Desmognathus pascagoula Pyron & O'Connell & Lamb & Beamer 2022, sp. nov.
Creators: name: Pyron, R. Alexander
name: O'Connell, Kyle A.
name: Lamb, Jennifer Y.
name: Beamer, David A.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Amphibia
Caudata
Plethodontidae
Desmognathus
Desmognathus pascagoula

description: Desmognathus pascagoula sp. nov.
D. auriculatus (Valentine 1963; populations from Jackson Co., Mississippi)
D. valentinei (Means et al. 2017; populations from Jackson Co., Mississippi and Mobile and Baldwin Co., Alabama)
Holotype: USNM 596040 (field tag RAP1106; Figs. 13, 14), collected by RAP on 11 December 2019 at 1410h in a small seep feeding into Ward Bayou at Ward Bayou WMA, Jackson Co., Mississippi (30.56, -88.62; 3m ASL).
Paratypes: MMNS 19623 (field tag JYL78; Figs. 15, 16), collected by JYL on 23 March 2013 at the type locality (30.56, -88.62, 3m ASL). AUM 45885 (field tag RAP1107; Fig. 17), collected by RAP on 10 December 2019 at ~1200h, and MNHN-RA 2021.0149 (field tag RAP1479), collected by DAB and RAP on 28 November 2020 at ~1000h, in a branch of Franklin Creek, Mobile Co., Alabama (30.45, -88.32; 15m ASL). ANSP 38808, AUM 45896–7, and MCZ A-153479 (field tags RAP1480–3), collected by DAB and RAP on 28 November 2020 at ~1200h and USNM 596044 (field tag RAP 2218) collected by RAP, DAB, and NA on 4 January 2022 at ~1700h in a branch of Franklin Creek at Number 12 Swamp, Mobile Co., Alabama (30.45, -88.35, 9m ASL). MMNS 19997 (field tag RAP1558), collected by RAP and DAB on 12 December 2020 at ~1600h in the floodplain of Cowart Branch, Greene Co., Mississippi (31.00, -88.78, 14m ASL). ANSP 38810, BMNH 2021.7559, and AMNH 193779 (field tags RAP1559–61) collected by RAP and DAB on 12 December 2020 at ~1900h and USNM 596041–3 (field tags RAP2208–10) collected by RAP, DAB, and NA on 3 January 2022 at ~1100h in a tributary seep of Sweetwater Creek, Perry Co., Mississippi (30.91, -88.86, 43m ASL).
Etymology: The species name is a noun in apposition, referring to the Pascagoula River drainage that comprises much of their known range. “Pascagoula” is derived from a Chahta Yakni (Choctaw) or Mobilian Jargon term meaning “bread people” or “bread nation” (Gallatin, 1836; Gannett, 1905; Iti Fabvssa, 2015). The Pascagoula tribe, after which the river is named, was one of the Indigenous peoples that lived in what is now south Mississippi prior to European colonization. The region continues to be home to the Chahta Yakni and the Biloxi.
Suggested Common Name: Pascagoula Dusky Salamander.
Diagnosis: Desmognathus pascagoula can be distinguished from all other similar or related species by the following combination of characters: adult body size moderate (mean 47 mm SVL, range = 32–56 mm); torso elongated (AG 58% of SVL, range 56–61%) and slender (CW = 13 [11–14]%); head narrow (HW = 15 [12– 16]%); eyes and nostrils closely set (IC and IN = 6 [5–7] % and 4 [4–5]%); snout rounded off giving a blunted or brachycephalic appearance (ES = 5 [4–6]%); tail fin-like and long (TL = 80% of SVL, 62–101%); dorsal color pattern distinct but irregular; ventrolateral (3 rd) row of “portholes” on the body and lateral (2 nd) row tail of “portholes” on tail usually visible but jagged or irregular, dorsolateral row (1 st row) typically indistinct or faded; postocular stripe distinct and bright, typically orange or yellowish orange.
