Journal archives for December 2020

06 December, 2020

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 on 06 December, 2020 00:35 <span class="translation_missing" title="translation missing: en-gb.by">by</span> djringer djringer | 10 comments | Leave a comment

30 December, 2020

A South Texas ID Frontier: Leaf Miners

Texas (and Texas-visiting) iNatters: We have a big ecological mystery on our hands. Most of the leaf-mining insects found on iconic Texas plants like Anacua, Mexican Olive, Coma, Zanthoxylum species, and even roadside composites like Palafoxia are poorly known or in some cases perhaps even new to science.

I found this leaf miner yesterday (12/29/20) on a Bernardia myricifolia plant at Resaca de la Palma State Park in Cameron County. The larva is visible near the top of the translucent mine. Its identity is unknown, though leaf miner expert Charley Eiseman thinks it may be a moth in the family Heliozelidae.

You may recall leaf structure diagrams like this from your biology textbooks -- a few cells, stacked in discrete and specialized layers, the whole thing often just a couple hundred micrometers thick:

Image CC-BY-SA Zephyris

Leaf miners are the larvae of insects -- moths, flies, sawflies, and beetles -- that are so tiny they live between the epidermal layers of the leaf, eating the cells of the mesophyll and creating distinctive, often beautiful patterns in the process.

Many leaf miners are highly specialized on certain species, genera, or families of plants, so knowledge of the host plant's identity along with the visible characteristics of the mine can often support field identification of the miner.

Charley Eiseman (@ceiseman) is the author of Leafminers of North America -- the first reference guide to these species -- and curator of the Leafminers of North America project here on iNaturalist, which I encourage you all to join, but more on that in a moment.

Over the last couple of moths as I've documented leaf miners in south Texas and corresponded with Charley, I've discovered that most of the apparently common leaf miners in south Texas are unknown -- either "known unknowns" or "unknown unknowns." Furthermore, there seem to be ample opportunities to document new plant-insect interactions and significant range extensions of known insect species.

What You Can Do

If you live in or visit south Texas, I encourage you to join the Leafminers of North America project here on iNaturalist and begin documenting leaf miners in the area. Here are some tips:

  • Begin to train your eye to spot the squiggles and patterns leaf miners create on foliage -- you'll get the hang of it fast.
  • Photograph the top and bottom of the leaf, even if you can't see anything on the underside.
  • Get a backlit shot of the leaf if you can.
  • Make sure to document the plant species on which you found the miner as well.
  • Manually add your observations to the Leafminers of North America project, and fill out the host plant species field that pops up when you add your observation to the project.
  • If you have no idea what made the mine, you can enter it as Pterygota (Winged and Once-winged Insects), which is the insect subclass that contains all the mining groups.

Ultimately, a lot of these insects will need to be reared to adulthood and analyzed by specialists to identify them (and, when warranted, name new species). That could be a great project for a Texas Master Naturalist chapter, grad students, etc., particularly so that appropriate permissions and ethics could be assured.

Maybe leaf miners will never have the status of birds or butterflies in south Texas, but what a great opportunity to advance scientific knowledge!

Here are some of my early observations organized by plant family (most of the information noted below comes from discussions with Charley Eiseman).

Plant Family Boraginaceae

There's a moth larvae that lives in the leaves of Anacua (Ehretia anacua). It seems to be a gracillariid moth in the genus Dialectica but the species is unknown.

And on Cordia boissieri (Anacahuita or Mexican Olive), there's a miner that also appears to be Dialectica sp., but it's also unknown. See comments here on a moth reared from Cordia sp. in Florida: https://bugguide.net/node/view/865617/bgpage

Plant Family Malvaceae

In November, I noticed blotch mines all over the Turk's Cap (Malvaviscus arboreus) at Sabal Palm Sanctuary. It turns out no miners are known from Malvaviscus, so this insect is a big mystery. I have been checking Turk's Cap plants ever since at other locations but have not found similar mines.

