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The lack of knowledge about freshwater biodiversity in remote areas like montane Andean rivers is noticeable and hinder the development of efficient conservation plans for aquatic ecosystems. Habitat requirements of tropical Andean fishes have been poorly analysed, despite the relevance of these ecological features on the fish conservation strategies. The present study aimed to examine fish assemblages along the altitudinal gradient in tropical Andean rivers and their relationship to habitat features to detect the most relevant abiotic factors and their implication on conservation. This study was conducted on a regional scale, along six basins located in tropical Andes (500 to 2,692 m a.s.l.). We studied fish diversity and distribution and their habitats along these elevation gradients. We found 6,320 specimens from 53 genera. Our analysis for the six most common and widely distributed genera (Astroblepus, Brycon, Bryconamericus, Chaetostoma, Pimelodella and Trichomycterus) underlines the relevance of hydromorphological variables on fish community structure in the Andean montane rivers, whereas human alterations seem to be less significant. These findings could be useful for current management and conservation strategies considering present threats over tropical montane rivers. [ABSTRACT FROM AUTHOR]

Our study analyzes the distribution of fish communities related to the environmental variables of the Alto Madre de Dios River, an Andean-Amazon watershed of southern Peru, between 300 and 2811 m a.s.l. within the Manu Biosphere Reserve. We provide new ecological and diversity data on fishes for these poorly studied rivers and new data for palm swamp habitats. With electric fishing techniques, we collected a total of 1934 fish specimens belonging to 78 species, 42 genera and 15 families. To assess main patterns of diversity we combined SIMPER and ANOSIM with canonical correspondence analysis to obtain an overview of the community structure of fish and their distribution related to aquatic habitats. Our results show an important shift on fish diversity at 700 m a.s.l. separating headwater and middle-lowland communities. Electrofishing was a hindrance due to the depth, flow and low conductivity of the rivers, but also allowed us to capture fish not observed with other techniques. We also compared the use of elevation with slope as an alternative variable for statistical analysis. Our results show that slope offers a solid and equivalent explanation for fish distribution variability, avoids redundance, and instead of giving geographical data offers ecologically solid information. [ABSTRACT FROM AUTHOR]

• Rarity and composition metrics better measure land use impacts in tropical systems. • Land use intensification reduces biodiversity irrespective of the metric applied. • Agroforestry systems resemble forest diversity patterns across taxa. Land-use change is a primary driver of biodiversity loss. Tropical ecosystems face rapid conversion rates due to the encroachment of agricultural lands and supply needs for goods and services from an increasing population and changing market demands. Measuring the effect of land conversion on species diversity is challenging due to incomplete and uneven knowledge of different taxonomical groups. Here, we contrast different metrics for measuring biodiversity loss across three land-use typologies: secondary forest, agroforestry, and monoculture for five taxonomic groups: birds, frogs, fish, dung beetles, and macroinvertebrates in the Andean piedmont forests of the western equatorial Andes. Albeit our limited and uneven sample in space and time, we found that rarity, Non-Metric Multidimensional Scaling, and Multinomial Classification Model (i.e., classifications of habitat specialists and generalists) constitute a more sensitive set of indicators to assess land-use change impacts on tropical mountain biodiversity compared to classical metrics. Likewise, our results showed that land-use intensification influenced community assemblages in the five taxonomic groups. These non-classical biodiversity metrics can provide better insight into the effect of land conversion on these highly biodiverse ecosystems composed of many rare species. [ABSTRACT FROM AUTHOR]