes in total body mass. This suggests that protein reserves were being compromised by increased fat deposition in dry years and offers an explanation for the observed delay in moult during drier winters. These results suggest that strategies for maximizing short‐term probability of survival translate into future fitness costs, and may shape long‐term life‐history strategies through simple physiological processes.
Viruses of the Serengeti: patterns of infection and mortality in African lions
Authors: Packer C. , Altizer S. , Appel M. , Brown E. , Martenson J. , O'Brien S. J. , Roelke‐Parker M. , Hofmann‐Lehmann R. , Lutz H. 
Published: March 2003

Summary1. We present data on the temporal dynamics of six viruses that infect lions (Panthera leo) in the Serengeti National Park and Ngorongoro Crater, Tanzania. These populations have been studied continuously for the past 30 years, and previous research has documented their seroprevalence for feline herpesvirus, feline immunodeficiency virus (FIV), feline calicivirus, feline parvovirus, feline coronavirus and canine distemper virus (CDV). A seventh virus, feline leukaemia virus (FeLV), was absent from these animals.2. Comprehensive analysis reveals that feline herpesvirus and FIV were consistently prevalent at high levels, indicating that they were endemic in the host populations. Feline calici‐, parvo‐ and coronavirus, and CDV repeatedly showed a pattern of seroprevalence that was indicative of discrete disease epidemics: a brief period of high exposure for each virus was followed by declining seroprevalence.3. The timing of viral invasion suggests that different epidemic viruses are associated with different minimum threshold densities of susceptible hosts. Furthermore, the proportion of susceptibles that became infected during disease outbreaks was positively correlated with the number of susceptible hosts at the beginning of each outbreak.4. Examination of the relationship between disease outbreaks and host fitness suggest that these viruses do not affect birth and death rates in lions, with the exception of the 1994 outbreak of canine distemper virus. Although the endemic viruses (FHV and FIV) were too prevalent to measure precise health effects, there was no evidence that FIV infection reduced host longevity.
Evaluating the severity of the population bottleneck in the Mauritius kestrel Falco punctatus from ringing records using MCMC estimation
Authors: Groombridge Jim J. , Bruford Michael W. , Jones Carl G. , Nichols Richard A. 
Published: March 2003

Summary

The Mauritius kestrel Falco punctatus (Temminck 1823) has recovered from very low numbers. In order to evaluate the severity of the population bottleneck that it experienced, we have developed a method for estimating the productivity of the nests that escaped detection. This method uses ringing records for MCMC estimation of parameters describing the recruitment of adults to the breeding population and the growth in productivity of undiscovered nests.
Comparison of the estimates for the two restored populations (eastern and western) showed a far lower proportion of undiscovered nests in the former, as predicted because of widespread use of nestboxes. This served to verify the method of estimation. The estimates show a steady increase in population size, in contrast with field estimates indicating a recent reduction in growth.
The results suggest that the alarmingly low estimates of population size in 1974 (two breeding pairs) were accurate, and that few undiscovered nests existed during the bottleneck.
The recovery of the population seems to have been initiated by the intensive conservation effort. The most rapid period of population growth coincides with the reintroduction programme. The results imply that the eastern population is much more reliant on intensive management for its future growth.
Resource partitioning among British and Irish mustelids
Authors: McDonald Robbie A. 
Published: March 2003

summary Seven species of mustelid carnivore live in the British Isles: weasel, stoat, mink, polecat, pine marten, badger and otter. Recent studies have hypothesized that coexistence of these species is facilitated by partitioning of resources according to prey size, particularly that of mammalian prey. This hypothesis has been supported by evidence of character displacement derived from even size ratios in skull length and canine diameter. To test whether this hypothesis is supported by empirical data, 98 studies of the diet of mustelids living in Great Britain and Ireland were analysed. Two main predictions were tested; that larger males ate larger prey than females and that larger species ate larger prey than smaller species. Male mustelids ate larger prey than females but there was no relationship between predator size and prey size, either for all species or when largely vermivorous badgers and piscivorous otters were excluded. There was no difference in dietary niche breadth between the sexes. Dietary niche breadth increased with body size in the assemblage excluding otters and badgers. The dietary niches of mustelids were partitioned along several axes, none of which was clearly related to prey size. The dietary niches of the five species living in Ireland (stoat, mink, pine marten, otter and badger) were more similar to one another in Ireland than in Great Britain and there was no difference in niche breadth between Irish and British mustelids. There was no evidence of competitive release in the diets of Irish mustelids. Resource partitioning according to prey size is apparent between the sexes within species, and this is probably correlated to sexual selection for size dimorphism. Empirical data do not, however, support a hypothesis of resource partitioning according to prey size between species. Interspecific aggression provides an alternative hypothesis explaining character displacement among mustelids.
Stress during feather development predicts fitness potential
Authors: Bortolotti Gary R. , Dawson Russell D. , Murza Gillian L. 
Published: March 2003

