What should represent a 'range' for a species in iNaturalist

[cazort]

I would answer this question very differently for different types of organisms, and I would hope iNaturalist handles it differently.

Birds are quite mobile, and vagrant birds far from their native range are a relatively frequent occurrence. Ornithologists distinguish different types of range: breeding range, wintering range, migration range, and then various other terms like “casual”, “accidental” or “vagrant”. Casual usually means more frequent than “vagrant” or “accidental”.

The terminology of these ranges are useful to experienced birders. If you count 10 nesting pairs of something in an area, you know you don’t need to check against the “accidental” species. But if a strange-looking gull shows up on the beach in winter, or an unusual warbler in migration, it might be time to check those things. I once saw and photographed a Tropical Kingbird in Philadelphia, and a friend of mine saw and photographed a Townsend’s warbler.

With plants, things are very different. Plants don’t fly around and don’t migrate, and you don’t have the same distinction of non-breeding individuals just hanging out vs. breeding pairs, but some of them do have seeds that blow very far in the wind, float in the ocean, or hitch rides with humans traveling far and wide.

I like how BONAP and the USDA Plants database in theory handle these things. In practice though I find their data is pretty incomplete. For example, the USDA database has categories including “Garden Persistent” and “Waif” for things not-quite-fully-established in the wild in sustaining populations. BONAP uses the “Waif” category but in practice has very few records where it identifies species as having this status in a particular county or region. Also, BONAP, which has more thorough and accurate data than the USDA in many cases, still lacks full-fledged and accurate data on relative rarity of various species in various locations. They usually seem to record this data only by state level, which leads to some weird inconsistencies in their maps, which tend to break down whether the species is present or not by the level of individual county.

I don’t know of any site or reliable source that has range map data that makes these distinctions. So…although when it comes to, say, birds, you can get good sources on the possible range of vagrancy for various species, with plants, you can’t really get this.

When you’re talking about the “range” of a species for the purpose of ID, I think the relevant question is…is there a decent chance of this occurring in the wild?

I.e. if something hasn’t been reported in the area but maybe has been reported in the wild 50 miles away, maybe…just to be safe, it’s worth checking the ID against it. If it has been reported in the immediate area, whether or not it’s native is irrelevant…it’s important to check against it for ID purposes. Then people can separately quibble or discuss about its native vs. introduced status.

I don’t know if this makes sense? Like this discussion arose because of the computer ID suggesting species not found in an area…and I think this is really bad. To this end I think we need to use the standard of whether or not a species is reasonably likely to be found in the general area.

[cmcheatle]

@cazort

Plants don’t fly around and don’t migrate

I’m not sure I would 100% agree with this. While unquestionably individual birds are more mobile than individual plants, as a species, I’d actually consider plants to be more mobile to expand beyond their natural range, especially if you are talking about persisting and expanding beyond their ‘landing point’.

Most vagrant birds are by their nature transient events, an individual ends up off course and in an unexpected place, they either die as a result of their decision, or they move on. But one individual can’t create a sustainable population.

And in terms of ‘flying around’, I think it is certain there is more human intervention in intentionally moving plants beyond their native ranges than takes place for birds or any vertebrates.

[cazort]

Yeah, this makes sense, I think this fits with the main point of what I was saying though, which is that the concept of vagrancy is different with birds.

A vagrant bird is unlikely to set up a stable breeding population…whereas if you see a single plant surviving in the wild, it is likely part of some sort of local population…and even if it isn’t initially, it might be able to start one from a single individual.

This is why I think it makes sense to have different ways of handling the concept of “range” for birds vs. plants. For birds, you need to track both the breeding range, wintering range, and migration range, and then a broader range of “vagrancy” for checking things against.

But with plants…there aren’t these distinctions. Usually I ask…is this plant near enough to places the plant is known to occur, that it could reasonably occur here? And if not, it’s also still possible due to human introductions.

[er1kksen]

It’s often also possible due to range disjunctions and poor prior documentation. I regularly find species in my home county with nearest records well over a hundred miles away, often species with a high Coefficient of Conservatism (very useful concept for working with this type of question specifically) tied to very specific habitat conditions. They’ve been here all along, but this county historically had pretty minimal botanical documentation over large areas, and is not included in the classic ranges of even many species common here, though BONAP is usually a bit better about those. Rarities hanging out in back fields and waste spaces and old woodlots waiting for the “range” we draw to catch up with them.

[cazort]

Yeah! I’ve noticed that certain areas are systematically under-surveyed. For example the USDA lacks data on many common species in Maryland…not only does it lack county-level data, but there are some fairly common plants that are not even marked as occurring in the state. BONAP is a bit better but still has weird gaps that often correspond to state borders, like a lot of species showing up just outside the border in nearly all counties of AL and SC but in very few counties in GA, which seems extremely unlikely.

I suspect that some sort of difference in state-sponsored or state-organized surveys may be responsible for this.

But there are definitely lots of unreported things everywhere!