Something very strange has happened to observations of rock elm (Ulmus thomasii) on iNat. There used to be a high density of observations in the Midwest (MN, WI and a few in IL, IN, MI, OH). Now, however, there is only one verifiable observation in MN and two in OH. When you include casual observations, only three additional observations show up - two in MI and one in OH.
Where did the rest of them go?? @owenclarkin, by far iNat’s top observer of rock elm, has observed the same phenomenon. We are out of explanations!
Thanks to @wdvanhem for raising this: I thought the one person who still has an observation from that area @danders4 had more than one observation for Rock Elm, but maybe I’m wrong. Also, my default map used to show records without media: e.g. a few Rock Elms I knew about in Michigan and Sarnia that I uploaded to get them into iNat used to show up, but now I have to change the map settings to show observations including those without verifiable media even though I link to media (websites, google streetview) in some of them. So it indeed seems to me that there may be some records in e.g. Minnesota/Wisconsin that are “gone” but I am not able to confirm this. I can say that the iNat observations have generally been Ontario dominated to date, as I look hard for Rock Elms and post the ones I find to iNat (so presumably there is sampling bias, with me filling in the range more thoroughly than is done in say Michigan and Wisconsin where the species is probably roughly as common)
I guess the question is whether any observations for Ulmus thomasii have actually disappeared from iNaturalist. I cannot confirm whether any have. I presume iNaturalist has robust backups of imported data, so I doubt anything would be “lost”.
The species’ reported “heartland” for range is typically given in textbooks as Ontario-Michigan-Wisconsin. I can say there have always been relatively few records from these USA states on iNaturalist which surprises me as the species is quite conspicuous (e.g. corky twigs are often present) and even in the post-Dutch Elm Disease world remains “findable” in Ontario/Quebec even if the species is, in my opinion, threatened due to a continually declining population.
The one user with a record in Wisconsin has confirmed that he only has uploaded the one record to iNaturalist, https://www.inaturalist.org/observations/6597749 (the record) https://www.inaturalist.org/observations/21409804 (his comment on one of my records)
@natdisc the NY observations show up for me but there have never been many from that area.
It could very well be the case that I was just imagining a cluster of observations in MN/WI. I know rock elm is somewhat rare, but the number of observations outside Ontario seems really low.
That’s funny. I doubt you were imagining it, but who knows!
In NY, it is listed as S2-S3/threatened, though I suspect it is more common than that implies. On the NY Flora atlas page you can see there are plenty of historical records http://newyork.plantatlas.usf.edu/Plant.aspx?id=3047 for NY. In northern NY (Jefferson and St. Lawrence Counties, close to Ontario) I think it is not that uncommon, but more local and easily overlooked (and I should be better at sending in records to Heritage or INat!). Easily found on alvar, and also (though less common) in other limestone areas, but I’ve seen it associated with sandstone as well in Jefferson County. In western NY I’ve only seen it once, on a limestone escarpment (between Rochester and Buffalo) - in that part of NY it is pretty uncommon.
It’s very rare in Vermont - maybe endangered - i don’t think I’ve ever seen it. No point to obscure it or anything, no one is gonna go dig it up. Neat edge of range thing though.