No abstract

the americas have an elevated number of leishmaniasis cases (accounting for two-thirds of the worldwide disease burden) and circulating Leishmania species, and are therefore of interest in terms of epidemiological surveillance. Here, we present a systematic review of Leishmania parasite species circulating in the countries of the american continent, together with complementary information on epidemiology and geospatial distribution. A database was built from data published between 1980 and 2018 on Leishmania species identified in most of the American countries. A total of 1499 georeferenced points were extracted from published articles and subsequently located to 14 countries in the Americas. this database could be used as a reference when surveilling the occurrence of Leishmania species in the continent.

A large-scale field survey was undertaken in the Neste system (South-West France) to investigate the impact of pesticide inputs on the structure of riverine benthic diatom communities. A total of 18 sites in the "Coteaux de Gascogne" study area were sampled during periods of pesticide use over two consecutive years (2005-2006). The typology of the diatoms collected was determined using artificial neural networks generating patterns in diatom community composition that indicated the species influenced by pesticide inputs, combined with organic pollution. Small, pioneer species of the Achnanthales group were more frequent in the pesticide-contaminated assemblages, whereas slower colonizers were more often found in the sites where disturbance was lower. The Phytopixal approach, a means to assess the spatial contamination potential, provided valuable information about pesticide exposure and was a successful means of discriminating diatom assemblages, suggesting that a global estimate of pesticide pollution risk, although rough, would be more appropriate and more representative than sporadic pesticide analyses.

Species cooccurrence patterns give significant insights into the processes shaping communities. While biotic interactions have been widely studied using cooccurrence analyses in animals and larger plants, studies about cooccurrences among micro-organisms are still relatively rare. We examined stream diatom cooccurrences in France through a national database of samples. In order to test the relative influence of environmental, biotic and spatial constraints on species’ incidence distribution, cooccurrence and nestedness patterns of real communities were compared with the patterns generated from a set of standard and environmentally constrained null models. Real communities showed a higher level of segregation than the most conservative standard null models, but a general aggregation of cooccurrences when compared to environmentally constrained null models. We did not find any evidence of limiting similarity between cooccurring species. Aggregations of species cooccurrences were associated with the high levels of nestedness. Altogether, these results suggested that biotic interactions were not structuring cooccurrences of diatom species at our study scale. Instead, the patterns were more likely to be related with colonization patterns, mass effect, and local temporal dynamics of diatom biofilms. We further highlight that the association of standard and environmentally constrained null models may give realistic insight into the cooccurrence patterns of microbial communities.