The combined effects of climate change and river fragmentation on the distribution of Andean Amazon fishes

Abstract

Upstream range shifts of freshwater fishes have been documented in recent years due to ongoing climate change. River fragmentation by dams, presenting physical barriers, can limit the climatically induced spatial redistribution of fishes. Andean freshwater ecosystems in the Neotropical region are expected to be highly affected by these future disturbances. However, proper evaluations are still missing. Combining species distribution models and functional traits of Andean Amazon fishes, coupled with dam locations and climatic projections (2070s), we (a) evaluated the potential impacts of future climate on species ranges, (b) investigated the combined impact of river fragmentation and climate change and (c) tested the relationships between these impacts and species functional traits. Results show that climate change will induce range contraction for most of the Andean Amazon fish species, particularly those inhabiting highlands. Dams are not predicted to greatly limit future range shifts for most species (i.e., the Barrier effect). However, some of these barriers should prevent upstream shifts for a considerable number of species, reducing future potential diversity in some basins. River fragmentation is predicted to act jointly with climate change in promoting a considerable decrease in the probability of species to persist in the long‐term because of splitting species ranges in smaller fragments (i.e., the Isolation effect). Benthic and fast‐flowing water adapted species with hydrodynamic bodies are significantly associated with severe range contractions from climate change.

Conservation of migratory fishes in the Amazon basin

“…Potential shifts in the range of migratory species to cope with expected temperature increases will be reduced or hampered by the fragmentation of river networks that result from hydroelectric dams and other infrastructure development in the Amazon basin (Myers et al, 2017). This situation is likely to be worse in the Andean portion of the basin, where most dams have been built or are planned (Anderson et al, 2018), interacting with climate change to decrease species ranges and prevent them from reaching suitable climatic areas in some regions (Herrera‐R et al, 2020).…”

Population responses to harvesting in fluctuating environments

“…Climate change and habitat loss are causing species distributions to shift and contract (Chen et al 2011, VanDerWal et al 2013, Herrera-R et al 2020, and species are encountering new dispersal barriers (Jenkins et al 2016, Peeters et al 2020. Such changes to dispersal pathways and spatial structure can alter the effects of harvesting regimes by, for instance, weakening the connection between unharvested and harvested areas and thus weakening the rescue effect from dispersal, or causing populations to move out of protected areas (Monzón et al 2011).…”

Conservation threats and future prospects for the freshwater fishes of Ecuador: A hotspot of Neotropical fish diversity

“…Fish in small mountain streams also have limited opportunities for habitat tracking and dispersal (Herrera‐R et al ., 2020 ; Taniwaki et al ., 2017 ). Recent studies from other areas suggest a range of potential impacts including changes in the distribution of species and trophic assemblages (Garzke et al ., 2019 ; Herrera‐R et al ., 2020 ), the age of sexual maturity (Shahjahan et al ., 2017 ), metabolic rates (Petitjean et al ., 2019 ), nutrient composition (Colombo et al ., 2019 ), contaminant absorption (Schartup et al ., 2019 ) and alterations in sex ratios (Fernandino & Hattori, 2019 ). Rarer cold water species at high elevations are likely to be impacted the most (Buisson et al ., 2008 ; Herrera‐R et al ., 2020 ), suggesting that high‐elevation Astroblepus spp.…”