Food web dynamics of irrigated rice fields at five elevations in Luzon, Philippines

Abstract

The above-water food webs of arthropod communities in irrigated rice fields on Luzon Island, Philippines, were studied over the growing season at five sites (Los Banos, Cabanatuan, Bayombong, Kiangan, Banaue) ranging in elevation from 22 m to 1524 m. Arthropod populations were vacuum-sampled at roughly weekly intervals from the date after seedlings were transplanted to flowering at each site. Site-and time-specific webs were constructed from a 687-taxa cumulative Philippines web and time-series of species present. Taxonomic composition, food web structure, and arthropod phenology were broadly similar across different sites. Arthropod abundance was inversely associated with altitude across the five sites, but numbers of taxa and links and six food web statistics showed no obvious increasing or decreasing trend with altitude. The rise of taxa, links and mean food chain length over the growing season at each site reflected an increase in plant size with age and, at some sites, an orderly accumulation of newly arriving herbivore, predator, parasitoid and omnivore species. At each site, herbivores built up faster than predators and parasitoids, and predators arrived faster than parasitoids; the difference between the latest and earliest sampling dates of first arrivals, averaged over the five sites, was 38, 63 and 73 days for herbivores, predators and parasitoids, respectively. Site-to-site consistencies in food web properties and first arrivals suggest that such patterns may be influenced more by crop age than by geography

Science-Based Risk Assessment for Nontarget Effects of Transgenic Crops

“…For example, even in the well-studied maize monoculture in north-central North America, there are more than 600 nontarget species (Warters 1969), of which nearly half have an unknown ecological role. The state of knowledge is similar for rice in Japan (Takahashi 1989) and in the Philippines (Schoenly et al 1996) and is likely to be worse for other crops and for nonagricultural ecosystems.…”

Diversity and abundance of arthropods in subtropical rice growing areas in the Brazilian south

“…The biodiversity existent in these locations is also of interest to other scientific disciplines such as ecology and conservation biology (Schoenly et al 1996;Bambaradeniya and Edirisinghe 2008). These studies are relevant because the arthropods play an important part in the structure and operation of the ecosystems and the maintenance of the biological diversity (Price 1984;Gullan and Cranston 1995;Tscharntke et al 2007;Scherr and McNeely 2008).…”

“…Many studies of diversity in arthropod communities in tropical areas all over the world have been published (Perfect and Cook 1994;Schoenly et al 1996;Kobayashi et al 1995;Bambaradeniya and Edirisinghe 2008;Latif et al 2009), but few on sub-tropical areas such as Southern Brazil are found in the literature at the present time.…”

Biological Control, Functional Biodiversity and Ecosystem Services in Insect Pest Management

“…In a crop like rice, intensive research has been carried out to study the food web patterns. Schoenly et al ( 1996 ) described 687 taxa consisting of pathogens, nematodes, mites, spiders, insects, snails and vertebrates and 10,000 consumer-resource trophic links. Rice crop is very unique in that it has three distinct ecological niches -the benthic, aquatic and the arboreal communities.…”

“…Arthropods were the dominant group of invertebrates (405 species), of which 55 species were rice pest insects, and 200 species were natural enemies of pest insects. It has been established that conserving the natural enemy guild directly helps in pest suppression (Way and Heong 1994 ;Schoenly et al 1996 ;Settle et al 1996 ) . In addition to invertebrate diversity rice paddies are also home to water birds (Acosta et al 2010 ) fi shes, frogs, molluscs, rats and snakes.…”