Parasitoid biodiversity in rice fields related to diversity of flowering flora in surrounding habitats in Hainan Island

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Alberto Barrion, S Villareal, J Catindig, International Rice Research Institute, Los Baños, Philippines and Ducheng Cai, Hainan University, Danzhou, Hainan, China

Nectar rich flowering plants and parasitoid biodiversity

In the July 2010 biodiversity exploration we collected a total of 3700 individuals of hymenopteran parasitoids using sweep nets in rice fields from 4 sites in Hainan Island. These samples were sorted, identified to species or morpho species and counted in the laboratory. Among the parsitoids we collected were several undescribed species, which were counted as morpho species. We computed the biodiversity index, species richness, S, using the rarefaction method available in ECOSIM (Gotelle and Entsminger, 2005) to enable the species richness index to be comparable between sites.

Map of Hainan Island showing the four sampling sites

In the rarefaction curves below, the species richness computed by ECOSIM were all significantly different.  Highest parasitoid biodiversity was found in Hai Kou which is more double that of  the lowest in Sanya.  The landscapes of these two sites were contrastingly different. In Hai Kou rice fields were mixed with other habitats with nectar rich flowering plants such as Ageratum sp and Lantana sp.  Since nectar is an important food resource for hymenopteran adults, rich diversity of such flowers can help conserve parasitoids. There is a huge diversity of parasitoids in rice fields and their contributions to natural biological control services to protect rice from pests are largely untapped. A recent review by Gurr et al 2011 showed that there are prospects of enhancing biological control through ecological engineering.  Researchers in Thailand found that when bunds were populated with flowering plants, parasitoid biodiversity doubled. In Vietnam parasitism of planthopper eggs significantly increased.

Rarefaction curves (species richness) of the four sampling sites

Table 1 summarizes parasitoid species richness in the four sampling sites with different landscapes, vegetation and agricultural practices.  The earlier analysis of samples showed that in Sanya, where is rice is grown intensively with highly simplified landscapes, the spider species biodiversity was also the lowest.

These studies indicate that bund conservation with nectar rich flowers can potentially restore biodiversity and resilience in rice ecosystems, thus replacing the need for prophylactic insecticide use. Labeled “Cong Nghe Sinh Thai” such practices are now carried out by hundreds of farmers in the Mekong Delta, Vietnam. In Thailand the Ministry of Agriculture is actively promoting ecological engineering approaches to restore biodiversity and resilience to pest attacks.

Reference

Gotelli, N.J. and Entsminger, G.L. 2005. Ecosim: Null Models Software for Ecology. Version 7.72. Acquired Intelligence Inc, & Kesey-Bear. Magurran, A.E. 1988. Ecological Diversity and Its Measurement. Croom Helm Ltd, London. http://www.garyentsminger.com/ecosim/index.htm

 

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