Summary

Measures of the quality of an individual are important in the study of proximate and ultimate factors in biology. Records of developmental history are particularly desirable, as many phenotypical traits are influenced by conditions during growth. Conspicuous irregularities in feathers, known as fault bars, result from a variety of stresses that occur during feather growth. The frequency of fault bars was evaluated on primary and tail feathers (grown 1 year previously) of 1919 adult American kestrels from a breeding population in Canada (1990–97).
Most (91·5%) birds exhibited some fault‐barring, although females had significantly more feathers with fault bars than males (17% vs. 14%, respectively). Body size, intensity of haematozoan infections and leucocyte differentials were all unrelated to fault bars; however, birds with many fault bars were in poor body condition during prelaying (males) and incubation (males and females).
Individual kestrels tended to be consistent in the number of feathers with fault bars from year to year.
The percentage of feathers with fault bars was not associated with the timing of arrival in spring or prey abundance per territory; however, birds of both sexes with many bars were less likely to breed. Birds paired non‐randomly, as mates tended to have a similar frequency of fault bars. Males and females with many bars had significantly later clutch initiation dates, but there were no negative consequences regarding clutch size or egg size.
Female kestrels with many fault bars had lower survival probabilities. Both sexes were also less likely to be recaptured in years following initial banding if they had many bars, suggesting that they were more likely to emigrate from the study area temporarily.
Fault bars on feathers appear to be indicative of an individual’s susceptibility to stress, and are useful in predicting components of fitness. The use of fault bars is a promising tool as they are easy to evaluate and can be assessed on live or dead birds, on moulted feathers and on individuals repeatedly over time.
Reindeer summer activity pattern in relation to weather and insect harassment
Authors: Hagemoen Rolf Iver M. , Reimers Eigil 
Published: March 2003

SummaryDuring the brief growing season in Arctic and high mountain ecosystems, undisturbed grazing is crucial in order to maximize growth and fattening. During summer 1997 we investigated the influence of weather and insect harassment on the behaviour and group dynamics of reindeer (Rangifer tarandus tarandusL.).Climatic data, activity of parasitic flies, and female reindeer behaviour were recorded from two wild reindeer populations in Southern Norway. Temperature and solar irradiation were good predictors of oestrid fly activity. Throughout the warm summer, reindeer were exposed to vigorous oestrid fly harassment, which caused dramatic decrease in feeding and lying, and increase in walking, running and standing. This behavioural change may compromise the physical condition of individuals entering winter.Mosquitoes had little influence on reindeer activity patterns. In the absence of oestrid flies, weather parameters had no influence on reindeer activity pattern. Even during the warmest days, no signs of heat stress were recorded. Accordingly, snow patches, marshes and windy mountaintops were used primarily to avoid oestrid fly harassment. Thus, most disruptions of feeding that are often reported on warm days are responses to oestrids, not thermal stress.
Peak morphological diversity in an ecotone unveiled in the chukar partridge by a novel Estimator in a Dependent Sample (EDS)
Authors: Kark Salit , Mukerji Tapan , Safriel Uriel N. , Noy‐Meir Imanuel , Nissani Rachel , Darvasi Ariel 
Published: March 2003

