A closer look at invasiveness and relatedness: life histories, temperature and establishment success of four congeners

Successful invasive species are often closely related to other invasive
species suggesting that shared traits contribute to their invasion
success. Alternatively, related species can differ in invasiveness, where
some are highly invasive yet congeners seem unable to invade. Here, we
compared the traits and establishment abilities of two highly successful
invasive species, Gambusia affinis and G. holbrooki to those of two close
relatives, G. geiseri and G. hispaniolae. Using laboratory experiments, we
compared low temperature tolerances and life histories of the four
species. In a semi-natural mesocosm experiment, we simulated the invasion
of standardized, simple pond communities and examined the effects of these
traits on each species’ ability to become established. The invasive
species, G. affinis and G. holbrooki, were more tolerant of low
temperature stress, had greater fecundities, higher growth rates, and
reached maturity sooner than G. geiseri and G. hispaniolae. In mesocosms,
the invasive Gambusia exhibited higher intrinsic growth rates and carrying
capacities and thus achieved and maintained larger populations than the
two congeners. Only G. affinis and G. holbrooki successfully established
long-term populations in these experimental communities. G. geiseri and G.
hispaniolae failed to establish as a result of 100 % overwintering
mortality. These results support the notion that the ability of invaders
to cope with the abiotic conditions of target communities has a major
effect on whether establishment occurs, while life histories play an
important secondary role. Our results showed that invasiveness is likely
not a trait of the entire genus Gambusia.