Amphipods are brooding peracaridan crustaceans whose young undergo direct development, with no independent larval dispersal stage. Most species are epibenthic, benthic, or subterranean. There are some 1,870 amphipod species and subspecies recognized from fresh or inland waters worldwide at the end of 2005. This accounts for 20% of the total known amphipod diversity. The actual diversity may still be several-fold. Amphipods are most abundant in cool and temperate environments; they are particularly diversified in subterranean environments and in running waters (fragmented habitats), and in temperate ancient lakes, but are notably rare in the tropics. Of the described freshwater taxa 70% are Palearctic, 13% Nearctic, 7% Neotropical, 6% Australasian and 3% Afrotropical.

In 1998, a unique subterranean ecosystem was discovered in numerous isolated calcrete (carbonate) aquifers in the arid Yilgarn region of Western Australia. Previous morphological and genetic analyses of a subterranean water beetle fauna suggest that calcrete aquifers are equivalent to closed island habitats that have been isolated for millions of years. We tested this hypothesis further by phylogeographic analyses of subterranean amphipods (Crangonyctoidea: Paramelitidae and Hyalidae) using mitochondrial DNA sequence data derived from the cytochrome oxidase I gene. Phylogenetic analyses and population genetic analyses (samova) provided strong evidence for the existence of at least 16 crangonyctoid and six hyalid divergent mitochondrial lineages, each restricted in their distribution to a single calcrete aquifer, in support of the 'subterranean island (archipelago) hypothesis' and extending its scope to include entirely water respiring invertebrates. Sequence divergence estimates between proximate calcrete populations suggest that calcretes have been isolated at least since the Pliocene, coinciding with a major aridity phase that led to the intermittent drying of surface water. The distribution of calcretes along palaeodrainage channels and on either side of drainage divides, have had less influence on the overall phylogeographic structure of populations, with evidence that ancestral crangonyctoid and hyalid species moved between catchments multiple times prior to their isolation within calcretes. At least two potential modes of evolution may account for the diversity of subterranean amphipod populations: dispersal/vicariance of stygobitic species or colonization of calcretes by surface species and independent evolution of stygobitic characteristics.

The pattern of decline in a mining region is examined using a case study of Schefferville. A critical examination is made of Lucas's model of youth to maturity in community development, and a further two stages are suggested -winding down and closure of a town. The discussion centres on the characteristics of community and corporate winding down in Schefferville: the restructuring of the local workforce, disinvestment, relocation of capital, and company withdrawal from housing, municipal affairs, and public services.Les auteurs entreprennent une Ctude du processus de dCclin dans les rCgions minikres en se servant de l'exemple de Schefferville. En partant d'une critique du modtle fait par Lucas sur les stages d'tvolution et de maturation d'une communautk, les auteurs proposent d'y ajouter deux autres Ctages, soit celui de dtclin et celui de la fermeture dkfinitive d'une ville. La p6riode de dCclin est donc caractCrisCe par la restructuration de la main d'ceuvre, par la diminution des investissements, par la relocalisation de capitaux, et par le retrait de la sociktk minikre au niveau du logement, des affaires municipales, et des services publics dans la ville.Single-industry towns and regions are a major feature of the economic geography of resource extraction in Canada. Almost 25 per cent of the population outside the metropolitan areas lives in these communities, and their dependence on a single economic base has been accompanied by a boom-and-bust pattern of development. Studies on the development of resource-based towns have ordinarily focused on the establishment of new communities, on town and regional planning, and on the growth of the economic base. ' Little attention has been paid to processes of decline or to the phase of uncertainty evident in settlements where decline is taking place. In this paper we seek to close this gap by examining the process of winding down and some of its social and economic impact, notably community instability, on the town of Schefferville in the subarctic iron-mining region of the Quebec-Labrador trough.* Long-term development in a mining region is subject to fluctuations in production and to cycles and phases of investment and disinvestment. Growth phases are marked by increases of production and investment and by expansion of physical facilities, while declining phases are characterized by contractions in production and expenditures, decrease in investment, loss of social capital, and loss of population. In the most extreme cases, townsites and communities may be abandoned. Indeed, plant or mine closures can result from many situations: from abrupt changes in mineral prices, from fluctuations in market conditions, from declines in the quantity or quality of ore, from technological changes, or from restructuring decisions. Such closures may be preceded or accompanied by a number of adjustments in the local industrial base, in the workforce, and in the community, as it enters a period of decline.

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