Diversity of Hymenopteran Egg Parasitoids in Organic and Conventional Paddy Ecosystems

Organic farming; cultivation without chemical pesticides and fertilizers, has been known to promote the general plant diversity as well as animal diversity including many groups of animal taxa. The objectives of this study was to prepare a generic level systematic inventory of egg parasitoids, and compare the species diversity and richness between organic and conventional paddy ecosystems, which are two differently managed agroecosystems. The study also aimed to examine whether the differences in the management practices have any vital effect on the diversity of the functional groups, the hymenopteran egg parasitoids in particular, when the major physical parameters like soil, temperature and rainfall, remained constant. Altogether 40 species of egg parasitoids in 23 genera belonging to 5 families (Platygastridae, Mymaridae, Encyrtidae, Eulophidae and Trichogrammatidae) were identified in both paddy ecosystems. Out of the 40 species, 29 belong to 16 genera of family Platygastridae. The number of species found in organic and conventional ecosystems was 32 and 22, respectively. Simpson’s diversity index was also higher (0.978) in organic ecosystem compared to conventional paddy ecosystem (0.878).The functional group analysis of hymenopteran egg parasitoids reflected a uniform pattern of higher functional redundancy in all the functional groups in the organic ecosystem than in the conventional ecosystem. However, egg parasitoid communities present in both ecosystems share less taxonomic similarities.

Tropical Agricultural Research Vol. 23 (4): 300-308 (2012)