Trait‐based prediction of extinction risk of small‐bodied freshwater fishes

Abstract

Small body size is generally correlated with r-selected life-history traits, including early maturation, short-generation times, and rapid growth rates, that result in high population turnover and a reduced risk of extinction. Unlike other classes of vertebrates, however, small freshwater fishes appear to have an equal or greater risk of extinction than large fishes. We explored whether particular traits explain the International Union for Conservation of Nature (IUCN) Red List conservation status of small-bodied freshwater fishes from 4 temperate river basins: Murray-Darling, Australia; Danube, Europe; Mississippi-Missouri, North America; and the Rio Grande, North America. Twenty-three ecological and life-history traits were collated for all 171 freshwater fishes of ≤120 mm total length. We used generalized linear mixed-effects models to assess which combination of the 23 traits best explained whether a species was threatened or not threatened. We used the best models to predict the probability of 29 unclassified species being listed as threatened. With and without controlling for phylogeny at the family level, small body size-among small-bodied species-was the most influential trait correlated with threatened species listings. The k-folds cross-validation demonstrated that body size and a random effect structure that included family predicted the threat status with an accuracy of 78% (SE 0.5). We identified 10 species likely to be threatened that are not listed as such on the IUCN Red List. Small body size is not a trait that provides universal resistance to extinction, particularly for vertebrates inhabiting environments affected by extreme habitat loss and fragmentation. We hypothesize that this is because small-bodied species have smaller home ranges, lower dispersal capabilities, and heightened ecological specialization relative to larger vertebrates. Trait data and further model development are needed to predict the IUCN conservation status of the over 11,000 unclassified freshwater fishes, especially those under threat from proposed dam construction in the world's most biodiverse river basins.

Susceptibility of European freshwater fish to climate change: Species profiling based on life‐history and environmental characteristics

“…, are found either exclusively in the Evrotas River basin, or in that and few neighboring systems(Barbieri et al, 2015). Smaller-bodied fish are facing elevated overall extinction risk in freshwater habitat due to multiple threats, such as habitat loss and fragmentation(Kalinkat, Jähnig, & Jeschke, 2017;Kopf et al, 2017;Olden et al, 2007), which explains higher threat level observed in climate-susceptible species in the present study. Observed lower commercial relevance and lower vulnerability to fishing of climate-susceptible species both stem from a smaller body size and related faster life history of such species.…”

“…These species, ranked among the 20 most susceptible species to climate change in the present study (Table 2) It is important to acknowledge certain limitations of the data sources used in this study, such as species and trait coverage, reliability of methods applied for threat and extinction risk classification, and potential assessors' biases (Clavero & García-Berthou, 2005;Keith et al, 2014;Trull, Böhm, & Carr, 2018). Taxonomic bias in conservation science (Clark & May, 2002) (Kopf et al, 2017). IUCN Red List is sometimes considered to understate or improperly account for climate change as a threat, mostly due to ambiguous definitions and criteria (Trull et al, 2018).…”

“…Furthermore, species that are not classified within IUCN Red List as threatened by climate change can comprise those that are not yet assessed for their major threats, or those where experts deem the threat from climate change negligible relative to other threats. Nevertheless, the focus of our study on a well‐studied group such as European species ensured that the basic life‐history data and IUCN Red List assessments were mostly available (Kopf et al, ). IUCN Red List is sometimes considered to understate or improperly account for climate change as a threat, mostly due to ambiguous definitions and criteria (Trull et al, ).…”

“…Species traits represent any morphological, physiological, or phenological feature that is measurable at the individual level of a species (Floeter, Bender, Siqueira, & Cowman, 2018). Trait-based evaluation has been demonstrated to be linked to the risk status of species and can be used to investigate mechanisms that contribute to imperilment, make predictions about unassessed species, or rank and prioritize species based on their relative risk (Bland & Böhm, 2016;Comte & Olden, 2018;Kopf, Shaw, & Humphries, 2017;Olden, Hogan, & Zanden, 2007).…”

Predation drives morphological convergence in the Gambusia panuco species group among lotic and lentic habitats

“…Two species of Gambusia that formerly lived in springs in Texas have already become extinct within the last century (Peden, ; Miller et al ., ) and numerous other spring‐dwelling Gambusia are listed as vulnerable, threatened or endangered on the IUCN Red List including G. alvarezi and G. hurtadoi (both vulnerable). Although the status of G. marshi has not been assessed, it too is predicted to be threatened (Kopf et al ., ). These systems are variably threatened by the introduction of novel predators (e.g.…”