This is the third post in a five-part series on Arctic flora research at the Canadian Museum of Nature. Join us as museum researcher Paul Sokoloff introduces the fieldwork and lab work involved in writing a new flora of the North American Arctic.
Each plant that we collect in the field (like that Oxytropis I got so excited about) goes into a clearly labelled plastic bag until we get back to camp. There, using a plant press—the state of the art back in the 1700s and changed very little today—we press and dry the plant for transport and long-term storage in a herbarium (a collection of dried plants). Further reading: an excellent description of the pressing and drying process.
In 2010, we brought back just shy of 1000 such plant specimens from our trip to Victoria Island, in the Northwest Territories. The year before that, we brought in 1000 as well. With the museum’s collecting legacy stretching back to the 1800s, and specimens donated by many generous collectors outside the museum, the numbers start to really add up.
Our last estimate puts the holdings of the Canadian Museum of Nature’s National Herbarium of Canada at more than 700 000 vascular plant samples, and that’s not even including the large collections of mosses and lichens.
So why keep all these dead plants glued to sheets anyways? In the inaugural post of this series, I mentioned that each herbarium sample becomes a record for our new flora. It goes much deeper than that: the National Herbarium of Canada, and all herbaria with Arctic collections, underpin the entire project.
We could not write this flora without them. These specimens provide the occurrence data by which we can plot the range of a species onto a map. Data on the habitat type and associated species, often found on the herbarium specimen, inform us about the ecology of the species.
However, the most important function of the collection is to establish and clarify the taxonomy of plants: the naming of natural evolutionary groups that we often call species. Through the examination of the morphology of an individual—the length and shape of the leaf or the microscopic structure of the flower, for instance—we can classify the plant.
A botanist examining a given specimen can assign a plant to a family, a genus and a species, each grouping (or taxon) being more morphologically similar than the last. Based on these increasingly fine morphological distinctions, a key for identifying a species based on shared physical characteristics can be written.
Ultimately, the herbarium is the reference by which a botanist can compare specimens and group them in this systematic manner. This is how we organize all known plant species, and in turn, our Arctic flora of Canada and Alaska.
Maintaining the collection permanently allows botanists to confirm the identity of specimens, correct a mistaken identification, re-evaluate the taxonomic boundaries of a species based on new data, or bring a new perspective to the group.
The truth is that botanists do sometimes disagree on what defines a species (fortunately, these are always civil interactions). However, the more a group of plants is looked at, examined and debated, the closer we can get to an understanding of the true evolutionary relationships within that group.
This is particularly the case when it comes to the recent advent of DNA sequencing and molecular systematics—which in some cases have upended the classification of entire groups. This however, is a story for my next instalment.