Assessing the Relationship Between Vegetation Structure and Harvestmen Assemblage in an Amazonian Upland Forest

Abstract

Abstract1. Arthropod diversity and non-flying arthropod food web are strongly influenced by habitat components related to plant architecture and habitat structural complexity. However, we still poorly understand the relationship between arthropod diversity and the vegetation structure at different spatial scales. Here, we examined how harvestmen assemblages are distributed across six local scale habitats (trees, dead trunks, palms, bushes, herbs and litter), and along three proxies of vegetation structure (number of palms, number of trees and litter depth) at mesoscale.2. We collected harvestmen using cryptic manual search in 30 permanent plots of 250 m at Reserva Ducke, Amazonas, Brazil. The 30 plots cover approximately 25 km2 of upland forests. At a local scale, harvestmen were most diverse and abundant on trees. The likely preference of trees by harvestmen may be related to the variety of local microhabitats offered by large trees. However, despite the strong link between number of harvestman species and individuals with large trees, only harvestmen assemblages composition were related with number of trees and with number of palms, at mesoscale.3. Harvestman richness and abundance were not related with any vegetation structure predictor at mesoscale. Therefore, areas of upland forest in the central Amazon with large trees and palms do not harbor more harvestman species nor individuals, but are suitable to maintain different harvestmen assemblages.

Marked compositional changes in harvestmen assemblages in Amazonian forest islands induced by a mega dam

“…In the Balbina archipelagic landscape, island size was a strong positive predictor of species richness in other taxonomic groups ─ including birds (Aurélio‐Silva et al ., ), small mammals (Palmeirim et al ., ) and large mammals (Benchimol & Peres, ). Although SAR is one of the few ironclad rules in ecology (Matthews et al ., ), we found that area failed in explaining richness patterns for harvestmen assemblages, the absence of this relationship has been documented before for this group in Amazonian upland forest sites where microhabitat structure and availability per unit area also explained patterns of harvestmen species composition but not species richness in harvestmen assemblages (Colmenares et al ., ). The same pattern was also found for other arthropods, such as macro‐moth communities in temperate woodland countryside landscapes, although in that case habitat amount, rather than patch size and isolation were the main drivers of species richness (Merckx et al ., ), both however have not explained it for harvestmen either.…”

“…Notably, this was an important variable structuring both harvestmen species composition and abundance across the Balbina islands. A positive association between harvestmen assemblages and fallen logs has not always been detected in undisturbed tropical forests, but this microhabitat type is often associated with some specific harvestmen species in Amazonian forests (Colmenares et al ., ).…”

“…Thus, larger islands harbouring higher forest basal area, particularly arborescent palms, are necessary to sustain larger populations of harvestmen species on islands. In fact, tree microhabitats harboured the most diverse and abundant harvestmen assemblages and was the only variable positively associated with harvestmen abundances in a Central Amazonian forest site distant ~190 km from Balbina (Colmenares et al ., ).…”

“…According to several other studies, the diversity of harvestmen recorded on the islands was low (Pinto‐da‐Rocha & Bonaldo, ; Bonaldo et al ., ; Tourinho et al ., ; ; Colmenares et al ., ; Porto et al ., ). The small number of species detected per island also reinforces diversity impoverishment in forest fragments, as suggested for the Atlantic Forest (Bragagnolo et al ., ) and temperate forests (Černecká et al, ; Mihál & Černecká, ).…”

“…Additionally, patterns of diversity in harvestmen assemblages are highly correlated with vegetation structure at meso and local scales and are especially responsive to the presence of large old trees and palms in Amazonian forests (Tourinho et al, 2014(Tourinho et al, , 2018Colmenares et al, 2016;Porto et al, 2016). This occurs because palms increase habitat complexity at ground level, as a consequence of the fallen litter trapped within their leaves (Vasconcelos, 1990;Franken et al, 2013).…”