bluuebunny/crossref_metadata_2025 huggingface dataset:
Classification of dental caries patterns in the primary dentition: a multidimensional scaling analysis
Authors: Psoter Walter J. , Zhang Heping , Pendrys David G. , Morse Douglas E. , Mayne Susan T.
Published: May 2003

Abstract –

Objective: Clinical patterns of early childhood caries (ECC) encompassing specific teeth or surfaces have been previously proposed on an a priori basis and have been used as case definitions. The underlying assumption is that the patterns result from different host response and environmental conditions. Identifying caries patterns has utility in refining case definitions of ECC. Well‐defined caries patterns should enhance the ability of an analysis to identify meaningful associations between suspected risk factors and ECC. The purpose of this project was to identify patterns of caries in the dentition of preschool children using multidimensional scaling without a priori pattern delineation.

Methods: Between February 1994 and September 1995, five examiners visually examined 5171 Arizona preschool children aged 5–59 months old. Multidimensional scaling (MDS) was used as a classification/taxonomy technique to identify any underlying structure of the caries data. MDS provided a classification scheme for individual tooth surfaces based on the dissimilarity measures of squared Euclidean distance and of variance using an alscal analysis. Both two‐ and three‐dimensional solutions were pursued; s‐stress, stress, R‐square and residual patterns were assessed in determining the best dimensional model, with the resulting quadrant positions of the tooth surfaces suggesting potential caries patterns.

Results:  All models demonstrated excellent fit. Two‐ and three‐dimensional solutions suggested four caries patterns: (i) any maxillary incisor surfaces, (ii) first molar occlusal surfaces, (iii) second molar pit and fissure surfaces, and (iv) any smooth surfaces, excluding the maxillary incisor surfaces.

Conclusions: This is the first delineation of primary dentition caries patterns produced by a classification analysis without a priori pattern definitions. The identified caries patterns may arise from specific risk factors and/or be a function of the timing of various risk factor exposures. Use of these patterns as case definitions should enhance the ability to identify associations between suspected risk factors and ECC.
Brainstem involvement by mycosis fungoides in a patient with large‐cell transformation: a case report and review of literature
Authors: Li Ning , Kim Jung H. , Glusac Earl J.
Published: May 2003

Background:  Central nervous system (CNS) involvement by mycosis fungoides (MF) is rare. As compared to meningeal involvement, intraparenchymal spread is especially rare. It is usually seen in advanced disease in conjunction with lymph node or visceral involvement. However, CNS involvement in the absence of progressive skin lesions or other extracutaneous involvement has been reported rarely in patients with transformed MF.

Method:  Case report and review of literature.

Results:  A 71‐year‐old female with long‐standing MF developed lymphomatous CNS involvement 10 years after the diagnosis of tumor stage MF. At this time, the patient presented with a transient episode of garbled speech followed by generalized weakness. Computerized tomography scan (CT scan) and magnetic resonance imaging scan (MRI scan) of the head revealed a subcortical lesion in the left temporo‐frontal lobe. Cerebrospinal fluid (CSF) examination showed atypical T cells, and brain biopsy confirmed parenchymal involvement by T‐cell lymphoma. Meanwhile, a biopsy of a skin lesion showed large‐cell transformation. No lymph node or other systemic involvement was noted at this time, and the patient was treated with chemotherapy. Twelve months later, the patient developed recurrent CNS lymphoma with multiple organ involvement and expired soon thereafter.

Conclusions:  This case illustrates the importance of awareness of the possibility of CNS involvement by MF, especially in transformed MF. CNS involvement may be the only site of extracutaneous involvement in patients with transformed MF, and mental status changes warrant CNS surveillance for this disease.
Reproduction biology of pikeperch (Sander lucioperca (L.)) – a review
Authors: Lappalainen J. , Dörner H. , Wysujack K.
Published: May 2003

Abstract –  The present review focuses on the reproduction biology of pikeperch (Sander lucioperca (L.)). Aspects like maturity, fecundity, spawning migrations, spawning habitats, onset of spawning, and development time of eggs were reviewed. The onset of maturity is reached at younger age in southern than northern populations due to higher growth rate in the south. Males mature at smaller size and are on average younger than females. Absolute fecundity is closely related to the length and weight, but no clear relationship could be found between relative fecundity and length. Statistically significant relationships were found between the onset of spawning and latitude, and between the duration of the development time of eggs and stable water temperature. Near the southern limits of distribution, the onset of spawning is in February while near the northern limits it is in June. The interannual variability in fecundity and in the onset of maturity and further the factors affecting them have not been studied much. Furthermore, it is not known whether these variations could affect the population dynamics of pikeperch. Little is also known about the actual spawning behaviour of pikeperch in natural habitats. This is probably due to the typical spawning habitats located at 1–3 m depth in waters with high turbidity and low visibility. Even though the homing behaviour to the same spawning areas is well developed in adults, it is not known whether the adults were actually born in the same area.
Habitat–predator association and avoidance in rainbowfish (Melanotaeniaspp.)
Authors: Brown Culum
Published: May 2003

