Filtering Effect of Large Rivers on Primate Distribution in the Brazilian Amazonia

Abstract

Over a century after Wallace’s proposition of the riverine barrier hypothesis, the role of rivers in the diversification of species remains a matter of interest in Amazon biogeography. Amazonian rivers, in particular those large and fast flowing rivers, are widely recognized to act as barriers to the dispersal of some organisms. However, the extent to which primate species changes across interfluves (β-diversity) in response to river features remains to be explicitly tested. In this study, we examine how river characteristics affect the variation in taxonomic and phylogenetic β-diversity to elucidate the ecological processes behind the differences in primate assemblages between neighboring interfluves in the Brazilian Amazonia. We compiled International Union for Conservation of Nature (IUCN) distribution maps of 80 river-bounded primate species in 10 interfluves separated by major rivers throughout the Brazilian Amazonia. We assessed both the taxonomic (disregarding phylogenetic relationships between species) and phylogenetic β-diversities. We applied multiple linear models to evaluate whether annual discharge, sinuosity, and reflectance (as a proxy for amount of sediments) in each river or river section that separates neighboring interfluves make rivers effective barriers to primates. We found that mean discharge has a positive effect, while both sinuosity and amount of sediments have negative effects on primate β-diversity. These variables have significant effects on total taxonomic and phylogenetic β-diversity between neighboring interfluves, and their species turnover components. River features, however, have no effect on species richness differences. Genera are capable of traversing almost all interfluves, but species are replaced by others in opposite interfluves. Discharge affected both small- and large-sized primate total β-diversity, but sinuosity only affected large-sized primate assemblages in neighboring interfluves. Our results indicate that although Amazonian rivers act as barriers for many primate species, this barrier effect seems limited to the short/medium time scales, as primate lineages are able to cross them over long-time scales.

Elevation drives taxonomic, functional and phylogenetic β‐diversity of phyllostomid bats in the Amazon biome

“…This connection, mainly in the extension between the Negro and Madeira rivers (Ruokolainen et al, 2019), may have allowed not only the dispersion of bat species through the tributary channel, but also the insects and plants that these bats consume. Therefore, our results contradict the theory that species distributions are strongly delimited by the great rivers, and areas of endemism delimited by rivers, in the Amazon (Wallace, 1854) and go against results from studies corroborating this theory using primates (Boubli et al, 2015;Fordham et al, 2020;Mourthé et al, 2022), terrestrial birds (Braga et al, 2022;Ribas et al, 2012;Silva et al, 2019) and bats (Silva et al, 2022). Bats have a high capacity of movement and displacement, and as a result these flying mammals relatively homogeneously occupy all of the Amazonian lowlands (Esbérard et al, 2017).…”

“…Although studies have already highlighted this for different taxa (Cracraft, 1985;Moraes et al, 2016;Mourthé et al, 2022), large rivers seem to act differently according to the taxon's dispersal capacity (Dambros et al, 2020). Whereas the turnover of taxa with limited dispersal capacities (e.g.…”

Primate conservation in the Arc of Deforestation: a case study of Vieira's titi monkey Plecturocebus vieirai

“…In this context, private landowners are the key stakeholders (Nepstad et al, 2002; Soares-Filho et al, 2006, Fearnside, 2017) for biodiversity conservation and the protection of representative tracts of remaining forests in the Arc of Deforestation, which would contribute to climate change mitigation (Fearnside, 2003, 2009; Nogueira et al, 2018). The owners of large farms are responsible for 70% of deforestation in private areas in Amazonia (Fearnside, 2017) but could change their model of land use, which is currently putting at risk the ecosystem services and the resources provided by the biome (Lovejoy & Nobre, 2018).…”

“…Using ArcGIS 10.1 (Esri, Redlands, USA), we delimited the geographical distribution of P. vieirai from the occurrence records, the ensemble model, knowledge of the distribution of congeneric, neighbouring species and considering that rivers restrict the occurrence of primate species in Amazonia (Mourthé et al, 2022). Finally, we overlaid the species distribution with raster layers of vegetation classes (Souza et al, 2020), elevation (which is a constraint for species occurrence; Jarvis et al, 2008) and forest cover (Soares-Filho et al, 2006), to extract the area of suitable habitat available for P. vieirai in the present (2020) and in the future (2044).…”

“…This region accounts for almost half of the total global land-use changes during 1990–2015 (FAO, 2016). Although sustainable development was expected for the Tapajós–Xingu region 2 decades ago (Nepstad et al, 2002), it became an epicentre of deforestation as a result of logging and slash-and-burn clearance for agriculture and cattle ranching as well as legal and illegal gold mining, affecting even protected areas and Indigenous lands (Printes, 2017; Montibeller et al, 2020).

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