Biodiversité des Isopodes terrestres dans les agroécosystèmes de la Majerda (Tunisie)

We studied the seasonal variation of isopods diversity and the effects of cultivation types on the isopods communities. The study consisted of twelve plots in the Majerda agroecosystems. We compared three types of cultivation : market gardening, vegetable crops and orchards at four seasons. For each season, isopods were collected by pitfalls traps and also by hand (handsearch) to complete the list of species in the studied plot. Overall, eight isopod species were found. Porcellionidae was the best represented family with five species, followed by Armadillidiidae and Philosciidae, represented by two and one species, respectively. Porcellio laevis and Porcellio variabilis were the most observed in all seasons and types of cultivation. According to the cultivation types, significant differences of activity-density of isopods were seen between autumn and spring. Whatever the season, isopods were more diverse in vegetable crops and orchards than in market gardening cultivation. Multivariate analyses showed a difference of species occurrence related to physical and chemical soil characteristicsNous avons entrepris l'étude de la variation saisonnière de la diversité et les effets des types de cultures sur les Isopodes dans douze parcelles de l'agroécosystème de la Majerda. Trois types de cultures ont été comparés (culture maraîchère, culture vivrière et arboriculture) durant quatre saisons. À chacune de ces saisons les Isopodes ont été collectés à l'aide de pièges-fosses ainsi que par collecte à la main afin de compléter la liste des espèces de chaque site. Huit espèces d'Isopodes ont été trouvées. Les Porcellionidés, avec cinq espèces, étaient la famille la mieux représentée, suivie par les Armadillidiidés et Philosciidés, avec respectivement deux et une espèces. Porcellio laevis et Porcellio variabilis furent les plus observés en fonction des saisons et des types de cultures. Des différences significatives d'activité et de densité des Isopodes sont apparues entre l'automne et le printemps selon les types de cultures. Quelle que soit la saison, les Isopodes s'avérèrent plus divers dans les cultures vivrières et les vergers que dans les maraîchages. Des analyses multivariée ont montré une différence de l'occurrence des espèces en fonction des paramètres physiques et chimiques du sol

The first record of translocated white-clawed crayfish from the Austropotamobius pallipes complex in Sardinia (Italy)

<p>The white-clawed crayfish <em>Austropotamobius pallipes </em>complex is native to Europe, being present in 18 European countries, Italy included. However, the number and abundance of its populations are today restricted and it has been recently classified as “endangered” by IUCN (International Union for Conservation of Nature). Here, we report the first record of this freshwater crayfish in Sardinia Island (Italy). Using a fragment of the mitochondrial DNA 16S rRNA gene, we identified three haplotypes that correspond to the <em>A. italicus meridionalis </em>subclade. We provide information about the sampling area, population density and finally discuss hypotheses about the occurrence of this population in Sardinia, comparing it with other Mediterranean populations. Our results improve the existing knowledge about the phylogeography of the taxon across Italy, confirming its complex pattern of distribution. In addition to the non-native status of the Sardinian <em>A. i. meridionalis</em> crayfish, we showed that the most proximal Mediterranean population of white-clawed crayfish existing in Corsica belongs to <em>A. pallipes</em> from Southern France.</p

A Thirty Million Year-Old Inherited Heteroplasmy

Due to essentially maternal inheritance and a bottleneck effect during early oogenesis, newly arising mitochondrial DNA (mtDNA) mutations segregate rapidly in metazoan female germlines. Consequently, heteroplasmy (i.e. the mixture of mtDNA genotypes within an organism) is generally resolved to homoplasmy within a few generations. Here, we report an exceptional transpecific heteroplasmy (predicting an alanine/valine alloacceptor tRNA change) that has been stably inherited in oniscid crustaceans for at least thirty million years. Our results suggest that this heteroplasmy is stably transmitted across generations because it occurs within mitochondria and therefore escapes the mtDNA bottleneck that usually erases heteroplasmy. Consistently, at least two oniscid species possess an atypical trimeric mitochondrial genome, which provides an adequate substrate for the emergence of a constitutive intra-mitochondrial heteroplasmy. Persistence of a mitochondrial polymorphism on such a deep evolutionary timescale suggests that balancing selection may be shaping mitochondrial sequence evolution in oniscid crustaceans

Effect of agricultural practices on terrestrial isopods: a review

Terrestrial isopods (approximately 3700 known species in the world) are encountered in temperate and tropical regions, from the seashore to high altitudes and from floodplain forests to deserts. They are known to contribute to soil biodiversity. Environmental factors and anthropogenic actions, particularly land use changes such as primarily agricultural practices, and urbanization affect soil biodiversity and their functions. Human practices, such as soil tillage, pesticide application, chemical pollution, along with soil acidification adversely affect isopod abundance and diversity. It is thus important to recognise the vital contributions of soil biodiversity in support of environmental quality protection through maintaining soil functions and their significance to sustainable land use. This review will also deal with recent studies attempting to evaluate the impact of returning to an environmentally friendly agriculture by restoring refuge habitats such as grass strips, hedges, and woodlands for terrestrial isopods