Abstract – The ability to recall the location of a predator and later avoid it was tested in nine populations of rainbowfish (Melanotaeniaspp.), representing three species from a variety of environments. Following the introduction of a model predator into a particular microhabitat, the model was removed, the arena rotated and the distribution of the fish recorded again. In this manner it could be determined what cues the fish relied on in order to recall the previous location of the predator model. Fish from all populations but one (Dirran Creek) were capable of avoiding the predator by remembering either the location and/or the microhabitat in which the predator was recently observed. Reliance on different types of visual cues appears to vary between populations but the reason for this variation remains elusive. Of the ecological variables tested (flow variability, predator density and habitat complexity), only the level of predation appeared to be correlated with the orientation technique employed by each population. There was no effect of species identity, which suggests that the habitat that each population occupies plays a strong role in the development of both predator avoidance responses and the cues used to track predators in the wild.
Body shape variation within and among three species of darters (Perciformes: Percidae)
Authors: Guill J. M. , Hood C. S. , Heins D. C.
Published: May 2003

Abstract –  Using geometric morphometric (GM) techniques, we quantified intra and interspecific variation in female body shape using five collections each of Etheostoma caeruleum Storer, Etheostoma nigrum Rafinesque, and Etheostoma stigmaeum (Jordan). Nested multivariate analysis of variance showed significant variation in body shape among populations (Wilks' Λ = 0.0687, F144,7585.1 = 19.35, P < 0.0001), as well as among species (Wilks' Λ = 8.7 × 10−6, F24,2 = 28.18, P = 0.0348). Etheostoma caeruleum displayed greater body depth relative to both E. nigrum and E. stigmaeum, whereas E. nigrum displayed a compressed arrangement of mid‐body landmarks relative to both E. stigmaeum and E. caeruleum. The broader implications of these findings highlight the value of geometric morphometrics as both an exploratory and analytical approach. Conclusions drawn from comparisons among moderately differentiated darter species in future studies of body size and shape are likely robust to intraspecific variation within species, and will permit more rigorous investigations into the ecomorphology of these benthic stream fishes.
Assemblage structure and habitat use of fishes in a Central European submontane stream: a patch‐based approach
Authors: Erős T. , Botta‐Dukát Z. , Grossman G. D.
Published: May 2003

Abstract –  We examined macrohabitat patch level assemblage composition and habitat use patterns of fishes over four seasons in a second‐order submontane stream (Danube drainage, Hungary). Rainfall data indicated that our study included both high‐ and low‐water periods, and hence our results may be applicable to broader time scales. Principal component analysis of physical habitat data from 13 macrohabitat patches indicated that these patches represented a riffle‐pool continuum. Correspondence analysis of fish assemblage structure data from these patches identified a continuum in assemblage composition that was positively correlated with the habitat continuum. The riffle fauna was dominated by stone loach (Barbatula barbatula), whereas chub (Leuciscus cephalus) were most abundant in pool patches. We detected little evidence of seasonality in either fish assemblage structure or habitat use. Fish density did not differ significantly among macrohabitat patches in two (summer and autumn 1999) of three seasonal samples, although riffle patches displayed significantly higher fish abundance in late spring 2000. This difference primarily was due to higher abundance of juvenile stone loach in riffles. Two species, stone loach and minnow (Phoxinus phoxinus), displayed generalized habitat use patterns, whereas chub and rare species (i.e., gudgeon, Gobio gobio; dace, Leuciscus leuciscus; Barbus petenyi; and burbot, Lota lota) were significantly over‐represented in pool habitats. We hypothesized that pool specialists (i.e., chub and rare species) were responding primarily to the increased depth of these habitats. Nevertheless, our data did not demonstrate the presence of separate pool and riffle habitat guilds. In conclusion, we believe that our understanding of stream fish ecology will be greatly facilitated by use of a ‘patch‐based approach’.
Ontogenetic changes in the diet of the black‐stripe minnow Galaxiella nigrostriata (Shipway, 1953) (Galaxiidae) and the salamanderfish Lepidogalaxias salamandroides (Mees, 1961) (Lepidogalaxiidae)
Authors: Gill H. S. , Morgan D. L.
Published: May 2003

Abstract –  Similarities in the diets of larval, juvenile and adult black‐stripe minnow (Galaxiella nigrostriata) and salamanderfish (Lepidogalaxias salamandroides), collected from ephemeral pools in south‐western Australia during the mid‐wet, late‐wet and dry seasons, were assessed. During the mid‐wet season, both intra‐ and interspecific competition for a diminishing food supply was minimised through differences in prey utilisation by the various developmental stages of both species. During the late‐wet season, the pools contained only juvenile G. nigrostriata and juvenile and adult L. salamandroides, the diets of which were vastly different. A shift towards terrestrial fauna by G. nigrostriata and the ingestion of greater proportions of larger benthic prey taxa by L. salamandroides minimised interspecific competition for food at a time when densities of zooplanktors were rapidly declining. Timing differences in the onset of aestivation ensures that no interspecific competition for food occurs during the dry season.
Size‐related changes in habitat selection by larval grayling (Thymallus thymallus L.)
Authors: Nykänen M. , Huusko A.
Published: May 2003

