Making the case for Spiranthes lacera var. lacera

Most Spiranthes lacera encountered in western North Carolina are expected to be Spiranthes lacera var. gracilis. We encountered plants that could most definitely be ascribed to Spiranthes lacera var. gracilis in one population. South of the first site, we discovered plants that looked suspiciously like the other variety, Spiranthes lacera var. lacera. Here, I make the case that these plants could possibly be Spiranthes lacera var. lacera, the northern slender ladies' tresses.

 

1. Regarding the arrangement of flowers on the stem.

Spiranthes lacera var. lacera = loosely arranged.

Spiranthes lacera var. gracilis = densely arranged on the stem.

I just don't see this as a valid taxonomic character for any species, ever. It is well-known that internode length is an extremely plastic character, and can vary based on light conditions, soil moisture conditions, how compacted the soil is, and the fertility of the soil. Maybe there really is a genetic basis to the difference, but I'm not convinced.

 

2. Regarding the distribution.

Spiranthes lacera var. gracilis is likely to be the more common of the two species found in this area.

Yes, southwestern NC may be a stretch, but according to distribution maps in the Flora of North America, it's still possible, even though it's not the more likely of the two varieties in the area. Also, what if var. lacera is thought to be even less common than it is because people simply aren't looking for it? In other words, they expect to see var. gracilis, and that's what they "see" (the self-fulfilling prophecy). It could be that most people don't examine every plant in every population, and that they are simply overlooking var. lacera because it is less common.

 

3. Regarding the pubescence.

Spiranthes lacera var. lacera = pubescent with capped hairs (capitate)

Spiranthes lacera var. gracilis = essentially glabrous

The plants were faintly pubescent. Most certainly not "essentially glabrous", as described in FNA (what "essentially" means, I don't know). So this is a sort of distinguishing feature...

 

4. Regarding the leaves.

Usually persisting through flowering in var. lacera or usually absent in var. gracilis.

This is another tricky character. It was a warm spring with a terrible heat wave, making me think that if the environment was going to cause leaves that are usually absent to be present at anthesis, this would not be the year. On the other hand, perhaps this site is more damp than most other sites where Spiranthes lacera var. gracilis is found. I can verify, however, that leaves were present on the plants in this population, but not at the population of plants noted as Spiranthes lacera var. gracilis.

 

( 5. Regarding the laceration of the lip. )

Luer (1975) observes that the lip of Spiranthes lacera var. gracilis is more undulate and less lacerate than that of Spiranthes lacera var. lacera.

These plants seems like they fall in line with this description, although Luer himself does not consider this to be a "binding distinction", so perhaps it is best not considered (even though it supports my case!).

 

So, where does that leave us? I haven't made up my mind, but I'm inclined to go with the less common answer of Spiranthes lacera var. lacera. But perhaps these two varieties should not even be separated at all, if distinguishing them requires that I write a thesis in defense of my position.

Done