Wednesday, May 25, 2016

Appalachia Darter: An Endemic Black-Blotched Darter of the New River, by Don Orth

The Appalachia Darter Percina gymnocephala is one of the rare, endemic darters of the New River.  It does not have any special state or federal status.   Darters are most derived members of the family Percidae, and their reduced or absent swimbladders and enlarged pectoral fins make them superbly adapted for benthic life. Percina is the second largest genus of the darters with 46 species.  Because members of the Percina genus are larger, with drab colors, and high meristic counts, Percina has more plesiomorphic traits than the more colorful and speciose Etheostoma (156 species).  The darters (Etheostomatinae) contains 250 species endemic to eastern North America.  

The Appalachia Darter has traditionally been classified in the subgenus Alvordius, which is the largest subgenus of Percina with 14 species.   Alvordius might be named the “black-blotched” darters in recognition of the 6 to 16 lateral black blotches that these fish all possess.  All members of this subgenus have a large terminal mouth, lateral blotches, dorsal saddles, and a broad frenum.      
F points to frenum on a darter. Illustration from Jenkins and Burkhead (1994).
The Appalachia Darter has 6-8 (sometimes 9) lateral blotches.  The blotches are may be oval, square, or rectangular, and are interconnected.  They have dorsal saddles that are sometimes interconnected to form chain-like pattern.  There is no pigmentation below the lateral band and the lateral band extends to the opercle and snout. The snout is moderately rounded and the mouth is terminal.  Appalachia Darters possess a teardrop-shaped dark spot below each eye.   Fins are mostly transparent with scattered melanophores.  There is a proximal dark band on the first dorsal fin.    
Appalachian Darter Percina gymnocephala holotype specimen from Beckham (1980)
Appalachian Darter Percina gymnocephala  photo from Jenkins and Burkhead (1994).

Early investigators recorded the presence of Appalachia Darter to be the more widespread Blackside Darter Percina maculata.   However, it was elevated to a new species after further examination of specimens by Eugene Beckham (1980).   It’s closest relatives are likely the Shield Darter Percina peltata and the Piedmont Darter Percina crassa, based on external characteristics.  In photos (below) you can observe the many similarities and differences among these darters. Much about the phylogeny of the Percina is yet to be fully explained (Near 2002; Near et al. 2011).   Several Alvordius species do not group strongly with any other Percina lineages, suggesting that presumed monophyly was inappropriate. Phylogeny is likely much more complicated that we can currently imagine.

There are many similar looking "black-blotched" darters that you may encounter; there are slight differences that may require a magnifying lens. Admittedly, the most efficient way to distinguish some of these "black-blotched" darters is to ask what drainage they are from. Many of these species do not overlap with the Appalachia Darter.   The Shield Darter Percina peltata is very similar but  has a large Atlantic slope distribution from the Hudson and Susquehanna rivers south to the James River.  The Shield Darter has rectangular or square lateral blotches that are not interconnected.

Shield Darter Percina peltata  Photo by J. Abatemarco, NJ DEP.
The Blackside Darter Percina maculata is also very similar.  It has a distinctive spot at the base of the caudal fin and possesses scales on the opercle and cheek, while the Appalachia Darter lacks all these traits. It also has a dark blotch on the front lower portion of the first dorsal finAppalachia Darter has only 1-5 scales along dorsal margin of opercle.
Blackside Darter Percina maculata Photo by Uland Thomas
Piedmont darter Percina crassa is from the Cape Fear, Pee Dee, and Santee drainages and does not overlap with the Appalachia Darter.   Otherwise it is very similar and distinguishing traits are larger scales (you have to count lateral line scales).
Piedmont Darter Percina crassa   Photo Scott Smith,
The Stripeback Darter Percina notogramma resembles the Appalachia Darter but is distributed in the Atlantic slope streams from the Patuxent in Maryland to the James River of Virginia.  

Stripeback Darter Percina notogramma. Photo from Jenkins and Burkhead (1994)
The Longhead Darter Percina macrocephala is another Appalachia Darter lookalike.  Note that the lateral blotches are more confluent with each other creating a lateral band pattern and the upper body lackwsdistinct saddles. 
Longhead Darter Percina macrocephala  Photo by Ohio DNR
The Dusky Darter Percina sciera has no teardrop under the eye.  Also, it has an irregularly shaped blotch on the caudal base that appears to be formed from three fused pigment spots. 