Abstract  – In a medium‐sized river in northern Finland, larval grayling shifted with growth from shallow habitats with slow velocities, fine substrata and abundant vegetation cover to deeper sites with swifter velocities, coarse substrata and sparse vegetation cover within 3 weeks. Small (17–21 mm) larvae preferred water depths 10–30 cm, substrata dominated by mud or sand (<2 mm), 10–70% vegetation cover and water velocities <10 cm · s−1. Middle‐sized (22–25 mm) larvae preferred 30–90 cm depths, sandy substrata, <40% vegetation cover and velocities <10 cm · s−1. Large (26–31 mm) larvae preferred >50 cm depths, substrata dominated by sand or boulders, <20% vegetation cover and 10–50 cm · s−1 velocities. The strict habitat requirements of the smallest larval group suggest that these habitats, in particular, are important to the early survival of grayling.
Movement of fish between a river and its backwater: diel activity and relation to environmental gradients
Authors: Hohausová E. , Copp G. H. , Jankovský P.
Published: May 2003

Abstract –  Movements of fish, in particular roach Rutilus rutilus, perch Perca fluviatilis, rudd Scardinius erythrophthalmus, bleak Alburnus alburnus and chub Leuciscus cephalus (age ≥ 1+) in relation to environmental variables were examined between the River Morava, Czech Republic, and a rehabilitated former meander. Data were taken over seven 24‐h periods in April–June 1997 using two back‐to‐back traps. Of 170 fish captured, 70% moved from the backwater to the river. Diel activity differed between sampling dates, but overall bleak, roach and chub moved mainly between dusk and dawn, whereas perch moved throughout most of the day. Rudd showed bi‐modal (mid‐day, midnight) activity. However, avoidance behaviour could have biased results for species known to be wary of traps. Water level changes, temperature and illumination were among the main environmental factors influencing fish movement, along with spawning migrations relevant for most species. In all specimens, over 65% individuals captured were ready to spawn. Most of them, except for perch, were moving out of the backwater towards the river.
Hematology and blood biochemistry in infant baboons (Papio hamadryas)
Authors: Havill L.M. , Snider C.L. , Leland M.M. , Hubbard G.B. , Theriot S.R. , Mahaney M.C.
Published: May 2003

Abstract: Although published normative reference standards for hematologic and clinical chemistry measures are available for adult baboons, their applicability to infants has not been addressed. We analyzed these measures in 110 infant baboons (55 females and 55 males) from a large breeding colony at the Southwest Regional Primate Research Center in San Antonio, Texas. The sample consists of olive baboons and olive/yellow baboon hybrids, 1 week to 12 months of age. We produced cross‐sectional reference values and examined the effects of age, sex, and subspecies on these variables. Hematology reference ranges for infant baboons are similar to, but wider than, those for adults. Reference ranges for blood biochemistry measures are generally more dissimilar to adults, indicating that for many variables, reference ranges for adult baboons are not adequate for infants. Although sex and subspecies differences are rare, age accounts for more than 10% of the variance in many of the variables.
Cortisol responses to immobilization with Telazol or ketamine in baboons (Papio cynocephalus/anubis) and rhesus macaques (Macaca mulatta)
Authors: Bentson K.L. , Capitanio J.P. , Mendoza S.P.
Published: May 2003

Abstract:  Little is known about the influence of Telazol on cortisol or of anesthetic agents on immunological measures, and reports of ketamine's effect on cortisol are inconsistent. We measured effects of Telazol, ketamine and blood sampling on cortisol in male rhesus macaques and male savannah baboons. We also obtained leukocyte counts in the macaques. In macaques, Telazol reduced cortisol in the morning but not in the afternoon; ketamine had no effect on cortisol in these animals. In baboons, cortisol changed little post‐Telazol but increased post‐ketamine. In macaques, lymphocyte numbers decreased following afternoon injection of Telazol, ketamine or saline. The injection and blood sampling process increased cortisol levels in monkeys not trained to extend an arm but exerted no effect on cortisol in trained macaques. Thus, the animals’ physiological responses to blood sampling and immobilization are influenced by such variables as anesthetic agent, species, time of day, and familiarity with the blood sampling process.
Effect of menstrual cycle on mucosal immunity to SHIV within the reproductive tract of baboons (Papio anubis): preliminary findings
Authors: Ochiel D.O. , Wango E.O. , Kigondu C.S. , Otsyula M.G.
Published: May 2003

