There is a subtle beauty to prairies. That prairies are not widely appreciated is not surprising given the amount of prairie one is likely to encounter while traveling through the Midwest. Those small parcels of pristine prairie that remain are often found along winding gravel roads away from tourist attractions, large towns, and interstates. This is unfortunate because a lack of knowledge contributes toward a lack of interest and thus to decreased public support for prairie preservation. Too few realize the pleasure that can come from visiting a prairie. There is an overwhelming sense of serenity that comes from standing amidst of a sea of grasses and prairie flowers as the wind gently rocks them back and forth in an almost hypnotic, wavelike motion.
As large and beautiful as Regal Fritillaries are, relatively few people have had an opportunity to see one. One reason, as I have already mentioned, is that there are few prairies remaining. In much of the Midwest, more than 99% of the original prairie landscape has either been altered or destroyed. As the first plow became readily available to settlers in the mid-19th century, the fertile prairie soil was almost entirely transformed to row crop agriculture. This fact alone has doomed several species of prairie plants and animals. The Regal however, is in dire straights because, among the few remaining suitable patches of habitat, only a fraction of them still have Regals. This means that the Regal is in the unfortunate predicament of being a rare species in a rare habitat.
of Regal Fritillaries
I set out to compile an up to date range map of the species by talking with all of the people I could who might have some information on where we could or could not find Regals. I am especially interested in finding populations of Regals rather than just single occurrences. A single sighting for a Regal is hard to verify and efforts to protect the species should be focused primarily on those populations which are large enough to be worth preserving. After talking with many active butterfly enthusiasts from around the country I was able to compile a map which has three major range components: 1) a region in the Great Plains (North Dakota south to Colorado and western Missouri) with several populations, 2) a region in the Midwest (Minnesota, Iowa, Wisconsin, Illinois, and Missouri) with relatively few, fragmented populations, 3) two isolated populations in the East (remnants of the former, much more extensive, range).
Many populations can still be found in the great plains. It has been my experience that much of the good prairie habitat I came across in this region still has Regals. As we move east of the Missouri river however, populations become harder to find. One of the main reasons populations are so difficult to find is that prairies themselves are so sparse. Even so, of the remaining prairies only a few still have Regals. It seems unlikely that we are overlooking the species in this region of the country. Several people are working on prairie butterflies in states like Iowa, Wisconsin, and Illinois (many have contributed to this magazine in the past) so if a large, mobile butterfly like the Regal was around we would expect that they would have found it by now. The disappearance of Regals has been so rapid that in many of the states where Regals are now feared extinct the species was never even listed as state threatened or endangered! For example, a survey compiled in 1973 by Roderick Irwin and John Downey at the Illinois Natural History Survey.
The situation becomes much worse once we move east of Illinois. No one recently has found a Regal Fritillary in any of the states east of the Illinois/Indiana border with the exceptions of Pennsylvania and Virginia, which harbor small, isolated colonies. The first colony is at Fort Indiantown Gap, Pennsylvania. This particular population is located on a military installation run by the United States Army and Pennsylvania national guard. Tank training and aerial bombing practices threaten to destroy valuable Regal habitat which has led to a hotly contested debate on the preservation of this population. Both the Nature Conservancy and NABA are working to protect it. NABA has been of particular importance by maintaining vocal opposition to proposed management plans for this population and by initiating litigation to protect it. The second population was a recent discovery in Virginia. Mark-recapture studies are currently underway but it appears that this is a relatively small population. Off-hand, this isn't a good sign. In most cases, Regals appear to be almost described three subspecies. So why is there no geographic variation in Regal Fritillaries? Paul Hammond, a Speyeria researcher from Oregon, points out that the Regal Fritillary is probably a highly mobile species that may be adapted to recolonizing large areas of prairie that have recently been burned. If the Regal can exchange several individuals among populations each year, then the continuous "mixing" of genetic material will prevent individuals in one region from diverging from those in another region. The result of all this mixing would a lack of geographic variation. If populations become separated from one another, as they have over most of the Regal's range, then mobility becomes an important issue. Once a population becomes isolated, then one bad year of weather or intense inbreeding can wipe out an entire population. A species which is not highly mobile cannot recolonize that area and the species' range starts to contract. So an important issue for the Regal centers around migratory ability.
