Diversity and composition of arbustive spiders in an Atlantic Forest fragment and two adjacent areas

Abstract

The present study preliminarily investigates the diversity and composition of arbustive spider assemblages occurring in an early stage (arbustive), an intermediate stage (early secondgrowth), and a mature stage area (Atlantic Forest fragment) in Torres municipality, Rio Grande do Sul. Spiders and other arthropods (potential prey) were caught during the day with beating trays inside ten 3 m2 plots randomly placed inside each area, during two fi eld trips in 2008. An individual-based rarefaction (with confi dence intervals) was utilized to access differences in spider richness between areas, spider assemblage composition variation among the three succession areas was accessed by a MANOVA via randomization test, and the correlation between arbustive spider composition and the composition of potential preys was analyzed by a Mantel test. There were no signifi cant differences in arbustive spider abundances between areas. Mature stage area presented higher arbustive spider richness compared to early stage area and intermediate stage area. The three habitats showed different compositions of arbustive spider assemblages, and the composition of arbustive spiders was not correlated with the composition of the potential preys. Higher richness of arbustive spiders in the mature area is probably due to a more diverse plant community. Compositions found in the three habitats indicate that many mature-forest species could not be capable of using matrix habitats. It seems that the mature patch is surrounded mainly by an inhospitable matrix, with little overlap in spider species composition between the habitats showing more similar vegetation composition (mature and intermediate). Our fi ndings outpoint to a habitat-selective spider assemblage in this Atlantic Forest fragment highlighting the importance of protecting Atlantic forest fragments to conserve arbustive spider assemblages. Moreover, intermediate stage areas contiguous to forest fragments could be important to some forest dwelling species and also needs attention.

Metacommunity Composition of Web-Spiders in a Fragmented Neotropical Forest: Relative Importance of Environmental and Spatial Effects

“…Therefore, there must be a web-spider community linked to the initial development of the understory vegetation after cattle disturbance. It is unlikely that this community comes from the intervening matrix (pasture), since a study performed in one of the fragments studied here showed that the composition of understory-dwelling spiders was completely different from that in the contiguous early-stage area, indicating that forest-spider species avoid matrix habitats [59]. This characteristic, coupled with the absence of dispersal limitation, suggests that the local web-spider communities in the early-disturbed patches are composed by individuals dispersing from other forest fragments.…”

Trap-nesting biology of an ectoparasitoid spider wasp, Auplopus subaurarius (Hymenoptera: Pompilidae): the importance of wooded environments for niche generalist species

“…Caution should be taken when drawing conclusions about the effect of the Eucalyptus areas due to the smaller sampling effort that we had in that area as the collections were made focusing on other purposes than the ecology of A. subaurarius, which could also explain the absence of natural enemies of A. subaurarius in this area. Although Eucalyptus areas are not a natural vegetation cover, they can provide resources such as shelter due to the greater production of leaf litter and present greater vegetational complexity for web building to spider species, compared to grassland areas (Baldissera et al, 2008;Rodrigues et al, 2010). Moreover, grassland areas are prone to higher light intensity, rainfall, wind, and greater visibility of predators than areas of natural forest and Eucalyptus plantations (Rodrigues et al, 2010), which can negatively affect both the abundance of A. subaurarius and its host spiders.…”