Abstract: The presence of human immunodeficiency virus (HIV) in genital secretions is regarded as a risk factor for sexual and perinatal transmission of HIV. A better understanding of correlates of genital shedding of HIV is crucial to the development of effective strategies against transmission of this virus. Events during menstrual cycle are likely to influence local immune responses and viral load in genital secretions, and hence determine susceptibility to HIV or efficiency of virus transmission. We report, in this study, preliminary findings on the relationship of menstrual cycle to genital mucosal and systemic immunity in female olive baboons (Papio anubis) experimentally inoculated with simian/human immunodeficiency virus (SHIV)89.6P.
Seasonal changes in the seminiferous epithelium of rhesus and bonnet monkeys
Authors: Bansode F.W. , Chowdhury S.R. , Dhar J.D.
Published: May 2003

Abstract: With a view to elucidate seasonal variations in testicular spermatogenesis, quantitative analysis of spermatogenic cells was carried out in non‐human primate species viz. rhesus (Macaca mulatta) and bonnet (M. radiata) monkeys during breeding (October–December) and non‐breeding (May–June) seasons. The results revealed significant inhibition of testicular germ cell population during non‐breeding compared with the breeding period in both the species. Quantitative determination of Sertoli cell–germ cell ratio showed a marked decrease in the number of type A‐spermatogonia, spermatocytes (non‐pachytene and pachytene) and spermatids (in steps 1–12 of spermiogenesis) in rhesus monkey during the non‐breeding period. Bonnet monkeys exhibited the significant decline in the number of primary spermatocytes and spermatids during the non‐breeding phase. In addition, average diameter of round seminiferous tubules and nuclear diameter of Leydig cells also decreased significantly in rhesus monkeys. However, bonnet monkeys did not show any significant change in nuclear diameter/morphology of Leydig cells, testicular tubular diameter and number of type A‐spermatogoniae. Sertoli cell number did not show any significant change during both breeding and non‐breeding periods in both the species. The results of this study indicate a prominent seasonal variation in testicular spermatogenic/Leydig cells in rhesus monkeys than those observed in bonnet monkeys.
Stereology of the myocardium inLeontopithecus(Lesson, 1840) callitrichidae – primates
Authors: Pissinatti A. , Burity C.H.F. , Mandarim‐de‐Lacerda C.A.
Published: May 2003

Abstract:Rare morphological features of theLeontopithecuscardiovascular system have been reported in the literature. The samples analyzed in this study came from 33 specimens ofLeontopithecusfrom the collection of the Center of Primatology of Rio de Janeiro‐FEEMA (CPRJ‐FEEMA). Morphometry and stereological data were obtained from all animals. Adult body weights ofL. rosaliawere the lowest, the greatest being those ofL. chrysopygus caissara; body weights ofL. chrysomelasandL. c. chrysopyguswere similar and in between those of the two former species. Cardiomyocytes (left ventricular myocardium) were bigger in adults than in infants. The myocardium ofL. rosaliashowed focal fibrosis, fatty vacuoles, and hyalinization. InL. chrysomelasthe myocardium showed areas of fibrosis and presence of mononuclear cells. Fibrosis and areas of congestion were observed inL. c. chrysopygus; areas of disorganization and vascular congestion were found inL. c. caissara. InL. rosaliainfants, a greater density of vessels per myocardial area and a greater length density of vessels were observed as compared with those ofL. chrysomelas. In adults,L. chrysomelasshowed greater density of connective tissue in the myocardium thanL. c. chrysopygusandL. c. caissaradid. InL. rosalia, cardiomyocyte nuclei had a greater area density than those of the other forms ofLeontopithecus. These characteristics may explain the faster development ofL. rosaliainfants as compared with that ofL. chrysomelasandL. c. chrysopyguskept under the same handling conditions at the CPRJ‐FEEMA.
The tree shrews: adjuncts and alternatives to primates as models for biomedical research
Authors: Cao J , Yang E.‐B , Su J.‐J , Li Y , Chow P
Published: May 2003

Abstract: The tree shrews are non‐rodent, primate‐like, small animals. There is increasing interest in using them to establish animal models for medical and biological research. This review focuses on the use of the tree shrews in in vivo studies on viral hepatitis, hepatocellular carcinoma (HCC), myopia, and psychosocial stress. Because of the susceptibility of the tree shrews (Tupaia belangeri) and their hepatocytes to infection with human hepatitis B virus (HBV) in vivo and in vitro, these animals have been used to establish human hepatitis virus‐induced hepatitis and human HBV‐ and aflatoxin B1‐associated HCC models. As these animals are phylogenetically close to primates in evolution and have a well‐developed visual system and color vision in some species, they have been utilized to establish myopia models. Because dramatic behavioral, physiological, and neuroendocrine changes in subordinate male tree shrews are similar to those observed in depressed human patients, the tree shrews have been successfully employed to experimentally study psychosocial stress. However, the tree shrews holds significant promise as research models and great use could be made of these animals in biomedical research.
Selection on Arctic charr generated by competition from brown trout
Authors: Forseth Torbjørn , Ugedal Ola , Jonsson Bror , Fleming Ian A.
Published: May 2003

