Necturus beyeri alabamensis Hecht, 1958

Guyer, Craig, Murray, Christopher, Bart, Henry L., Crother, Brian I., Chabarria, Ryan E., Bailey, Mark A. & Dunn, Khorizon, 2020, Colour and size reveal hidden diversity of Necturus (Caudata: Proteidae) from the Gulf Coastal Plain of the United States, Journal of Natural History (J. Nat. Hist.) 54 (1 - 4), pp. 15-41 : 33-36

Necturus beyeri alabamensis Hecht, 1958 , in part

Necturus alabamensis Neill 1963 , in part and misidentification Necturus beyeri Mount 1975 , in part Necturus cf beyeri Bart et al. 1997 , in part Necturus (Parvurus) lodingi, Dubois and Raffaëlli, 2012 , in part Necturus cf lodingi Escambia lineage, Chabarria et al. 2017

Holotype. AUM 40698 ( Figure 13 ), a female collected 14 February 2014 at Camp Creek where it crosses Conecuh National Forest Road 332 (31.16427 –86.53378; WGS84 ), Covington County, AL, by David Laurencio.

Paratypes. AUM 37483 (a female), FLMNH 68839 (a male), and MMNS 1248 (a male) .

Diagnosis. Membership of this species in the genus Necturus is demonstrated by retention of external gills in adults, presence of pigmented skin, presence of four welldeveloped limbs, and reduction of digits on hind limbs to four toes. This species is unique in possessing a larval stage lacking numerous small white spots and an adult stage that is small in size, possesses dark dorsal and lateral spotting that is no larger than the size of the eye, and lacks evidence of spotting on the chin or belly. Ten sequence autapomorphies diagnose N. mounti , one of which is unambiguous ( Chabarria 2008). The species is sister to all other Necturus of the Gulf Coastal Plain ( Figure 1 ).

Comparisons. Larvae of N. mounti are uniform pinkish grey in life, typically lacking any small white spots, features that distinguish this species from the Mobile, Pearl, Pontchartrain and Western lineages of N. beyeri (numerous small white spots); N. alabamensis (light dorsolateral stripes); N. lewisi (middorsal light stripe); and N. maculosus (light dorsolateral stripes). Larvae of N. mounti are indistinguishable from those of the Apalachicola lineage and N. punctatus . Adults of N. mounti typically possess small (no larger than size of eye) dark dorsal and lateral spots, features that distinguish this lineage from the Pearl, Pontchartrain and Western lineages of N. beyeri and from N. lewisi (large dark dorsal spots); adults of North Carolina populations of N. punctatus are similar in adult dorsal colour pattern to N. mounti while South Carolina and Georgia populations typically lack dark spots. Adults of N. alabamensis and N. maculosus frequently have large dark spotting on the dorsal and lateral surfaces (rarely seen in N. mounti ) but may retain faded evidence of the dorsolateral light stripe of the larval stage (never seen in N. mounti ). The belly of N. mounti , in life, is white, changing abruptly to the dark lateral colouration, and the chin also is immaculate. These features differ in the Apalachicola, Pearl, Pontchartrain, and Western lineages of N. beyeri (ventrolateral dark spots; spotting on mandibles of chin, occasionally to level of gular fold).

Description of holotype. In preservation, the type specimen is 143 mm TOT, 103.0 mm SVL, and 40 mm TL (but tail cut for tissue sample); number of costal grooves is 16. The dorsal ground colour in preservation is uniform dark grey brown and the dorsum has distinct round dark spots that are approximately the size of the eye. This colour pattern also characterises the dorsal surface of the tail. The head is uniformly dark slate brown, lacking a dark stripe from the nostril through the eye. The dark dorsal colouration extends onto the lateral surface of the venter; changing abruptly to immaculate white at midventer; the edge of this transition zone is scalloped. The chin is immaculate white. The holotype has the following values for measured morphological features – ED: 1.3 mm; EL: 2.0 mm; GD: 2.3 mm; GEL: 15.7 mm; GL: 17.2 mm; HWE: 11.4 mm; HWG: 16.1 mm; POL: 15.9 mm; REW: 2.4 mm; SL: 4.6 mm; SRE: 6.4 mm; SW: 4.4 mm; WBW: 18.1 mm.

Variation. Necturus mounti achieves relatively small adult sizes, with a maximum male size of 116 mm SVL (+ 49 mm TL) and a maximum female size of 110 mm SVL (+ 53 mm TL). Mean male size is 108.4 mm SVL (n = 9) and mean female size is 94.8 mm SVL (n = 11). Approximately 80% of specimens conform to the dorsal colour categories described above. About 10% of specimens lack dark dorsal and lateral spots and about 10% have large dark dorsal spots. Ventrally, about 5% of specimens have spots along the mandibles with all others being spotless. Similarly, about 15% of specimens have ventrolateral spots on the belly with the rest being spotless. Modal value for costal grooves is 17 (n = 17), with 47% of specimens having 16.

