Biological plant invasions pose a serious threat to native biodiversity and have received much attention, especially in terrestrial habitats. In freshwater ecosystems impacts of invasive plant species are less studied. We hypothesized an impact on organisms from the water column and from the sediment. We then assessed the impact of three aquatic invasive species on the plants and macroinvertebrates: Hydrocotyle ranunculoides, Ludwigia grandiflora and Myriophyllum aquaticum. Our research on 32 ponds in Belgium indicated that the reduction in the native plant species richness was a common pattern to invasion. However, the magnitude of impacts were species specific. A strong negative relationship to invasive species cover was found, with submerged vegetation the most vulnerable to the invasion. Invertebrate richness, diversity and abundance were measured in sediments of invaded and uninvaded ponds along a gradient of H. ranunculoides, L. grandiflora, and M. aquaticum species cover. We found a strong negative relationship between invasive species cover and invertebrate abundance, probably due to unsuitable conditions of the detritus for invertebrate colonization. Taxonomic compositions of aquatic invertebrate assemblages in invaded ponds differed from uninvaded ponds. Sensitive benthos, such as mayflies were completely absent in invaded ponds. The introduction of H. ranunculoides, L. grandiflora, and M. aquaticum in Belgian ponds has caused significant ecological alterations in the aquatic vegetation and the detritus community of ponds.

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This article provides a meta-analysis of quantitative data available in literature regarding the relation between termite numbers and the volume of their mounds for 24 species belonging to 13 genera. The leading question behind this analysis is: ''how do the respiratory gas exchanges regulate the size of termite mounds?'' This question is answered through the analysis of the log-log regression between the volume of the mound and the number of inhabitants. The most confident data support the hypothesis of a respiratory regulation that can be achieved through a relation between the termite numbers and (1) the volume of their mounds (slope of the regression near 1, Noditermes), (2) the surface of the outer walls of their mounds (slope of the regression near 0.67, Termitinae and Nasutitermes) or (3) a compromise between the surface of the outer walls of their mounds and some linear structures of their nests (slope of the regression between 0.67 and 0.33, Trinervitermes and Macrotermes). The way this is achieved is linked with the architecture of the mound. A confident relation was found between the number of individuals and the epigeal volume of their mounds for 18 species for which the most reliable data were provided. Three more accurate models are proposed for estimating the termite population based on the nest material and architecture and on the size of the termites.

Samples issued from intensive sampling in the Netherlands (1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001) and from extensive sampling carried out in the context of international campaigns (1998, 2000 and 2001) were revisited. Additional samples from artificial substrates (1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003) and other techniques (various periods) were analysed. The combined data provide a global and dynamic view on the Peracarida community of the River Meuse, with the focus on the Amphipoda. Among the recent exotic species found, Crangonyx pseudogracilis is regressing, Dikerogammarus haemobaphes is restricted to the Condroz course of the river, Gammarus tigrinus is restricted to the lowlands and seems to regress, Jaera istri is restricted to the 'tidal' Meuse, Chelicorophium curvispinum is still migrating upstream into the Lorraine course without any strong impact on the other amphipod species. After a rapid expansion Dikerogammarus villosus has continued its upstream invasion between 1998 and 2002 at a rate of 30-40 km per year, but no further progression was noticed in 2003. Locally and temporarily the native species (Gammarus fossarum and G. pulex) and naturalized species (G. roeseli and Echinogammarus berilloni) may have been excluded by the most recent invaders (mainly D. villosus), but none of the native and naturalized species has disappeared completely. Therefore, the number of amphipod species found in the River Meuse has increased. Moreover, the native and naturalized species keep on dominating the tributaries from which the recent invaders seem to be excluded. A changing Peracarida community structure is observed along the course of the River Meuse: four native or naturalized species inhabit the upstream (Lorraine) course, three invasive species dominate in the middle reach (Ardenne-Condroz zone), one exotic species is housed in the Border Meuse and three or four invasive species dominate the assemblages in the lowlands.

