Three species of Junonia buckeye butterflies in South Texas

After decades of confusion about Junonia buckeyes in South Texas (and just about everywhere else), help has arrived by way of a massive study, Speciation in North American Junonia from a genomic perspective (Cong et al. 2020).

In short, three species occur in South Texas:

  • Junonia coenia (Common Buckeye), the familiar species widespread across the eastern U.S. and found statewide in Texas
  • Junonia neildi varia, a newly named subspecies of Black Mangrove-feeding buckeye found along the coast up to about Aransas County
  • Junonia stemosa, a newly named "dark" buckeye of South Texas that's genetically distinct from the similar Junonia nigrosuffusa of the southwestern U.S. (including the Trans-Pecos)

According to Cong et al., the following species do NOT occur in South Texas:

  • Junonia evarete - South America only
  • Junonia genoveva - South America only
  • Junonia litoralis - South America only
  • Junonia nigrosuffusa - but this species does occur in the Trans-Pecos
  • Junonia zonalis - Caribbean islands and South Florida only

This figure from the paper lines up the three South Texas species and points out key field marks: https://onlinelibrary.wiley.com/cms/asset/c1a158a4-db65-4346-ad45-1b8d19754cfa/syen12428-fig-0004-m.jpg

And this figure has a geographic map and visual depictions of how the genes cluster: https://onlinelibrary.wiley.com/cms/asset/42873b04-4bef-449a-9181-7a7cdba2d832/syen12428-fig-0006-m.jpg

The full paper (http://www.butterfliesofamerica.com/docs/Junonia-syen.12428.pdf) has rich detail and figures. Variability among individuals and hybridization between species can make things complicated, but most individuals should be readily identifiable. And even better if you can photograph the underside of the antennal clubs, the color of which is important to species identification.

Common Buckeye, Junonia coenia

This is the familiar, abundant, statewide species with cream-colored stripes on both sides of the large eyespot on the dorsal forewing, as if melted white chocolate is flowing around the spot. That eyespot has a complete brown ring surrounding a pale inner ring -- it looks like a bullseye. This species also has a dark underside on the antennal club, if you can photograph that (get low and shoot from in front or in profile).

Common Buckeye (Junonia coenia), Georgetown, cc-by-nc @jcochran706

Common Buckeye (Junonia coenia), National Butterfly Center, cc-by-nc @kristybaker

"Mangrove" Buckeye, Junonia neildi varia

This newly named subspecies (the nominate subspecies occurs in Florida and the Caribbean) feeds on Black Mangrove as a caterpillar and is found along the immediate Gulf Coast. It's a large, orange buckeye, and one of the most striking field marks is that the large eyespot on the dorsal forewing is surrounded by orange and generally lacks a dark ring enclosing the eyespot. The eyespots on the dorsal hindwing approach each other in size (one tends to be much larger than the other in Common Buckeye), and the underside of the antennal club is dark.

"Mangrove" Buckeye (Junonia neildi varia), South Padre Island, cc-by-nc @javigonz

"Mangrove" Buckeye (Junonia neildi varia), South Padre Island, cc-by-nc @taogirl

"Twintip" Buckeye, Junonia stemosa

Named for its larval host plant, this is the "dark" buckeye of South Texas, a newly described cryptic species. It lacks the creamy forewing band of Common Buckeye -- that area of the wing is brown, pale, or orange -- and can be quite dark brown. Like Common Buckeye and unlike the mangrove species, this species tends to show a complete brown ring around the large eyespot on its forewing. The undersides of its antennal clubs are pale, setting it apart from the other two species in the region. Cong et al. note that adults can occur in the same fields as the other two species, but the larva have special adaptations to feed on Stemodia lanata, which Common Buckeye larva cannot do because of the plant's wooly leaves.

"Twintip" Buckeye (Junonia stemosa), Padre Island, cc-by-nc @mako252

"Twintip" Buckeye (Junonia stemosa), National Butterfly Center, cc-by-nc @armanmoreno

Oddballs

Hybrids among these three species do occur, and each species has quite a bit of potential for intraspecific variation as well, which means that some individuals we encounter are not going to fall neatly into one category or another. Here's an example -- is this a darker-than-usual Common Buckeye or a lighter J. stemosa?

Buckeye (Junonia sp.), South Padre Island, cc-by-nc @sunnyspi

Cong et al. note that J. coenia and its western counterpart J. grisea have a "dark form, which may be induced by environmental conditions" and that this form "may easily be mistaken for J. nigrosuffusa, J. stemosa, or hybrids between species." Figure 19 on page 31 of the paper shows examples.

