Rosy boas in California - orcutti vs trivirgata

I haven’t found any of these boas yet inperson (although I hope to…), but I’ve been incredibly confused by the taxonomy and was hoping someone could maybe clarify this. Apparently there are two recognized species of rosy boa on iNaturalist, common names coastal and desert rosy boa.

Here (http://www.californiaherps.com/noncal/baja/bajasnakes/pages/l.trivirgata.html) there is a map showing that the desert rosy boa is only in Baja, Sonora and Arizona while all of the California snakes are coastal rosy boas. On the other hand this source (https://animaldiversity.org/accounts/Charina_trivirgata/) claims that trivirgata is in California. To make matters worse half the websites I can find list them in subspecies instead, and I don’t know if there are even easily seen physical differences between the species. And on iNat itself, there are lots and lots of desert rosy boa IDs in California.

Any boa experts out there?

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I have one of very few sightings of rosy boa in Orange County, California, and identifiers unanimously called it Lichanura orcutti. I don’t know anything about snakes though.

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I’m not an expert (finally saw my first one last month while herping with people familiar with them, woo hoo!) but I think it depends on who you ask. Because taxonomy often changes and because iNat doesn’t want to be a place for people to argue about taxonomy, we try to follow external taxonomic authorities, and for reptiles we follow The Reptile Database for our reptile taxonomy, although deviations agreed on by the community are allowed. This should (in theory) allow everyone to know what is meant by each taxon on iNat, even if everyone doesn’t agree that it’s correct.

Here are The Reptile Database’s page for the species: http://reptile-database.reptarium.cz/species?genus=Lichanura&species=trivirgata and http://reptile-database.reptarium.cz/species?genus=Lichanura&species=orcutti

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And if you want to go to the source of the names currently in use, there is this paper by Wood et al. (2008):

Wood, Dustin A.; Robert N. Fisher and Tod W. Reeder 2008. Novel patterns of historical isolation, dispersal, and secondary contact across Baja California in the Rosy Boa (Lichanura trivirgata). Molecular Phylogenetics and Evolution 46 (2): 484-502.

I didn’t provide the URL since it was very long, but you can google it. You have to wade through a lot of genetic analysis and discussion to get to the taxonomy and distribution information.

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I don’t have at hand my Peterson Field Guide to Western Reptiles and Amphibians by Stebbins and McGinnis (2018) – it’s in my office which I can’t access due to COVID – but maybe that book splits them out and illustrates the range and distinguishing characteristics. But that book has some issues (which is another topic) so might not be a good source.

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For those without access, here are the relevant figures from that article. They group the northern lineages A & B into L. orcutti and they call the southern lineage C L. trivirgata. In their specimens, there was very little geographic overlap between the three lineages.

If I’m reading the paper correctly, prior to this, all rosy boas were considered members of L. trivirgata, which would explain the broader use of that name for Californian individuals. The authors do not propose physical diagnostic characteristics, though a lot may have happened since '08. (These range limits might have been subsequently challenged as well, I am not a herpetologist).

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That map is really interesting. Seems based on this all of the California trivirgata IDs should be re-IDed as orcutti unless they are in that one tiny section of San Diego county by Dulzura/Otay mountain. Thanks to all for the help!

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More or less, yes. All Lichanura in California are currently considered L. orcutti unless they are in the Otay or Tijuana riversheds of extreme southern San Diego county (and in some of these areas, the two species live in sympatry). The authors do propose some characters to separate the two lineages in the species description. They describe these characters as tentative, but they might be helpful to some. From the paper:

Mean scale counts of both ventral and subocular scales in Lineage A + B are higher (ventral scales ~235 and subocular scales ~3–7) than Lineage C (ventral scales ~228 and subocular scales ~0–2).

Lineage A + B here corresponds to L. orcutti and Lineage C is L. trivirgata.

However, many people ID things without understanding the current state of the taxonomy, or more insidiously, because they think the taxonomy is “wrong.” This happens with the Arizona Mountain Kingsnake complex as well. It’s largely responsible for why I’ve stopped IDing reptiles and amphibians on iNat- I’ve often run into ID-ers who have been rude about these things.

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Indeed. There are strong opinions among some ophidiophiles about current snake taxonomy. I’m skeptical myself about some current taxonomy but not enough to refuse to acknowledge what is in use either on iNat or elsewhere. I suspect some species splits will eventually be reversed but in the mean time I try to follow what is being recognized.

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I think that’s the way it’s supposed to go. Personal opinions about snake taxonomy aside, iNaturalist follows specific taxonomic standards for reptiles and amphibians in North America (the SSAR North American checklist) and so identifications on the site should reflect the SSAR taxonomy to the best of the ID-er’s ability.

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Welcome to the forum!

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What about the trivs out on black mountain (Lineage A, C21)? I thought that the boas on black mountain were desert rosys. They look more like trivs than B11

According to the paper, the boas on Black Mountain, Imperial County are L. orcutti because they’ve got haplotype C21 (part of lineage A).

I’m not sure what to say about “looking” more like L. trivirgata than the B11 haplotypes in the Otay/TJ river watersheds. Morphological work sounds like it’s messy and there may not be a 1:1 correspondence between morphology and species limits as they’re currently described.

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