04045naa a2200157 a 450000100080000000500110000800800410001910000190006024501080007926000090018752033220019670000180351870000150353670000150355177303210356613148192008-09-16       2008    bl uuuu     u00u1 u    #d1 aQUADROS, A. F.  aCoexistence of two Neotropical terrestrial isopodsbdynamics, reproductive strategies and resource use.  c2008  aTerrestrial isopods are important members of the macrodecomposer community in forest soils. In southern Brazil, native species such as Atlantoscia floridana (van Name, 1940) (Philosciidae) and Balloniscus glaber Araujo & Zardo, 1995 (Balloniscidae) constitute a considerable fraction of soil invertebrate biomass. It is estimated that they may process up to 16% of the annual leaf litter input, producing 620 kg of feces per ha per year and thus contributing to soil humus formation. These isopods represent two very distinct eco-morphological groups, ?runners? (A. floridana) and ?clingers? (B. glaber), and this study has been conducted to correlate their patterns of resource use and their body morphology. Their population ecology and reproductive strategies were accessed through a one-year field survey, in a semi-deciduous forest in Parque Estadual de Itapuã, RS, Brazil. Their survivorship curves and life-tables were obtained. Their activity pattern was studied in the laboratory. Behavioral acts and habitat choice were quantified and compared through non-parametric MANOVA. To evaluate feeding preferences, we determined the five most abundant arboreous plants in the leaf litter and offered them to the isopods in multiple and no-choice experiments, and the results were further correlated to leaf characteristics. The field studied revealed large differences in their population ecology: Atlantoscia floridana reproduces over the entire year and shows a higher reproductive investment; Balloniscus glaber, on the other hand, reproduces in spring and summer but shows a higher survivorship of its young. A. floridana showed a shorter generation time (8 months) and a higher net reproductive rate (1.9 offspring) than B. glaber (12 months, 1.4 offspring, respectively). The species differ in respect to their timing of activity: A. floridana is more active in the hours following dusk while B. glaber is more active before dawn. During the resting period, B. glaber digs and hides into burrows, while A. floridana remains immobile at the surface. Probably due to its burrowing habits, B. glaber shows more cleaning acts than A. floridana. The species do not differ with respect to frequencies of feeding, interactions and exploitation behaviors. The MANOVA results suggest that behavior is altered with respect to the timing and frequency of activities in both species, when they co-exist. The five plant species most abundant in the studied area were Lithraea brasiliensis (Anacardiaceae), Machaerium stipitatum (Leguminosae), Myrsine umbellata (Myrsinaceae), Roupala brasiliensis (Proteaceae) and Inga vera (Fabaceae). The isopods showed the same preference ranking: M. stipitatum and L. brasiliensis were the most preferred (&gt80% total consumed), M. umbellata represented 15% of total consumed and R. brasiliensis and I. vera were clearly avoided by the isopods. Preference ranking was negatively correlated to leaf toughness and independent of phenolic content, as the most and least preferred leaves had high amounts of phenolics (2.3 to 2.9% dry weight). We conclude that, in spite of marked differences in body morphology, the species highly overlap in resource use. On the other hand, reproductive strategies are contrasting and may be partially explained by their morphological characteristics.1 aARAUJO, P. B.1 aZIMMER, M.1 aCAUBET, Y.  tIn: INTERNATIONAL COLLOQUIUM ON SOIL ZOOLOGY, 15; INTERNATIONAL COLLOQUIUM ON APTERYGOTA, 12., 2008, Curitiba. Biodiversity, conservation and sustainabele management of soil animal: abstracts. Colombo: Embrapa Florestas. Editors: George Gardner Brown; Klaus Dieter Sautter; Renato Marques; Amarildo Pasini. 1 CD-ROM.