We experimentally explored population‐ and individual‐level effects on Arctic charr (Salvelinus alpinus) resulting from resource competition with its common European competitor, the brown trout (Salmo trutta). At the population level, we compared performance of the two species in their natural sympatric state with that of Arctic charr in allopatry. At the individual level, we established selection gradients for morphological traits of Arctic charr in allopatric and in sympatric conditions. We found evidence for interspecific competition likely by interference at the population level when comparing differences in average performance between treatments. The growth and feeding rates did not differ significantly between allopatric and sympatric Arctic charr despite lower charr densities (substitutive design) in sympatric enclosures indicating that inter‐ and intraspecific competition are of similar strength. The two species showed distinct niche segregation in sympatry, and brown trout grew faster than Arctic charr. Arctic charr did not expand their niche in allopatry, indicating that the two species compete to a limited degree for the same resources and that interference may suppress the growth of charr in sympatric enclosures. At the individual level, however, we found directional selection in sympatric enclosures against individual Arctic charr with large head and long fins and against individuals feeding on zoobenthos rather than zooplankton indicating competition for common resources (possibly exploitative) between trout and these charr individuals. In allopatric enclosures these relations were not significant. Diets were correlated to the morphology supporting selection against the benthic‐feeding type, i.e. individuals with morphology and feeding behaviour most similar to their competitor, the benthic feeding brown trout. Thus, this study lends support to the hypothesis that Arctic charr have evolved in competition with brown trout, and through ecological character displacement adapted to their present niche.
Are fast growing birch leaves more asymmetrical?
Authors: Kozlov Mikhail V.
Published: May 2003

Two recent papers (Martel et al. 1999, Lempa et al. 2000), linked rapid leaf growth in birches with high level of developmental instability, measured by leaf fluctuating asymmetry (FA). I discuss methodological approaches used in the referred papers and conclude that none of them provided incontrovertible support for the hypothesis on positive correlation between FA and leaf growth rate. A field study designed to test this hypothesis by an independent data set revealed no correlation between FA and either relative or absolute leaf growth rate in mountain birch either in within‐tree or in between‐tree comparisons. Character of the relationships between FA and growth may change with the index used to quantify developmental instability.
Predatory fish impact on competition between stream insect grazers: a consideration of behaviorally‐ and density‐mediated effects on an apparent coexistence pattern
Authors: Miyasaka Hitoshi , Genkai‐Kato Motomi , Kuhara Naotoshi , Nakano Shigeru
Published: May 2003

A manipulative field experiment and theoretical analyses of a simple competition model were used to show how exploitative competition between a caddisfly (Glossosoma sp.) and three mayfly grazers (Ameletus sp., Baetisthermicus and Cinygmula sp.) was mediated by a predatory fish, freshwater sculpin (Cottus nozawae). The field experiment followed a two‐factorial design, with Glossosoma densities (natural vs reduced) and sculpin presence (present vs absent) as treatments. Diet analysis revealed that all four prey species were eaten under the natural condition and the sculpin preferred mayfly grazers to Glossosoma. Our experiment showed that although mayfly densities in the presence of either sculpin or Glossosoma were lower than in the no‐sculpin plus reduced‐Glossosoma treatment, no difference in mayfly densities was found between the following three treatments: sculpin plus natural‐Glossosoma, no‐sculpin plus natural‐Glossosoma, and sculpin plus reduced‐Glossosoma. These results indicated that fish predator produced no effects additive to the competitive operation on the mayfly density, and also that competitive operation of Glossosoma on the mayfly densities produced no additional effects to fish predators. In addition, although the competitive effect of the mayflies on Glossosoma could not be manipulated in isolation, the density of Glossosoma in the presence of sculpin was greater than that in the absence of sculpin in the natural‐Glossosoma treatment. Thus, the densities of these competing grazers either stayed the same or increased in the presence of the fish predator relative to predator‐free treatments. A theoretical model, developed to explain the experimental results here, predicted that the densities of the two competing prey under predation pressure could be simultaneously greater than those under predator absent conditions when the behaviorally‐mediated effects of the predator were strongly operative. Although we were unable to distinguish experimentally the two different effects of predator on the prey competition, the behaviorally‐ and density‐mediated effects, the reality of the behaviorally‐mediated effects in the experiment was discussed.
Dietary conservatism may facilitate the initial evolution of aposematism
Authors: Thomas R. J. , Marples N. M. , Cuthill I. C. , Takahashi M. , Gibson E. A.
Published: May 2003

