Length-mass relationships for aquatic insects of Navarino Island, extreme southern Chile

In aquatic insects, body size and shape are key traits that may indicate phenotypic plasticity or adaptations to their hydrological landscape. Liodessus chilensis is a small and poorly-known aquatic beetle that inhabits permanent and temporary bodies of water. Accompanying the report of the species in different habitats of Navarino Island, an update of its description is presented. Additionally, body shape variation of different populations of L. chilensis is evaluated. Geometric morphometric analysis and multivariate regressions on the body shape of L. chilensis show variation mainly in the posterior part of the elytra and could indicate plasticity linked to the nature of the habitats in which they occur. The population of temporary pools presents shorter and broader elytra in their terminal part, while those that inhabit peat bogs and wetlands are longer and elongated. Additionally, a positive allometric effect was found, indicating that in addition to the differences in body shape, populations inhabiting temporary pools tend to be smaller in size. The plasticity of forms of L. chilensis as well as their permanent and temporary habitats can be considered as sentinels of environmental changes. These results are relevant for the Magallanes region, which has recently been declared prone to drought.