Blue Dasher (Pachydiplax longipennis), Boise, Idaho. 10 June 2021. Photo: Kim Chmura.
May Species of the Month
Blue Dasher (Pachydiplax longipennis)
Our May DSA species of the month is the Blue Dasher dragonfly (Pachydiplax longipennis) in the Skimmer family Libellulidae. It’s the only member of its genus. According to ode expert Dennis Paulson, the size is variable; with a range of 28-45 mm (one to 1.7 inches); and it is often abundant where it’s found. Look for the Blue Dasher in ponds and lakes in most of the central to eastern United States, north to Canada and south into Mexico. Join dragonfly chaser Ethan Tolman as he researches this common but fascinating species.
The Blue Dasher: An Urban Species Extraordinaire
A May 2023 edition of “Species of the Month” featured an excellent piece about observing the Blue Dasher (Pachydiplax longipennis) in the prairies of Illinois. The sheer volume of Blue Dashers present during surveying efforts was also noted. It is not uncommon for Blue Dashers to be found at this density throughout their range. In fact, within their range Blue Dashers are the 40th most observed species on the community science platform “iNaturalist”, the most observed aquatic insect, and the most observed Odonata.
Blue Dasher (Pachydiplax longipennis) used for comparative morphological study, Boise, Idaho. 1 July 2024 Photo: Dick Jordan
Intriguingly, despite their overall abundance, Blue Dashers are observed less frequently in non-degraded habitats—such as those found in national parks—compared to areas with high community science activity in more altered environments. Indeed, in our recent survey of the Odonata within the city of Boise, Idaho, Pachydiplax was the most observed genus, even though it is monotypic (Uche-Dike et al. 2024).
“The Lake” in Central Park, New York, New York, where the Blue Dasher (Pachydiplax longipennis) is one of the most abundant Odonata. 5 January 2022. Photo: Ethan Tolman
Why then, are Blue Dashers so abundant in human altered habitats? This question has driven much of our research program through the past few years, as finding this answer could help us to build aquatic habitats more friendly to a diverse array of Odonata.
Blue Dasher (Pachydiplax longipennis), Boise, Idaho. 10 June 2021. Photo: Kim Chmura.
While our work is still very preliminary, we have some exciting hypotheses to explore! One of our most promising avenues of research involves how the Blue Dasher handles an increased load of oxidative stress. Oxidative stress is an imbalance between free radicals and the body's antioxidant defenses. This imbalance leads to damage of cells, proteins, and DNA. Oxidative stress can very rapidly impact an organism’s reproductive fitness. Animals inhabiting urban habitats are generally exposed to more free radicals than their counterparts in less altered habitats, and thus experience more oxidative stress (Salmón et al. 2018).
A team of students and volunteers in Boise, Idaho. The Blue Dasher (Pachydiplax longipennis) used to generate a reference genome assembly was collected by the team shortly after this picture. 23 June 2023. Photo: Dick Jordan
The Blue Dasher appears to have evolved robust molecular machinery to help it solve the problem of oxidative stress. Its genome contains several expanded gene families related to the “response to oxidative stress” compared to other dragonflies of the family Libellulidae (Tolman, Beatty, et al. 2024). We were very excited when we gathered population level data for the Blue Dasher, and discovered genes involved in the response to “oxidative stress” that are shared between populations, and other genes implicated in this process that are very population specific (Tolman, Gamett, et al. 2024). This suggests both shared and local adaptations to oxidative stress throughout the range of the Blue Dasher.
Ethan Tolman and DSA President Chris Beatty help students model the population structure of the Blue Dasher (Pachydiplax longipennis), Boise, Idaho. 21 October 2024. Photo: Dick Jordan
Ethan Tolman (etolman@vt.edu) first began pursuing studying the genomics of Odonata as an undergraduate research assistant. Ethan continued to study the evolutionary genomics of Odonata as a PhD student at the City University of New York and the American Museum of Natural History. Ethan is currently a postdoctoral research associate in the Department of Biological Sciences at Virginia Tech in Blacksburg, Virginia, where he is continuing to use genomic tools to study the evolution of Odonata.
Dr. Manpreet Kohli (manpreet.kohli@baruch.cuny.edu) has led the collaborative Blue Dasher research project since 2019 as a research associate at the American Museum of Natural History, and now as an assistant professor at Baruch College, New York City, New York.
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