Coexisting Cyclic Parthenogens Comprise a Holocene Species Flock in Eubosmina

Background: Mixed breeding systems with extended clonal phases and weak sexual recruitment are widespread in nature but often thought to impede the formation of discrete evolutionary clusters. Thus, cyclic parthenogens, such as cladocerans and rotifers, could be predisposed to ‘‘species problems’ ’ and a lack of discrete species. However, species flocks have been proposed for one cladoceran group, Eubosmina, where putative species are sympatric, and there is a detailed paleolimnological record indicating a Holocene age. These factors make the Eubosmina system suitable for testing the hypotheses that extended clonal phases and weak sexual recruitment inhibit speciation. Although common garden experiments have revealed a genetic component to the morphotypic variation, the evolutionary significance of the morphotypes remains controversial. Methodology/Principal Findings: In the present study, we tested the hypothesis of a single polymorphic species (i.e., mixing occurs but selection maintains genes for morphology) in four northern European lakes where the morphotypes coexist. Our evidence is based on nuclear DNA sequence, mitochondrial DNA sequence, and morphometric analysis of coexisting morphotypes. We found significant genetic differentiation, genealogical exclusivity, and morphometric differentiation for coexisting morphotypes. Conclusions: We conclude that the studied morphotypes represent a group of young species undergoing speciation wit

L'applicabilité des métriques de composition de macrophytes pour étudier l'eutrophisation des lacs européens

International audienceThe European Water Framework Directive adopted in 2000, despite being prescriptive, has stimulated the development of a diverse array of biological assessment methods in Europe. The multitude of indicators currently used in biomonitoring lacks consistency and thus constrains the comparability of assessments at an international scale. Therefore, there is an argument to define and validate metrics with more universal application that can be applied EU-wide. We explored two metrics based on macrophyte taxonomic composition, the empirically based Intercalibration Common Metric for lake macrophytes (ICMLM) and the expert-based Ellenberg Index (EI), for their ability to detect eutrophication in different types of European lowland lakes. Data from 1474 unique lake-years from 11 countries were used to explore relationships between these metrics and the seasonal mean concentration of total phosphorus (TP) using linear regression. ICMLM gave a linear and relatively strong (R = 0.72, p 0.2 meq L-1 and significantly weaker in less buffered lakes. EI performed better in lakes with alkalinity < 1.0 meq L-1, whereas in high alkalinity lakes the response was significantly weaker. In all the lakes and in lakes from all the size, depth and alkalinity types, ICMLM was more strongly correlated with TP than EI and was proportionally less sensitive to alkalinity. We also tested the effect of including helophytes on the metric response to eutrophication pressure by comparing the strength of the relationships to TP of the Ellenberg Index calculated firstly using only hydrophyte taxa (EI HYDR) and secondly using all macrophyte taxa including both hydrophytes and emergent vegetation (EI TOT). The differences in metric performance in all the lakes and all the size, depth and alkalinity types, except for the Nordic lakes, were non-significant. Thus, including helophytes generally did not significantly improve the strength of the EI-TP relationships

Directive Cadre Européenne sur l'Eau, rapport technique : Méthodes d'évaluation de l'état écologique basées sur les macrophytes pour les lacs du Central Baltic

The European Water Framework Directive (WFD) requires the national classifications of good ecological status to be harmonised through an intercalibration exercise. In this exercise, significant differences in status classification among Member States are harmonized by comparing and, if necessary, adjusting the good status boundaries of the national assessment methods. Intercalibration is performed for rivers, lakes, coastal and transitional waters, focusing on selected types of water bodies (intercalibration types), anthropogenic pressures and Biological Quality Elements. Intercalibration exercises were carried out in Geographical Intercalibration Groups - larger geographical units including Member States with similar water body types - and followed the procedure described in the WFD Common Implementation Strategy Guidance document on the intercalibration process (European Commission, 2011). In a first phase, the intercalibration exercise started in 2003 and extended until 2008. The results from this exercise were agreed on by Member States and then published in a Commission Decision, consequently becoming legally binding (EC, 2008). A second intercalibration phase extended from 2009 to 2012, and the results from this exercise were agreed on by Member States and laid down in a new Commission Decision (EC, 2013) repealing the previous decision. Member States should apply the results of the intercalibration exercise to their national classification systems in order to set the boundaries between high and good status and between good and moderate status for all their national types. Annex 1 to this Decision sets out the results of the intercalibration exercise for which intercalibration is successfully achieved, within the limits of what is technically feasible at this point in time. The Technical report on the Water Framework Directive intercalibration describes in detail how the intercalibration exercise has been carried out for the water categories and biological quality elements included in that Annex. The Technical report is organized in volumes according to the water category (rivers, lakes, coastal and transitional waters), Biological Quality Element and Geographical Intercalibration group. This volume addresses the intercalibration of the Central Baltic Macrophyte ecological assessment methods