Abstract
It is proposed that lichen photobionts, compared to mycobionts, have very
limited capacity to evolve adaptations to lichenization, so that the symbionts in
lichens do not co-evolve. This is because lichens have (a) no sequential selection of
photobiont cells from one lichen into another needed for Darwinian natural selection
and (b) no photobiont sexual reproduction in the thallus. Molecular studies of lichen
photobionts indicate no predictable patterns of photobiont lineages that occur in
lichens so supporting this proposal. Any adaptation by photobionts accumulating
beneficial mutations for lichenization is probably insignificant compared to the rate
of mycobiont adaptation. This proposal poses questions for research relating the
photobiont sexual cycle (genetic and cellular), the fate of photobiont lineages after
lichenization, whether lineages of photobionts in thalli change with time, thallus
formation by from spores as well as carbohydrate movement from photobionts to
mycobionts and regulation of co-development of the symbionts in the thallus.
| Translated title of the contribution | Asymmetric Co-evolution in the Lichen Symbiosis Caused by a Limited Capacity for Adaptation in the Photobiont |
|---|---|
| Original language | English |
| Pages (from-to) | 326 - 338 |
| Number of pages | 13 |
| Journal | Botanical Review |
| Volume | 75 |
| Publication status | Published - 2009 |