Migratory ability is difficult to measure for several reasons. The first step is to mark all the individuals in several sites before they can move from one population to the next. The next step involves recapturing those same individuals to see if any of them have moved from one place to the next. If an unmarked individual arrives at a site it could be because it is a new immigrant, a newly emerged adult, or it was not captured on the first attempt. If an individual is captured that has moved between populations then one must establish that it and its offspring can survive in the new environment. All of these steps are required to show successful migratory ability in a species and are clearly labor intensive. But there is another way to get a similar sort of information. DNA.
As you might have already guessed, there are pieces of DNA that are ideal
for looking at differences between populations as well. My graduate research
has focused on using DNA to look at the relationships among populations
of Regal Fritillaries. Despite the long-winded discussion above, the basic
premise is rather simple. If all individuals from one population have
the same types of DNA in the same proportion as those from another population,
then the two populations are essentially the same and must be sharing
several migrants. If the types of DNA and their respective proportions
are very different among populations then they must not be sharing migrants
or they would appear more similar. There are various mathematical techniques
for deciphering this relationship in detail but the basic premise is the
same. There are a couple of points that make this method rather attractive.
First, because the information is genetic, only individuals moving between
populations and successfully reproducing will be detected. Second, based
on how quickly the DNA mutates you can get different measures of how long
it has been since they last shared migrants. If the DNA mutates very quickly
then differences among populations must be fairly recent. But differences
at a more slowly mutating piece of DNA will reveal more ancient genetic
exchange or lack thereof.
The preliminary results of my analysis are still being prepared for publication and are therefore tentative until they can be reviewed by members of the scientific community, but I will provide a short summary here. There are very few differences among all populations in the great plains and Midwest. The Pennsylvania population, however, has several mutational differences that all Pennsylvania individuals share but no other population has. This particular piece of DNA mutates at a slow rate so that is not surprising that we don't find differences in the great plains and Midwest. Because we do see differences in the Pennsylvania population, it is likely that this populations has been separated from any of the other populations I examined for quite some time. The estimated rate of mutation for this region of DNA is roughly 2% per million years. If this rate holds for the Regal (there is variation in the estimated rate for this molecule) then it will have been on the order of 400,000 years since these populations last mixed.
There is some supportive evidence of such evolutionary separation in the literature. Despite my primary focus on prairies of the Midwest early in this paper, initial descriptions of Regal Fritillary in the eastern U.S. have described it as being associated with mesic (wet) habitats, such as marshes. Midwestern populations are most certainly associated with dry sand prairies. Differences in habitat type may be due to an underlying evolutionary pattern where butterflies from one region are adapted to specific ecological conditions unlike those in another region. If this is the case for Regals, than there are both genetic and ecological differences which make the eastern populations unique and worth protecting. Clearly, more research on host plant use and habitat requirements is needed.
The DNA data has particular importance in the ongoing litigation between the North American Butterfly Association and the Army base at Fort Indiantown Gap. It is possible that this analysis alone will lead to a subspecific standing for this population and therefore protection under the Endangered Species Act. I am working on more rapidly mutating regions of DNA to provide supporting evidence for this data and better resolution of the relationships among Midwestern populations. These data can then be used to look at the amount of inbreeding and estimate the number of breeding individuals in different populations.
don't they look different?
This brings me to my final point concerning the Regal. How do you raise a Regal Fritillary? Speyeria have proven themselves a difficult group of butterflies to raise. Heroic efforts by people like Carol Boggs at Stanford University, Dave McCorkle in Oregon, Mark Roberts at Princeton University, and Dave Wagner at the University of Connecticut among others have led to a greater appreciation for what it takes to successfully raise a species like the Regal Fritillary. However, to my knowledge, no one has yet been able to successfully raise more than a single generation of Regals. Even those who can get adults in the first generation have trouble obtaining more than a few individuals. This number seems bleak given each female will lay hundreds of viable eggs.
The Regal Fritillary is a beautiful species in a beautiful setting. While we have gained much information over the last few years there is much more to be done. Hopefully articles like this one will lead to a better appreciation of this species. Maybe more people will stop on their way through the Midwest in hopes of spotting a glimpse of iridescent blue as the Regal glides across a prairie. Maybe people will start to demand that we do something to protect this rapidly disappearing "flagship species" of the prairie. One thing is certain, if we don't do something to protect it the rapid decline and extinction of the Regal Fritillary in the eastern U.S. will be a pattern repeated in the remainder of the species' range.Copyright © 1999 by the North American Butterfly Association, Inc. All rights reserved.
19 March 2000