Investigating the coevolution of the microbiome of surface and cave populations of the amphipod crustacean Gammarus minus

This thesis aims to elucidate the evolution of the microbiome between surface and cave-dwelling organisms using the organism, Gammarus minus. Standard molecular techniques were used to extract bacterial DNA from the G. minus guts and fecal matter and used for bacterial species analysis. Results showed that different geographically separated populations harbored unique microbiome signatures, where Alphaproteobacteria and Gammaproteobacteria were the only shared classes across all four populations used. Diminishing of bacterial diversity was seen between paired sister surface and cave populations as well as increase in a trace species in the cave populations when compared to its sister surface counterparts. These results point to a bottlenecking effect when the G. minus species moves from surface to cave habitats. It also supports opportunistic bacterial fixation in cave-dwelling G. minus.