Extinction of rare fish predicts an abrupt loss of ecological function in the future of Amazonian streams

Abstract

Species are going extinct 1,000 times faster than expected due to human impacts. When the extinction of species culminates in functional loss, ecosystem functioning is altered. Functional extinction risk depends on taxonomic and functional rarity, with the non‐redundant traits found in rare species being the most vulnerable. To investigate the relationship between taxonomic rarity and functional extinction, we ran extinction simulations driven by taxonomic rarity. Firstly, we sampled the fish fauna of 40 pristine Amazonian streams and compiled functional traits related to the body size, defence, diet, stratification, and activity of species. Then, we removed species, beginning with the rarest and ending with the commonest (and vice‐versa) and compared the observed patterns with random extinction at local and regional scales. Following the removal of rare species, the functional rarity and body size of the community both decreased, and functional extinctions occurred after less than 10% of extinction at both spatial scales. Otherwise, the removal of common species resulted in an increase in functional rarity at the local scale, although widespread species ensured the persistence of a set of unique functional traits at a regional scale. Additionally, more than 60% of the common species had to go extinct before any functional extinction occurred at either scale. If the ongoing mass extinction targets rare species, Amazonian stream ecosystems will be impacted by the loss of fish species associated with vulnerable functions. We propose an extinction risk assessment based on the ecosystem and recommend that future studies apply our approach to other taxa and ecosystems, to better understand the effects of human impacts on ecosystem functioning.

Functional Diversity and Primary Production Predict Future Patterns of Periphyton Productivity after Species Extinction

“…On the other hand, at the regional scale, the regional species pool supports at least 30% of species extinction before any indication of poor-productive streams in the region. These findings may be crucial for the conservation of temperate freshwater network systems, since they indicate that conservation initiatives focusing on the conservation of the whole region may prevent the loss of functionality and productivity during the sixth mass extinction event [1,54].…”

“…Because species with low abundance, restricted geographical distribution, and narrow habitat breadth are at higher risk of extinction [5,[54][55][56], we calculated an extinction risk index based on species rarity and habitat breadth. To assess the rarity of species, we considered two spatial scales: local, at the stream level, and regional, considering all streams sampled in this study.…”

Threatened fish species in the Northeast Atlantic are functionally rare

“…functionally distinct species; Violle et al, 2017), can have major impacts on ecosystem stability and functioning if no other species can compensate for the potentially lost functions (Mouillot et al, 2013a(Mouillot et al, , 2013b. Shifts in energy and/or nutrient inputs in ecosystems or disequilibrium in the structure of trophic webs have already been documented in response to the loss of these species (Carmona et al, 2021;Colares et al, 2022;McLean et al, 2019).…”

The Role of Rare Avian Species for Spatial Resilience of Shifting Biomes in the Great Plains of North America

“…These examples show that rare species may provide a relevant but, to some extent, unpredictable degree of an ecosystem's capacity to adapt to change (i.e., adaptive capacity). However, due to their rarity, many species have been shown to be particularly vulnerable to environmental change and extinction (Colares et al, 2021). Yet, how rare species of one spatial regime influence a system's adaptive capacity once it has shifted into a novel spatial regime is not well understood.…”