Contrasting associations between habitat conditions and stream aquatic biodiversity in a forest reserve and its surrounding area in the Eastern Amazon

<b>Does riparian vegetation affect fish assemblage? A longitudinal gradient analysis in three Amazonian streams

“…Fish composition varied along the longitudinal gradient as a function of riparian vegetation, with a conspicuous differentiation of forest environment communities in relation to the altered pasture environment. Longitudinal variations in the composition of riparian communities are naturally expected (Mendonça et al, 2005;Montag et al, 2018), but changes in riparian vegetation were more pertinent to determine the fish composition in the low-order streams sampled. This fact is directly associated with degradation of the marginal physical habitat, which causes homogenization of riparian vegetation, substrate microhabitats, water column reduction due to excessive sedimentation and silting (Casatti et al, 2006;Ramalho et al, 2014;Montag et al, 2018).…”

“…In the case of G. rondoni for example, the sediment dependence, sand-dwelling habit and morphology makes the species highly specialized (Schwassmann, 1976;Zuanon et al, 2006;Soares, Rosa, Silva, Albrecht, & Caramaschi, 2017). Thus, the maintenance of riparian forest environments is extremely important for the survival of these and other species because they provide a wide supply of resources and maintain these resources (Castello et al, 2013), mainly in terms of woody debris (Montag et al, 2018). The vulnerability of these species (Ancistrus spp., F. smithi, G. rondoni, R. lanceolata and S. macrurus) due to alterations in riparian vegetation is reflected in the rarity or total absence in the stretches modified due to pasture insertion.…”

The importance of common and the irrelevance of rare species for partition the variation of community matrix: implications for sampling and conservation

“…In tropical countries, where species diversity is high 29 , big knowledge shortfalls regarding biodiversity distribution 30 (known as the Wallacean shortfall 31 ) exist. Additional financial crisis may reduce research investments 32 , so it is common for the biological sample to be from one sole sampling/field trip 13 , 26 , 33 , 34 . These sampling strategies can result in a low representation of rare species, and, consequently, can affect the detection of diversity patterns 35 .…”

“…Though this is a widely accepted method for investigating the effects of niche and neutral mechanisms in community ecology, a recent meta-analysis 7 revealed it is common for the residual portion of the model to be higher than the explained portion (> 50%) 5 . This was shown in very metacommunities with fish 13 , Odonata 14 , 15 and termites 16 in Amazonian streams, macroinvertebrates in the south 17 and southeast 18 of Brazil, and in macrophytes 19 and beetles 20 in temperate regions. The high residual variation is associated with environmental or spatial predictors that were not included in the models 5 , 7 and/or with a subset of species that have antagonistic responses to the environmental and/or spatial gradients due to autoecological characteristics 21 .…”

“…Considering studies in stream ecology to jointly evaluate taxa that use different parts of the habitat (e.g. : fish, exclusively aquatic organisms, and Zygoptera adults, which live in the riparian vegetation 13 , 26 ) may provide robust results which could be extrapolated for other organisms of the aquatic biota living in similar habitats.…”