Studies on diving beetles Coleoptera Dytiscidae of Kerala

Abstract

Diving beetles (Coleoptera: Dytiscidae) are the largest family of aquatic beetles. They inhabit almost all kinds of freshwater habitats but preferably lentic habitats. Their morphology is highly adapted to lead an aquatic life. They are holometabolous insects and are univoltine, semivoltine or multivoltine. They are consumed as food in various countries around the globe including India. They are also linked to different human cultures and mentioned in literature.This study deals with the taxonomy, phylogeny and association of species presenceand absence with different habitats based on the presence or absence of species and selected water parameters. Different freshwater habitats in the 14 districts were sampled. One hundred and sixty sites were involved in the study. The freshwaterhabitats were classified into 34 different types. Fifty-three species were observed andrecorded. Subfamily Hydroporinae formed the largest subfamily and Colymbetinae formed the smallest subfamily. Two species are new reports to India. Eight speciesare reported first time from Southern India. One subfamily, four genera and 23 speciesare new records to Kerala state. Detailed descriptions, information on habitat andlocation data and distribution of the species in India are provided.A checklist for the diving beetles of Kerala was prepared by compiling the speciesreports in previous studies and the current study. This has increased the number of diving beetles reported from Kerala from 51 species to 74 species.The phylogenetic study of Dytiscidae involving 26 sequences from 24 species underfive subfamilies and 10 generareveals monophyly of genera Leiodytes,Hydroglyphus, Clypeodytes, Hydrovatus and Sandracottus. Meanwhile GeneraCopelatus, Laccophilus and Hydaticus form paraphyletic groups. The higher-level phylogeny could not resolve indicating the need for further studies involving more species and gene sequences. Similarity of different habitats based on the presence and absence of 36 species indifferent habitats and the effect of selected water parameters on species cooccurrence was examined based on data collected from 160 study sites. The results showed thatthere is similarity between smaller habitats, larger habitats and between smaller andlarger habitats. Similarity between smaller habitats can be due to the presence ofspecialists and also due to water depth. Similarly larger habitats shows similarity due to the specialists of that particular habitat. Similarity between smaller and largerhabitats could be due to the dispersal of species from larger habitats to new temporary habitats for their survival. Congeneric species (e.g. Copelatus boukali, C. davidi and C. sociennus) as well as species in different genera were found to be coexisting (e.g. Lacconectus regimbarti, Hydaticus ricinus and Hyphydrus renardii). This study presents pioneering and baseline data on diving beetles of Kerala from a taxonomical,phylogenetic and ecological perspective. Many species commonly distributed in Kerala as well as the neighbouring states have never been formally reported and this study thus becomes a pioneering document for the same. Many first reports from the study area indicate the lack of intensive studies on this group. Based on the experiences of this study it is recommended that intensive and repeated sampling in a smaller study area and phylogenetic examinations based on a multigene and morphometric approach could yield novel species to the fauna and insights in the systematics and evolution.