Date of Award
2026
Document Type
Honors Thesis (Open Access)
Department
Colby College. Biology Dept.
Advisor(s)
Suegene Noh
Abstract
Local adaptation occurs when populations evolve traits that improve their fitness within their local biotic and abiotic environments. In host–symbiont systems, repeated interactions between hosts and microbes can generate reciprocal selective pressures that promote local adaptation. This study tested whether infection prevalence dynamics in symbiotic associations provide evidence of host adaptation to a local symbiont in the Dictyostelium discoideum–Paraburkholderia system. Amoeba hosts were infected with fluorescently labeled Paraburkholderia species and grown over five successive passage cycles. Infection prevalence was quantified by flow cytometry, and changes over time were analyzed using a linear mixed-effects model and bootstrap confidence intervals. Infection prevalence varied by treatment and species. P. bonniea showed increasing infection prevalence in sympatric and parapatric combinations but stable or declining prevalence in allopatric hosts, consistent with local maladaptation. P. agricolaris and P. hayleyella exhibited similarly increasing infection prevalence across both parapatric and sympatric conditions. These results suggest that prior ecological exposure to symbionts may shape host defense more strongly than geographic distance alone. This work also highlights how symbiont prevalence, dispersal, and opportunities for exposure may influence coevolutionary dynamics.
Keywords
Local adaptation, Parabukholderia, Dictyotelium discoideum, exposure, host-parasite, infection
Recommended Citation
Mancini, Faith V., "The effect of geographical context on persistent amoeba-bacterial symbiotic associations" (2026). Honors Theses. Paper 1555.https://digitalcommons.colby.edu/honorstheses/1555