Trophic Structure of Small Invertebrates Inhabiting Litter of a Monsoon Tropical Forest
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Trophic Structure of Small Invertebrates Inhabiting Litter of a Monsoon Tropical Forest E. E. Semeninaa, *, O. L. Rozanovaa, Nguyen Van Thinhb, and A. V. Tiunova, b aSevertsov
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Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, 119071 Russia Russian–Vietnamese Tropical Scientific and Technological Center, Southern Branch, Ho Chi Minh, 700000 Vietnam *e-mail: [email protected] Received January 31, 2020; revised February 20, 2020; accepted February 26, 2020
Keywords: detrital food webs, body size, trophic level, insect larva, microarthropods, stable isotopes DOI: 10.1134/S1067413620050112
The distribution of organisms by their size may be one of the mechanisms forming the food web structure. The size of an organism is a fundamental property determining its trophic interactions, metabolism intensity, and population density [1]. The expectable increase of the trophic level with the body size is clearly manifested in aquatic ecosystems where microalgae are the primary producers [2, 3]. However, the basic food resource of soil food webs (detrital) has no characteristic particle size. The analysis of a large volume of data has established the absence of correlation between the body size of terrestrial animals, including soil inhabitants, and their trophic level [4]. The variety of body sizes of terrestrial organisms, combined with the absence of a clear dimensional structure of the soil food web, implies the presence of dimensional compartments in it; members of such compartments have similar sizes [4]. This does not annul, though, the dimensional orderliness within individual food chains; on average, predators are bigger than their prey [5]. Food web reconstructions normally use species as the primary units. However, each soil invertebrate species is represented by a number of ontogenetic stages whose body masses may differ by orders of magnitude. Furthermore, detrital food web reconstructions often ignore larval stages of invertebrates because it is difficult to identify larvae to the species level. In view of this, it was decided to test the hypothesis of a correlation between the body size and trophic position using the individual approach (i.e., using individuals as operational units). Small soil animals (mites, collembolans, and larva of macrofaunal invertebrates) are mostly represented by microbophages, but many of them gladly switch to a carnivorous diet [6]. The larger the size, the higher the chance to prey on larger organisms, including facultative carnivorism or cannibalism. As a matter of fact, trophic positions of soil sapro/microbophages
may change in the course of their ontogenesis, although this process is poorly researched [7, 8]. Therefore, a correlation between the size and trophic level can be expected within individual compartments of the food web both for generalist predators and saprophages. The animal population inhabiting the litter of a monsoon tropical forest was chosen as a model community. The litter is ephemeral; it is formed as a defined stratum only
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