Know this butterfly? It’s OK, no one really does. It is in the genus Apodemia (Riodinidae), but the taxonomy of this group is a disaster… and don’t even get me started on the subspecies. This specimen was photographed in September, meaning it is most likely to be Apodemia mormo (mormo) based on flight time. A. mormo is a fall flyer and A. virgulti is a spring flyer. While some forms seem distinctive, there is massive morphological overlap and they are usually identical and sympatric – actually down to living on the same plants. But according to lab experiments it is impossible to get the pupae to break diapause so they remain reproductively isolated. So are they different? While molecular work is being conducted the verdict is out, but it does seem like these two species may be retained in the end. And of course, each mountain range has it’s own subspecies. Who knows, I sure don’t. I’m glad I don’t work on butterflies.
Species concepts are a fuzzy line and it’s never clear exactly where to make the cut. When asked what a species is most people default to the Mayr concept of Biological Species (BSC), where reproductive isolation = new. This is all well and good but we have to keep in mind that this is not the ONLY species concept. There are dozens, and not one is perfect. Groups like Grammia (Noctuidae: Arctiinae) exhibit high levels of hybridization, which does not adhere well to the BSC. I like to apply as many criteria as possible to delimit a species and it seems like the line is all too commonly thin within insects. I like to see a distinguishing morphological trait, if not in wing color or pattern, at the least in the genitalia or antennae. This is not always the case however and you have to look at the biology and/or DNA. I have looked at two insects that are for all intents and purposes identical. But the biology is radically different and a large % difference (over 8% – yes, arbitrary) in their DNA makes it unquestionable that they are separate.
And if species weren’t contentious enough subspecies stir the pot even more. I’m skeptical about the entire concept, but there are cases in which it seems plausible and necessary. A subspecies is a more formal definition of a geographical “form” and usually exhibits a blend zone into another subspecies. For instance if you look at the 27 different populations of Plebejus icarioides there are large differences between northern and southern populations, but very subtile difference along the gradient. It is that persistent gradient that creates one dynamic species instead of 27 separate species – at least according to current research. Moths have been lucky and have thus far avoided the plague of over-subspeciation, butterflies not so much. There may even be instances where greedy collectors have named new subspecies of Parnassius for profit (new rare butterfly subspecies sell for big bucks).
The truth is that species concepts are artificial, poorly understood and dynamic at best; at worst it approaches a soft science with no real possibility of proof. Yet species are real and theories will continue to adapt while we sit here and scratch our heads.