It has generally been assumed that warningly coloured organisms pay a cost associated with their increased visibility, because naïve predators notice and eat them. This cost is offset by their enhanced protection from educated predators who associate the colour pattern with unprofitability. However, some studies have suggested that avoidance of novel prey by avian predators (“dietary conservatism”) can actually place novel colour morphs at a selective advantage over familiar ones, even when they are highly conspicuous. To test this idea, we experimentally simulated the appearance of a single novel‐coloured mutant in small populations (20 individuals) of palatable artificial prey. The colour morph frequencies in each “generation” were determined by the relative survival of the previous generation under predation by birds. We used wild‐caught European robins Erithacus rubecula foraging on pastry “prey” of different colours. The aim was to test whether prey selection by predators prevented or facilitated the novel colour morph persisting in the prey population over successive generations. We found that the novel colour morph quickly increased to fixation in 14/40 prey “populations”, and at least once each in 8 of the 10 birds tested. Novel mutants of the classic aposematic colours (red and yellow) reached fixation most frequently, but even the green and blue novel morphs both increased to fixation in 2/40 trials. Novel colours reached fixation significantly faster than could be accounted for by drift, indicating active avoidance by the birds. These results suggest that a novel colour morph arising in a prey population can persist and increase under the selective pressure imposed by predators, even to the local exclusion of the original morph, despite being fully palatable. The consequences of this finding are discussed in relation to receiver psychology, the evolution of aposematism and the existence of polymorphism in Müllerian mimics.
Herbivores do not discriminate between leaves of female and hermaphrodite individuals of gynodioecious Daphne laureola (Thymelaeaceae)
Authors: Alonso Conchita
Published: May 2003

The outcome of plant‐animal interactions in dioecious plant species frequently depends on the gender of the plant individuals. It has even been proposed that these interactions could mediate the evolution of plant reproductive systems from hermaphroditism to dioecy. Gynodioecy is the most frequent intermediate stage in this evolutionary process, however, little is known about the relevance of gender dimorphism in plant‐animal relationships others than pollination for gynodioecious species. In this study herbivores (Noctuid larvae) were used as subjective referees to detect differences between leaves of female and hermaphrodite Daphne laureola individuals. Larvae collected in the field were allowed to choose between leaves of female and hermaphrodite individuals at both flowering and fruiting period. There was no preference for either of the genders suggesting that the absence of male reproductive function in D. laureola shrubs does not cause dissimilarities in leaf characteristics that can affect herbivores.
Explaining productivity‐diversity relationships in plants
Authors: Rajaniemi Tara K.
Published: May 2003

Relationships between productivity and diversity in plant communities have been widely documented. Unimodal productivity‐diversity relationships are most common along natural productivity gradients, and fertilization generally reduces diversity. Five distinct hypotheses invoke changes in competition to explain why diversity should decline from intermediate to high productivity. Because experiments measuring the effects of competition on diversity are rare, four of the five hypotheses have not been directly tested, but each hypothesis makes unique predictions that allow for indirect tests. The indirect evidence is often conflicting, and while none of the hypotheses can be rejected, only the dynamic equilibrium hypothesis is consistently supported. A new hypothesis, however, is supported by indirect evidence and may help to explain the variation in the shape of productivity‐diversity relationships, as well as the most common patterns. Diversity may be high in environments that promote size symmetric competition, where soil resources limit growth and are homogeneously distributed within the soil volume explored by individual plants. Conversely, diversity may be low in environments that promote size asymmetric competition, where light is limiting, or where soil resources are limiting and are patchily distributed within rooting zones.
Ants in your plants: effects of nectar‐thieves on pollen fertility and seed‐siring capacity in the alpine wildflower, Polemonium viscosum
Authors: Galen Candace , Butchart Brian
Published: May 2003

Flowers of the alpine skypilot, Polemonium viscosum, are attacked by nectar thieving ants of Formica neorufibarbus gelida. Ants exert selection on flower scent, size and shape in skypilots by damaging the pistils. Here, I report on the frequency and nature of contact between ants and pollen‐bearing anthers and determine the consequences of such contact for pollen performance and pollen donor paternity. In laboratory trials, ants entered flowers with full intact anthers and emasculated (female) flowers equivalently. Similarly, flower visitation rates of ants foraging naturally were not affected by the frequency of male phase flowers per plant. Ants actively interacted with the pollen‐bearing anthers during 21% of flower visits, on average. The rate at which such interactions occurred was predicted by the proportion of flowers in the male phase, under a random foraging model. The effect of ants on pollen fertility was tested experimentally by enclosing ants in male‐phase flowers on intact inflorescences. Adjacent control flowers were left un‐occupied. Pollen from flowers with a history of ant occupancy had significantly lower germination on virgin recipient stigmas than pollen from unoccupied control flowers. With hand‐pollination, sufficient pollen was transferred from ant‐occupied flowers to saturate seed set. However, a model based on the relationship between seed set and compatible pollen delivery by natural pollinators indicated that ant damage to pollen should reduce paternity accruing per flower visit by 20–26% on average, in nature. Results support the hypothesis that in P. viscosum, selection on floral traits by nectar‐thieving ants operates through male as well as female function.
Is the relation between nutrient supply and biodiversity co‐determined by the type of nutrient limitation?
Authors: Aerts R. , De Caluwe H. , Beltman B.
Published: May 2003

