In invasion processes, both abiotic and biotic factors are considered essential, but the latter are usually disregarded when modeling the potential spread of exotic species. In the framework of set theory, interactions between biotic (B), abiotic (A), and movement-related (M) factors in the geographical space can be hypothesized with BAM diagrams and tested using ecological niche models (ENMs) to estimate A and B areas. The main aim of our survey was to evaluate the interactions between abiotic (climatic) and biotic (host availability) factors in geographical space for exotic symbionts (i.e., non-free-living species), using ENM techniques combined with a BAM framework and using exotic Entocytheridae (Ostracoda) found in Europe as model organisms. We carried out an extensive survey to evaluate the distribution of entocytherids hosted by crayfish in Europe by checking 94 European localities and 12 crayfish species. Both exotic entocytherid species found, Ankylocythere sinuosa and Uncinocythere occidentalis, were widely distributed in W Europe living on the exotic crayfish species Procambarus clarkii and Pacifastacus leniusculus, respectively. No entocytherids were observed in the remaining crayfish species. The suitable area for A. sinuosa was mainly restricted by its own limitations to minimum temperatures in W and N Europe and precipitation seasonality in circum-Mediterranean areas. Uncinocythere occidentalis was mostly restricted by host availability in circum-Mediterranean regions due to limitations of P. leniusculus to higher precipitation seasonality and maximum temperatures. The combination of ENMs with set theory allows studying the invasive biology of symbionts and provides clues about biogeographic barriers due to abiotic or biotic factors limiting the expansion of the symbiont in different regions of the invasive range. The relative importance of abiotic and biotic factors on geographical space can then be assessed and applied in conservation plans. This approach can also be implemented in other systems where the target species is closely interacting with other taxa.

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This study was carried out as a survey of the species of decapod Crustacea found along the Black Sea coasts of Istanbul. It also aims to report on some of their ecological properties. Samples were collected at 36 stations during 2000 and 2001 from depths of 0.5-65 m using a scoop net, dredge, beam-trawl, or trammel net. A total of 15 species of decapod crustaceans was identified. One of these, Philocheras fasciatus (Risso, 1816), is herein reported for the first time from the Turkish coastal waters of the Black Sea. Primary hydrographie conditions such as temperature (range 8.0-21.8°C), salinity (16.7-17.8%o), and dissolved oxygen (4.5-9.0 mg/1) were recorded at each sampling occasion. RÉSUMÉCette étude a été réalisée pour recenser les espèces de Crustacés décapodes trouvés le long des côtes de la mer Noire à Istanbul. Elle avait aussi pour but d'établir certaines de leurs caractéristiques écologiques. Des échantillons ont été collectés dans 36 stations en 2000 et 2001 à des profondeurs de 0,5 à 65 m en utilisant un filet écope, une drague, un chalut à perche, ou un trémail. Un total de 15 espèces de crustacés décapodes ont été identifiées. L'une de celles-ci, Philocheras fasciatus (Risso, 1816), est mentionnée ici pour la première fois des eaux côtières turques de la mer Noire. Les caractéristiques hydrographiques principales telles que la température (intervalle 8,0-21,8°C), la salinité (16,7-17,8%o), et l'oxygène dissous (4,5-9,0 mg/1) ont été mesurées à chaque échantillonnage.

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