Aquatic Biodiversity in the Amazon: Habitat Specialization and Geographic Isolation Promote Species Richness

Abstract

Simple SummaryThe immense rainforest ecosystems of tropical America represent some of the greatest concentrations of biodiversity on the planet. Prominent among these are evolutionary radiations of freshwater fishes, including electric eels, piranhas, stingrays, and a myriad of small-bodied and colorful tetras, cichlids, and armored catfishes. In all, the many thousands of these forms account for nearly 10% of all the vertebrate species on Earth. This article explores the complimentary roles that ecological and geographic filters play in limiting dispersal in aquatic species, and how these factors contribute to the accumulation of species richness over broad geographic and evolutionary time scales.AbstractThe Neotropical freshwater ichthyofauna has among the highest species richness and density of any vertebrate fauna on Earth, with more than 5,600 species compressed into less than 12% of the world's land surface area, and less than 0.002% of the world's total liquid water supply. How have so many species come to co-exist in such a small amount of total habitat space? Here we report results of an aquatic faunal survey of the Fitzcarrald region in southeastern Peru, an area of low-elevation upland (200–500 m above sea level) rainforest in the Western Amazon, that straddles the headwaters of four large Amazonian tributaries; the Juruá (Yurúa), Ucayali, Purús, and Madre de Dios rivers. All measures of fish species diversity in this region are high; there is high alpha diversity with many species coexisting in the same locality, high beta diversity with high turnover between habitats, and high gamma diversity with high turnover between adjacent tributary basins. Current data show little species endemism, and no known examples of sympatric sister species, within the Fitzcarrald region, suggesting a lack of localized or recent adaptive divergences. These results support the hypothesis that the fish species of the Fitzcarrald region are relatively ancient, predating the Late Miocene-Pliocene (c. 4 Ma) uplift that isolated its several headwater basins. The results also suggest that habitat specialization (phylogenetic niche conservatism) and geographic isolation (dispersal limitation) have contributed to the maintenance of high species richness in this region of the Amazon Basin.

Effects of reduced‐impact logging on physical habitat and fish assemblages in streams of Eastern Amazonia

“…Despite their importance in nutrient cycling, water quality maintenance and runoff-evapotranspiration balance, stream ecosystems have been frequently threatened by increasing anthropogenic activities that modify the native vegetation in the region (Nepstad et al, 1999;Morton et al, 2006;Foley et al, 2007). However, studies relating the effects of these activities, such as wood harvest, on the structure and function of Amazon streams are still scarce (Albert et al, 2011;Allard et al, 2015;Bordignon et al, 2015;Datry et al, 2016).…”

Systematics and biogeography of Sternarchellini (Gymnotiformes: Apteronotidae): Diversification of electric fishes in large Amazonian rivers

“…Other gymnotiform clades are also diverse in the deep-channel habitat, including the sternopygids Eigenmannia and Rhabdolichops, and the rhamphichthyid Rhamphichthys (Albert et al, 2011b;Carvalho, 2013). The presence of multiple sympatric congeners within this habitat, including several instances of sister-species pairs, is unusual among Neotropical fishes, where most sister-species pairs are distributed in allopatry (Albert & Crampton, 2001;Albert & Reis, 2011;Albert et al, 2011a). The Sternarchellini is part of the diverse assemblage of apteronotid fishes that inhabits the large rivers of tropical South America (Mago-Leccia et al, 1985;Lundberg & Lewis, 1987).…”

The Long and Short of Biodiversity: Cumulative Diversity and Its Drivers

“…However, because environments are dynamic, fluctuations of physicochemical variables-the temporal dimension of the environment-may strongly influence the build-up and maintenance of diversity [22]. On the organismal supply side, members of the regional species pool may be specialized (e.g., life history traits) to thrive in specific, even variable environments and so boost local diversity [23][24][25].…”