Trait structure reveals the processes underlying fish establishment in the Mediterranean

Abstract

Aim Typically, non‐indigenous species have been studied in relation to either the invaded (recipient) community or the donor community. However, we still lack a broad understanding of the mechanisms underlying the establishment of non‐indigenous species that combines both perspectives. Since the opening of the Suez Canal, hundreds of species have invaded the Mediterranean from the Red Sea, forming a unique system in which the entire species pool (donor, non‐indigenous and recipient) is known. Focusing on species ecological traits, we assess the drivers underlying the establishment of non‐indigenous species from the onset of the invasion to the present. Location The Mediterranean and Red Seas. Methods We compiled traits for shallow‐water hard‐bottom‐associated fishes in the Mediterranean (recipient community) and the Red Sea (donor community). We compared the multivariate community trait structure of non‐indigenous species with the donor and recipient assemblages, using a novel method to objectively assign trait‐weights, thereby increasing the robustness of the results. Patterns were contrasted with two types of null models which provide distinct insights into the ecological processes. Results Non‐indigenous fishes are very diverse ecologically, substantially increasing the total community trait diversity of the Mediterranean. Trait similarity between non‐indigenous and indigenous Mediterranean species was lower than expected, indicating that non‐indigenous fishes tend to occupy relatively vacant niches within the Mediterranean. However, we further found that over time non‐indigenous species display increased trait similarity to indigenous Mediterranean species. This suggests that trait constraints associated with successful establishment are weakening. Main conclusions Non‐indigenous species establish in relatively vacant ecological niches, opening the possibility for predicting establishment using ecological traits. However, the weakening of trait constraints through time suggests that forecasting future establishment may be difficult. Faced with an accelerating pace of invasion, it appears that the Mediterranean is going to be transformed into an extension of the Red Sea in terms of trait and species composition.

Alien species stabilize local fisheries catch in a highly invaded ecosystem

“…] what can be sustained at the maximum carrying capacity of the environment. Together with the finding that alien species in this system tend to occupy empty niches (Givan et al 2017), interspecific competition for resources between aliens and indigenous species may be limited.…”

Climate change, biological invasions, and the shifting distribution of Mediterranean fishes: A large‐scale survey based on local ecological knowledge

“…Despite the magnitude of these changes and their relevance for conservation and adaptation policy (Givan, Parravicini, Kulbicki, & Belmaker, 2017;Marras et al, 2015), observational studies are often fragmented in space (Elmendorf et al, 2015) and methodologically heterogeneous (Coll et al, 2010). This also applies to the northward expansions of warmwater species, a phenomenon that has been mostly described in the northwestern sectors of the Mediterranean basin, probably due to the uneven distribution of research efforts (Boero et al, 2008;Lejeusne, Chevaldonné, Pergent-Martini, Boudouresque, & Pérez, 2010;Marbà, Jordà, Agustí, Girard, & Duarte, 2015;Sabatés, Martín, & Raya, 2012).…”

Evaluating functional diversity conservation for freshwater fishes resulting from terrestrial protected areas

“…Fish trait variables ( n = 17) were gathered from various sources (Coker, Portt, & Minns, ; Eakins, ; Frimpong & Angermeier, ; Holm, Mandrak, & Burridge, ) to characterise the ecological niche of each species (Givan, Parravicini, Kulbicki, & Belmaker, ; Lamothe, Alofs, et al., ) including components of the species’ diet, modes of reproduction, substrate associations, and habitat–depth relationships (Table ). Diet traits were sourced from the literature and included binary variables representing a preference for algae, phytoplankton, or filamentous algae, macrophytes and vascular plants, detritus, or unidentifiable vegetative matter, fish, crayfish, crabs, or frogs, and eggs of fish or other organisms (Frimpong & Angermeier, ; Table ).…”

“…Fish trait variables (n = 17) were gathered from various sources (Coker, Portt, & Minns, 2001;Eakins, 2017;Frimpong & Angermeier, 2009;Holm, Mandrak, & Burridge, 2009) to characterise the ecological niche of each species (Givan, Parravicini, Kulbicki, & Belmaker, 2017;Lamothe, Alofs, et al, 2018) (Table 1). Habitatdepth relationships were measured in the field and represent the depth at which species were caught including median depth, maximum depth, and minimum depth (Table 1).…”