Description: All but one known specimen appears to be adult or subadult; nothing is known of egg or juvenile morphology, habits, or behavior. A potential larval specimen with gills (DAB16336; 18 mm SVL) was captured at the Sweetwater Creek site on 12 December 2020 and bears little obvious distinctiveness from the larvae of Desmognathus valentinei (see Means et al. 2017). Several larvae were observed at the Chickasaw Creek site, all of which bore superficial resemblance to those of D. valentinei. Mature D. pascagoula are moderately large dusky salamanders, with a tail that is thick, girthy, long, and compressed laterally into a fin- or blade-like shape towards the tip. Adults generally have a ground color of dark brown/black or tan/beige, a distinct dorsal color pattern separated from a lighter dorsoventral coloration, and a ventral coloration similar to the sides, typically with melanophores in the stellate condition (Fig. 16). The dorsal color pattern is typically a solid brown or reddish-brown stripe, edged with roughly 8–10 indistinct chevrons on either side, likely representing the remnants of larval spots. Other Desmognathus including D. valentinei can have dorsal color patterns including a reddish-brown stripe, but with more rounded or scalloped edges. In D. pascagoula these edges are more angular in nature, hence our description as “chevrons.” The dorsoventral surfaces are noticeably lighter, with an abrupt transition from darker dorsally to lighter laterally and ventrally creating a “two-toned” effect (Figs. 15–18). The distinct dorsal stripe is often visible onto the tail. The lateral surfaces of the trunk and tail usually have the round, whitish “portholes” characteristic of many swamp-dwelling Desmognathus species. The dorsolateral (1 st) row on the body is usually small and indistinct, and the lateral (2 nd) row on the body may be incomplete or less pronounced than is the ventrolateral (3 rd) row. When “portholes” are present, they often have jagged, uneven edges rather than being circular and smooth-edged. In the holotype, which is lighter and more tan or beige colored overall, they are barely noticeable in any of the three rows. The head is indistinct from the neck, and the snout is blunt or brachycephalic, rounded off in front. The dorsal stripe in the nuchal region occasionally has lighter or more distinct margins, giving the slight appearance of a paired stripe on the neck. The postocular stripe characteristic of Desmognathus is bright orange or yellowish orange in all known specimens.
Comparison: Only two species are likely to be confused with Desmognathus pascagoula: D. conanti C (Kozak et al., 2005; Fig. 11); and D. valentinei (Figs. 12, 19–22), the sister species of D. pascagoula with which it has been conflated in print (Beamer and Lamb, 2020; Means et al. 2017; Pyron et al., 2020, 2022a). The swamp-dwelling D. valentinei replaces D. pascagoula to the north and west and can be distinguished based on several characteristics. Adult D. valentinei get substantially larger than D. pascagoula (maximum 62 mm SVL vs. 56). Large adults of D. valentinei typically lack bold, distinct dorsal color patterns on the body (Means et al., 2017), unlike larger D. pascagoula (Fig. 15). Juvenile D. valentinei exhibit bold, reddish orange dorsal color patterns with clearly scalloped edges (Means et al., 2017). This type of pattern is lacking in juvenile or smaller D. pascagoula (Figs. 13, 14, 18; see Means et al., 2017). Round “portholes” on the lateral surfaces of the trunk and tail form up to three visible rows that are usually obvious, distinct, and occasionally reddish in D. valentinei, but less distinct or jagged and always whitish in D. pascagoula (Figs. 13–18).
Ravine and stream-dwelling populations of Desmognathus conanti representing the C lineage (see Beamer and Lamb, 2020) are sympatric with D. pascagoula at the type locality, from which they can be distinguished based on several characteristics. The dorsal color pattern of D. conanti C is typically a more distinct paired row of square or round blotches originating as larval dorsal spots, while the dorsal stripe of D. pascagoula is indistinct or with angular, “chevron” edges. The tail of D. conanti C is more slender and less compressed than D. pascagoula, which has a heavily keeled fin- or blade-like tail. The dorsolateral surfaces of D. conanti C are typically heavily pigmented with irregular, light-colored flecking or spotting of various sizes, often extending onto the lateral surfaces of the tail, while D. pascagoula has lighter colored dorsoventral surfaces usually lacking any obvious patterning. An exception are the light-colored “portholes” that are usually indistinguishable from the wash of light-colored flecking in D. conanti C, but usually visible in D. pascagoula. The postocular stripe in D. conanti C is usually indistinct and typically white in color, while in D. pascagoula it is typically bright orange or orangish yellow. Finally, the snout of D. conanti C is typically pointed and somewhat spatulate in a “duck-bill” morphology (Fig. 11), while D. pascagoula is more rounded, with a blunt or brachycephalic appearance (Figs. 13–18).
