Differential diet breadths and species coexistence in leafroller-hunting eumenid wasps

There are, at least, three possible ways in which similar species coexist; resource partitioning, interference competition, and exploitation competition. Here, I investigated which way contributed to the coexistence of leafroller-hunting eumenid wasp species. Resource partitioning and, in addition, differential diet breadths proved to promote species coexistence in this case. First, I analyze the prey records and diet overlap of four eumenid species in a local area. The larger two eumenids hunted similar-sized prey items and had similar potential taxonomic prey uses. But the diet breadth of the subsocial eumenid was much wider than that of the solitary one. As a result, the diet overlap between the two large eumenids decreased. This was because the solitary eumenid attend repeatedly to the same hunting site inhabited by one abundant prey species, while the subsocial one made random hunting. On the other hand, the two medium-sized eumenids partitioned resources according to prey size. Secondly, I related these results to prey choice by several other species of eumenid obtained from literature sources. Ten Japanese common eumenids were divided into four groups according to their prey size. In each of the four groups, 2 to 3 wasp species differentiated the habitat (1 group) or coexisted by means of differential diet breadths (parallel with differential sociality, 2 groups).     

Effect of heating on properties of some soils from Southern Nigeria and growth of rice

Summary The effect of heating on the properties of Apomu (Psammentic Usthorthent), Egbeda (Oxic Paleustalf) and Gambari (Typic Plinthustalf) surface soils were studied under laboratory conditions. Heating at low temperatures (100°C) have no detrimental effects on soil properties, on the contrary it increased the soil extractable P, Mg, Fe, Mn and Zn levels. Pronounced reductions in total N, Org. C, Org. P and extractable Ca and Mg levels and marked increases in extractable P, Zn, Mn and Fe were observed by heating to 200°C. Heating to 500° had an adverse effect on soil chemical and physical properties.Plant height and dry matter yeild of rice plants were higher when grown on Egbeda soil previously heated to 100°C. With addition of N, P and K there was no observed beneficial effect of the heating treatment. Rice plants grown on Egbeda soil previously heated to 200°C showed high uptake of Mn. Plants grew badly in soil previously heated to 500°C.     

Oxygen availability,redox and the distribution of some Turbellaria Schizorhynchidae and other forms

Records from a considerable number of meiofaunal samples are reexamined in relation to the depth within sediment distribution of various taxa especially Schizorhynchidae and the main turbellarian orders.Frequency and density records in samples with particular oxygen flow rates and redox potentials confirm that the ranges of Schizochilus, Proschizorhynchus and Neoschizorhynchus spp. within these factors may help account for congeneric occurrence within cores. However, statistical analysis of the records is seldom able to confirm apparent differences. There is, for example, a statistically significant difference in distribution in relation to redox potential between the red schizorhynchians Pseudoschizorhynchides ruber, Diascorhynchus rubrus and the red acoelan Paratomella rubra but not in relation to oxygen availability and depth within sediment. On one beach Gnathostomula aff. paradoxa was found at Eh and O₂ availability values under which it must be assumed to be living anaerobically.Contingency and other analyses are extended to differences between higher taxa and the results discussed in relation to habitat evolution of the Turbellaria. The suggestion that structural complexity of turbellarians has increased with increased oxygenation of the environment is tentatively supported.     

Declining body size in an endangered large mammal

Body size affects almost every aspect of the biology of a species. According to the ‘resource rule’, decreasing resource availability (e.g. prey density) will lead to a reduction in body size or, alternatively, a decline in mass‐independent energy expenditure. In the present study, we provide a test of this hypothesis, assessing the effect of significantly decreasing prey density on endangered African wild dog (Lycaon pictus) body size and energy expenditure over a 20‐year period. As predicted from the ‘resource rule’, decreasing resource availability resulted in energetic re‐allocation: wild dogs' body size decreased significantly (both shorter and slimmer), whereas our fitness‐related measure of energy expenditure (i.e. litter size) remained constant over time. A phenotypic change of up to 17% within 20 years, as found in the present study, appears to be unprecedented in a nonharvested large mammal, thus advancing the emerging field of eco‐evolutionary dynamics. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 8–12.     

Effects of cryopreservation techniques on the preservation of ear skin – An alternative approach to conservation of jaguar,Panthera onca (Linnaeus, 1758)

Currently, it has been observed that a considerable segment of the jaguar population is declining mainly because of hunting, and destruction and fragmentation of habitat. Given this scenario, efforts of the scientific community have been concentrated on the development of conservation strategies, such as the formation and use of somatic sample banks. We aimed to assess the effects of cryopreservation techniques of the ear skin of jaguar [slow freezing (SF) or direct vitrification in cryovials (DVC) or solid-surface vitrification (SSV)] on the morphological analysis and cell ability during the culture. All cryopreserved fragments regardless of the technique used, showed a reduction in the dermis and total thickness of the skin. Although a collagen matrix similar to the control group (fresh) has been observed only for the fragments from SF and SSV groups, all cryopreserved techniques were able to maintain normal patterns of the fibroblasts. Moreover, DVC and SSV methods maintained the proliferative activity of the tissues even after warming. After the culture, SF and SSV techniques were efficient for the recovery of the somatic cells according to most of the evaluated parameters, especially with regard to the duration of culture and cell metabolic activity. In conclusion, SSV was found to be a more efficient technique for cryopreserving jaguar skin when compared to DVC and SF. These results are relevant for the formation of somatic resource banks of this species, directed at cryopreserving adequate samplings of different individuals and generations for future applications in regenerative medicine, and assisted reproductive technologies.     

