Body size and fecundity of Hemileius suramericanus (Acari: Oribatida) in a native forest in Southeast Buenos Aires

Abstract

This work analyses the eventual changes of the body size and fecundity of an edaphic microarthropod, living in a native forest soil and in the surrounding area. Hemileius suramericanus (Hammer 1958) is an oribatid mite broadly distributed in the Neotropical Region. We studied the variation in male and female length and width, and in egg number in gravid females, in adults of H. suramericanus from Celtis tala wood patches and surrounding grassland. Samples were taken from soils of two different sized patches of a natural forest of Celtis tala and the grassland area (Pastizal) in the “Estancia Nahuel Rucá”, Mar Chiquita District, Buenos Aires Province, Argentina. In each patch two zones were considered: center and periphery where, litter cover and mechanical resistance, as an estimator of soil compaction, were measured in addition to H. suramericanus population parameters. Females of H. suramericanus were bigger than males in general. Females from the grassland were narrower than those found in the forest patches. Males from the grassland were the smallest. The modal number of eggs per female were two in the bigger patch, and zero in Pastizal and the periphery of the patch smaller. Soil compaction was greater in the grassland than in the forest patches. We propose that litter cover and soil compaction can be factors that determine body size and fecundity, mainly through its effect on food availability.