Abstract
Terrestrial isopods are important and dominant component of meso and macrodecomposer soil communities. The present study investigates the diversity and species composition of terrestrial isopods on three forests on the Serra Geral of the state of Rio Grande do Sul, Brazil. The area has two natural formations (Primary Woodland and Secondary Woodland) and one plantation of introduced Pinus. The pitfall traps operated from March 2001 to May 2002, with two summer periods and one winter. There were 14 sampling dates overall. Of the five species found: Alboscia silveirensis Araujo, 1999, Atlantoscia floridana (van Name, 1940), Benthana araucariana Araujo & Lopes, 2003 (Philoscidae), Balloniscus glaber Araujo & Zardo, 1995 (Balloniscidae) and Styloniscus otakensis (Chilton, 1901) (Styloniscidae); only A. floridana is abundant on all environments and B. glaber is nearly exclusive for the native forests. The obtained data made it possible to infer about population characteristics of this species. The Similarity Analysis showed a quantitative difference among the Secondary forest and Pinus plantation, but not a qualitative one. The operational sex ratio (OSR) analysis for A. floridana does not reveal significant differences in male and female proportions among environments. The reproductive period identified in the present study for A. floridana was from spring to autumn in the primary forest and Pinus plantation and during all year for the secondary forest. The OSR analysis for B. glaber reveals no significant differences in abundance between males and females for secondary forest, but the primary forest was a significant difference. The reproductive period for B. glaber extended from summer to autumn (for primary and secondary forest). This is the first record for Brazil of an established terrestrial isopod population in a Pinus sp. plantation area, evidenced by the presence of young, adults and ovigerous females, balanced sex ratio, expected fecundity and reproduction pattern, as compared to populations from native vegetation areas.
Highlights
Terrestrial isopods are known as pillbugs and are included in the Oniscidea suborder, presently including 3,939 known species as of 2011 (Schmalfuss, 2003; Ahyong et al, 2011)
Many species of terrestrial isopods are not limited to natural environments, with most introduced species associated to anthropogenic environments
Atlantoscia floridana was abundant in all areas, with the second most abundant being B. glaber, significantly present in primary and secondary forests
Summary
Terrestrial isopods are known as pillbugs and are included in the Oniscidea suborder, presently including 3,939 known species as of 2011 (Schmalfuss, 2003; Ahyong et al, 2011). The terrestrial isopod fauna in forest ecosystems is important for organic matter processing and nutrient cycling. These organisms are responsible for fragmenting the accumulated leaf litter, along with other members of the detritivore guild (Quadros & Araujo, 2008; Boelter et al, 2009). Areas with ecological dominance from a single tree species can be expected to harbour fewer animals and reduced arthropod species diversity (Battirola et al, 2007). This reduction has consequences for ecosystem functioning, as smaller populations of fewer species in the soil fauna would lead to slower and less efficient soil nutrient cycling. The impact of Pinus must be evaluated in terms of species diversity alone, and considering the life history of the species present
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