Body size clines in the European badger and the abundant centre hypothesis

Aim To test the abundant centre hypothesis by analysing the physical and climatic factors that influence body size variation in the European badger (Meles meles). Location Data were compiled from 35 locations across Europe. Methods We used body mass, body length and condylo‐basal length (CBL) as surrogates of size. We also compiled data on latitude, several climatic variables, habitat type and site position relative to the range edge. We collapsed all continuous climatic variables into independent vectors using principal components analysis (PCA), and used a general linear model to explain the morphometric variation in badger populations across the species’ range. Results Body mass and body length were nonlinearly and significantly related to latitude. In contrast, CBL was linearly related to latitude. Body mass changed nonlinearly along the temperature (PC1) gradient, with the highest values observed at mid‐range. Furthermore, body mass, body length and CBL differed significantly among habitats, with badgers showing larger size in temperate habitats and core areas relative to peripheral zones. Main conclusions Our analysis supports the nonlinear pattern predicted by the abundant centre hypothesis only for body mass and body length. These results imply that individuals are largest and heaviest at the centre of the climatic range of badger distribution. Variation of CBL with latitude follows a linear trend, consistent with Bergmann’s rule. Our results provide mixed support for the abundant centre hypothesis, and suggest food availability/quality to be the main mechanism underlying body size clines in this species.     

Bottom‐up Conservation

Conservation initiatives that have worked well in temperate and developed regions have often been applied in the tropics but with only limited success. Part of this failure is due to top–down conservation planning that has been conducted without taking local socio‐economic considerations into adequate account. Here, we argue that conservation approaches would benefit from a deeper understanding of human–nature interactions.     

An individual-based model for competingDrosophila populations

An individual-based model forDrosophila is formulated, based on competition amongst larvae consuming the same batch of food. The predictions of the model are supported by data for single speciesDrosophila populations reared in the laboratory. The model is used to build a simple discrete model for the dynamics ofDrosophila populations that are kept over a number of generations. The dynamics of a single species is shown to give either a stable equilibrium or fluctuations which can be periodic or chaotic. When the dynamics of a species in the absence of the other is periodic or chaotic, we found coexistence or two alternative states, on neither of which the species can coexist.     

Life‐history constraints in grassland plant species: a growth‐defence trade‐off is the norm

Plant growth can be limited by resource acquisition and defence against consumers, leading to contrasting trade‐off possibilities. The competition‐defence hypothesis posits a trade‐off between competitive ability and defence against enemies (e.g. herbivores and pathogens). The growth‐defence hypothesis suggests that strong competitors for nutrients are also defended against enemies, at a cost to growth rate. We tested these hypotheses using observations of 706 plant populations of over 500 species before and following identical fertilisation and fencing treatments at 39 grassland sites worldwide. Strong positive covariance in species responses to both treatments provided support for a growth‐defence trade‐off: populations that increased with the removal of nutrient limitation (poor competitors) also increased following removal of consumers. This result held globally across 4 years within plant life‐history groups and within the majority of individual sites. Thus, a growth‐defence trade‐off appears to be the norm, and mechanisms maintaining grassland biodiversity may operate within this constraint.     

Complex Genetic Effects on Early Vegetative Development Shape Resource Allocation Differences Between Arabidopsis lyrata Populations

Costs of reproduction due to resource allocation trade-offs have long been recognized as key forces in life history evolution, but little is known about their functional or genetic basis. Arabidopsis lyrata, a perennial relative of the annual model plant A. thaliana with a wide climatic distribution, has populations that are strongly diverged in resource allocation. In this study, we evaluated the genetic and functional basis for variation in resource allocation in a reciprocal transplant experiment, using four A. lyrata populations and F₂ progeny from a cross between North Carolina (NC) and Norway parents, which had the most divergent resource allocation patterns. Local alleles at quantitative trait loci (QTL) at a North Carolina field site increased reproductive output while reducing vegetative growth. These QTL had little overlap with flowering date QTL. Structural equation models incorporating QTL genotypes and traits indicated that resource allocation differences result primarily from QTL effects on early vegetative growth patterns, with cascading effects on later vegetative and reproductive development. At a Norway field site, North Carolina alleles at some of the same QTL regions reduced survival and reproductive output components, but these effects were not associated with resource allocation trade-offs in the Norway environment. Our results indicate that resource allocation in perennial plants may involve important adaptive mechanisms largely independent of flowering time. Moreover, the contributions of resource allocation QTL to local adaptation appear to result from their effects on developmental timing and its interaction with environmental constraints, and not from simple models of reproductive costs.