The Moss Bosses

By Liz Darling (Sears) and Jesse Sills

Hi everyone! Now that the vascular plants of Canada DNA barcoding project is all finished (Read about it here), the team here at the Centre for Biodiversity Genomics has moved on to another group of plants: the Bryophytes.  This term broadly encompasses all land plants that do not have any true vascular tissue, which includes the mosses, liverworts and hornworts. 

No rolling stones, we can’t seem to stop gathering moss! Liz and Jesse pose with the boxes of specimens
No rolling stones, we can’t seem to stop gathering moss! Liz and Jesse pose with the boxes of specimens

For the first two weeks of February, Jesse Sills, Masha Kuzmina and Liz Darling (Sears) headed off to the capital of Canada to collect mosses from the Canadian Museum of Nature.  We were working out of their herbarium, which is located in the secondary collections building, rather than the main building that is accessible to the public (and contains many amazing exhibits!).  When creating a reference database, it is incredibly useful to have access to well-curated collections such as this one in order to allow us to take samples from species that have been examined and identified by multiple experts.   The idea is basically to collect roughly three specimens of each species available, preferably as widely spread across Canada as possible.  This allows us to curate a database of DNA from not only as many species as possible, but also try to investigate whether a species experiences genetic drift when separated by thousands of kilometers.  By collecting and barcoding these known species, we can then form a basis to identify unknown species by comparing to the reference database.

There is a plethora of striking similarities between sampling vascular plants and mosses, but several differences actually make sampling the bryophytes significantly more difficult.  Firstly, instead of being mounted on herbarium sheets like vascular plants, mosses are stored in envelopes.

The envelopes of mosses are stored upright in boxes within the herbarium cabinets
The envelopes of mosses are stored upright in boxes within the herbarium cabinets

Although this doesn’t sound like a big difference, having to open and close each envelope to be able to look at the specimens drastically slows down the process.  Secondly, mosses are generally a lot smaller than vascular plants, making sampling under a microscope necessary.

Masha peers through the microscope, carefully choosing the material to sample
Masha peers through the microscope, carefully choosing the material to sample
Jesse sampling at the second microscope station
Jesse sampling at the second microscope station

Thirdly, mosses have a most inconvenient habit of growing in groups with many other species, often closely related to them. This can make it quite difficult to determine which species in the moss clump is the one you are trying to collect. Microscopes and identification books quickly became our best friends when it came to sampling these tiny plants. The museum envelopes can vary from containing a large rock with a small speck of moss on it, to a handful of dirt with some small pieces of moss to a huge piece of moss containing up to 7 different species.

An example of a messy sample, this envelope was mostly gravel and dirt (CCDB-28007-C02)
An example of a messy sample, this envelope was mostly gravel and dirt (CCDB-28007-C02)
Some of the specimens were in absolutely beautiful condition (CCDB-28051-B09)
Some of the specimens were in absolutely beautiful condition (CCDB-28051-B09)
An example of a specimen with multiple species present. Each arrow points to another species – the red one even points to a mollusk! (CCDB-28095-B02)
An example of a specimen with multiple species present. Each arrow points to another species – the red one even points to a mollusc! (CCDB-28095-B02)

We also took images of each specimen using scanners and a camera.  Impressively, over the span of 8 days we managed to sample all of the green mosses in the collection – a total of 1805 specimens!  This brings the total for the project up to 1981 specimens representing 792 different species of moss.

Setting up the specimens to be imaged involves laying them out on white cardstock with all possible identification sheets easily legible
Setting up the specimens to be imaged involves laying them out on white cardstock with all possible identification sheets easily legible
Liz taking high resolution scans of the specimens
Liz taking high resolution scans of the specimens

As a relatively poorly studied group of plants, it is not really known how many species of moss there are in Canada, with estimates ranging from 1100 – 2400 species.  Wherever the true number lies, it is definitely much higher than we have currently collected, which means we still have a lot of work to do!  It just might be that our work helps to uncover some of the mysteries of this microscopic world!

-Liz & Jesse

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