Variability in life-history traits is correlated with establishment success of alien mammals
Introduced and invasive species are the focus of considerable research and management efforts, as these species can have substantial ecological and socio-economic impacts. Many studies have aimed to identify key predictors of successful introductions and invasions, but this search has had limited success. Past studies focused on mean trait values and largely disregarded the role of intraspecific trait variability, even though this variability is known to influence population dynamics. In fact, the plasticity hypothesis proposes that more plastic or variable species should have greater probability of establishing a population once introduced, but its general relevance is currently unknown. We evaluated this hypothesis using a global database of mammalian introductions including 511 introductions representing 97 mammal species with detailed information on the number of released individuals. In addition, we estimated the average and observed intraspecific variation in nine life-history and ecological traits for these mammals. Using taxonomically corrected generalized linear mixed models we evaluated if the establishment success of mammalian introductions could be predicted based on species traits and introduction characteristics.
Our analyses show that variation in diverse life-history traits is strongly associated with establishment success of global mammal introductions. Intraspecific variation in adult body size, neonate body size, and gestation length are good predictors of establishment success, even when controlling for the positive effect of propagule pressure (the number of introduced individuals). As expected under the plasticity hypothesis, more variation in adult body mass and gestation length is associated with greater establishment success. However, species with less variation in neonate body size are apparently more likely to establish successfully, suggesting that not all trait variation is advantageous. Our results emphasize the importance of considering intraspecific variation to predict establishment success of introduced species, and generally to understand population dynamics. This understanding can also contribute to the management of introduced species and facilitate intentional invasions, e.g. biocontrol or reintroductions.