I found this solitary mine on Malachra capitata at Resaca de la Palma State Park. No miners are known from Malachra, but this appears to be an agromyzid fly.

Plant Family Sapotaceae

These beautiful little mines seem to be common on Coma (Sideroxylon celastrinum) across the Rio Grande Valley, but there's apparently no scientific documentation of a leaf miner on this species. The leading candidate seems to be the moth Parcetopa bumeliella, which is known from other species in genus Sideroxylon.

Plant Family Rhamnaceae

This is one of those "unknown unknowns" -- a small blotch mine on the thin leaves of Condalia hookeri (Brasil or bluewood). @ceiseman's comment on this one was, "Something completely unknown... the only Condalia leafminer I know of is an undescribed nepticulid I found on another Condalia species in Texas."

Plant Family Rutaceae

Sierra Madre Torchwood (Amyris madrensis) can have abundant mines on its leaflets, but the insect species that makes them is unknown.

Recently I've noticed these very tiny mines on Zanthoxylum fagara leaflets (Wild Lime or Lime Pricklyash). This is also an unknown species; Charley Eiseman thinks it may be a moth that mines early in its life and then exits the leaf to continue larval development somewhere else.

This mine on Zanthoxylum hirsutum (Texas Hercules' Club, etc.) at Aransas NWR may represent the first record of the moth Fomoria pteliaeella on this plant species.

Plant Family Asteraceae

This mine, apparently from a Liriomyza fly, was on a dwarfed Texas Palafoxia (Palafoxia texana) plant in a mowed strip adjacent to a parking lot at the South Padre Island Convention Center. And it turns out to be not only the first record of a leaf miner from the genus Palafoxia but one of only two for the tribe Bahieae.

This blotch mine on Blue Boneset (Tamaulipa azurea) is the presumptive first record of a leaf-mining fly (family Agromyzidae) from Tamaulipa.

They fly that makes these linear mines on Mexican Trixis (Trixis inula) is an unknown species.

Plant Family Cactaceae

The moth Marmara opuntiella makes mines (technically stem mines, in this case) on prickly pear pads. I've recorded the species on Opuntia alta and O. gomei in Cameron County, both of which are presumptive new host records for this species.

Plant Family Rubiaceae

I have found two miners on West Indian Milkberry (Chiococca alba). The first is an unknown species of Marmara moth.

The second is apparently an ermine moth called Podiasa chiococcella that has previously been recorded only from Florida.

Plant Family Sapindaceae

This little miner was working on a leaflet of Urvillea ulmacea (Apaac) at Resaca de la Palma State Park. No leaf miners are known from the genus Urvillea, so its identity is a complete mystery.

Plant Family Apocynaceae

While some Liriomyza flies are known to mine milkweed leaves, there are no known species that specifically mine Pearl Milkweed (Matelea reticulata), like this one on the bird blind at Resaca de la Palma State Park.

Plant Family Cannabaceae

This is one of the "known unknowns" -- an unknown species of Stigmella moth that occurs on Celtis pallida (Spiny Hackberry or Granjeño).

Unknown Plant Family

I think I said, "Oh, cool!" out loud when I saw this herringbone-pattern mine, but I haven't been able to figure out the plant species it's on. The plant observation is here: https://www.inaturalist.org/observations/67272345 -- can anyone shed a little light?

I hope this will serve as an inspiration to some and a step toward greater knowledge about these interesting organisms. Thanks to those of you who have been helping with my plant IDs, by the way, which is an important part of this process!

Tagging a few of you who may be interested: @jciv @matushkaelizabethperdomo @bcfl14 @dingooctavious @javigonz @vanwest @gcwarbler @johnyochum @ernest5h @oleanderseth @sambiology @greglasley @maraleemoats @jcochran706 @sa88lebags @joshua_tx @beschwar

Posted on 30 December, 2020 19:55 <span class="translation_missing" title="translation missing: en-gb.by">by</span> djringer djringer | 5 comments | Leave a comment

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