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  • Species Dive 5 – Desmognathus conanti: A common salamander of complicated classification

    Desmognathus conanti, commonly referred to as the Spotted Dusky Salamander, is currently known to be a wide-ranging, stream-dwelling dusky salamander. In previous decades, this salamander underwent a few taxonomic revisions. Since then, some researchers have been using modern techniques to gradually build evidence that this species could be more than we thought.

    A ‘vibrant’ (for a dusky salamander) D. conanti from Claiborne Co., MS

    The Spotted Dusky Salamander inhabits a variety of wetlands, from small sandy or muddy seepages, to slightly larger rocky streams. The sizes of these streams may swell or recede depending on the season and precipitation. Within and along the streams the salamanders and their larvae eat various invertebrate prey. Walking along a stream or seepage, one may observe this species by flipping adjacent rocks or logs, often when those objects are partially submerged in the water or loose mud (be very careful when flipping and returning the object to its original placement!). They are adept at quickly escaping into their habitats, so only a glimpse of their brownish/reddish coloration may be seen.

    Like many of the dusky salamanders, their patterns may not be very appealing at first glance. Many species in this genus look the same; “drab” mottled browns and reds, occasionally spotted on the sides with markings on the fin-like tail (some more terrestrial species have rounded tails, though). Upon closer inspection and observation of many individuals over time, I learned a different story. This species can be quite diverse in appearance.

    Their affinity for streams and very small dispersal ranges are likely causes for diversification over time. In the past couple of decades, a few scientists have widely sampled this genus of salamanders throughout their entire range. They are learning just that: watershed-level diversity is present among all of the dusky salamanders. And their evolutionary relationships among one another are often unlike anything previously described. What we currently know and call Desmognathus conanti is one of the most complicated groups of this discovery.

    Since the species is currently known to range so widely, they inhabit many different watersheds and drainages. While Pyron et al. (2022) suggest this species is likely comprised of a total of ~ 5 species, I’m only going to highlight their diversity in Mississippi. D. conanti may eventually be split into two distinct species in MS, one found in the southeastern river drainages (D. conanti “C”) and one found in the mid-upper portions of the state often associated with older geologic deposits (D. conanti “B/D”; see map below). They suggest potential species-level diversity for these two groups, however time will tell as analyses progress and descriptive papers are developed.

    from Pyron et. al 2022 “Candidate‐species delimitation in Desmognathus salamanders reveals gene flow across lineage boundaries, confounding phylogenetic estimation and clarifying hybrid zones

    Because of my interested in biodiversity, I eagerly await the developments of this exciting work on dusky salamanders. Due to their near-identical morphology between many species, we did not know how truly diverse they were until new scientific techniques were developed. While burdensome to update legislation and public knowledge about big changes to a group’s taxonomy and names, this work is crucial in the human need to give something a name. Knowing and naming new species is a critical part of conservation too; without this step, losing hidden diversity to human-caused pressures on the natural world is inevitable.

    References and readings

    Pyron, R. A., K. A. O’Connell, E. M. Lemmon, A. R. Lemmon, and D. A. Beamer. 2022. Candidate‐species delimitation in Desmognathus salamanders reveals gene flow across lineage boundaries, confounding phylogenetic estimation and clarifying hybrid zones. Ecology and Evolution 12. <https://onlinelibrary.wiley.com/doi/10.1002/ece3.8574>. Accessed 22 Feb 2022.

    Rossman, D. A. 1958. A new race of Desmognathus fuscus from the south-central United States. Herpetologica 14:158–160.

    Titus, T. A., and A. Larson. 1996. Molecular phylogenetics of desmognathine salamanders (Caudata: Plethodontidae): a reevaluation of evolution in ecology, life history, and morphology. Systematic Biology 45:451–472.