[Ctleps-l] Commentary on 'Searching for ‘Appalachian’ Tiger Swallowtails in the North Carolina Mountains' in American Butterflies

[hpazures at aol.com]

All:
After publication of Glassberg's article, several people have inquired with me regarding the status of the Appalachian Tiger Swallowtail (Pterourus appalachiensis), thinking it is now just a "subspecies" of the Eastern Tiger Swallowtail because that is Dr. Glassberg's opinion based on viewing two single specimens during a brief trip!  Sorry, but this is just plain wrong.
Commentary on Searching for ‘Appalachian’ TigerSwallowtails in the North Carolina Mountains by Jeffrey Glassberg (AmericanButterflies 29(3), page 22, by Harry Pavulaan.


 
In this article, Dr. Glassberg’s personal view that“it’s not clear that Canadian and Eastern Tiger Swallowtails are actually twospecies…” contradicts what several experts in the field have concluded manydecades ago with numerous scientific studies. I grant him his personal view that these are a single species,but he’s in the minority view and does not concur with the actual experts onthe subject who have done the research. So much for scientific research.


 
At issue here is that many species are no longer considered clear-cut“black and white” entities by those doing actual research.  There are gray, mosaic or checkerboard areasof many degrees between many species.  Speciesboundaries are apparently being discovered to be fluid or porous, leading toexchange of genes between closely-related species (introgression).  Some taxa fly together in some areas andbehave as separate species, while in other areas, they comingle and interbreedfreely.  Tiger Swallowtails aside, thewestern Fritillaries and Blues all present a similar challenge to the biologist.  Dr. Glassberg cites his doubt of speciesstatus of Canadian and Eastern Tiger Swallowtails as “they appear to hybridizeover a large area in the northeast”. It’s not that simple.  Several studieshave demonstrated that the purported northeastern hybrid zone consists of atleast four distinct taxa: Pterourus glaucus, P. canadensis, an “earlyflight” (EF) taxon and a “late flight” (LF) taxon.  The EF and LF taxa occur north (or above) ofwhere glaucus is able to produce two annual generations and where it is generallytoo cold for glaucus to survive the winter.  The EF and LF taxa are stable entitiesproduced over thousands of years of hybridization between glaucus and canadensisduring the last glacial maxima.  They maynot fit traditional characterizations as “species” but are uniquely evolved taxathat may or may not be considered species, depending on which “species concept”you follow.  Yet they are not activehybrid populations, though some research points to the LF taxon as a possible recentdevelopment of introgression of glaucus genes into canadensis inplaces like Vermont.  In Ontario, it isbelieved that the LF taxon represents a valid species-level taxon – the“Mid-summer Tiger Swallowtail”.  Whateverthe case, one must be careful not assume that two species, glaucus and canadensis,are individually cross-mating throughout a purported “hybrid zone”.


 
I will admit that there appears to be active hybridizationgoing on in New England, but all evidence I’ve seen shows it is NOT glaucus xcanadensis.  It is likely that glaucusis hybridizing with the LF (Mid-summer Tiger Swallowtail) taxon in southern NewEngland, as there are appears to be a broad range of intermediates between thetwo in summer, but it’s still not so simple. There are other factors at work. Thus, species are not “black and white” and we have to accept that thereare other classes of taxa that are of unique status.  The EF Tiger appears quite distinct from glaucusin New England, and could be much older than the LF Tiger that could be a muchmore recent development.


 
The Appalachian Tiger Swallowtail is one such “hybrid” taxon,though it has fully speciated since the last ice age.  It is not, as Dr. Glassberg suggested: a“subspecies” of the Eastern Tiger Swallowtail. It is accepted by biologists that two subspecies cannot be fully (100%)sympatric, and do not occupy the same range, habitats, and flight period.  The Appalachian Tiger inhabits higherelevations of the southern and central Appalachian Mountain region.  Unfortunately, Dr. Glassberg did not spendenough time in the N.C. mountains to see the females, that are strikinglydifferent from Eastern Tiger females. Females of both species can be found together, and over many years ofstudying these, I have found no “intermediates” suggestive that they are thesame species, nor clear evidence of hybridization.  Dr. Glassberg’s two sightings of males inNorth Carolina does not weigh against decades of research by the “experts” onthe subject.