Variation: Like many Desmognathus species, D. pascagoula exhibits substantial variation in color pattern, seemingly (at least in part) as a local adaptive response to their primary substrate (see Grobman, 1950). Most of the Grand Bay specimens and the Ward Bayou paratype are dark colored and were found in leafy pools of dark-colored muck. Some of the Grand Bay specimens were lighter in color, but still with a dark gray ground color (Fig. 18). In contrast, the holotype was captured in light-gray silty muck (Fig. 5) and is accordingly much lighter-colored (Fig. 13). This type of substrate-specific variation has previously been noted in Coastal Plain Desmognathus by numerous authors (Means et al., 2017; Valentine, 1963). We did not observe any noticeable metachrosis in numerous specimens captured alive and held for>24 hours.
Reproduction: Nothing is known of the reproduction of this species, as no populations have been studied in detail, to our knowledge.
Dimorphism: Little is known about sexual variation in this species. As with most Desmognathus, large adult males seem to exhibit peramorphic jaw musculature as in their sister species D. valentinei (Means et al., 2017). Other characteristics related to peramorphic cranial ontogeny may also differ sexually (see Means 1974).
Habitat: All known specimens have been found in or near a similar type of microhabitat, comprising seeps or pools of leafy muck in the floodplains or swampy lowlands adjacent to larger creeks or rivers. At the three Mobile Co. sites, most specimens were found in the leaf/water/muck matrix and were uncovered by raking through this habitat, while a few were in the muck underneath debris dams of accumulated leaves and sticks. Both Ward Bayou specimens were found under partially submerged logs in a seep consisting primarily of leafy muck (similar to the Grand Bay site) and some flowing water. The Cowart Branch specimens were found under logs in lowland blackwater cypress swamp habitat, while the Sweetwater Creek specimens were primarily in sphagnum mats at the base of ravine seeps. In contrast to Desmognathus auriculatus A and D. valentinei, which are often found to be more active and closer to the surface, D. pascagoula appears, from our limited sample, to be more secretive and prefer more concealed or obscured microhabitats, deep under logs or in the aquatic sediment and vegetation layers.
Referred Material: Only a few specimens referred to Desmognathus auriculatus are known from Jackson Co., Mississippi, potentially representing D. pascagoula or D. valentinei. A collection from north of Cumbest Bluff dates to 1954 (CM 130968 -70), and one from 1957 (FMNH 193516, 193811) bears only the locality “Jackson Co.” A MMNS series collected by L.H. Kendall in 1963 includes individuals from Ocean Springs (MMNS 11395), Moss Point (MMNS 11432–4), Kreole (MMNS 11598–9, 11905–6), and Escatawpa (MMNS 11847–8), and a single specimen (MMNS 16064) was reported in 2007 from Ward Bayou WMA. We did not examine these specimens; it is thus possible that some represent D. conanti, with which D. auriculatus has been confused in the area (see Beamer and Lamb, 2008; Valentine 1963).
We examined five historical collections possibly referable to Desmognathus pascagoula. First, USNM 51142–51 dates to 19 Feb 1914 from Biloxi, Harrison Co., Mississippi. These specimens resemble D. valentinei, populations of which exist in that county confirmed by DNA sequencing (Means et al., 2017), and the locality is outside the Pascagoula drainage, suggesting that they are likely indeed D. valentinei. Nevertheless, a contact zone between the D. pascagoula and D. valentinei likely occurs somewhere in this region.
Second, USNM 57226, 57228, 57232–36, and 51142–51 lack specific localities, but 57226 dates to Sep 1894 from Baldwin Co., Alabama; 57228 dates to 1909 from Mobile Co., Alabama; and 57232–36 dates to 28 May 1910 from Mobile Co., Alabama. None are particularly well-preserved, but all have a distinct auriculatus- type morphology, including a blunt or brachycephalic snout, slender, elongated trunk, white lateral portholes of varying degrees of distinctiveness, and long, keeled tails. We tentatively conclude that these are D. pascagoula based on locality and appearance.
