The role of preadaptation, propagule pressure and competition in the colonization of new habitats

To successfully colonize new habitats, organisms not only need to gain
access to it, they also need to cope with the selective pressures imposed
by the local biotic and abiotic conditions. The number of immigrants, the
preadaptation to the local habitat and the presence of competitors are
important factors determining the success of colonization. Here, using two
experimental set-ups, we studied the effect of interspecific competition
in combination with propagule pressure and preadaptation on the
colonization success of new habitats. Our model system consisted of tomato
plants (the novel habitat), the two-spotted spider mite (Tetranychus
urticae) as our focal species and the red spider mite (Tetranychus evansi)
as a competitor. Our results show that propagule pressure and
preadaptation positively affect colonization success. More successful
populations reach larger final population sizes either by having higher
per capita growth rates (due to preadaptation effects) or by starting a
population with a larger number of individuals. Although populations are
more successful colonizing non-competitive environments than competitive
ones, propagule pressure and preadaptation counteract the negative effects
of competition, promoting colonization success. Our study shows the
importance of propagule pressure and preadaptation for successful
colonization of new habitats by providing the ability to cope with both
the exigencies of new environments and the community context.