Arthropod diversity and abundance in sugarcane germplasm at Kannur, India

The diversity and abundance of terrestrial arthropod fauna were assessed in sugarcane germplasm collection maintained in a crop-island scenario in the heartland of the Kannur district, Kerala State, India. A total of 523 invertebrates belonging to ten taxonomic orders viz., Orthoptera, Coleoptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera, Odonata, Blattodea, Mantodea and Araneae were recorded in the study. In terms of abundance, Hymenoptera recorded the highest constituting 21.41% of all individual morpho-species recorded, followed by the Coleoptera with 20.84% and Hemiptera with 19.50%. Arthropod richness across crop assemblages revealed that various crop assemblages tend to support specific arthropod groups in greater abundance. The mean arthropod taxa diversity per week differed significantly between different crop assemblages and there was a considerable level of decrease in number in the post man-made disturbance scenario. In both pre and post-man-made disturbance scenarios, the highest mean arthropod per week was recorded in the blocks of Saccharum officinarum followed by the blocks of foreign hybrids, Saccharum species complex and Indian hybrids block. The Shannon index value ranged from 1.86 to 2.12. The highest diversity (H’= 2.12) of communities was found in the block of foreign hybrid crop assemblage whereas lowest diversity (H’= 1.86) was recorded in the Saccharum species complex. The Simpsons index complemented the results of Shannon index. Importantly, the man-made disturbance had contributed negatively to the community diversity in the crop assemblages. In a pair-wise comparison measured through Jaccard’s Index revealed that crop assemblages had expressed considerable differences in the community and diversity among them in both pre and post man-made disturbance scenarios.