Limenitis Complexities

A “white admiral” butterfly in South Jersey? Photo by Kerri Sellers, Rancocas Nature Center, 8-2-12

Kerri Sellers of the Rancocas Nature Center managed to photo the eye-catching butterfly above with her cell phone on Thursday, Aug 2.

The Nature Center has a rock driveway which frequently attracts red-spotted purples basking and sometimes puddling. This morning at about 9:30 I spotted this individual take off from the driveway and land on the front porch in front of me. I grabbed my phone to take a picture, but it flew away before I could get the shot.

Knowing that butterflies tend to linger in the driveway area, I came back out about 15 minutes later and [refound] it. This time it landed right in front of me, but in an effort to photograph it, I scared it away and lost it.

Once again, I came back inside, and went out to look for it 15 minutes later. [This time] it landed on a vine that is growing on the barn [and] I finally got the picture.

Overall, it hung around the same area for about an hour or so, although only present for a minute or so each time. I was outside fairly frequently for the rest of the day and did not see it again.

Close-up of same “white admiral” type at Rancocas Nature Center, cell phone photo by Kerri Sellers, 8-2-12.

Some of us have dreamed about finding a white admiral in South Jersey — that is, the northern subspecies of the red-spotted purple/white admiral complex, Limenitis arthemis. White admirals are the sub-species L. a. arthemis; our local red-spotted purples are the subspecies, L.a. astyanax. They mate with each — as subspecies are supposed to do –in the overlapping areas of their range in northern Pennsylvania, New York, and New England.

Could Kerri’s butterfly be a true white admiral or perhaps a hybrid from a pairing of those two subspecies?

The answer seems to be that a pure-bred white admiral is very unlikely and a hybrid perhaps only slightly more possible.

Gochfeld and Burger report in their Butterflies Of New Jersey that white admirals are rare even in northwestern New Jersey, noting the form “may be a vagrant to northern New Jersey, but is not a resident there.” A browse through recent issues of the Pearly Eye confirms that this seems still to be the status of the subspecies in North Jersey.

Also, as Kerri herself noted at first sight, the pattern on the Rancocas individual does not match white admiral exactly. Among other things, the white stripe is not wide enough on the hindwing and there is red in the forewing apex.

Well, how about hybrid? Is it possible that an offspring of a white admiral x red-spotted purple could find its way this far south — from interbreeding by parents who are most likely to have met each other north of Sussex County?

Art Shapiro in his Butterflies of the Delaware Valley (1966) writes, “Specimens representing the so-called ‘hybrid’ forms occur with some regularity in our area, the southern limit being Camden, Tinicum, and northern Delaware.” Shapiro seems to uses the phrase “so-called ‘hybrid’” because the off-spring of two sub-species are not a true hybrids — they are members of the same species. But, perhaps “so-called” reflects the genetic complexities described briefly in two more recent books:

Gochfeld and Burger note:

In New Jersey the identification of the two subspecies [true white admiral and red-spotted purple] is confused by the presence of intergrades (“albofasciata”), which can have a complete white band. This is due to introgression of white admiral genes from former or occasional interbreeding… There are records of “albofasciata” from various parts of New Jersey, including the Delaware Valley… The white banding is controlled by a single pair of autosomal genes with incomplete dominance.

Cech and Tudor in Butterflies Of The East Coast report that the genes controlling for the white striping in the complex is “a recessive trait that might appear in any population, even those completely isolated from nearby white admirals.”

Perhaps it is more likely that that the Rancocas individual is not a hybrid but instead a genetic oddity, showing evidence of those recessive genes, expressed rarely in southern New Jersey but carried in recessive form by red-spotted individuals.

Do any readers of this blog have experience with butterflies similar to Kerri’s find? Or a better understanding of these genetics? If so, please let us know.

Pat and Clay Sutton had a puzzling Limenitis of their own in their yard in Goshen in early July:

Oddly-marked red-spotted purple type, photo by the Suttons in their garden in Goshen, early July, 2012.

Standard-issue red-spotted purple, Jesse Connor’s garden, Port Republic 6-9-05.

The lighting and angles are different, but look closely and you will see that the Suttons’ butterfly shows more orange on both wing margins, especially the hindwing.

Odd markings are more obvious in this photo from above:

Ventral view of oddly-marked individual, photo by the Suttons, July, 2012. Note the orange tips highlighting the blue along the hindwing margins.

Normal red-spotted purple, Jesse Connor’s garden, 8-26-08. No orange highlights.

There are at least three possibilities here:

a) as may be the case in Kerri Seller’s individual, the odd markings could be evidence of rarely-expressed genes showing themselves.

b) it could be a hybrid. Clay wondered if the odd markings hinted at the contribution of a viceroy parent or grandparent, as viceroy x red-spotted purple is a relatively frequent hybrid pairing. That would be a true hybridization — between two different species of the Limenitis genus, L. archippus and L. a. sytanax.

c) CMBO’s Mike Crewe had a third suggestion:

One other possibility is atavism. This is the tendency of ‘mutant’ individuals to show the characteristics of an ancestral species and is the reason why occasional odd individuals can show the features normally associated with a sibling species. For example, it occurs periodically with European starlings, where you get an individual closely resembling the related rose-colored starling – but with subtle differences that reveal the truth! Atavism is also thought to be the reason for recurring traits that show up in more than one group of species within a single family, but in species that don’t appear to have a direct lineage. For example dark and light coloration in egrets (especially in little blue heron and a number of old world species) and the dark hoods found in several groups of gulls.
Maybe this butterfly is showing the colors of an ancestral species that is no longer around.

Who’s out there who wants to solve this puzzle for us — or perhaps suggest a fourth possibility? Email or post a comment here.

jc

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