Threatened fish species in the Northeast Atlantic are functionally rare

Abstract

AimThe criteria used to define the International Union for Conservation of Nature (IUCN) Red List categories are essentially based on demographic parameters at the species level, but they do not integrate species' traits or their roles in ecosystems. Consequently, current IUCN‐based protection measures may not be sufficient to conserve ecosystem functioning and services. Some species may have a singular combination of traits associated with unique functions. Such functionally distinct species are increasingly recognized as a key facet of biodiversity since they are, by definition, functionally irreplaceable. The aim of this study is to investigate whether threatened species are also functionally rare and to identify which traits determine extinction risk.LocationEuropean continental shelf seas.Time period1984–2020.Major taxa studiedMarine fish.MethodsUsing newly compiled trait information of 425 marine fish species in European waters, and more than 30 years of scientific bottom trawl surveys, we estimated the functional distinctiveness, restrictedness and scarcity of each species and cross‐referenced it with their IUCN conservation status.ResultsIn European continental shelf seas, 38% of the species threatened with extinction (9 out of 24 species) were identified as the most functionally distinct. By mapping extinction risk in the multidimensional species trait space, we showed that species with the greatest risk of extinction are long‐lived and of high trophic level. We also identified that the most functionally distinct species are sparsely distributed (4% of the total area on average) and have scarce abundances (<1% of the relative mean abundance of common species).Main ConclusionsBecause a substantial proportion of threatened species are functionally distinct and thus may play unique roles in ecosystem functioning, we stress that species traits—especially functional rarity—should become an indispensable step in the development of conservation management plans.

Northeast Atlantic elasmobranch community on the move: Functional reorganization in response to climate change

“…Species traits were collected by extracting traits values from Coulon et al. (2023) and Ocean Biodiversity Information System (OBIS, 2022). From the OBIS data, the geographic range was calculated as the difference between the highest and lowest latitudes in the distribution, given the spatial extent of the study area and after removing the first and last percentiles of the latitude distribution, to limit false presences due to species misidentification.…”

“…We selected six species traits reflecting trophic ecology, life history, and ecological versatility that are expected to be implicated in the species' response to environmental changes (McLean et al, 2018;Murgier et al, 2021) and geographic range shifts (Albouy et al, 2015;Sunday et al, 2015; Appendix S1-Table S5 for reasoning). Species traits were collected by extracting traits values from Coulon et al (2023) and Ocean Biodiversity Information System (OBIS, 2022). From the OBIS data, the geographic range was calculated as the difference between the highest and lowest latitudes in the distribution, given the spatial extent of the study area and after removing the first and last percentiles of the latitude distribution, to limit false presences due to species misidentification.…”

“…Elasmobranchs contribute to ecosystem functioning with unique combinations of physiological, morphological, reproductive, or behavioral traits (Tilman, 2001) that have no functional equivalent (i.e., functionally distinct species; Coulon et al, 2023;Leitão et al, 2016;Mouillot et al, 2013;Violle et al, 2017). They are known for exerting top-down regulation (Barley et al, 2017a(Barley et al, , 2017bRuppert et al, 2013) but they are also linked to other ecosystem functions such as promoting energetic connectivity between neritic, oceanic, and deep-sea ecosystems (Shipley et al, 2023).…”

A trait‐based approach to assess niche overlap and functional distinctiveness between non‐indigenous and native species

“…numerical, categorical, or ordinal) (Pavoine et al, 2009). However, to avoid potential biases owing to one or a few traits having a disproportional effect on functional distances and distinctiveness, we performed an integrated process to compare the outcomes for multiple combinations of randomly selected traits (Coulon et al, 2023; Figure 1). As a sensitivity test, we first estimated and compared the functional distances and associated distinctiveness for all possible combinations of four, six and eight traits (Figure S2a-c).…”

“…This metric has not been used within a formal framework to address NIS and biotic invasions in general, but recently gained considerable attention in ecology (Gaüzère et al, 2023;Munoz et al, 2023). For example, to assess the current threats of functionally unique species involved in key ecosystem processes (Coulon et al, 2023;Loiseau et al, 2020;Murgier et al, 2021) or to detect the competitive performance of individuals within the same species (Mahaut et al, 2023). Functional distinctiveness offers a precise measure of functional dissimilarity for each single species within a community, thus providing greater resolution compared to other metrics also based on species dissimilarities, but which only allow comparisons between communities as a whole (Mammola et al, 2021).…”