 
For those of you still doubting the status of theAppalachian Tiger Swallowtail, do your own research.  See what the experts (and some observantauthors) are finding.  Here is some help:


 
BIBLIOGRAPHY OF PTEROURUS APPALACHIENSIS LITERATURE


 
Belth, J.E.  2013.  Butterflies of Indiana – a Field Guide.  Indiana University Press, Bloomington,IN.:  328 pp.  https://books.google.com/books?hl=en&lr=&id=c9B4x7j6cJEC&oi=fnd&pg=PP1&dq=papilio+appalachiensis&ots=15RTJIUunp&sig=nI_RcB7WojxYV0SirwkjkzfF2FY#v=onepage&q=papilio%20appalachiensis&f=false


 
Borchelt, R. 2014.  Side by SideSwallowtails:  Eastern and AppalachianTigers.  LepLog.  May 20, 2014.

https://leplog.wordpress.com/2014/05/20/side-by-side-swallowtails-eastern-and-appalachian-tigers/


 
Bright, S.B., V. Charny & W.M. Howell.  2013. Butterflies: New records for Alabama. Journal of Alabama Academy of Science 84(1):  37-42. https://alabama.butterflyatlas.usf.edu/static/documents/JAAS_Vol_84_No1_37-42.pdf


 
Chapman, P.D., S.P. Bradley, E.J. Haught, K.E. Riggs, M.M.Haffar, K.C. Daly & A.M. Dacks. 2017.  Co-option of amotor-to-sensory histaminergic circuit correlates with insect flightbiomechanics.  Proceedings of the RoyalSociety B 284: 20170339.  http://dx.doi.org/10.1098/rspb.2017.0339


 
Cong, Q., D. Bork, Z. Otwinowski & N.V. Grishin.  2015. Tiger Swallowtail genome reveals mechanisms for speciation andcaterpillar chemical defense.  CellReports 10(6):  910-919.

https://doi.org/10.1016/j.celrep.2015.01.026


 
Kunte, K., C. Shea, M.L. Aardema, J.M. Scriber, T.E.Juenger, L.E. Gilbert & M.R. Kronforst. 2011.  Sex chromosome mosaicismand hybrid speciation among Tiger Swallowtail butterflies.  Plos Genetics 7(9): e1002274. https://doi.org/10.1371/journal.pgen.1002274


 
Mavárez, J. & M. Linares. 2008.  Homoploid hybrid speciationin animals.  Molecular Ecology 17:4181-4185.  doi:10.1111/j.1365-294X.2008.03898.x  

https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.531.8795&rep=rep1&type=pdf


 
North Carolina Dept. of Parks.  2021. Butterflies of North Carolina: their Distribution and Abundance.  Online: https://auth1.dpr.ncparks.gov/nbnc/a/accounts.php?acctID=6


 
Ogard, P.H. 2010.  Butterflies of Alabama –Glimpses into Their Lives.  University ofAlabama Press

https://books.google.com/books?hl=en&lr=&id=TtgtDwAAQBAJ&oi=fnd&pg=PT12&dq=butterflies+of+alabama&ots=CYa8yIplf5&sig=cc9kU5Au0qpYOk15E3Y836L1zLI#v=onepage&q=butterflies%20of%20alabama&f=false


 
Ording, G.J., R.J. Mercader, M.L. Aardema & J.M.Scriber.  2010.  Allochronic isolation and incipient hybridspeciation in tiger swallowtail butterflies. Oecologia: DOI 10.1007/s00442-009-1493-8.  9 pp.

https://d1wqtxts1xzle7.cloudfront.net/43328971/Allochronic_isolation_and_incipient_hybr20160303-26273-q7ohdq.pdf?1457046190=&response-content-disposition=inline%3B+filename%3DAllochronic_isolation_and_incipient_hybr.pdf&Expires=1631839179&Signature=Grnec6NqNsIe66MYEdcB2KTTIWfvti~cD6Cy-p0xp~ow2hDsbQQzo96CBH7ZklPTC--ueTx5paEjgjOaxdBUBH2iQGt9BzhwuZcHTGxsr9ArCzEo0QXcv1n~uyugb84~YR9ZqJfGmLQa2PDWWjJ5g-rISo2WJWLnwEIFJYLFzB2X9RnCCKx3RoBRueSGGAL-e716pNUClC6BaismukGZly-9k~3p5GViUjx~OQcyJ0QxCLdf1HTwE1Zw35GJivYyEj~S5pVkNJJKivlN7CC-Y9-0E81mTuXNXLsRIs6yUdeFqrB569RiRiln1jKXdxuACzlfDoIYmUiq9Pb2itztLA__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA


