Abstract
Invasive alien species are driving global biodiversity loss, compromising ecosystem function and service provision, and human, animal and plant health. Habitat characteristics and geographical origin may predict invasion success, and in aquatic environments could be mediated principally by salinity tolerance. Crustacean invaders are causing global problems and we urgently require better predictive power of their invasiveness. Here, we compiled global aquatic gammarid (Crustacea: Amphipoda: Gammaroidea) diversity and examined their salinity tolerances and regions of origin to test whether these factors predict invasion success. Across 918 aquatic species within this superfamily, relatively few gammarids (n = 27, 3%) were reported as aliens, despite extensive invasion opportunities and high numbers of published studies on amphipod invasions. However, reported alien species were disproportionately salt-tolerant (i.e. 32% of brackish-water species), with significantly lower proportions of aliens originating from freshwater and marine environments (both 1%). Alien gammarids also significantly disproportionally originated from the Ponto-Caspian (20% of these taxa) when compared with all ‘other' grouped regions (1%), and principally invaded Eurasian waters, with translocations of salt-tolerant taxa to freshwaters being pervasive. This suggests habitat characteristics, alongside regional contexts, help predict invasibility. In particular, broad environmental tolerances to harsh environments and associated evolutionary history probably promote success of aliens globally.
Highlights
The translocation of alien species to novel regions is one defining feature of anthropogenic global change [1], and this spread has increased in recent decades with no sign of saturation [2]
The multi-stage process of biological invasion, including transport, introduction, establishment and spread, acts as an often unpredictable impediment to invasion success, with introduced taxa frequently failing to establish in novel habitats [9]
Total global biodiversity of fully aquatic gammarids was determined from the World Amphipod Database, reported in the World Register of Marine Species in February 2017
Summary
The translocation of alien species to novel regions is one defining feature of anthropogenic global change [1], and this spread has increased in recent decades with no sign of saturation [2]. Phenotypic plasticity and preadaptation to changeable environments are thought to assist alien species in withstanding the invasion process and establishing new and viable populations [11,12,13]. This conjecture, still lacks rigorous testing and our predictive power for new invasions remains low
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