Preservation of bryophytes under lab conditions

Some bryophytes are quite rare and have small populations, making them vulnerable to local extinction due to habitat changes or extreme weather conditions. One such species is known by the scientific name Frullania austinii; the English name is Austin’s scalewort. This liverwort grows on tree trunks of grey alder, common hazel or ash in a moist environment in a swamp forest, usually along brooks. It appears to be quite vulnerable to habitat changes, such as clear-cutting. There are only a few known sites in Scandinavia, and the world distribution is somewhat uncertain due to similarities with a related species, Frullania bolanderi. Observations are known from northern N America (Quebec and Labrador), Russia and Japan. The species is listed as endangered in both Sweden and Norway. In Sweden, it was first discovered at a single site in 1986 and has since been found at a handful of additional locations. The first find was extremely perplexing because another Frullania species, Frullania oakesiana, was discovered to be new to Sweden simultaneously on the same tree trunks. The first finding of F. austinii from Norway is nearly 100 years older.

This liverwort has numerous aggregated branchlets, resembling a fir at a distance, hence the Swedish name “pälsfrullania” (päls = fur). The branchlets have small leaves that can easily break away, acting as vegetative dispersal agents. 

A secondary objective of Bryomolecules is to apply methods developed in the project for what is known as ex situ preservation, that is, maintaining collections of endangered species in laboratory cultures. It is undoubtedly always best to preserve the species in their natural environment, but sometimes this is not enough. Lab cultures could potentially be used to replace populations that have gone extinct or reinforce those that are weak. We are gradually building up a pipeline for such efforts.

Procedures include sampling of threatened species; only minuscule plant material is needed because bryophytes can regenerate new tissue from small structures, such as leaves or even occasional cells – it is said that bryophytes are ”totipotent”. Thus, there is no risk that the sampling is hampering the populations. 

The next step is to sterilise the plant to efficiently propagate the shoots, without disturbing the growth of microbial organisms such as bacteria and fungi. We have developed improved methods for achieving sterile conditions during the initial phase of the Bryomolecules project. Notably, blue-green bacteria have been a significant problem, which we have overcome through the application of antibiotics.

We can then start propagating the plant material on agar plates or on a larger scale in bioreactors. It is possible to keep the cultures growing over time under lab conditions. 

It could be problematic to reintroduce plants into their native habitats after being grown under protected and optimal lab conditions. They need to be hardened. This process involves exposing them gradually to the microclimatic and microbial challenges present in nature. We are experimentally trying to do this by varying the climate inside our bioreactors.

To restore reproducing populations, there is a need to reintroduce both male and female plants, and, even more challenging, to ensure that the populations are genetically variable, possessing a representative gene pool. This might be less of a problem for species like F. austinii, which is rarely fertile in Scandinavia and is likely to be intensely dependent on vegetative dispersal, and thus possibly consists of few genetic individuals.

Author: Nils Cronberg, Senior Lecturer at Biodiversity and Evolution – Lund University

Retour en haut