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Over the past decade, Europe's Water Framework Directive provided compelling reasons for developing tools for the biological assessment of freshwater ecosystem health in member States. Yet, the lack of published study for Europe's overseas regions reflects minimal knowledge of the distribution patterns of aquatic species in Community's outermost areas. Benthic invertebrates (84 taxa) and land-cover, physical habitat and water chemistry descriptors (26 variables) were recorded at fifty-one stations in Martinique, French Lesser Antilles. Canonical Correspondence Analysis and Ward's algorithm were used to bring out patterns in community structure in relation to environmental conditions, and variation partitioning was used to specify the influence of geomorphology and anthropogenic disturbance on invertebrate communities. Species richness decreased from headwater to lowland streams, and species composition changed from northern to southern areas. The proportion of variation explained by geomorphological variables was globally higher than that explained by anthropogenic variables. Geomorphology and land cover played key roles in delineating ecological sub-regions for the freshwater biota. Despite this and the small surface area of Martinique (1080 km 2 ), invertebrate communities showed a clear spatial turnover in composition and biological traits (e.g., insects, crustaceans and molluscs) in relation to natural conditions. RÉSUMÉPatrons de distribution des invertébrés et typologie des rivières pour la mise en oeuvre de la Directive Cadre Européenne sur l'Eau en Martinique, Antilles Françaises Mots-clés :indicateurs biologiques, outre-mer, Au cours de la dernière décennie, la Directive Cadre Européenne sur l'Eau a promu le développement d'outils de bioindication de la qualité des eaux douces au sein des états membres. L'absence de travaux sur l'Outre-Mer révèle une connaissance minimale de la distribution des espèces aquatiques dans ces régions de l'Europe. Les invertébrés benthiques (84 taxons), ainsi que des variables décrivant l'utilisation des terres, l'habitat physique et la chimie de l'eau (26 variables) ont été

Over the past decade, Europe's Water Framework Directive (WFD) has prompted a large amount of ecological research aiming at establishing river typologies and ecological indicators in member States. Yet, the lack of robust bioindicators in Europe's overseas regions arguably reflects minimal knowledge of the distribution patterns of aquatic species in the Community's outermost areas. Specifically, there has been no published classification of rivers for any European overseas region. Fifty‐one sites were sampled for benthic invertebrates and environmental variables (land‐cover, physical habitat, and water chemistry) in Guadeloupe, French Lesser Antilles. Redundancy analysis and k‐means clustering were used to bring out spatial patterns in species composition in relation to environmental conditions. Our results highlighted the importance of land cover and geomorphology in delineating three ecological sub‐regions (clusters) for freshwater invertebrates. Deviation from predictable community structure only occurred when river sites were subjected to harsh water chemistry alterations (urban runoff, wastewaters). Changes in species richness did not detect environmental stress efficiently within a given sub‐region, probably because most sites are naturally species‐poor due to the insular context and/or because disturbance is often weak. However, differences existed between clusters in terms of species identity and numerical dominance. Our a posteriori typology of sites was compared to local a priori expert opinion of river health, in an attempt to better characterize the network of survey sites, and to target sites for reference conditions.

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