Molecular phylogeny of South Indian aphthona spp. (Coleoptrea:chrysomelidae)

Abstract

Molecular phylogenetics is a disciplinary research of developmental relations among species using molecular sequences. The analytical methods used in molecular phylogenetics were originally developed to reveal developmental patterns, but now it is used in several fields, such as systematic biology and biodiversity, molecular epidemiology, cell function recognition etc. For such purposes, molecular phylogenetics is a basic area of science that most scientists need to comprehend the background. Phylogenetic analysis of DNA sequences has become an important tool for studying the evolutionary history of organisms. Since the rate of sequence evolution varies extensively with gene or DNA segment; one can study the evolutionary relationships of virtually all levels of classification of organisms. Phylogenetic analysis is also important for clarifying the evolutionary pattern of multigene families as well as for understanding the adaptive evolution at the molecular level.

The flea beetle genus Aphthona is broad and contains over 350 species that are spread across the biogeographic regions of the Palearctic, Oriental, African, and Australian Old World. Aphthona species are generally mesophilous, however they are diverse ecologically, so that they occur in a wide variety of biogeographic regions and inhabit almost all known habitat ranging from low land rainforest to high altitude coniferous mountains and from desert s to sub artic environs. Most frequently, Aphthona is discovered in wet meadows or on vegetation along waterways and streams. This flea beetle genus is important because of the usefulness of some species in controlling invasive weeds. The fact that a number of Aphthona species feed on Euphorbiacea and the tendency towards monophagy makes them ideal candidates for biological control against weed plants belonging to Euphorbiacea family. Although several Indian workers like Prathapan (2003&2010) have contributed towards classical studies which helped to resolve the taxonamic mystery of Indian Aphthona species, information on the molecular systematic of Indian Aphthona spp. is scant. Through this study the phylogenetic status of the south Indian Aphthona spp. is investigated.

The study entitled Molecular phylogeny of south Indian Aphthona spp. was conducted at Dept. Plant Biotechnology and Dept. Agricultural Entomology, College of Agriculture, Vellayani. The objective of the study was to identify the genetic structure of South Indian Aphthona spp. using mitochondrial DNA markers and to identify patterns of intra generic genetic diversity among South Indian Aphthona spp. For this Aphthona beetles were collected from various parts of western ghats including different sites of Kerala and Karnataka. Plants from which Aphthona beetles were collected belong to the family Euphorbiaceae. The ten collected specimens were identified using the morphological keys. From the identified specimen’s total genomic DNA was isolated using the Rogers and Benedict (1994) protocol. The DNA was used to amplify the cytochrome oxidase subunit 1 gene, using the selected primers. Both the primers gave amplicons in the size range 650-680. These amplicons were successfully sequenced. All the 10 sequences were used to generate an intragenomic phylogenetic tree using MEGA software. The phylogenetic tree differentiated all the 10 species. Out of the ten species, A. glochidionae & A. tamila, A. chrozophorae & A. chrozophorae 2, A. marataka & A. macarangae were found to be closely related. From the genetic distance calculated based on the CO1 sequences the species A. tamila & A. glochidionae, A. marataka & A. macarangae, A. chrozophorae & A. chrozophorae 2 were found to be synonymous respectively. The morphological and molecular results correlated in confirming the colour polymorphism among the south Indian Aphthona spp. The species A. tamila & A. glochidionae, A. marataka & A. macarangae were confirmed as colour morphs.