Network analysis reveals contrasting effects of intraspecific competition on individual vs. population diets

Optimal foraging theory predicts that individuals should become more opportunistic when intraspecific competition is high and preferred resources are scarce. This density-dependent diet shift should result in increased diet breadth for individuals as they add previously unused prey to their repertoire. As a result, the niche breadth of the population as a whole should increase. In a recent study, R. Svanb?ck and D. I. Bolnick confirmed that intraspecific competition led to increased population diet breadth in threespine stickleback (Gasterosteus aculeatus). However, individual diet breadth did not expand as resource levels declined. Here, we present a new method based on complex network theory that moves beyond a simple measure of diet breadth, and we use the method to reexamine the stickleback experiment. This method reveals that the population as a whole added new types of prey as stickleback density was increased. However, whereas foraging theory predicts that niche expansion is achieved by individuals accepting new prey in addition to previously preferred prey, we found that a subset of individuals ceased to use their previously preferred prey, even though other members of their population continued to specialize on the original prey types. As a result, populations were subdivided into groups of ecologically similar individuals, with diet variation among groups reflecting phenotype-dependent changes in foraging behavior as prey density declined. These results are consistent with foraging theory if we assume that quantitative trait variation among consumers affects prey preferences, and if cognitive constraints prevent individuals from continuing to use their formerly preferred prey while adding new prey.     

Seed choice by rodents: learning or inheritance?

Learning plays a central role in animal life, and it has received special attention in the context of foraging. In this study, we have tested whether learning operates in seed choices by rodents using the Algerian mouse (Mus spretus) and Holm oak (Quercus ilex) acorns as a model. At the laboratory, those rodents captured in the field during the acorn fall period (experienced individuals) rejected weevil-infested acorns, presumably because of their lower energetic value. By contrast, rodents born in captivity and reared without any contact with acorns (naïves) predated weevil-infested acorns at similar rates than sound ones. After exposing naïves to infested and sound acorns during 15 days, they rejected infested acorns as the experienced individuals. In the field, predation on weevil-infested acorns was lower than on sound ones. Predation rates on infested acorns were lowest at the end of the acorn fall season, whereas predation rates of sound acorns increased along the same period. This might be explained by the improved ability to reject infested acorns because of the accumulated experience acquired by the initially naïve rodents along the acorn fall season. We show that learning shapes strongly seed choices by rodents, and it may be advantageous over inherited behaviors in variable unpredictable situations, such as acorn infestation rates that vary strongly between years and trees. We consider that the role of learning has to be taken into account in future studies on seed predation by rodents.     

Informative content of multiple plumage-coloured traits in female and male European Rollers

Animals may assess the quality of other individuals by using information that different ornaments may provide. The European Roller (Coracias garrulus) is a socially monogamous species in which males and females display highly conspicuous plumage colouration. According to the mutual selection hypothesis, we predicted that, in this species, plumage coloration could signal individual quality in both sexes because both female and male rollers invest a considerable amount of time caring for their offspring. We used spectrophotometric measurements to investigate the information content of multiple plumage colour traits. We found that the roller is actually a sexually dimorphic and dichromatic species. Different plumage colours from different origins were correlated within individual. Head and back brightness correlated with body condition in both sexes, and in males, head brightness correlated with the number of fledglings in successful nests, while head green-yellow saturation correlated with parental provisioning. Meanwhile, in females, back brightness was related to the number of fledglings in successful nests and to parental provisioning rate. In addition, there was a positive assortative mating in relation to weight, body condition, head green-yellow saturation and back brightness. Finally, we found a positive correlation between parent and offspring coloration. Altogether, these results suggest that multiple colour traits may act as quality indicators in the roller and that they may be used by the two sexes to assess potential mate quality.     

Land poverty and emerging ruralities in Cambodia: insights from Kampot province

Rural change in Cambodia manifests itself in rapidly declining land availability for the smallholder sector, posing the question of how farmers may be able to deal with limited access to land. In this paper, we discuss with a case study village and household livelihood strategies of smallholders currently operating under land-constrained conditions. Based on an integrated assessment of a smallholder village in Kampot province, we illustrate in quantitative terms how land shortage is creating problems of surplus generation and liquidity issues in monetary and non-monetary flows. At the household level, livelihood diversification based on the involvement of productive resources other than land may play an increasing role, particularly in the future, when levels of land shortage may increase. At the village level, smallholder may respond through institutional innovation, in particular through the establishment of a community banking system and a paddy rice bank to provide money and rice credits to overcome transitory shortages and to cover investment costs for additional productive resources. Thus, in this case, we observe the emergence of new patterns of livelihood in rural areas, based on the integration of non-land-based economic activities and new institutional settings.     

