Consequences of the introduction of exotic and translocated species and future extirpations on the functional diversity of freshwater fish assemblages

Abstract

Aim To explore the effects of the introduction of exotic and translocated species and possible future extirpation of native species on the functional diversity (FD) of freshwater fish assemblages. Location Japanese archipelago. Methods We examined spatio‐temporal changes in species richness, FD, functional richness (the number of trait‐based functional groups), and the functional group composition between historical and current fish assemblages for 27 eco‐regions, and compared the relative effects of the introduction of exotic and translocated species on FD. We also used a null model approach to determine the assembly patterns and the extent of functional redundancy. Finally, we determined the effect of the loss of endangered species on FD by comparing the observed losses with simulated random loss. Results Through the introductions of non‐native species, the species richness, FD and functional richness of the fish assemblages increased 2.4‐, 1.6‐ and 2.1‐fold, respectively. The functional group composition also changed largely through the additions of new functional groups. Exotic species had a significantly greater effect size than translocated species, but there were no differences in the overall net effects of exotic and translocated species. Null modelling approaches showed that the observed FD was higher than expected by chance (i.e. trait divergent) in both historical and current assemblages. There was also low functional redundancy. In our simulation, FD decreased in proportion to the loss of species, independent of whether the species were endangered. Main conclusions We demonstrated that both exotic and translocated species may change FD and functional group composition, which might have dramatic consequences for ecosystem processes. We suggest that the future extirpation of even a few native species can cause a substantial loss of FD. Our findings emphasize the need to improve conservation strategies based on species richness and conservation status, and to incorporate translocated species into targets of the management of non‐native species.

Environmental and spatial controls of macroinvertebrate functional assemblages in seagrass ecosystems along the Pacific coast of northern Japan

“…In support of this idea, Yamada et al (2011) concluded that the functional diversity of the macrocrustacean community in seagrass ecosystems is the variable at the local patch scale, but homogeneous (i.e., occurrence of functional redundancy) at the regional scale (e.g. Matsuzaki et al, 2013;Sasaki et al, 2014).…”

“…By using groups and diversity based on ecological traits, i.e., ''functional group'' and ''functional diversity'', that is the value and range of functional traits and ecosystem function of organisms present in a community (e.g., Mouillot et al, 2013;Storkey et al, 2013), can lead to elucidate community assembly rules and/or ecosystem processes (Yamada et al, 2011;Matsuzaki et al, 2013;Sasaki et al, 2014). Functional diversity was measured based on the values and range of ecological traits of species such as microhabitat, dispersal ability, habitat type, life history, and trophic level (e.g., Schleuter and Daufresne, 2010).…”

Genetic characterization of native and invasive Plagioscion squamosissimus (Perciformes, Sciaenidae) populations in Brazilian hydrographic basins

“…In fact, the impact of this phenomenon has been the theme of several studies (Pinto-Coelho et al, 2008;Matsuzaki et al, 2013).…”

From current distinctiveness to future homogenization of the world's freshwater fish faunas

“…Current situation corresponds to present species composition, whereas historical situation refers to composition two centuries ago, that is, before human-induced changes in compositions through non-native introductions and extirpations of native species (Olden & Rooney, 2006). Although the patterns and determinants of changes in taxonomic similarity between assemblages from historical to current situation have been increasingly studied (Rahel, 2000;Olden & Poff, 2004;Leprieur et al, 2008b;Spear & Chown, 2008;Winter et al, 2009;Vill eger et al, 2011;Hermoso et al, 2012), much less attention has been devoted to future trends (but see Duncan & Lockwood, 2001;Olden & Poff, 2004;Olden et al, 2008a;Matsuzaki et al, 2013), especially at large spatial scales. Although the patterns and determinants of changes in taxonomic similarity between assemblages from historical to current situation have been increasingly studied (Rahel, 2000;Olden & Poff, 2004;Leprieur et al, 2008b;Spear & Chown, 2008;Winter et al, 2009;Vill eger et al, 2011;Hermoso et al, 2012), much less attention has been devoted to future trends (but see Duncan & Lockwood, 2001;Olden & Poff, 2004;Olden et al, 2008a;Matsuzaki et al, 2013), especially at large spatial scales.…”