Adult males (n = 7) have the following mean (and range) values for measured morphological features – ED: 1.4 mm (0.1–2.9); EL: 1.9 mm (0.7–2.9); GD: 3.2 mm (2.2–3.9); GEL: 15.6 mm (12.6–18.4); GL: 18.2 mm (15.2–20.9); HWE: 11.9 mm (9.4–14.3); HWG: 18.4 mm (13.9–21.5); POL: 16.9 mm (11.0–21.8); REW: 2.7 mm (2.3–3.0); SL: 6.5 mm (5.3–7.8); SRE: 8.0 mm (5.9–9.2); SW: 4.6 mm (2.4–5.8); WBW: 16.9 (12.8–18.9).

Adult females (n = 10) have the following mean (and range) values for measured morphological features – ED: 0.7 mm (0.02–2.4); EL: 1.9 mm (0.3–2.6); GD: 3.0 mm (2.3–3.9); GEL: 14.8 mm (8.4–18.8); GL: 16.6 mm (12.1–21.2); HWE: 10.8 mm (9.2–13.3); HWG: 16.8 mm (14.7–19.3); POL: 14.4 mm (8.0–20.9); REW: 2.2 mm (1.5–2.6); SL: 5.2 mm (4.4–6.4); SRE: 7.0 mm (5.6–8.9); SW: 4.7 mm (3.3–6.3); WBW: 15.9 mm (12.6–18.1).

Etymology. The specific epithet is a noun in the genitive case honouring Robert H. Mount, the curator of Herpetology at Auburn University for many productive years and the person who pointed out the taxonomic challenge that was represented by the waterdogs of Alabama. The recommended English common name is Escambia Waterdog.

Distribution and natural history. Necturus mounti occurs in the Blackwater, Escambia (Conecuh in Alabama), Perdido, and Yellow River drainages of Alabama and the western Panhandle of Florida ( Figure 14 ). No published study has documented the life history of N. mounti . But this taxon is common at the type locality where, for the past 30 years, we have made haphazard samples because the site contains a large, permanent leaf pack from which we have rarely failed to detect N. mounti in dipnet samples of those leaves. Juveniles are detected year-round, with detections of adults being concentrated in January and February. Siren intermedia , Desmognathus conanti, Ichthyomyzon gagei, dragonfly naiads, and small crayfish are frequent associates of N. mounti when they occupy these leaf packs. Samples from the surface of the leaf pack rarely yield specimens. Instead, samples from greater than two feet below the water surface, which are associated with cooler waters, yield these salamanders. Heavy silt appears to reduce the chances of detection as does heavily decayed leaves. We infer from these observations that adults migrate to leaf packs to mate. We suspect that nesting takes place in the leaf packs. However, nesting might take place elsewhere, with juveniles and adults migrating to leaf packs, as has been observed for the Pearl lineage of N. beyeri ( Shoop 1965; Sever and Bart 1996). Nevertheless, juveniles of N. mounti appear to remain in leaf packs as they grow to adulthood.

Figures

Figure 1. Geographic distribution and phylogeny of six mitochondrial lineages (boldface) of Gulf Coast waterdogs typically assigned to Necturus beyeri. Tree is rooted by N. punctatus and paraphyly of N. beyeri is shown by inclusion of N. alabamensis and two lineages of N. maculosus. Phylogenetic construction and lineage names are from Chabarria et al. (2017). Drainages for each lineage are Apalachicola lineage – Apalachicola,Chipola, Choctawhatchee,Econfina, Ochlockonee, and Pea Rivers; Escambia lineage – Blackwater, Escambia (Conecuh in Alabama), Perdido, and Yellow Rivers; Mobile lineage – Dog, Escatawpa, Fish, Mobile, Pascagoula, and Biloxi Rivers; Pearl lineage – Pearl and Wolf Rivers; Pontchartrain lineage – Amite, Bayou Bonfouca, Bayou Lacombe, Blind, Tangipahoa, Tchefuncte, and Tickfaw Rivers; Western lineage – Calcasieu, Cedar Bayou, Old, Neches, Sabine, San Jacinto, and Trinity Rivers.

Figure 13. Photo of dorsum (a) and venter (b) of type specimen of N. mounti (AUM 40698; Covington County, AL; photos by Craig Guyer).

Figure 14. Distribution of localities of specimens assigned to N. mounti. Open circle is approximate location of type specimen.