Alasmidonta, 1818

Whelan, Nathan V., Johnson, Nathan A., Ashantye, Williams, S., Perkins, Michael A., Beaver, Caitlin E. & Mays, Jason W., 2023, Hidden in the hills: phylogeny of the freshwater mussel genus Alasmidonta (Bivalvia: Unionidae) and description of a new species, Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 198 (2), pp. 650-676 : 670-673

ALASMIDONTA UWHARRIENSIS WHELAN, PERKINS & MAYS SP. NOV.

ZooBank registration: urn: lsid: zoobank. org:act: 62A595FF-6578-4D34-AD98-6410E74D839A

Material examined

Holotype: USNM 1675684 : Barnes Creek , Montgomery County, NC, USA; latitude 35.4782 °, longitude: −79.9584 °; J.W. Mays, M.A. Perkins; 31 August 2020; shell and whole body, minus a small clip of the mantle, preserved in 100% ethanol; shell width = 5.5 cm, shell height = 3.1 cm. GenBank ON164869 , ON157856 , ON164933 and ON197381 ( Fig. 8A ).

Paratypes: U S N M 1 6 7 5 6 8 3: Barnes Creek, Montgomery County, NC, USA; latitude 35.4782 °, longitude −79.9584 °; J.W Mays, M.A. Perkins; 31 August 2020; shell preserved dry; whole body removed by cut of adductor muscles and gentle removal of mantle from shell, both preserved in 100% ethanol; shell width = 5.4 cm, shell height = 3.1 cm. GenBank ON164868, ON157855, ON164932 and ON197380 ( Figs 7A–C , 8D, E ). USNM 1675685: Barnes Creek, Montgomery County, NC, USA; latitude 35.4344 °, longitude −79.9999 °; J.W. Mays, M.A. Perkins; 31 August 2020; whole body removed by cut of adductor muscles and gentle removal of mantle from shell, both preserved in 100% ethanol; shell width = 4.5 cm, shell height = 2.4 cm. GenBank ON157857, ON164934 and ON197382 ( Figs 7D–F , 8F, G ). USNM 1675686: Densons Creek, Montgomery County, NC, USA; latitude 35.3927 °, longitude −79.8778 °; J.W. Mays, M.A. Perkins; 30 August 2020; shell and whole body, minus a small clip of the mantle, preserved in 100% ethanol; shell width = 6.6 cm, shell height = 3.8 cm. GenBank ON164870, ON157858, ON164935 and ON197383 ( Fig. 8B ). USNM 1675687: Densons Creek, Montgomery County, NC, USA; latitude 35.3927 °, longitude −79.8778 °; J.W. Mays, M.A. Perkins; 30 August 2020; shell and whole body, minus a small clip of the mantle, preserved in 100% ethanol; shell width = 5.9 cm, shell height = 3.3 cm. GenBank ON164871, ON157859, ON164936 and ON197384 ( Fig. 8C ).

Othermaterialexamined: MontgomeryCounty, NC, USA: (1) NCSM 102780, Densons Creek; one paired dry bivalve; latitude 35.3939 °, longitude −79.8797 °; J.M. Alderman, J.A. Johnson; 15 June 2000 ( Fig. 6A ); (2) NCSM 45651, Densons Creek; one whole specimen in ethanol; latitude 35.3925 °, longitude −79.8768 °; J.M. Alderman, N. Medlin; 5 June 2006 ( Fig. 6D ); (3) NCSM 29538, Barnes Creek; one whole wet specimen in ethanol; latitude 35.4400 °, longitude −79.9994 °; C.B. Eads, P. Hubert, E. Schubert; 29 March 2004 ( Fig. 8C ); (4) NCSM 47178, Barnes Creek; three paired dry bivalves; latitude 35.4729 °, longitude −79.9741 °; C.B. Eads, R.A. Harrington; 1 April 2010 ( Fig. 6B ); (5) NCSM 33169, Densons Creek; one paired dry bivalve; latitude 35.3870 °, longitude −79.8678 °; E.P. Keferl; 28 July 1987. Randolph County, NC, USA: (6) NCSM 29435, Little River; one paired dry bivalve; latitude 35.5737 °, longitude −79.8415 °; A.E. Bogan, J.M. Smith, M.E. Raley; 16 January 2004.

Non-lethal tissue swabs were collected from the following localities: Montgomery County, NC, USA: (1) Densons Creek (three individuals); latitude 35.3864 °, longitude −79.8679 °; J.W. Mays; 19 July 2017; GenBank ON164904–ON164906, ON157893– ON157895, ON164967–ON164969 and ON197415– ON197417; (2) Dumas Creek (two individuals); latitude 35.3938 °, longitude −79.8972 °; J.W. Mays; 25 July 2017; GenBank ON164910, ON164911, ON157897, ON157898, ON164971, ON164972, ON197419 and ON197420; (3) Barnes Creek (four individuals); latitude 35.4798 °, longitude −79.9527 °; J.W. Mays; 20 July 2017; GenBank ON164912– ON164914, ON157899–ON157902, ON164973– ON164975, ON197421 and ON197422; Randloph County, NC, USA: (4) Hannah’s Creek (one individual); latitude 35.5846 °, longitude −79.9434 °; J.W. Mays; 17 July 2017; GenBank ON157909, ON164983 and ON197429; (5) Tom’s Creek (one individual); latitude 35.6399 °, longitude −79.9792 °; J.W. Mays; 17 July 2017; GenBank ON157910, ON164984 and ON197430.