Summary

Areas of environmental transition (i.e. ecotones) have recently been shown to play an important role in the maintenance of genetic diversity, divergence and in speciation processes. We test the hypothesis that ecotone populations maintain high phenotypic diversity compared to other populations across the distribution range.
Focusing on the chukar partridge (Alectoris chukar Gray), we study trends in morphological diversity across a steep ecotone within the species native range in Israel and Sinai. Using 35 traits and 23 ratios between traits, we apply a novel weighted average statistic that we term ‘Estimator in a Dependent Sample’ (EDS). This estimator enables us to compare levels of diversity across populations using multiple‐correlated traits and is especially useful when sample sizes are small.
We provide a program for calculating the EDS and a bootstrapping procedure to describe its confidence interval and standard deviation. This estimator can be applied widely in a range of studies using multiple‐correlated traits in evolutionary biology, ecology, morphology, behaviour, palaeontology, developmental biology and genetics.
Our results indicate that within‐population diversity peaks in chukar populations located in the Mediterranean‐desert ecotone in Israel. However, had we not included the ecotone region in our study, we would have drawn different conclusions regarding patterns of morphological diversity across the range. We suggest that ecotones should be given higher priority in future research and conservation planning, potentially serving as within‐species diversity hotspots.
Modelling hantavirus in fluctuating populations of bank voles: the role of indirect transmission on virus persistence
Authors: Sauvage Frank , Langlais Michel , Yoccoz Nigel G. , Pontier Dominique 
Published: March 2003

Summary

Using field data published in the literature, we investigated pathogen dynamics and conditions of persistence in a mathematical model of the bank vole (Clethrionomys glareolus)–Puumala hantavirus system. The host population is assumed to have a 3‐year periodic cycle. The duration of very low host density is critical for virus transmission and survival.
Field epidemiological data strongly suggested a transmission of the hantavirus by the contaminated environment. We thus studied whether this ‘indirect’ transmission affected the virus persistence in the host population.
The model assumptions were derived from the following conditions found in the literature: (1) there is no additional mortality nor fecundity loss due to the virus in infected hosts, thus the cyclic demographical pattern is not due to the virus; (2) no remission has been observed, thus we did not consider the existence of recovered individuals; (3) adult females are territorial and juveniles disperse to find a new territory and reach sexual maturity. A fragmented landscape was assumed to occur: individuals can live in favourable or unfavourable patches.
The model was a compartmental model; the population was structured into susceptible or infectious individuals. We considered two age classes, juveniles and adults, and two sites (populations) connected by juvenile dispersal.
Model dynamics accurately predicted the cyclic trend in disease prevalence as observed in epidemiological studies. They also showed that indirect transmission significantly increased the probability for the virus to persist during the low‐density period of the host population. More precisely, even a low survival rate of the virus outside the host was sufficient to decrease extinction risk of the infection by stochastic events.
Elasticity analysis showed a high robustness of the model to changes in the parameters of indirect transmission but a high sensitivity to changes in adult density.
Mammal species richness and habitat use in rainforest and abandoned agricultural fields in Chiapas, Mexico
Authors: MedellÍN Rodrigo A. , Equihua Miguel 
Published: March 2003

1.  We evaluated the potential of small, isolated cornfields embedded in a large forest matrix as an appropriate compromise between conservation and sustainable development. 2.  We examined the relationship between habitat structure and diversity with overall mammal species richness and abundance of six common small mammals in four 6‐year‐old abandoned cornfields (oldfields) and four continuous rainforest sites in the most speciose region in Mexico, the Selva Lacandona, Chiapas. 3.  Species richness did not differ between forests and oldfields, indicating that forest‐dependent mammals penetrate oldfields of size 0·9–2·9 ha, presumably because forest cover and resources are nearby. Even species which strongly selected forest habitat, such as H. desmarestianus and D. marsupialis, were present in oldfields, and only the latter showed a significant decline in the number of captures as a function of distance from forest edge. 4.  The Lacandon Indian use of the land for agriculture in the form of small (> 3 ha) agricultural plots embedded in a large forest matrix increases spatial heterogeneity and promotes mammal diversity. 5.  Those small plots (in agricultural production terms) are intermediate in size when the whole continuum of the local natural and anthropogenic disturbance sizes are considered; more common are the extensive clearings for agriculture or cattle ranching, whereas the most common forest disturbance is treefall gaps, at least 20 times smaller than oldfields. 6.  This form of land use should be considered as an important, appropriate productive element when decisions are made about managing reserves and pursuing sustainable development.
Effects of habitat fragmentation and road density on the distribution pattern of the moor frog Rana arvalis
Authors: Vos C.C. , Chardon J.P. 
Published: March 2003

