Watching Washington Butterflies with Bob Pyle: Number Thirty Eight

The field of biogeography treats of the whereabouts of plants and animals across the landscape-not only where organisms occur, but why they occur here, and not over there. This means that biogeography is extremely important to the conservation of butterflies and other creatures, because-as the motto of The International Lepidoptera Survey says “We cannot protect that which we do not know.” And that certainly includes where they live. Biogeography is also fun. Since its operating currency is dots on the map, it means we get to go out and find those dots in the form of sightings, photographs, and voucher specimens: and who doesn’t love a treasure hunt?

Sometimes we spot a species far out of its known range, and this is always exciting. But it also sets up the big ask: WHY is it there, when it hasn’t been found thereabouts in the past? Sometimes such a discovery is simply an artifact of what biologists call “undersampling”-the common phenomenon of certain places, especially near roads, being scouted much more frequently than other, out of the way localities (see my previous column, “Where Are the Back- packing Butterfliers?” ) Other times widely spaced records denote range expansions, emigratory movements, or “strays.” These are not to be confused with actually disjunct resident populations, likely in place for a very long time, that simply haven’t been found before.

We have some spectacular examples of well-known disjuncts revealed by Washington butterfly study. But first, two words: “disjunct”-occurring at a far remove from the next nearest known population; and “relict” (not “relic,” that refers to an object)-a colony that has been left behind from a formerly widespread population that has since contracted through geologic or other disruptive events. All relicts are disjuncts, but not all disjuncts are relicts.

A relictual species, most commonly, has been pushed around by glaciation and left to survive in suitable remnants of habitat while the rest of the landscape around it has grown too warm, too dry, or otherwise unacceptable. Most of these post-glacial relicts occur at high elevations, where Pleistocene-like conditions remained long after the ice-sheets melt- ed. Some of them survived in refugia called “nunataks”-islands of terrain protruding above the line of glaciation. Not surprisingly, it is these ice-stranded butterflies (and other organisms) that are most vulnerable to the warming and drying trends caused by climate change. We worry about Melissa’s Arctics (Oeneis melissa beani) and other arctic-alpine species being pushed right off the tops of the North Cascades as warming trends advance. But other factors can lead to relictualism and disjuncture as well, such as afforestation and deforestation, agriculture, vulcanism, island-making and rejoining through sea-level change, and other landscape-scale changes in the vegetation, hydrology, soils, or any other ecological conditions. Disjuncture can also arise from causes other than relictualism, such as different colonization routes, rafting, or human-caused introduction. So with all that in mind, let’s look at some of the notable Washington disjuncts, and ask how they might have gotten that way.

One of the oddments we’ve long noticed is the presence of certain species in the Olympics that live in the eastern Cascades but skip the west side. While there is a lot of affinity be- tween the Cascades and the Olympics, with some shared subspecies (Erebia vidleri, Boloria titania rainieri, and Lycaena mariposa cascadia, for example), certain other east-siders make a big leap across seemingly suitable habitat west of the crest, only to show up again in the Olympics. Among these are the Lilac-bordered Copper (Lycaena nivalis) and the Spring White (Pontia sisymbrii). This may be a factor of ecological differences we have yet to ap- preciate, such as moisture gradients. Or it could indicate separate colonizations from different directions.

More dramatic than these is the remarkable case of the Hoary Elfin (Callophrys polios). The stronghold is in the north- east, reaching across and down from the Canadian Shield. Fair enough. But then there are robust populations in the Puget Trough/Salish Sea and northeastern Oregon, and tiny dabs and dribbles down the Oregon and northern California coasts. This is a classic post-Pleistocene relict, a cool-country butterfly drying up in a warming climate, much as a tadpole puddle evaporates bit by bit with the advancing summer. In fifty or a hundred years this elfin might be solely a creature of the Canadian taiga and certain cooler ranges. But why it doesn’t occur now up and down the kinnikinnick-rich Cascades, and along the Washington coast, is a mystery to me.

