Freshwater vertebrate and invertebrate diversity patterns in an Andean-Amazon basin: implications for conservation efforts

Abstract

The Napo Basin in Ecuador is an important drainage of the Amazon Basin, the most biodiverse ecosystem for freshwater species. At the same time, this basin has conspicuous information gaps on its biodiversity patterns and human threats. Here, we estimated the diversity distribution patterns of freshwater vertebrates and invertebrates in the Napo Basin, as a tool for present and future management and conservation efforts. Also, we assessed the spatial congruence of the diversity patterns observed between aquatic vertebrates and invertebrates. For this, we compiled occurrence records for 481 freshwater vertebrate species (amphibians, birds, mammals, reptiles, and fish), and 54 invertebrate families obtained across an altitudinal gradient of the basin (200-4500 m). Using these occurrence records and environmental variables, we modeled the distribution of each vertebrate species and invertebrate family. Then, we stacked these distributions to build species richness maps for vertebrates, and a family richness map for invertebrates. We found that the most diverse areas for vertebrate species are the lowlands (<600 m), whereas richness of invertebrate families peaks at higher elevations (lower montane forests). Congruence among species richness patterns of the five vertebrate groups was high (r = 0.66), with fish being the best predictor for vertebrates (r = 0.78). However, congruence decreased at higher elevations (r = 0.14), suggesting that specific species or habitat-based approaches should be used in the highlands. Also, we found a high correlation between species and family richness of freshwater invertebrates (r = 0.66), suggesting that family richness of invertebrates could be used as a surrogate of species richness in this basin. We highlight this correlation because, at the watershed scale, it allows working with family groups where species-level taxonomy is challenging. Our results provide the first comprehensive representation of freshwater biodiversity patterns at high resolution in an Andean-Amazon basin, and calls attention to the need for incorporating different taxonomic groups when assessing diversity patterns. Given these different diversity patterns, conservation programs for this basin should incorporate both vertebrate and invertebrate groups as biodiversity indicators. Finally, our study provides a practical methodological guidance in the estimation of freshwater diversity in regions of scarce information with high conservation priority, such as the Andean-Amazon basins.

Narrow thermal tolerance and low dispersal drive higher speciation in tropical mountains

“…We collected aquatic insect samples from small (first-third order), minimally impacted montane streams at ∼200-m elevation intervals from 1,556 to 3,478 meters above sea level (m asl) in Colorado (Cache la Poudre basin in the Front Range of the Rocky Mountains) (9) and 1,664-4,248 m asl in Ecuador (Napo basin in the Oriental Andean Cordillera) (41). To collect insects, we used D-frame nets with 500-μm mesh and searched under available substrates.…”

Spatial prediction of stream physicochemical parameters for the Napo River Basin, Ecuador

“…The Napo River Basin is estimated to harbor over 500 freshwater fish species, many of which are endemic to the region (Barriga 1994;Galacatos et al 2004). It is also one of the most biologically diverse ecoregions in the world for amphibians, birds and mammals (Olson 1998;Bass et al 2010;Jenkins et al 2013aJenkins et al , 2013bLessmann et al 2016). This high diversity in the Napo Basin can be attributed to several factors including its high altitudinal gradient (100-5500 m) which provides a great variety of physical and climatic conditions (Mena et al 2006) and incredible heterogeneity of habitats.…”

“…We sampled physicochemical parameters in situ at 165 field sites throughout the Napo River Basin from 2012 to 2014 to assess ecological integrity and species distribution modeling (see Lessmann et al 2016, Figure 1). To assess the biological composition, we sampled aquatic macroinvertebrates classified into families and rated by their physiological tolerance according to the Andean Biotic Index (ABI; Acosta et al 2009).…”

“…Major threats to freshwater resources in the Andean-Amazon region include agriculture, deforestation, point and nonpoint source pollution, hydroelectric dams, oil extraction, mining and road building (Mena et al 2006;Potes 2010;World Wildlife Fund 2014). In Ecuador, little is known about the current state of rivers and streams and how expanding urban, industrial and agricultural activities could affect these freshwater resources and their diversity (Ibarra 2010;Lessmann et al 2016).…”

“…The Napo Basin, part of the Ecuadorian Amazon, is one of the largest and most diverse systems in the Andean-Amazon region (Bass et al 2010), comprising an altitudinal gradient of more than 5000 m that includes thousands of stream and rivers (Lessmann et al 2016). Despite the high level of biodiversity of the Napo Basin, over the last few decades there has been a dramatic increase and acceleration of human land use and extractive practices in the basin (World Wildlife Fund 2014).…”