Diversity and abundance of different groups of insects attracted to light traps in dryland agro-ecosystem and temporal associations among these groups

Abstract

A study was conducted to assess (a) temporal patterns of insect activity and (b) the diversity measures of biological heterogeneity using insects attracted to light at UAS, GKVK. A total of 209,098 individuals belonging to 764 morpho-species or Operational Taxonomic Units (OTUs), representing 101 families from 12 orders were collected through the two years of sampling. The Simpson's index of diversity computed for all insects was (0.9732), the Shannon-Wiener index was 4.4443 and Avalanche index was 1.1693. Insect diversity and abundance exhibited clear temporal patterns through the two-year study. Number of OTUs collected increased nonlinearly with the number of insets collected in the 26 samples from the light trap. Thus, the species richness appeared to exhibit the typical 'Specie-Area relation', with the number of individuals collected. Insects were abundant and also diverse during summer and post rainy seasons but decreased during winter and rainy seasons. In fact, all the five species orders showed similar trend through the seasons. Our results also showed that the Coleoptera is a good indicator of the total insect diversity perhaps because it is the most predominant component of the collections made in our study; since Coleoptera constitutes about 40 per cent of all insects known, diversity of this group it is not unexpected that it is a good indicator of total diversity. Further, diversity of this group was also correlated with the diversity of Hemiptera and Lepidoptera.