The role of phenotypic plasticity and genetic diversity in the colonization of novel environments

Phenotypic plasticity and genetic diversity are theorized to contribute to species’ successful colonization and range expansion; however, there is a lack of consensus in the invasion biology literature about their role in predicting invasion success. Much of the existing empirical research suffers from a lack of knowledge regarding failed or unsuccessful invasions. This reflects the scientific community’s priority for understanding the worst invaders. To address these gaps in knowledge, I used a novel comparative approach of taxonomically and geographically paired invasive species, representing successful and less-successful invaders, to investigate the potential of phenotypic plasticity for gene transcription and genetic diversity at both neutral and functional genetic markers to predict invasion success (Chapters 2, 4 and 5). I also addressed genetic and environmental underpinnings of phenotypic plasticity for gene transcription (Chapter 3) to improve the use of transcriptional variation to predict invasion success and range expansion. A highly successful biological invader was more transcriptionally plastic to temperature change, with a stronger transcriptional response and wider range of biological functions, than a comparatively less successful invader (Chapter 2). Transcriptional variation for core metabolic and stress response genes is primarily driven by the environment (Chapter 3) suggesting that, while transcription for potential invaders must be assayed under a range of conditions, knowledge of these responses will allow prediction of transcriptional profiles and thus an organism’s potential performance in, as yet, un-invaded areas. Low relative invasion success was associated with decreased levels of within- but elevated levels of among-population genetic diversity for two of four species pairs (Chapter 4). These results imply that genetic diversity is limiting for some invasive species’ range expansions and highlight the role that intraspecific hybridization may play in promoting invasion success. Compared to native range populations, tubenose goby have experienced a loss of genetic diversity while round goby have not. Round goby exhibit more adaptive divergence within the invaded range indicating that tubenose goby range expansion may be limited by its inability to evolve to facilitate range expansion (Chapter 5). Thus, both phenotypic plasticity and genetic diversity are important for successful range expansion and predicting colonization potential