We can find various similar examples of relictualism and disjuncture across our fauna and our state. One that was long thought to be truly unusual was the colony of Silver- bordered Fritillaries (Boloria selene), a northern, wet-loving species, isolated at Moxee Bog, deep in the dry Columbia Basin. Dave McCorkle worked with The Nature Conservancy to make this one of the first butterfly preserves in the country, and David James and others are working with TNC to try to restore the habitat and the butterfly, which has since flickered out with shrub succession and the loss of accessible violets. But happily, the discoveries of John Baumann and others have revealed that there are many more colonies of this classic post-Pleistocene relict than we had ever guessed. We hope they will withstand the coming changes, but at least they have a better chance than had they really been limited to Moxee Bog.

We have three really dramatic examples of disjuncture that I must mention, all of which have turned up in the past thirty years, the newest and weirdest one only this year. First off, back in the early 1980s, Jonathan Pelham and Jim Reed independently discovered some big golden skippers at Sun Lakes in Grant County. Pelham recognized these as a state record, the Yuma Skipper (Ochlodes yuma), which had theretofore been known no closer than northern Nevada-skipping Oregon altogether! Yuma has had quite a history since: being mistaken for the very pale Ochlodes sylvanoides bonnevilla; almost getting sprayed out of existence when its giant reed foodplant was mistaken for an exotic relative; and turning up in a few other spots in southern Washington and northern Oregon near little relict stands of reeds, but nowhere in numbers. Another echo of an earlier Ice Age, it remains one of the great Washington butterfly finds ever.

The same can be said for the Island Marble (Euchloe ausonides insulana), which John Fleckenstein discovered at American Camp on San Juan Island while undertaking grassland butterfly surveys for the state in 1998. Last seen near Victoria in 1908 and long considered extinct, the rediscovered subspecies has now been federally listed as Endangered. The Island Marble is removed from its nearest relatives (Euchloe ausonides transmontana), somewhere near Mazama, by over a hundred miles. As the only colony of Large Marbles west of the Cascades in Washington, how it got there remains a matter of conjecture. I think it must have been much more widespread in the region during warmer, drier times in the past, and have slowly dissipated (there’s that puddle in the sun again) ever since, eventually leaving only the sole colony intact in the dry rain shadow of San Juan Island. Or, it might have colonized up the coast from California, instead of westerly from the Rockies. This is one species that may actually spread with climate change, perhaps one day meeting up again with its cousins across the mountains.

But the true climax in Washington butterfly disjuncture has only recently come to light. This entirely unlooked-for addition to our state checklist was discovered by avid butter- flier and photographer Dennis Deck, of Tigard, Oregon. In early summer, 2018, Dennis brought back a photograph of a little butterfly from Klickitat Canyon that for all the world looked like the Gold-hunter’s Hairstreak (Satyrium auretorum), which should fly nowhere near there. This area harbors large numbers of California and Sylvan Hairstreaks (S. californica and S. sylvinus), and those are what I found when I went back to his site for a look. Jon Pelham confirmed the ID, but we didn’t know what to think: the nearest known record for this species was in southernmost Oregon—an entire large state away! Could it have hitchhiked in as a chrysalis on a camper, we wondered? Or was it a case of atavism-some strange genetic throwback? For the time being, we consigned it as a rogue record, and put it in abeyance.

But, lo! come June 2019, and Dennis again found the butterfly-several individuals in different locations, miles apart! He and his field companions got good, clear photographs of both males and females. Now there was no doubt: we had Gold-hunter’s Hairstreak as the newest known member of the Washington butterfly fauna! So what’s the deal? This species does not stray or wander much, but tends to be a sedentary resident. A chance introduction of both sexes or a gravid female seems unlikely. Perhaps it is an ancient relict of a once-wider range, since wiped out by recent vulcanism in intervening areas of Oregon. But how has it remained unspotted till now, in a canyon frequently haunted by butterfliers, not to mention Jim Reed’s net wielding high-school biology classes, for many years? A delicious, if maddening, mystery to ponder through dark winter nights while the butterflies sleep.

Such is the nature of our crazy disjuncts: when they first turn up, far from the next nearest dots, they surprise or even shock us. Maybe we should get over that. Species, after all, have been fluid gliders over the face of the earth ever since they came ashore. Nothing should really surprise us in the way of animal and plant movement. But I like surprises, and that’s one reason I love studying distribution. Informed guesswork? Maybe, but also an ever-fresh puzzle, punctuated by the occasional sizzling discovery or insight. Paraphrasing Dr. Johnson’s quip about London, when you’re bored with biogeography, you’re bored with life.

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