Does the Tachet trait database report voltinism variability of aquatic insects between Mediterranean and Scandinavian regions?

Abstract

Labile traits are those that are not constrained by phylogeny and should respond directly to the environment through local adaptation or phenotypic plasticity. For example, voltinism (number of generations per year) is a labile trait that has been consistently related to latitude and, in particular, to temperature and photoperiod changes. Current trait databases include several labile traits that, at best, are coarsely coded to include potential intraspecific trait variability obtained from different literature sources. Given that these databases are used across large regions with contrasting environmental conditions or in small regions with particular environmental conditions, the reliability of these studies could be compromised at least for labile traits because of interpopulation variability. Based on a review of the literature on the life cycles of 317 aquatic insect species, we compared their types of voltinism in two regions with contrasting environmental conditions (the Mediterranean Basin and Scandinavia) with the information published by Tachet et al. (Invertebres d’eau douce: systematique, biologie, ecologie, 3rd edn. CNRS Editions, Paris, 2010) (i.e., potential number of generations per year). We found the expected higher prevalence of multivoltine life cycles in the Mediterranean Basin, whereas univoltine and semivoltine life cycles showed trends of prominence in Scandinavia. In addition, the life-cycle profiles of the genera included in the Tachet et al. database (hereafter TAC) were situated between those found in the Mediterranean Basin and Scandinavia, suggesting that this database properly represents voltinism variability across Europe. However, the use of this database exclusively for the northern or southern regions may be challenging because TAC is not able to accurately represent the life cycles of the species in these regions, especially for univoltine and multivoltine species. Future studies in stream ecology should thus put efforts into quantifying and understanding the role of intra-taxon trait variability in community assembly, at least for labile traits, to better understand trait-environment relationships.