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

Abstract

Mega hydroelectric dams have become one of the main drivers of habitat loss in tropical forests, converting large tracts of pristine forests into isolated forest islands. Understanding how biodiversity cope with landscape modification in these archipelagic landscapes is of paramount importance to assess the environmental consequences of dam infrastructure and propose mitigation actions for biodiversity conservation. In this context, harvestmen (Opiliones, Arachnida) comprise an excellent indicator taxon of habitat quality, given their high sensitivity to desiccation and microclimatic change. We investigate the effects of landscape change induced by a mega hydropower dam on forest harvestmen species richness, abundance and composition within the Balbina Hydroelectric Dam, Central Brazilian Amazon. We sampled 20 islands and 5 mainland continuous forests, relating our biological response variables to local, patch and landscape scale metrics. Although unexpectedly species richness was unaffected by any local, patch and landscape variables, species composition and abundance were differentially affected by a set of predictor variables at different scales. Forest cover and fallen woody stems were significant predictors of species composition, whereas vegetation density, forest cover, island area, abundance of palm trees, and fallen woody stems best explained harvestmen abundance. Our results indicate that both islands embedded within greater and lower amount of forest cover are important to ensure high diversity of harvestmen. We recommend retaining large forest habitat patches surrounded by a large amount of forest cover to minimise forest disturbance effects and enhance long‐term persistence of harvestmen sensitive species in large hydroelectric dams.

Riparian Vegetation Structure Influences Terrestrial Invertebrate Communities in an Agricultural Landscape

“…Our results are similar to those of Ramberg et al [4], who found that the web-building family, Linyphiidae, was more abundant in buffered sites, while the Lycosidae was abundant in unbuffered sites [4]. Higher abundances of web-building spiders in forested riparian zones have been associated with vegetation structure (e.g., the presence of trees and dead wood structures) that aids the construction of webs [42,43]. Moreover, the Tetragnathidae are a web-building family that typically rely on aquatic prey from streams, meaning that they may respond numerically to changes in abundances of emergent stream insects [44,45].…”

“…Due to their invertebrate faunas [83][84][85][86][87], riparian zones are extremely valuable for invertebrate conser-vation [88,89]. Our study and others have shown that woody riparian buffers are important habitat patches by providing food for terrestrial invertebrates (e.g., Cicadidae), sites for web construction (e.g., Tetragnathidae) and ambush-hunting (e.g., Thomisidae and Clubionidae), life-stage microhabitats and shelter (e.g., Culicidae), and sites for overwintering and laying eggs (e.g., Carabidae) [9,43,49,90,91]. Woody riparian buffers may provide essential habitat diversity (via plant diversity) that helps support diverse assemblages of riparian invertebrates (e.g., consumers) [81].…”

Determinants of population persistence and abundance of terrestrial and arboreal vertebrates stranded in tropical forest land‐bridge islands

“…2018; Tourinho et al. 2020). Our new findings consistently showed that population sizes and biomass density were generally low on most islands even for those species that had somehow avoided extirpation so far.…”

“…Terrestrial vertebrates and invertebrates have been extirpated at massive rates on Amazonian forest islands formed in the aftermath of dam construction (Benchimol & Peres 2015 a , 2015 b ; Tourinho et al. 2020). In particular, most arboreal and terrestrial species have been extirpated from large numbers of small islands that are human‐made archipelagos (Benchimol & Peres 2015 b ), yet the status of extant insular populations remains poorly investigated.…”

Effect of dominant parabiotic Ant‐Garden ants on the understory and ground‐dwelling ant assemblage in the Amazon rainforest

“…The partial regression coefficients (hereafter b) of an MRM model provided a measure of the rate of change in the partition of the ant community similarity in the variables of interest. For this reason, it was used in ecological studies with different approaches (Walter et al, 2017;Busse et al, 2018;Tourinho et al, 2020).…”