A historical study of mineral elements in forest plants from South Norway

Herbarium plants were used as a material to study possible long-term changes in mineral elements of forest plants. Plants from South Norway collected in the period 1870 to 1930 were compared to plants collected in 1982. Relative to mineral contents in plants from 1870 to 1930, the 1982 material showed elevated levels of Zn, Cd, Rb, K, Mn and Ti and decreased levels of Sr, B, Ca and Mo in some of the plant species analysed. Most of these differences may be explained by changes in the environmental conditions, due to differences in chemical composition of precipitation, accelerated soil acidification and subsequent increasing mineral weathering. Consequently analysis of herbarium plants seems to provide valuable information about preindustrial levels of mineral elements and seems to detect changes in mineral elements brought about by recent anthropogenic activity.     

Enhanced water resource base for sustainable integrated water resource management

The article states the case for greatly enhanced reliance on desalination in the provision of freshwater. It argues that the concept of integrated water resource management (IWRM), should be expanded to routinely include desalination, and that sea water and brackish water should be listed among available sources of freshwater. In recent years, the price per m3 of freshwater obtained from desalination has steadily declined, and is now within competitive range of conventional sources, especially as extracting water from surface sources (rivers, lakes) is becoming increasingly expensive as well as ecologically harmful, and groundwater in many locations is saline or depleted. With the expectation that by 2020, five billion people will reside in megacities, today's conventional water resources are likely to become insufficient. As many of these megacities are located near ocean coasts, sea water seems a logical solution.     

Docosahexaenoic acid (DHA) content of membranes determines molecular activity of the sodium pump: implications for disease states and metabolism

The omega-3 polyunsaturate, docosahexaenoic acid (DHA), plays a number of biologically important roles, particularly in the nervous system, where it is found in very high concentrations in cell membranes. In infants DHA is required for the growth and functional development of the brain, with a deficiency resulting in a variety of learning and cognitive disorders. During adulthood DHA maintains normal brain function and recent evidence suggests that reduced DHA intake in adults is linked with a number of neurological disorders including schizophrenia and depression. Here we report a high positive correlation between the molecular activity (ATP min^–1) of individual Na⁺K⁺ATPase units and the content of DHA in the surrounding membrane bilayer. This represents a fundamental relationship underlying metabolic activity, but may also represent a link between reduced levels of DHA and neurological dysfunction, as up to 60% of energy consumption in the brain is linked to the Na⁺K⁺ATPase enzyme.     

A synthesis of the arctic terrestrial and marine carbon cycles under pressure from a dwindling cryosphere

The current downturn of the arctic cryosphere, such as the strong loss of sea ice, melting of ice sheets and glaciers, and permafrost thaw, affects the marine and terrestrial carbon cycles in numerous interconnected ways. Nonetheless, processes in the ocean and on land have been too often considered in isolation while it has become increasingly clear that the two environments are strongly connected: Sea ice decline is one of the main causes of the rapid warming of the Arctic, and the flow of carbon from rivers into the Arctic Ocean affects marine processes and the air–sea exchange of CO₂. This review, therefore, provides an overview of the current state of knowledge of the arctic terrestrial and marine carbon cycle, connections in between, and how this complex system is affected by climate change and a declining cryosphere. Ultimately, better knowledge of biogeochemical processes combined with improved model representations of ocean–land interactions are essential to accurately predict the development of arctic ecosystems and associated climate feedbacks.     

Multiple mating increases the sperm stores of Atta colombica leafcutter ant queens

Multiple mating is likely to be costly for ant queens and yet it is common. Whether multiple mating brings benefits to queens that outweigh the costs has, therefore, received considerable theoretical attention. Empirical tests of hypotheses have been scarce and no clear evidence has been reported. We tested the “multiple-mating-for-more-sperm” hypothesis on individual young queens in a natural population of the leafcutter ant Atta colombica, a monogynous ant characterised by very large colonies and high colony longevity. We found that the number of sperm stored by queens was positively correlated with the number of mates per queen estimated through mother-offspring analysis with microsatellite DNA markers. Queen sperm stores increased on average by 30 million sperm for each additional mate. Life-history information for Atta indicate that the number of stored sperm observed is likely to constrain the reproductive lifespan of queens in nature. Multiple mating, despite costs, may therefore enhance the fitness of Atta queens because it enables them to store more sperm. Received: 19 September 1997 / Accepted after revision: 7 December 1997     

Mating strategies of queens in <Emphasis Type="Italic">Lasius niger</Emphasis> ants—is environment type important?

High relatedness among society members is believed important for the evolution of highly cooperative behaviours, yet queens of many social insects mate with multiple males which reduces nestmate relatedness and imposes also direct costs on queens. While theoretical models have suggested explanations for this puzzling queen behaviour, empirical studies fail to provide consistent answers especially for species with moderate levels of multiple mating. This may result from multiple mating only conferring benefits in some environments, as suggested by recent genetic variance theory and considerations on types of traits, direct costs and benefits. All concur in an expectation of higher levels of multiple mating in more complex or milder environments, and we perform a first, broad test of this idea by comparing mating strategies of queens in Lasius niger ants from northern (harsh, cold stressed) and southern populations (milder, greater bio-complexity). First, we collected new genetic data from Ireland and Southern France and then compared these to data on Swiss and Swedish populations. Queens from northern populations were near exclusively single mated and even at times inbred (in Ireland), whereas southern queens showed high levels of multiple mating, leading to more genetically diverse colonies in the south. Equally, paternity skew was greater in the north, as expected if northern queens only remate when their first mate transfers few sperm. Our findings are consistent with the idea that environment type may affect mating strategies in social insects and calls for an exploration of such effects.