Healing with animals in a semiarid northeastern area of Brazil

This study presents information on the use of medicinal animals in a semiarid area of northeast Brazil, a region where animals have recognized importance in local popular medicine. The information on the use of animals for medicinal purposes was obtained through semi-structured questionnaires, complemented by free interviews and informal conversations. The results obtained showed that the residents of the area studied utilize a considerable richness of animal species (n = 42) for medicinal purposes, as occurs in other areas of Brazil’s semiarid region, demonstrating that zootherapy represents an alternative form of health care that is important to the inhabitants of the region. There is a need for new investigations on medicinal fauna, aimed at promoting the sustainable use of eventual medicinal species and preserving popular knowledge associated with the use of animal species.     

Assessment of National Parks affected by naturbanization processes in Southern Europe

This paper assesses land-use changes related to naturbanization processes on three biosphere reserves in Southern Europe. A comparative analysis has been done on the National Parks in Peneda-Gerês in North Portugal, Cévennes in South France and Sierra Nevada in South Spain, using Corine Land Cover data from 1990 until 2006. Results indicate that the process of land-use intensification is taking place in the frame of naturbanization dynamics that could jeopardize the role of Protected Areas. Focusing on the trends faced by National Parks and their surrounding territories, the analysis demonstrates, both in quantitative and spatial terms, the intensification processes of land-use changes and how it is important to know them for coping with increasing threats. The article concludes that in the current context of increasing stresses, a broader focus on nature protection, encompassing the wider countryside, is needed if the initiatives for biodiversity protection are to be effective.     

Effect of the pesticide lindane on the biomass of the microalgae Nannochloris oculata

This study assesses the growth of the microalgae Nannochloris oculata in the presence of lindane and the ability of N. oculata to remove lindane from media. Algal biomass increased with 0.1 and 0.5 mg L^?1 of lindane, and lindane concentrations in the media decreased. N. oculata removed 73% and 68.2% of lindane in the 0.1 and 0.5 mg L^?1 media concentrations, respectively. Algal biomass decreased to the level of the control at lindane concentrations greater than 2.5 mg L^?1, probably due to toxicity. N. oculata removed lindane from the media at concentrations lower than 1.0 mg L^?1. Thus, N. oculata may be useful for lindane bioremediation in contaminated aquatic systems.     

Polarographic determination of the stability constant of the ternary complex formed between cocaine and cobalt thiocyanate

The interactions between cocaine -- Co(II) and thiocyanate (or dimethylglyoxime) have been studied by electrochemical means, assuming the existence of a ternary complex with the stoichiometry [(H₂O)₃Co(SCN)(C₁₇H₂₁NO₄)]⁺ and the absence of similar ternary species containing dimethylglyoxime. The formation constant of the complex has been evaluated by polarographic titrations because of the irreversibility of electrochemical processes. This relatively small value of 2.37 × 10⁵ is in agreement with the experimental conditions at which Scott's method is typically carried out to detect cocaine in solid samples by reaction with Co(II) thiocyanate.     

Community engagement in the Transition movement: views and practices in Portuguese initiatives

As the need to address climate change is ever more urgent, many have emphasised the importance of community-level responses. The Transition movement has advanced community-based action to increase resilience for over a decade and has expanded significantly. Thus, it is a critical setting for examining community engagement towards climate change in practice. Our study is based on 39 interviews with facilitators of Transition initiatives in Portugal, coupled with observational data, and is guided by two main research questions: how do Transition initiatives promote community engagement at the local level? What are the factors constraining or facilitating community engagement within Portuguese Transition initiatives? We identify several aspects of Transition’s constructions of community resilience and engagement that indicate ambivalence towards, or avoidance of, certain issues. They relate do agency, structure, power and inclusion, as well as to the modes of engagement and the communication practices of Transition initiatives. We argue that strategies for community engagement should be specific to social contexts rather than internationally uniform and be based on participatory approaches. Drawing on an extensive empirical analysis, the article contributes to theory building on the Transition movement beyond the Anglo-Saxon context and to the wider field of community-based environment initiatives.