Correlative studies have shown a ‘hump‐backed’ relation between the vegetation N:P ratio and plant species diversity with the highest diversity at balanced N:P ratios (between 10 and 14). We tested the hypothesis that adding growth‐limiting nutrients to mesotrophic grasslands that were in shortage of either N (N:P ratio<10) or P (N:P ratio>14) would lead to an increase of plant diversity. Thereto, we studied the effects of long‐term (11 yr) experimentally increased N and/or P supply on soil nutrient pools, vegetation nutrient dynamics and biodiversity in a riverine grassland in the Netherlands with a low soil N:P ratio (N shortage) and a peat grassland with a high soil N:P ratio (P shortage), respectively. Eleven years of nutrient addition hardly had any effects on the total stocks of C, N and P in the soils of both sites, due to the large size of the soil nutrient pools already present and to the management at both sites (annual hay‐making and ‐removal). However, in the riverine grassland the treatments increased the cycling of the small pool of labile N and P compounds resulting in large increases in annual fluxes of especially N. In the unfertilised controls, species establishments balanced more or less species losses during an 11 year period, thus leading to a dynamic equilibrium of the species pool. However, contrary to our hypothesis, addition of the growth‐limiting nutrient led at both sites to a reduction of species diversity even when total biomass remained below critical levels. Species diversity and species evenness were strongly determined by N mineralisation and to a lesser extent by total soil N and extractable P, respectively. Total aboveground biomass of the vegetation was determined by total soil N.

Our study shows that patterns found in correlative studies of the relation between plant diversity and soil and vegetation N:P ratio can not be translated into successful experimental manipulations to enhance biodiversity. The most likely explanation is that colonization limitation occurred in the fertilized plots and that not sufficient diaspores of potentially new species could reach and/or colonize the plots to compensate for the species extinctions as a result of increased nutrient supply.
Assessing differential prey selection patterns between two sympatric large carnivores
Authors: Husseman Jason S. , Murray Dennis L. , Power Gary , Mack Curt , Wenger C. R. , Quigley Howard
Published: May 2003

Several conceptual models describing patterns of prey selection by predators have been proposed, but such models rarely have been tested empirically, particularly with terrestrial carnivores. We examined patterns of prey selection by sympatric wolves (Canis lupus) and cougars (Puma concolor) to determine i) if both predators selected disadvantaged prey disproportionately from the prey population, and ii) if the specific nature and intensity of prey selection differed according to disparity in hunting behavior between predator species. We documented prey characteristics and kill site attributes of predator kills during winters 1999–2001 in Idaho, and located 120 wolf‐killed and 98 cougar‐killed ungulates on our study site. Elk (Cervus elephus) were the primary prey for both predators, followed by mule deer (Odocoileus hemionus). Both predators preyed disproportionately on elk calves and old individuals; among mule deer, wolves appeared to select for fawns, whereas cougars killed primarily adults. Nutritional status of prey, as determined by percent femur marrow fat, was consistently poorer in wolf‐killed prey. We found that wolf kills occurred in habitat that was more reflective of the entire study area than cougar kills, suggesting that the coursing hunting behavior of wolves likely operated on a larger spatial scale than did the ambush hunting strategy of cougars. We concluded that the disparity in prey selection and hunting habitat between predators probably was a function of predator‐specific hunting behavior and capture success, where the longer prey chases and lower capture success of wolf packs mandated a stronger selection for disadvantaged prey. For cougars, prey selection seemed to be limited primarily by prey size, which could be a function of the solitary hunting behavior of this species and the risks associated with capturing prime‐aged prey.
Do seedlings in gaps interact? A field test of assumptions in ESS seed size models
Authors: Silvertown Jonathan , Bullock James M.
Published: May 2003

ESS models for the evolution of seed size variation assume that seedlings compete with each other for the occupancy of ‘safe sites’ or vegetation gaps. If mortality rates are high and/or frequency‐independent, ESS models reduce to the classical model of Smith and Fretwell which predicts that a single, optimum seed size should occur. We tested whether seedlings compete with one another by following the survival of seedlings colonizing experimental gaps in a grazed grassland community. In small gaps (3 cm diameter) the proximity of established plants slightly, though significantly reduced seedling survival, but density‐dependent mortality also occurred among seedlings in these gaps. In larger gaps (6 cm, 9 cm diameter) survival was significantly positively frequency‐dependent. These results strongly support the validity of ESS models.
Predation rate, prey preference and predator switching: experiments on voles and weasels
Authors: Sundell Janne , Eccard Jana A. , Tiilikainen Raisa , Ylönen Hannu
Published: May 2003

