From time to time here at Butterflies and Science we’ll pick out a fun scientific paper about butterflies and highlight why we think it’s cool and important. This week has been a good one for butterflies with two cool news stories about them! The first one is about new species being formed as a hybrid of two others!
Scientists at the University of Texas-Austin and Harvard University have discovered this new species of swallowtail living in the Appalachian Mountains. The Appalachian tiger swallowtail has evolved as a hybrid of the Eastern tiger and Canadian tiger swallowtail. The Canadian tiger swallowtail is found in the northern US and is more adapted to colder climates than the Eastern tiger swallowtail which is found well, in the Eastern US. The Eastern tiger swallowtail is unique in the ability to have two forms (colorations). One of these forms is the usual yellow wings with black stripes, but the other is an all black form that mimics the more poisonous Pipevine swallowtail.
What’s so cool about this hybridization is that the Appalachian tiger swallowtail inherited some of its cold tolerant genes from the Canadian tiger swallowtail and the genes to have the mimic form from the Eastern tiger swallowtail. It is a true hybrid of its parents both inside and out! Now the Appalachian tiger swallowtail is its own species that rarely mates with either the Canadian or Eastern tiger swallowtail.
So how do these sorts of hybrids arise? Glad you asked!
Generally when we think of new species arising it happens when one species splits into two and becomes isolated over time. In the rare case of hybrids two different, yet related species are able to mate with each other to create viable and fertile offspring. This happens a lot in plants, but is pretty rare in animals. The key is that the Eastern tiger and the Canadian swallowtail have only been unique species for about 600,000 years, before that they were the same. That may seem like a long time, but in evolutionary time that’s barely a blip! Because they were so closely related they were still able to mate with each other and have healthy, fertile offspring. Those offspring then diverged from both parents and have now become their own unique species. That is what makes this study so unique and exciting! It’s not often that conditions for this kind of speciation are right.