Third, a lot of four specimens originally catalogued under MCZ A-2783 as Desmognathus “ cf. auriculatus ” were collected by Julius Hurter Sr. from Mobile Co., Alabama in February 1911. Of these, three were later re-catalogued as MCZ A-4745–7, of which A-4745 is a Plethodon glutinosus complex. The remainder are Desmognathus, of which A-4746 is D. conanti C, collected on 13 February 1911, and A-2783 & A-4747 appear to be D. pascagoula, collected on 5 & 10 February 1911, respectively. We again base this on a blunt or brachycephalic snout, slender, elongated trunk, white lateral portholes of varying degrees of distinctiveness, and long, keeled tails. No additional locality data are contained in the MCZ catalogue.
Fourth, the University of South Alabama museum has an extensive collection of Desmognathus from Mobile Co. Based on photographs of some specimens provided by D. Bruce Means, most appeared to represent D. conanti C. However, two collections may represent D. pascagoula. The first is “U. of S.A. #966–7” from “ 2 mi. N.W. of Semmes along N side of G.M.&O. Railroad” collected 26 November 1968. The second is “U. of S.A. #1517” from “2 ½ air miles SW of Semmes on Wolff Rd. at small stream” collected 18 November 1969. These specimens are faded and poorly preserved, but resemble D. pascagoula in having slender trunks, long laterally compressed tails, and relatively short toes. These localities are ~ 15km WSW of the Chickasaw Creek site and occur near what is or would have been suitable lowland swamp habitat. It seems likely that D. pascagoula occurs or occurred in this region. We did not examine other specimens in person; more D. pascagoula may be present in this collection.
Fifth, a specimen of exceptional interest is AUM 10543 (Fig. 23), collected 30 March 1968 by J. Byford “ 5 miles SW Tensaw, approx 2 miles East of bend in Alabama River, on Ft Pierce Hunting Club.” This locality is a significant distance from the other historical Alabama populations of Desmognathus auriculatus which occurred west of the Apalachicola River in the Florida panhandle and adjacent southeastern Alabama (Means, 1999). The specimen was considered to represent D. auriculatus by Graham et al. (2010) and D. valentinei by Means et al. (2017: their Fig. 5). Due to preservation differences, we did not take measurements to include in our linear morphometric analyses. Nevertheless, several features suggest that this specimen represents D. pascagoula. These are an elongated head and relatively blunt or brachycephalic snout; relatively closely set eyes and nostrils; a relatively slender, elongated trunk; a distinct orbito-labial stripe (faded in preservative, but of an apparently bright color in life); a distinct dorsal color pattern; noticeable lateral “portholes” on the trunk and lateral side of tail; ventral melanophores in the “stellate” condition; and a heavily keeled, “fin-like” or “blade-like” tail. Of these, we consider the distinctiveness of the dorsal color pattern and indistinctiveness of the lateral “portholes” as the strongest evidence for conspecificity with D. pascagoula.
Finally, we refer AUM 45536–7 (field tags RAP2222 & 2223) and USNM 596045–6 (field tags RAP 2221 & 2224), collected by RAP, DAB, and NA on 5 January 2022 at ~1200h in a ravine tributary of Chickasaw Creek, Mobile Co., Alabama (30.78, -88.09, 6m ASL) to this species. Given the overall extreme level of mitochondrial divergence in this group compared to most congeners, the presence of higher levels of infraspecific divergence within other similar candidate species (e.g., D. auriculatus A = 6.8%, D. auriculatus B/C = 8.4%), the apparent lack of morphological differentiation, and their spatial proximity (~ 42km between the Chickasaw Creek and Franklin Creek sites), we continue to treat the Mobile drainage population as D. pascagoula, representing a distinct phylogeographic lineage sensu Pyron et al. (2022a). There is a clear need to sample additional individuals from the Mobile-Tensaw River delta in Baldwin and Mobile Co. and include them in phylogenomic analyses.