We studied the predation rate and prey selection of the least weasel (Mustela nivalis nivalis) on its two most common prey species in boreal environments, the bank vole (Clethrionomys glareolus) and the field vole (Microtus agrestis), in large outdoor enclosures. We also studied the response of weasels to odours of the two species in the laboratory. The enclosure experiment was conducted using constant vole densities (16 voles/ha) but with varying relative abundance of the two species. Weasels showed higher predation rates on bank voles, and males had higher predation rate than females. Females killed disproportionately more of the more abundant prey species, but they preferred bank voles to field voles when both were equally available. Overall, the predation rate also increased with increasing abundance of bank voles. Therefore our results are in agreement with earlier laboratory results showing preference for bank voles, even if no intrinsic preference for odours of either species was observed in our laboratory study. We suggest that the least weasel hunts according to prey availability, prey aggregation and suitability of hunting habitat, and that this causes the observed dependence of least weasels on field voles and emphasises the role of the field vole in the vole‐weasel interaction in cyclic vole populations. Furthermore, our results suggest that predation by weasels may facilitate the coexistence of the two vole species via predator switching, and that it may cause the observed synchrony in dynamics between vole species.
Intraspecific competition and density dependence in an Ephestia kuehniella–Venturia canescens laboratory system
Authors: Lane Stephen D. , Mills Nicholas J.
Published: May 2003

A model host‐parasitoid system of Ephestia kuehniella and Venturia canescens was used to examine the influence of host and parasitoid density on host and parasitoid life‐history parameters via a two‐way factorial experimental design (5 initial host densities×3 parasitoid densities). In the absence of parasitoids, E. kuehniella experienced scramble‐type competition with reduced growth, diminished adult size and a subsequent fecundity trade‐off for mortality. The mortality that did occur was confined to the late larval and pupal stages. In the presence of parasitoids attacking the late larval stage, competition changed from scramble for food to contest for enemy‐free space, with hosts escaping parasitism being small with low fecundity and reduced egg size, and with parasitoid adult size inversely dependent on host density. Total insect emergence (host+parasitoid), a measure of the influence of host resource competition on survivorship, exhibited a threshold effect as a function of initial host density; the threshold value was increased to a higher initial host density in the presence of parasitoids. Models of host self‐limitation were fitted to the data, with the generalized Beverton‐Holt model that incorporates a threshold effect providing the best fit, and the Ricker model with no threshold providing a very poor fit to the data.
A particular case and a general pattern: hyperaggressive behaviour by one species may mediate avifaunal decreases in fragmented Australian forests
Authors: Piper Scott D. , Catterall Carla P.
Published: May 2003

We quantitatively assessed edge effects associated with elevated abundance of a hyper aggressive bird species, the noisy miner Manorina melanocephala, in fragmented eucalypt forest adjoining developed land. Long‐term data from Toohey Forest, subtropical Australia, show that noisy miner colonies intensively occupy a zone of 20 m from the forest edge, with frequent use occurring up to 100 m from the edge, but little beyond 200 m. Within noisy miner colonies, the abundance and species richness of other birds were both about half those recorded at nearby transects which were outside the colonies' main activity area. Bird species smaller than noisy miners, which are also those with similar diets, were collectively 20–25 times more abundant, and their species richness tenfold greater, outside miner colonies than within them, whereas larger species, which have less dietary overlap, did not differ. Exclusion of small insectivorous birds has been hypothesised to cause elevated insect herbivore density, but we found no difference between tree crown defoliation or dieback rates within versus outside miner colonies.

Aggression by noisy miners can be viewed as a mechanism of interspecific competition, since miners have a relatively large body size for their diet and are hence able to exclude virtually all potential competitors at relatively little cost. We examine evidence indicating that reduced bird diversity in eucalypt forest fragments of eastern Australia is often simply the effect of noisy miner occupancy of edges, acting directly on the densities of other species through their aggressive behaviour. With an edge effect 200 m deep, a remnant 10 ha in size is likely to become entirely occupied by noisy miners, and this is a size threshold that has been commonly reported in association with area‐standardised avian diversity reductions. Convergent patterns of species loss from small forest fragments in different continents are the result of different underlying ecological processes.
Keystone predator effects and grazer control of planktonic primary production
Authors: Steiner Christopher F.
Published: May 2003

If prey species exhibit trade‐offs in their ability to utilize resources versus their ability to avoid predation, predators can facilitate prey turnover along gradients of productivity, shifting dominance from edible to inedible prey (the keystone predator effect). I tested this model under controlled, laboratory conditions, using a model aquatic system composed of zooplankton as the top consumer, a diverse community of algae as prey, and nutrients as basal resources. Nutrient manipulations (low and high) were crossed with presence–absence of zooplankton. Results supported theoretical predictions. Algal biomass increased in response to enrichment regardless of predator presence/absence. However, predators and nutrients had an interactive effect on algal biomass and size structure. At the low nutrient level, algal‐prey were dominated by edible forms and attained similar biomass regardless of zooplankton presence/absence. At the high level of enrichment, presence of zooplankton favored higher levels of algal biomass and shifted dominance to large, inedible taxa. At the termination of the experiment, I performed a series of lab‐based assays on the resultant algal community in order to quantify trade‐offs among algal size classes in maximal population growth rates (as a measure of competitive ability for nutrients) and susceptibility to zooplankton grazing. Assays provided support for a size‐based keystone trade‐off. Small size classes of algae displayed higher maximal growth rates but were more susceptible to grazing effects. Large size classes were protected from grazing but showed low rates of population growth in response to enrichment.