The role of the microbiome relative to the genome for niche width and host adaptation.

Surviving global change is possible through genetic adaptation and phenotypic plasticity, being the main mechanisms considered to improve an organism’s fitness. However, recent studies show that microbiomes (communities of microbiota inside hosts and their genome expression) play an important role as well. As microbiota are known to influence multiple processes, such as nutrient uptake and detoxification, they might expand species niche width through their influence on host performance. As such, they contribute to species survival and may even affect the resilience of entire food webs. I will use the two-spotted spider mite, Tetranychus urticae, in combined observational and experimental research. Although individual niches are narrow, this spider mite has a broad niche width, occurs on more than 900 plant species, and is known to adapt fast to environmental changes. I will (1) perform a field study to discover how niche width correlates with the microbiome, host genetic diversity or the environment; (2) maintain these populations in a laboratory setting to test the influence of the microbiome on host adaptation through experimental evolution; (3) perform transplant experiments modifying the microbiome to discover its direct influence on species niche width. My findings will give fundamental insight into the influence of host-microbiota interactions on niche width and will further disentangle the role of the microbiome during host adaptation.