1.  The effects of habitat fragmentation on the distribution pattern of the moor frog Rana arvalis were investigated. Also, the possible isolation effects of the road network were taken into account. 2.  Indications were found that habitat fragmentation partly explains the distribution pattern of the moor frog. The statistical models showed a positive effect of pond size (or marsh area) and a negative effect of road density on the probability of occupation of a moorland pond. 3.  Because of the strong correlation between habitat quality variables and isolation variables, no unambiguous effects of isolation, described as the amount of suitable terrestrial habitat (moorland) in the surroundings of a moorland pond in a radius of 100–2000 m, could be demonstrated. 4.  Spatial differences in road density can play a role in the selection of optimal locations for nature protection areas. The regression model used in this study predicts a reduced occupation probability in 55% of the study area. In the part of the study area adjacent to a motorway, occupation probability is lowered to less than 30%. 5.  European studies of habitat fragmentation on amphibian species revealed a mean distance between occupied ponds of <1 km in all studies. This could be a general rule of thumb for persistent amphibian populations. Effects of pond size on the probability of occupation were more variable. 6.  When discussing the effects of habitat fragmentation on amphibians and other ground dwelling species, the negative effects of roads are often underestimated.
An estimate of the sustainable rate of shell extraction from the Dutch Wadden Sea
Authors: Beukema J. J. , Cadée G. C. 
Published: March 2003

1. Shell production by cockles Cerastoderma edule was studied to examine whether or not the present licensed rate of shell extraction in the Dutch Wadden Sea exceeds the current rate of shell addition to the exploitable stocks. 2. Long‐term data on numbers of cockles and weights of their shells were used to estimate their annual production on Balgzand, a 50‐km2 tidal flat area in the western‐most part of the Wadden Sea. During the 1969–97 period, it amounted to an average of 125 g m–2, including 107 g m–2 of shells large enough to be exploitable for shell‐lime fishery. 3. The very irregular annual recruitment of cockles was the main cause of the wide 95% confidence limits (74 and 140 g m–2 year–1) of this 28‐year estimate. Moreover, high mortality rates in severe winters substantially reduced production per recruit in some year classes. 4. About one‐third of the estimated production does not reach exploitable stocks, because it is fragmented by birds (particularly eider ducks), permanently buried in the sediment, or removed by the fishery for live cockles. 5. During the last few decades, the estimated mean amount added annually to the exploitable stocks was 88 million kg or 132 000 m3 of large cockle shells. This amount compares favourably with the current annual level of removal of 134 000 m3 of shells, three‐quarters of which are cockles. 6. Even at temporarily lower production rates, the exploitation of shell stocks at its present rate is not expected to lead to a rapid exhaustion of the existing stocks in the tidal inlets of the Dutch Wadden Sea, as these stocks will be in the order of a few million m3.
Seasonal variation in the abundance, biomass and biodiversity of earthworms in soils contaminated with metal emissions from a primary smelting works
Authors: Spurgeon D. J. , Hopkin S. P. 
Published: March 2003

1.Earthworms (Annelida: Oligochaeta) were sampled on four occasions (spring, summer, autumn and winter) at 14 sites along two transects from a primary lead/ zinc/cadmium smelting works at Avonmouth, UK.2.Total abundance and biomass of earthworms decreased with proximity to the smelter. No worms were collected from the two sites closest to the factory (<0·6 km) and catches were significantly lower than controls at a further five sites (<3 km).3.Seasonal composition of sampled communities differed only for summer with lower numbers of individuals and species collected at all sites. Reduced catches in the summer sample is a response to drought.4.Species richness was lowest at sites close to the factory. For example, worms such asAporrectodea caliginosa(Savigny) andAllolobophora chlorotica(Savigny) that were dominant at relatively clean sites further from the smelter are absent from the most contaminated soils.5.Reduced species richness resulted in lower Shannon–Weiner diversity and higher Berger–Parker dominance. Multivariate cluster analysis for spring, summer and winter indicated that sites could be split into three groups based upon relative species composition. In autumn, two clusters were identified.6.The absence of sensitive species from sites close to the smelting works supports the inclusion of earthworms as a key group in a terrestrial prediction and classification scheme for quantifying the effects of pollutants on soil biodiversity. However, sampling should be carried out in spring or autumn to obtain an accurate picture of community structure.