Dusky Darter Percina sciera Photo by Uland Thomas
The Roanoke Darter Percina roanoka is the one black-blotched darter that also occurs in the New River and may overlap some with the Appalachia Darter. The snout of the Roanoke Darter is blunter than the Appalachian Darter.  The blotches of the Roanoke Darter are more vertically elongated and there two bands of pigment (one orange, one black) in the first dorsal fin.  Roanoke Darter is the most colorful of these black-blotched darters.
Roanoke Darter, Percina roanoka. Photo by Uland Thomas
I sampled the Federally Threatened Leopard Darter Percina pantherina in southeastern Oklahoma streams many years ago (Jones et al. 1984).  It too resembles these black-blotched darters but the blotches are disconnected and the combination of blotches and saddles form "leopard" spots.  

Leopard Darter Percina pantherina  Photo by Daniel Fenner.
The Appalachia Darter are not common at the locations where they do exist.  Steven Chipps and associates (1994, while studying habitats of other darters, described habitats used by the Appalachia Darter.  Appalachia Darters were usually found in runs and shallow pools with cobble substrate.  They were observed swimming above the streambed, a trait referred to as hyperbenthic. Depths averaged 44-55cm and current velocity has 11-13 cm/s.  The associated Candy Darter Etheostoma osburni and Fantail Darter Etheostoma flabellare were in shallow and faster riffle habitats.  With such habitat affinities, the Appalachia Darter would be easy prey for large bodied sunfish, Rock Bass, and Smallmouth Bass in larger streams.   

Appalachia Darters were rarely encountered in samples from the mainstem New River in West Virginia (Easton et al. 1994) but appear to be more associated with stream reaches in the Blue Ridge province (Jenkins and Burkhead 1994).   Based on collection records summarized by Beckham (1980), the Appalachia Darter occupies cool and warm rivers with an upland gradient
Distribution of captures of Percina gymnocephala from Beckham (1980). 
Recently Jian Huang and others (2016) developed a species distribution model to predict probability of occurrence for several New River fishes.  The map below color codes the stream segments according to likelihood that the segment will support the Appalachia Darter.  However, we need to sample more segments in order to better define the factors that drive the distribution and abundance of the Appalachian Darter. 
Predicted species occurrence of Percina gymnocephala from Frimpong et al. (2014).
Beckham, E.C. 1983. Systematics and redescription of the blackside darter, Percina maculata (Girard), (Pisces:Percidae). Occasional Papers of the Museum of Zoology, Louisiana State University 62.
Beckham, E.C. 1980. Percina gymnocephala, a new percid fish of the subgenus Alvordius from the New River in North Carolina, Virginia and West Virginia.  Occasional Papers of the Museum of Zoology, Louisiana State University 57.
Chipps, S.R., W.B. Perry, and S.A. Perry.  1994.  Patterns of microhabitat use among four species of darters in three Appalachian streams.  The American Midland Naturalist 131:175-180.
Easton, R. S., and D. J. Orth.  1994. Fishes of the main channel New River,West Virginia. Virginia Journal of Science 45:265-277.
Frimpong, E.A., J. Huang, and Y. Liang.  2014.   Preliminary Application of a framework for modeling habitat suitability and distribution of stream fishes with field testing.  Final Report submitted to U.S. Geological Survey. Reston, Virginia.  24 pp.
Huang, J., E.A. Frimpong, and D.J. Orth. 2016. Temporal transferability of stream fish distribution models: can uncalibrated SDMs predict distribution shifts over time? Diversity and Distributions 1-12.  DOI: 10.1111/ddi.12430
Jenkins, R.E., and N.M. Burkhead.  1994.  Freshwater fishes of Virginia.  American Fisheries Society, Bethesda, Maryland.  1037pp.
Jones, R.N., D.J. Orth, and O.E. Maughan. 1984.  Abundance and preferred habitt of the leopard darter, Percina pantherina, in Glover Creek, Oklahoma.  Copeia 1984:378-384
Near, T.J. 2002.  Phylogenetic relationships of Percina (Percidae: Etheostomatinae). Copeia 2002(1):1-14.
Near, T.J., C.M. Bossu, G.S. Bradburd, R.L Carlson, R.C. Harrington, PR. Hollingsworth, Jr., B.P. Keck, and D.A. Etnier.  2011.  Phylogeny and temporal diversification of darters (Percidae: Etheostomatinae).  Systematic Biology 60(5):565-595.  doi: 10.1093/sysbio/syr05

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