Diagnosis

Shell: Subovate shell, umbo moderately inflated and projecting slightly above hinge line. Specimens examined not exceeding 6.6 cm in length and 3.8 cm in shell height. Hinge ligament broad, thick and strong. Shell thickness moderate to thin, but not delicate. Periostracum of adults extremely eroded at umbo, erosion extending down posterior ridge to include as much as one-third of shell in some individuals. Shell base colour light brown to yellow; pigmentation rays numerous, green to brown and variable in width and number when present, sometimes obscured by dark periostracum in older individuals especially on anterior of shell. Ornamentation and corrugations of shell variable; weakly pronounced corrugations appearing on posterior slope when present, but absent in some individuals. A single lateral tooth present, small, slender and poorly developed, indented on right valve. Prominent, hooked pseudocardinal tooth on right valve, bending anteriorly. Moderately prominent pseudocardinal tooth on left valve, not hooked, but projecting slightly towards posterior. Pseudocardinal teeth lacking serration. Adductor muscles placed high and wide on shell, with anterior adductor nearly on anterior edge of shell. No obvious sexual dimorphism in shell shape. No obvious geographical variation in shell shape.

Distribution and ecology: Narrow-range endemic, occupying tributaries that flow into the east side of the upper Pee Dee River drainage. The known range is in the Uwharrie Mountains region in North Carolina, mostly in the Uwharrie National Forest ( Fig. 1 ). This species appears to prefer a heterogeneous mixture of gravel, cobble and sand in second- to fourth-order streams and rivers with high water quality and low to moderate gradient ( Fig. 1 ).

Molecular characterization: Comprises a monophyletic group sister to A. varicosa , with private ITS1 alleles and unique COI and ND1 haplotypes. Approximately 7.4% uncorrected genetic distance at mitochondrial loci from A. varicosa .

Etymology: The name refers to the Uwharrie Mountains region, where the species is endemic. The common name will be Uwharrie elktoe, also representing the type location of the species. We note that the species name is intentionally spelled differently from Unio uhareensis Lea, 1868 , which is a junior subjective synonym of Elliptio complanata (Lightfoot, 1786) .

Remarks: The shell of this species most closely resembles A. varicosa , but internal features of the shell and placement of the adductor mussels most closely resembles A. marginata ( Figs 7–9 ; Supporting Information, Fig. S1 ). No other Alasmidonta is known to be sympatric with A. uwharriensis . The species is more phylogenetically distinct from its closest known relative than any other Alasmidonta species. Thus, molecular barcoding should be a useful method for future, non-lethal identification if a putative population is found outside its currently known range. A previous study on what was then identified as A. varicosa from Densons Creek found gravid females in October, and viable glochidia were released in laboratory conditions in December and February; sunfish ( Lepomis spp. ) and Piedmont darter, Percina crassa (D.S. Jordan & Brayton, 1878), were identified as potential larval hosts ( Eads et al., 2007). Additional information about the ecology of the species is currently unknown.

Figures

Figure 1. Terrain map of survey locations and the known range of Alasmidonta uaeharriensis sp. nov. Red stream segments indicate the known range of the species from element occurrence data (North Carolina Wildlife Resources Commission and North Carolina Museum of Natural Sciences records) with ~1 km up- and downstream buffers. Black circles indicate survey locations where the species has not been recorded. Green shading represents conserved or protected land boundaries; grey shading represents developed areas. Inset A, the boundaries of North Carolina and surrounding states (grey shading represents the Yadkin–Pee Dee River basin; red shading represents the Uwharrie and Little River watersheds). Inset B, an example of typical habitat preferred by the species in Barnes Creek (September 2020; photograph credit M. A. Perkins).

Figure 6. External Ʋieae of Alasmidonta uaeharriensis sp. nov. shell from across its range. A, NCSM 102870 from Densons Creek. B, NCSM 47178 from Densons Creek. C, NCSM 29538 from Barnes Creek. D, NCSM 45651 from Densons Creek.

Figure 7. Images showing pseudocardinal teeth of Alasmidonta uaeharriensis sp. nov. Arrows point to pseudocardinal teeth. A, USNM 1675683, left valve, umbo pointing away from camera. B, USNM 1675683, right valve, umbo away from camera. C, USNM 1675683, right valve, umbo towards camera. D, USNM 1675685, left valve, umbo pointing away from camera. E, USNM 1675685, right valve, umbo away from camera. F, USNM 1675685, right valve, umbo towards camera.

Figure 8. Type series for Alasmidonta uaeharriensis sp. nov. A, holotype, USNM 1675684. B, paratype, USNM 1675686. C, paratype, USNM 1675687. D,E, paratype, USNM 1675683. F, G, paratype, USNM 1675685. Abbreviations: aa, anterior adductor muscle; pa, posterior adductor mussel. Scale bar: 5 cm.