Distribution: The species is currently known definitively from only six sites, one near the confluence of the Leaf and Chickasawhay Rivers in Green Co., Mississippi; a nearby site on Sweetwater Creek, a tributary of Black Creek draining into the Pascagoula River in Perry Co., Mississippi; one at Ward Bayou WMA on Ward Bayou of the Pascagoula River in Jackson Co., Mississippi; two on a tributary of Franklin Creek within the city limits of Grand Bay, Mobile Co., Alabama, draining into the Escatawpa River; and one along Chickasaw Creek, a tributary of the Mobile River. Strong evidence exists for a historical population in Baldwin Co., Alabama, on the NE side of the Mobile-Tensaw River Delta. Additional historical and recent records of potentially conspecific individuals exist from Cumbest Bluff and other sites in Jackson Co., Mississippi, within several kilometers of the type locality at Ward Bayou.
Thus, confirmed sites include the lower Pascagoula, Escatawpa, and Mobile River drainages, while suspected sites enlarge this to include the Mobile-Tensaw Delta. The full geographic extent of Desmognathus pascagoula is unknown. In Mississippi to the west, sites from the Mississippi Coastal drainages and sites to the north from the Lower Leaf River drainage represent D. valentinei (Figs. 7, 8; Means et al. 2017). In Alabama, the northernmost extent along the Escatawpa is unknown.
Similarly, if the Tensaw specimen (AUM 10543) is in fact D. pascagoula, then the species may range extensively to the north along the Mobile, Alabama, and Tombigbee Rivers in Mobile, Baldwin, Clarke, Washington, and Monroe Co., and to the south and east in Baldwin Co. A record of D. auriculatus from Ferry Pass in Pensacola, Escambia Co., Florida (Bishop, 1943) could possibly represent the easternmost extent of the species, before it was historically replaced by what is currently considered D. auriculatus A in Santa Rosa Co., Florida, east of the Blackwater River (Means 1975; Means et al. 2017). A hiatus of D. auriculatus has historically been recorded between the Blackwater and Perdido Rivers in Florida (Means 1999, 2015). All historical populations of D. pascagoula east of Grand Bay and of D. auriculatus A west of the Apalachicola River are apparently extirpated (Graham et al., 2010; Means and Travis, 2007).
Conservation: The estimated range of the species encompasses numerous state and federal protected areas of relatively intact habitat, including the USFS De Soto National Forest, USFWS Grand Bay National Estuarine Research Reserve and Grand Bay and Mississippi Sandhill Crane National Wildlife Refuges, the ADCNR Forever Wild Grand Bay Savanna Tract and numerous WMA and FW tracts within the Mobile-Tensaw Delta complex, and the MDWFP Pascagoula River and Ward Bayou Wildlife Management Areas. In combination with the surface abundance of the known populations and their observed persistence over several years, we suggest that this species is likely of low conservation concern and should be assigned to the IUCN Red List categories “LC” or “NT” (Maes et al. 2015).
We note that other swamp-dwelling populations of southeastern U.S. Coastal Plain dusky salamanders have declined drastically in recent years (Dodd, 1998; Graham et al., 2010; Hibbitts et al., 2015; Maerz et al. 2015; Means and Travis, 2007), including D. valentinei in Louisiana (J. Boundy, pers. comm.). Furthermore, the potential for D. pascagoula to inhabit deeper, difficult to access microhabitats could make it challenging to detect and monitor populations. Thus, locating additional populations of this species and monitoring their health should be an immediate priority. At the Chickasaw Creek site, the ravine tributary originates in sight of U.S. Interstate 65, and during our visit the upper sections were filled with trash discarded from the roadway. Yet, an abundant salamander community nevertheless persists farther downstream where the intact hydrology supports sufficient microhabitat and vegetation. The site is heavily trafficked by humans and in close proximity (<5 km) to recreation, urban development, industrial activity, and interstate runoff. Other nearby sites with altered stream dynamics lacked this species or other salamanders, suggesting that hydrological damage, rather than environmental contamination, is a key driver of declines in this and potentially other swamp-dwelling species.
description: Published as part of Pyron, R. Alexander, O'Connell, Kyle A., Lamb, Jennifer Y. & Beamer, David A., 2022, A new, narrowly endemic species of swamp-dwelling dusky salamander (Plethodontidae: Desmognathus) from the Gulf Coastal Plain of Mississippi and Alabama, pp. 53-82 in Zootaxa 5133 (1) on pages 66-76, DOI: 10.11646/zootaxa.5133.1.3, http://zenodo.org/record/6521455