BACKGROUND: A host obtains symbionts by horizontal transmission when infected from the environment or contagiously from other hosts in the same generation. In contrast, vertical transmission occurs when a host obtains its symbionts directly from its parents. Either vertical or horizontal transmission can sustain an association between a host and its symbiont. QUESTIONS: What evolutionary forces are necessary to evolve from an ancestral state of horizontal transmission to a derived state of vertical transmission? MATHEMATICAL METHODS: We explore a general model of fitness interaction, including both additive and epistatic effects, between host and symbiont genes. Recursion equations allow us to analyse the short-term behaviour of the model and to study long-term deterministic effects with numerical iterations. KEY ASSUMPTIONS: Obligate interaction between a symbiont and a single host species with genetically determined horizontal and vertical transmission. No free-living symbionts or uninfected hosts and each host is infected by only a single symbiont genetic lineage (no multiple infections). No population structure. CONCLUSIONS: Epistasis for fitness between host and symbiont genes, like that in a matching alleles model, is a necessary condition for the evolution of vertical from horizontal transmission. Stochastic individual-based simulations show that (1) mutation facilitates the switch to vertical transmission and (2) vertical transmission is a stable evolutionary endpoint for a matching alleles model.
BACKGROUND: A host obtains symbionts by horizontal transmission when infected from the environment or contagiously from other hosts in the same generation. In contrast, vertical transmission occurs when a host obtains its symbionts directly from its parents. Either vertical or horizontal transmission can sustain an association between a host and its symbiont. QUESTIONS: What evolutionary forces are necessary to evolve from an ancestral state of horizontal transmission to a derived state of vertical transmission? MATHEMATICAL METHODS: We explore a general model of fitness interaction, including both additive and epistatic effects, between host and symbiont genes. Recursion equations allow us to analyse the short-term behaviour of the model and to study long-term deterministic effects with numerical iterations. KEY ASSUMPTIONS: Obligate interaction between a symbiont and a single host species with genetically determined horizontal and vertical transmission. No free-living symbionts or uninfected hosts and each host is infected by only a single symbiont genetic lineage (no multiple infections). No population structure. CONCLUSIONS: Epistasis for fitness between host and symbiont genes, like that in a matching alleles model, is a necessary condition for the evolution of vertical from horizontal transmission. Stochastic individual-based simulations show that (1) mutation facilitates the switch to vertical transmission and (2) vertical transmission is a stable evolutionary endpoint for a matching alleles model.
Authors: Dongying Wu; Philip Hugenholtz; Konstantinos Mavromatis; Rüdiger Pukall; Eileen Dalin; Natalia N Ivanova; Victor Kunin; Lynne Goodwin; Martin Wu; Brian J Tindall; Sean D Hooper; Amrita Pati; Athanasios Lykidis; Stefan Spring; Iain J Anderson; Patrik D'haeseleer; Adam Zemla; Mitchell Singer; Alla Lapidus; Matt Nolan; Alex Copeland; Cliff Han; Feng Chen; Jan-Fang Cheng; Susan Lucas; Cheryl Kerfeld; Elke Lang; Sabine Gronow; Patrick Chain; David Bruce; Edward M Rubin; Nikos C Kyrpides; Hans-Peter Klenk; Jonathan A Eisen Journal: Nature Date: 2009-12-24 Impact factor: 49.962
Authors: Dongying Wu; Sean C Daugherty; Susan E Van Aken; Grace H Pai; Kisha L Watkins; Hoda Khouri; Luke J Tallon; Jennifer M Zaborsky; Helen E Dunbar; Phat L Tran; Nancy A Moran; Jonathan A Eisen Journal: PLoS Biol Date: 2006-06 Impact factor: 8.029
Authors: Francy L Crosby; Sveinung Eskeland; Erik G Bø-Granquist; Ulrike G Munderloh; Lisa D Price; Basima Al-Khedery; Snorre Stuen; Anthony F Barbet Journal: Pathogens Date: 2022-05-21