DOI: 10.5061/dryad.mw6m905z9
title: How hydrology and landscape shape Odonata assemblages in marshlands crossed by ditches

description: One of the major current ecological challenges is to understand how to
 reconcile human activities with biodiversity conservation concerns. This
 issue is particularly relevant in freshwater ecosystems where biodiversity
 is globally under severe threat. Artificial waterbodies, such as ditch
 networks, are part of the few remaining wetlands in agricultural
 landscapes and hence play a crucial role in maintaining aquatic
 biodiversity in these landscapes. We investigated the responses of adult
 Odonata assemblages at different spatial scales in a marshland crossed by
 ditches to two factors expected to be pivotal influences on assemblages.
 At the local scale, this was mainly the water regime in ditches and, at a
 broader scale, the composition of the landscape. Both taxonomic alpha and
 beta diversity, and functional trait composition were considered as
 response variables. Significant differences were found between the
 responses of the two Odonata suborders. We showed that Zygoptera species
 richness decreased and species turnover increased with the duration of
 drying episodes in ditches. Geographical distances between local
 assemblages as well as landscape characteristics, notably woodland cover,
 meadow cover, and ditch network length, also significantly shaped the
 distribution of Zygoptera. For Anisoptera, species richness was not
 explained by environmental variables and beta diversity was associated
 only with local conditions; it increased with increasing dissimilarity in
 water quality and riparian vegetation. We also found evidence of
 functional trait syndromes (combinations of correlated traits) in Odonata
 assemblages, but without clear relationships to environmental gradients.
 This study reveals the structuring role of water regime for Odonata in
 ditch networks and demonstrates the need to jointly consider environmental
 variables at different spatial scales to properly understand the
 distribution of Odonata. Our findings have important conservation
 implications as the water regime is heavily managed in such ecosystems.
 Even though the relationship between functional composition and
 environmental gradients was found to be of limited extent in this study,
 we discuss how it might provide new insights for Odonata assemblage
 structure and be useful, locally, for stakeholders and managers. Lastly,
 we call for further multiscale investigations considering both the
 taxonomic and functional responses of Odonata assemblages (functional
 analyses with multiple traits and several species being scarce in this
 taxonomic group) in other anthropogenic freshwater ecosystems to gather
 more lessons for their conservation.
description: The traits database is a compilation of different sources from
 the literature (all sources provided in the readme file).
 The Odonata were sampled and the environmental variables measured
 between 2015 and 2019 on 22 transects in the Marais poitevin, second
 largest marshland in France. All the protocoles are available in the
 associated paper in <em>Freshwater Biology</em>.