title: A trait-based approach reveals the feeding selectivity of a small endangered Mediterranean fish.
abstract: Functional traits are growing in popularity in modern ecology, but feeding studies remain primarily rooted in a taxonomic-based perspective. However, consumers do not have any reason to select their prey using a taxonomic criterion, and prey assemblages are variable in space and time, which makes taxon-based studies assemblage-specific. To illustrate the benefits of the trait-based approach to assessing food choice, we studied the feeding ecology of the endangered freshwater fish Barbus meridionalis. We hypothesized that B. meridionalis is a selective predator which food choice depends on several prey morphological and behavioral traits, and thus, its top-down pressure may lead to changes in the functional composition of in-stream macroinvertebrate communities. Feeding selectivity was inferred by comparing taxonomic and functional composition (13 traits) between ingested and free-living potential prey using the Jacob's electivity index. Our results showed that the fish diet was influenced by 10 of the 13 traits tested. Barbus meridionalis preferred prey with a potential size of 5-10 mm, with a medium-high drift tendency, and that drift during daylight. Potential prey with no body flexibility, conical shape, concealment traits (presence of nets and/or cases, or patterned coloration), and high aggregation tendency had a low predation risk. Similarly, surface swimmers and interstitial taxa were low vulnerable to predation. Feeding selectivity altered the functional composition of the macroinvertebrate communities. Fish absence favored taxa with weak aggregation tendency, weak flexibility, and a relatively large size (10-20 mm of potential size). Besides, predatory invertebrates may increase in fish absence. In conclusion, our study shows that the incorporation of the trait-based approach in diet studies is a promising avenue to improve our mechanistic understanding of predator-prey interactions and to help predict the ecological outcomes of predator invasions and extinctions.
authors.affiliation: Freshwater Ecology and Management (F.E.M.) Research Group Departament d'Ecologia Facultat de Biologia Universitat de Barcelona Avda. Diagonal, 643 E-08028 Barcelona Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Rodríguez-Lozano
authors.affiliation: Freshwater Ecology and Management (F.E.M.) Research Group Departament d'Ecologia Facultat de Biologia Universitat de Barcelona Avda. Diagonal, 643 E-08028 Barcelona Spain.
authors.forename: Iraima
authors.initials: I
authors.lastname: Verkaik
authors.affiliation: Departament of Integrative Ecology Estación Biológica de Doñana Avda. Américo Vespucio, s/nE-41092 Sevilla Spain; Institut de Recerca de Biodiversitat (IRBio) Universitat de Barcelona E-08028 Barcelona Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Maceda-Veiga
authors.affiliation: Institut de Recerca de Biodiversitat (IRBio) Universitat de Barcelona E-08028 Barcelona Spain; Departamento de Biología Ambiental Universidad Jorge Tadeo Lozano Bogotá Colombia.
authors.forename: Mario
authors.initials: M
authors.lastname: Monroy
authors.affiliation: Institut de Recerca de Biodiversitat (IRBio) Universitat de Barcelona E-08028 Barcelona Spain; Departament de Biologia Animal (Vertebrats) Facultat de Biologia Universitat de Barcelona Avda. Diagonal, 643 E-08028 Barcelona Spain.
authors.forename: Adolf
authors.initials: A
authors.lastname: de Sostoa
authors.affiliation: Freshwater Ecology and Management (F.E.M.) Research Group Departament d'Ecologia Facultat de Biologia Universitat de Barcelona Avda. Diagonal, 643 E-08028 Barcelona Spain; Institut de Recerca de Biodiversitat (IRBio) Universitat de Barcelona E-08028 Barcelona Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Rieradevall
authors.affiliation: Freshwater Ecology and Management (F.E.M.) Research Group Departament d'Ecologia Facultat de Biologia Universitat de Barcelona Avda. Diagonal, 643 E-08028 Barcelona Spain.
authors.forename: Narcís
authors.initials: N
authors.lastname: Prat
keywords: Fish diet; food webs; functional traits; intermittent streams; macroinvertebrates; species extinction