They suggest the color of the underside of the antennal club (called the "nudum") is the best way to identify a confusing individual -- it would be pale in J. stemosa and brown in J. coenia. But most photos posted to iNaturalist don't show this detail. Here's what they authors say in this case (emphasis mine -- and as you read, note that that neither J. grisea nor J. nigrosuffa occur in South Texas1):

If inspection of the nudum is not possible, the single most reliable character to distinguish between J. grisea/coenia and J. nigrosuffusa is the coloration of the area by the dorsal forewing costa near apex: between the postdiscal paler band (or its remnants in J. nigrosuffusa) and apical paler spots. This area is covered by extensive pale overscaling in J. nigrosuffusa and is mostly brown in J. grisea/coenia. Identification of J. stemosa may be more challenging, because many individuals, especially females, lack the pale overscaling, and their more rounded shape of wings may be the best character besides from the pale colour of the nudum. Then, some J. stemosa males (e.g. Fig.8, right specimen in the second row) and most females (Fig. 9, specimens on the right) may not be very dark, and the otherwise indistinct postdiscal forewing band is orange or even whitish, resembling J. grisea/coenia. Finally, to add to these complexities, a number of J. coenia individuals may have similar orange band. This form even received an infrasubspecific (and thus ICZN-unavailable) name, ‘tr. f. rubrosuffusa’ (W. D. Field). Not knowing the nudum colour, it may be impossible to identify such specimens with confidence, and the only other general character (which needs some practice to recognize) is the wing shape: more rounded in J. stemosa and J. nigrosuffusa, and more angular in J. coenia and J. grisea.

So, if you see an intermediate-looking buckeye, do try to get an image that shows the underside of the antennal clubs!

1Melanie Lalande's work shows J. grisea occurring in the Trans-Pecos, however: https://www.butterfliesofcuba.com/uploads/3/0/6/1/30612147/melanie_lalonde_finalized_thesis_reduced_size_4__junonia.pdf -- and as I noted previously, J. nigrosuffusa occurs in the Trans-Pecos as well.

iNat Taxonomy and IDs

The Pelham catalog has integrated Cong et al. into its taxonomy: https://www.butterfliesofamerica.com/US-Can-Cat.htm, but as of early December 2020, the iNaturalist taxonomy hasn't been fully updated yet. Junonia stemosa does not exist in the iNaturalist taxonomy (and the split of western Junonia grisea from J. coenia hasn't been done -- though that's not an issue for South Texas). However, J. neildi varia does exist in the iNaturalist taxonomy, so we can identify the Texas mangrove buckeyes at least.

Update July 5, 2021: The iNat taxonomy has been updated thanks to @nlblock and others!

I created an Observation Field that we could use to track some of these things but haven't started using it yet: https://www.inaturalist.org/observation_fields/12818

There appear to be 300-400 observations that will need to get sorted out to reflect this new approach to the taxonomy of our buckeyes once the iNat database is updated -- though of course some individuals will never fit neatly into our categories, and that's part of the fun.

FYI if of interest @aguilita @brdnrdr @hydaticus @gcwarbler @jrcagle @kathrynwells333 @kbbutler @maractwin @nlblock @sambiology @stomlins701

Posted by djringer djringer, 06 December, 2020 00:35

Comments

This is so great! Thanks for explaining it so nicely here and using iNat observations.

Posted by javigonz about 2 years ago (Flag)

Super interesting, David. Thanks!

Posted by sambiology about 2 years ago (Flag)

Outstanding post -- thanks for the detailed summary.

@pattypasztor @tonzetich You may find this of interest.

Posted by kbbutler about 2 years ago (Flag)

Great stuff!

Posted by hydaticus about 2 years ago (Flag)
Posted by jrcagle about 2 years ago (Flag)

Great (and helpful!) information; thanks so much!

Posted by kathrynwells333 about 2 years ago (Flag)

Great and super interesting!

Posted by brdnrdr about 2 years ago (Flag)

Thanks, David! This is really an outstanding discussion and summary of the Texas situation.

Posted by kennkaufman about 2 years ago (Flag)

wonderful! Thanks for doing the work and pulling this together.

Posted by taogirl about 2 years ago (Flag)

This will help tremendously, there has been so much confusion in this genus, including from published texts.

Posted by stomlins701 over 1 year ago (Flag)

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