Biogeography of Amazonian fishes: deconstructing river basins as biogeographic units

Fernando C P Dagosta,Mário De Pinna

doi:10.1590/1982-0224-20170034

Fernando C P Dagosta, Mário De Pinna

Open Access

https://doi.org/10.1590/1982-0224-20170034

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Abstract

ABSTRACT Biogeography of Amazonian fishes (2,500 species in vastly disjunct lineages) is complex and has so far been approached only partially. Here, we tackle the problem on the basis of the largest database yet on geographical distribution and phylogenetic relationships of Amazonian fishes, including all information available. Distributions of 4,095 species (both Amazonian and outgroups) and 84 phylogenetic hypotheses (comprising 549 phylogenetically-informative nodes) were compiled, qualified and plotted onto 46 areas (29 Amazonian and 17 non-Amazonian). The database was analyzed with PAE, CADE, BPA and BPA0, yielding largely congruent results and indicating that biogeographic signal is detectable on multiple dimensions of fish distribution, from single species ranges to cladistic congruence. Agreement is especially pronounced in deeper components, such as Trans-Andean, Cis-Andean, Western Amazon and Orinoco basins. Results show that all major Amazonian tributaries, as well as the Amazon basin itself, are non-monophyletic and constitute hybrid sets of heterogeneous biotic partitions. Amazonian drainages should not be assumed a priori as historically cohesive areas, contrary to widespread practice. Our hypothesis allows re-evaluation of broader issues in historical biogeography, such as the predictive power of biogeographic hypotheses, the vicariant/dispersal duality, the significance of widely distributed taxa, and the need for temporal dimension in biogeographic patterns.

Highlights

The Amazon basin is the largest hydrographic system in the world (Goulding et al, 2003) and covers an area of over 8,000,000 km2 (Sioli, 1984)
The phylogenetic database utilized in BPA (Brooks Parsimony Analysis) and BPA0 includes 84 phylogenetic hypotheses for clades with Amazonian representatives, including 951 species representing 33 families and 6 orders (S4 - Available only as online supplementary file accessed with the online version of the article at http://www.scielo.br/ni) in a total of 549 phylogenetic nodes
We chose methods which in practice can be implemented for large databases such as ours and at the same time have been demonstrated to detect some biogeographic signal. Those are presently limited to PAE (Parsimony Analysis of Endemicity), CADE (Cladistic Analysis of Distributions and Endemism), BPA (Brooks Parsimony Analysis) and BPA0

Summary

Introduction

The Amazon basin is the largest hydrographic system in the world (Goulding et al, 2003) and covers an area of over 8,000,000 km (Sioli, 1984). The Amazon basin is formed by multiple distinct physiognomies, determined by terrains of vastly different composition and geological origins, generating diverse soil kinds, vegetation and water types (cf Goulding et al, 2003). All those factors are related to an immensely rich and complex geomorphological history (cf Lundberg et al, 1998) influenced by a series of large-scale events (e.g., Gondwana separation, uplift of the Andean range, course shifts of the main Amazon river, drainage capture, marine transgressions and regressions) which are not yet entirely understood. Such historical factors imply both increased diversification rates and decreased extinction rates, resulting in extraordinary richness of the freshwater biota as seen today (Albert, Reis, 2011; Reis et al, 2016)

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