Ptomaphagus hirtus now at least 5 million years old
Hello there, dear friends of the cave beetle, and happy new year... !
Writing this post, I am realizing that 2018 went by without a single update. Not that nothing important happened. As a matter of fact, a brave group of undergraduate students completed the first short-term temperature tolerance experiment series. While yielding quite surprising results, I abstained from posting in the hope of repeating the experiment in due course. But then life and other projects came in the way. And now here we are, 2019, with this project still in the works. So more about that at a later time point.
Today, I am happy to announce that P. hirtus and its closely related friends in the so-called hirtus-group species cluster started the new year with a big bang: The publication of a long-term collaboration with the Zigler lab, which was generous enough to include us in their comprehensive molecular survey of the diversification of the hirtus-group:
There are many important findings in this paper we are excited about. Most significant for P. hirtus, the molecular clock findings reveal the beloved species to be at least 5 million years of age! Now, while perfectly in the range of European cave beetle ages found by Ignacio Ribera's group with the molecular clock methodology we adopted (Ribera et al. 2010: Ancient origin of a Western Mediterranean radiation of subterranean beetles. BMC Evolutionary Biology 201010:29), 5 million years of age is very different from the 200,000 to 350,000 years estimate fully reasonably developed by Stewart Peck given the available data and tools at the time (Peck 1984: The distribution and evolution of cavernicolous Ptomaphagus beetles in the southeastern United States (Coleoptera; Leiodidae; Cholevinae) with new species and records. Canadian Journal of Zoology 62: 730–40).
Besides the staggering difference of an order of magnitude, the revised P. hirtus age has important functional implications. Most important perhaps, while it was previously reasonable to consider the miniaturized visual system of P. hirtus a transient state on its way towards complete loss, it seems not so likely anymore. This is because of the long time we now have to assume to span between the onset of adaptation to cave life and the existence of its highly regressed, and yet functional, visual system today. It is now more reasonable to hypothesize that P. hirtus [and most of the hirtus-group species] represents an example of long-term preservation of vision in a cave-adapted species, thus raising questions regarding the fitness benefits that sustain the conservation of a minimal visual system in such a case. While we have some ideas here [such as Sonya's finding of the entrainable circadian clock], I'll spare you the details for a time when we published them. Until then, enjoy the new study on the diversification of the entire hirtus-group and share with your friends the news of P. hirtus' ancientness.
Again, happy new year, and thanks for your support which has come a long way.
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