Sympatric Dreissena species in the Meuse River : towards a dominance shift from zebra to quagga mussels

The rapid spread of the quagga mussel, Dreissena rostriformis, in Western Europe is of particular concern since the species is known to have serious ecological and economic impacts, similar to those of the well-established zebra mussel, Dreissena polymorpha. This study aimed (1) to provide an update on the quagga mussel distribution in several Belgian inland waterways, and (2) to check if a shift in dominance between Dreissena species is occurring. Using density measurements and artificial substrate samplers, we compared population dynamics for both species at different time-points based on size-frequency distribution. Our results show that quagga mussels are spreading rapidly throughout Belgium via a number of possible invasion fronts based around large rivers and canals. The quagga mussel became the dominant dreissenid species in both the Meuse River and a number of Belgian canals. In just three years, quagga mussel’s relative abundance increased from 2.9% (±2.9) to 52.6% (±43.1) of the total dreissenid population in the Meuse River. The most rapid increase in abundance has occurred in the Albert Canal, where quagga mussels achieved a mean relative abundance of 80% two years after the first observation. In the Meuse River, the quagga mussel displays a faster growth rate and/or earlier reproduction than the zebra mussel. We discuss different mechanisms that could explain the quagga mussel’s apparent competitive advantage over the zebra mussel

Loss of genetic diversity and increased genetic structuring in response to forest area reduction in a ground dwelling insect: a case study of the flightless carabid beetle Carabus problematicus (Coleoptera, Carabidae)

1.Old growth temperate broadleaved forests are characterised by a large proportion of forest specialists with low dispersal capability. Hence, species bound to this habitat are expected to be highly susceptible to the effects of decreasing patch size and increasing isolation. 2. Here, we investigate the relative effect of both factors by genotyping individuals of a flightless and forest specialist beetle Carabus problematicus from 29 populations, sampled in 21 different forest fragments in Belgium, at eight microsatellite loci. 3. A high degree of genetic differentiation among fragments was observed, with populations from smaller forests being considerably more differentiated and characterised by a lower genetic diversity compared to those of larger forests. 4. A more detailed study on forest remnants of a former historic continuous woodland area revealed that population differentiation was high among, but not within remnants, irrespective of geographical distance. This suggests that patch fragmentation rather than geographical distance is the ultimate factor that hampers gene flow in this species. 5. he results indicate that gene flow among suitable habitat patches is primarily reduced by the inability of this specialised species to traverse the landscape matrix. This lack of dispersal may pose a serious threat for the persistence of C. problematicus and ecologically similar species, and suggests that present populations can best be protected by securing or increasing the size of existing habitat patches

Degenerate Tetraploidy Was Established Before Bdelloid Rotifer Families Diverged

Rotifers of Class Bdelloidea are abundant freshwater invertebrates known for their remarkable ability to survive desiccation and their lack of males and meiosis. Sequencing and annotation of approximately 50-kb regions containing the four hsp82 heat shock genes of the bdelloid Philodina roseola, each located on a separate chromosome, have suggested that its genome is that of a degenerate tetraploid. In order to determine whether a similar structure exists in a bdelloid distantly related to P. roseola and if degenerate tetraploidy was established before the two species separated, we sequenced regions containing the hsp82 genes of a bdelloid belonging to a different family, Adineta vaga, and the histone gene clusters of P. roseola and A. vaga. Our findings are entirely consistent with degenerate tetraploidy and show that it was established before the two bdelloid families diverged and therefore probably before the bdelloid radiation.Molecular and Cellular BiologyOrganismic and Evolutionary Biolog

First records of Dreissena rostriformis bugensis (Andrusov 1897) in the Meuse River

info:eu-repo/semantics/publishe

Salinity appears to be the main factor shaping spatial COI diversity of Corbicula lineages within the Chinese Yangtze River Basin

info:eu-repo/semantics/publishe

Phylogeny and androgenesis in the invasive Corbicula clams (Bivalvia, Corbiculidae) in Western Europe

info:eu-repo/semantics/publishe

Identification of the invasive form of Corbicula clams in Ireland

The basket clam genus, Corbicula, commonly known as the Asian clam, has become one of the most internationally high-profile and widespread aquatic invasive species. This genus is now considered to comprise a polymorphic species complex. The international invasion of Corbicula is characterised by four lineages, each fixed for one morphotype, genotype and haplotype combination: the American form (A) and European round form (R), the American form (C) and European saddle from (S), American form B, form round light colour (Rlc) and an intermediate between forms R and S known as Int. We investigated the genetic and morphometric makeup of each Irish population in order to establish which invasive lineages were present so as to identify the number of introductions to Ireland. A combination of morphometric, mitochondrial cytochrome oxidase subunit I (mtCOI) gene analysis and microsatellite markers were used to determine the invasive form at each Irish site. All Irish Corbicula samples conformed morphometrically to the invasive form A/R. All mtCOI sequences retrieved for 25 Irish individuals were identical to the international A/R form, while microsatellite markers again showed a common clustering with the international A/R forms of Corbicula. The combined approach of morphometries, total genomic DNA and microsatellite markers indicate only one form of Corbicula invaded Ireland; the international A/R form