Under the scope

I have been busy in the herbarium. I want to write about two problems that I am currently tackling. The first is determining key diagnostic characters useful in identifying and distinguishing two varieties (var. for short) of a species.  My quarry, Schoenoplectus acutus var. acutus (the autonym) and Schoenoplectus var. occidentalis are nearly indistinguishable.  S. var. occidentalis supposedly has three-parted styles and trigonous achens while the autonym has two-parted styles and plano-convex achenes.  I say supposedly, because I’ve found this trait to be unreliable among other sub-specific taxa in Schoenoplectus.  It takes an examination of several specimens to determine whether a character state is consistent or not. The CMC herbarium has specimens of both Schoenoplectus acutus varieties on loan and from field collections made by Central Michigan faculty and students.

Several specimens on loan have been annotated in the past by a recognized Cyperaceae expert. These are the specimens to really clue into to determine consistent diagnostic features. The unofficially word with these varieties… is again styles are not a reliable character as I found a three-parted style on at least one individual identified as the autonym.

The dissecting scope is a necessary tool to track down three-parted styles!

 

The second endeavor I am engaged in is to annotate all of our loaned Schoenoplectus and Schoenoplectiella specimens. Many of these specimens are from Africa and Asia and that means there is a whole new set of characters and different character states that may differentiate these taxa from each other and from the North American (N.A.) relatives. Luckily, I love learning and identification! To complicate things though, the keys and field guides are often not as well developed for these taxa as they are for the N.A. ones. So my hunt of the specimens also becomes a hunt into the literature to find the keys and species descriptions left by past botanists.

 

I learned that a handful of Schoenoplectiella species have clearly-visible septate culms (see picture below). None of the N.A. taxa display this feature. As an aside, do you see the need to examine the global diversity of a plant genus before you can adequately describe the features that encompass that genus; and the enormous time and collaboration that such a task would entail?

 

A look at septate culms

 

One key I found from a 1981 paper was helpful but the author had only examined species from Australia. When I pulled from the cabinet other similar species that did not occur in Australia I found that what I would have identified as one species was actually one of these newly pulled species. It came down to the number of wrinkles on the achenes! It may seem that adding more species to the mix might confuse things but the opposite is actually true; only when I had all of the known Schoenoplectiella species with septate culms from around the globe was I able to confidently distinguish the [6] distinct taxa.

Happy ID’ing

Derek