Termites are important ecosystem engineers. Yet they are often difficult to identify due to the lack of reliable species-specific morphological traits for many species, which hampers ecological research. Recently, termitologists working with West African termites (West African Termite Taxonomy Initiative) convened for a workshop with the aim of beginning to address this problem. Repeated determination of the same termite samples by the most renowned taxonomists for West African termites identified the huge scale of the problem, as less than 10% of all species could be unambiguously determined to the species level. Intensive discussions and comparisons increased the identification success to around 25% at the end of the workshop. Yet many groups remained problematic and molecular markers and barcoding techniques combined with species delimitation approaches will be needed to help resolve these existing taxonomic problems. Based on the outcome of this workshop, we propose concerted initiatives to address termite taxonomy on a global scale. We are convinced that dedicated workshops on regional taxonomy that follow a similar structured approach, with repeated determination of the same sample, will help overcome the difficulties that termite taxonomy faces. This initiative can also serve as a blueprint for other taxonomical groups that are difficult to identify.

Abstract-The larvae of Issoria lathonia L. feed in natural conditions on several Viola spp., among which are the zinc-accumulating Viola calaminaria (Gingins) Lej. and the nonmetal-accumulating Viola tricolor L. To examine how I. lathonia caterpillars cope with the naturally high foliar zinc concentration of V. calaminaria, we compared the growth of caterpillars reared on leaves varying in zinc concentration. Larvae were fed in controlled conditions with V. calaminaria and V. tricolor grown on noncontaminated soil (i.e., two low-Zn diets) and with V. calaminaria grown on zinc-enriched soil (i.e., one high-Zn diet). Larvae had a higher growth rate when fed with noncontaminated V. calaminaria compared to zinc-enriched V. calaminaria, suggesting that zinc slows down larval growth. However, larvae consumed more leaves of zinc-enriched V. calaminaria (ϩ45%; estimated from fecal mass) compared with noncontaminated V. calaminaria, suggesting that zinc accumulation would not be advantageous to plants. Caterpillars reared on high-zinc leaves regulate their internal zinc concentration through excretion of highly metal-concentrated feces. When kinetics of growth on both low-zinc diets were compared, it appeared that larval development was faster on noncontaminated V. calaminaria than on V. tricolor. This suggests that more nutrients or less feeding inhibitors in V. calaminaria account for fastest growth. Developmental rates on V. tricolor and on zinc-enriched V. calaminaria were similar, despite the high leaf zinc concentration of the latter species. Together with the abundance of V. calaminaria on calamine soils, this may explain why the largest populations of I. lathonia develop on V. calaminaria in Belgium.

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Seventy-four species, forms and varieties of Cubitermes Wasmann, 1906 have been studied, including taxa placed in synonymy with other species. Within this group of taxa, the enteric valve, mainly of the workers and soldiers, provided the best and the only clear-cut criteria for distinguishing some major subsets that are proposed here as species groups.The genus Cubitermes is re-described; the morphologies of the enteric valves are described in detail including the number of spatulae at the downstream end of the primary cushions; the possible presence of crests or bulges near the downstream end of the primary cushions; the overall shape of the primary cushions; the number of lateral supporting bristles; the kind of symmetry of the valve; and the structure of the secondary cushions. These characteristics are used to define nine species groups. For now, these groups have no taxonomic ranking but are helpful as regards species recognition. Identification keys for species groups are provided for soldiers and workers together with a partial key for imagines. Geographical ranges of the groups are also provided. On the basis of enteric valve morphology, some synonymies can no longer be validated: (a) C. planifrons Sjöstedt, 1924 is not a synonym of C. fungifaber (Sjöstedt, 1896); (b) C. kemneri Emerson, 1928 is not a synonym of C. zenkeri (Desneux, 1904); and (c) C. fungifaber var. elongata Sjöstedt, 1924 does not belong to the species C. fungifaber. Cubitermes planifrons and C. kemneri become valid again and C. fungifaber var. elongata is an invalid name.