 
Pavulaan, H. & D.M. Wright.  2002.  Pterourusappalachiensis (Papilionidae: Papilioninae), a new swallowtail butterflyfrom the Appalachian region of the United States.  The Taxonomic Report of the InternationalLepidoptera Survey 3(7):  20 pp.  http://www.lepsurvey.carolinanature.com/ttr/ttr-3-7.pdf


 
Pavulaan, H. & D.M. Wright.  2004. Discovery of a black female form of Pterourus appalachiensis (Papilionidae:Papilioninae) and additional observations of the species in West Virginia.  The Taxonomic Report of the InternationalLepidoptera Survey 6(1):  10 pp.  https://www.lepsurvey.carolinanature.com/ttr/ttr-6-1.pdf


 
Schmidt, B.C. 2019.  More on Ontario TigerSwallowtails.  Ontario Insects 2019:  11 pp.

https://www.ontarioinsects.org/publications/Summaries/2019_tigers.pdf


 
Scriber, J.M. 2010.  Impacts of climate warmingon hybrid zone movement: Geographically diffuse and biologically porous“species borders”.  Insect Science18(2):  121-159.    https://onlinelibrary.wiley.com/doi/10.1111/j.1744-7917.2010.01367.x


 
Scriber, J.M. 2013.  Climate-driven reshufflingof species and genes: Potential conservation roles for species translocationsand recombinant hybrid genotypes. Insects 5(1): 1-61.

https://www.mdpi.com/2075-4450/5/1/1/htm


 
Scriber, J.M. 2015.  Tales of Three Tigers: A50-Year Career-Shaping Journey Chasing Swallowtail Butterflies.  In: Dyer, L. & M. Forister (eds),The Lives of Lepidopterists.  SpringerInternational Publishing, Switzerland.  https://doi.org/10.1007/978-3-319-20457-4_10


 
Scriber, J.M. B. Elliot, E. Maher, M. McGuire & M.Niblack.  2014.  Adaptations to “thermal time” constraints in Papilio:Latitudinal and local size clines differ in response to regional climatechange.  Insects 5: 199-226.  file:///C:/Users/harry/Downloads/insects-05-00199-v2%20(2).pdf


 
Scriber, J.M. & G.J. Ording.  2005. Ecological speciation without host plant specialization; possibleorigins of a recently described cryptic Papilio species.  Entomologia Experimentalis et Applicata115(1): 247-263.  https://doi.org/10.1111/j.1570-7458.2005.00285.x


 
Scriber, J.M., G.J. Ording & R.J. Mercader.  2008. Introgression and Parapatric Speciation in a Hybrid Zone.  Chapter 6. In: Tilmon, K. (ed.). Specialization, Speciation, and Radiation: The Evolutionary Biology ofHerbivorous Insects.  CaliforniaScholarship Online: 69-87.  https://california.universitypressscholarship.com/view/10.1525/california/9780520251328.001.0001/upso-9780520251328


 
University of Texas at Austin.  2011. Appalachian tiger swallowtail butterfly is a hybrid of two otherswallowtails, scientists find.  Phys Orgonline, Sept. 8, 2011. 

https://phys.org/news/2011-09-appalachian-tiger-swallowtail-butterfly-hybrid.html


 
Zhang, W., K. Kunte & M.R. Kronforst.  2013. Genome-wide characterization of adaptation and speciation in tigerswallowtail butterflies using de novo transcriptome assemblies.  Genome Biology and Evolution 5(6):1233-1245.  https://academic.oup.com/gbe/article/5/6/1233/619586?login=true


 
Seeing is believing. If anyone is interested in viewing this magnificent swallowtailfirsthand, please write to me and I’ll consider organizing a field trip to thebest location to see it in West Virginia, or provide directions.

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