How organisms adapt to their environment is becoming increasingly relevant in our changing world. The overall aim of my PhD is to test for the existence and importance of two neglected mechanisms of adaptation to new habitats. I. Selective pre-establishment filters during biological invasion Before an invasive species can become established in a non-native range, individuals of this species will have to successfully pass the stages of uptake, transport, and introduction. There is some evidence for a species bias in invasion success. However, in general what exactly happens during the pre-establishment stages is hardly studied. Moreover, it is likely that during these stages there is also selection on certain traits at the individual level. This pre-establishment selection could change the composition of introduced populations, and with this their invasion potential. We will test this novel hypothesis by following the fate of a set of individuals from their capture in the native range (Senegal) through transport and until their simulated release in a non-native range (Spain), characterising various traits thought to be important for invasion success (condition, parasite load, stress resistance, immune system genotype, behaviour/personality, morphology). II. Matching Habitat Choice If individuals vary in which habitat yields best performance and highest fitness, it would benefit them to settle in those habitats that best match their phenotypes. Such Matching Habitat Choice (MHC) will lead to the clumping of similar individuals, and to the adaptation of local populations. Here we aim to assess the presence, functioning, relative importance and consequences of Matching Habitat Choice for adaptation to different and novel environments. We will experimentally compare the speed and efficiency of natural selection, phenotypic plasticity and MHC to drive local adaptation, and also assess the consequences of MHC for assortative mating and the ability to invade novel environments.