Effect of environment on functional traits of co-occurring water beetles

Abstract

We investigated trait-environment relationships of co-occurring aquatic Coleoptera specifically true water beetles in anthropogenic ponds from the Western Ghats, India for the first time. Our objectives were to: (1) identify species assemblages; (2) study species traits; (3) study trait-environment relationships of co-occurring species. We analysed 132 samples collected using standardised quantitative method during the years 2016 and 2017. We found 16 significant assemblages using Fager's index, where most of the pairs have body size ratio of 1.3 or more. For example, Laccophilus parvulus and Hydaticus satoi pair has body size ratio of 3.98, and both are predators, indicating that body size is a function of food size. Moreover, factor analysis revealed three major swimming categories of studied beetles, namely fast swimmers, maneuverers and poor swimmers. Further, the RLQ analysis, and combined approach of RLQ and fourth-corner analysis showed that environmental variables affected species traits. For instance, odonate nymphs and submerged vegetation were positively associated with fast swimmers like Laccophilus inefficiens and Hydaticus satoi. The assemblage of congeners Hydroglyphus inconstans and H. flammulatus can be predator-mediated as these beetles showed negative association with odonate nymphs as well as competitive to obtain resource by showing positive association with chironomid larvae. Therefore, the traits studied were important for ecological performances of species in ponds. This study has also highlighted the importance of anthropogenic ponds in the Western Ghats as biodiversity refuges of ecologically unique and evolutionary old major extant lineages of water beetles.