Bufo (Anaxyrus) williamsi, Tracy, 2017

Michelle R. Gordon, Eric T. Simandle & C. Richard Tracy, 2017, A diamond in the rough desert shrublands of the Great Basin in the Western United States: A new cryptic toad species (Amphibia: Bufonidae: Bufo (Anaxyrus )) discovered in Northern Nevada, Zootaxa 4290 (1) : 127-136

publication ID	https://doi.org/ 10.11646/zootaxa.4290.1.7
publication LSID	lsid:zoobank.org:pub:8F0A8A4C-CD1D-4838-93F0-A821A4E81E11
DOI	https://doi.org/10.5281/zenodo.6034940
persistent identifier	https://treatment.plazi.org/id/E3749753-F37D-FFF5-6C89-BF69F522F9BE
treatment provided by	Plazi
scientific name	Bufo (Anaxyrus) williamsi
status

Treatment

Bufo (Anaxyrus) williamsi View in CoL . sp. nov.

DIXIE VALLEY TOAD

( FIG. 2b View FIGURE 2 , FIG.4 View FIGURE 4 )

Holotype. CAS 259271 (CALIfORNIA AcADEMY Of ScIENcE HERPETOLOGY COLLEcTION), ADULT MALE ( FIG. 4 View FIGURE 4 , TAbLE 1), DIXIE VALLEY, CHURcHILL COUNTY, NEVADA, UNITED STATES (39°47'39.02"N, 118° 3'32.08"W), ON 3 JUNE 2015 bY M. R. GORDON, K. NIcHOLSON, C. MO AND C. GIbSON. GoogleMaps

Paratypes. UNR 7918, ADULT MALE; UNR 7919, ADULT fEMALE; UNR 7920, SUbADULT; UNR 7921, ADULT MALE; UNR 7922, ADULT fEMALE; UNR 7923, SUbADULT; UNR 7924, ADULT MALE. SAME LOcALITY, cOLLEcTION DATE, AND cOLLEcTORS AS HOLOTYPE .

Diagnosis. Bufo (Anaxyrus) williamsi IS DISTINGUISHAbLE fROM B. boreas bY A cOMbINATION Of DIAGNOSTIc MORPHOLOGIcAL cHARAcTERS ( FIG. 4 View FIGURE 4 ; TAbLE 1, TAbLE 2), GENETIc EVIDENcE ( FIG.3 View FIGURE 3 , FIG. 6 View FIGURE 6 ), AND LOcALIZED DISTRIbUTION ( FIG. 2b View FIGURE 2 ). Bufo (Anaxyrus) williamsi IS DISTINcT fROM B. boreas bY: A SMALL ADULT bODY SIZE (SVL IS MORE THAN 2.5 cM SMALLER THAN B. boreas ; TAbLE 1); SIGNIfIcANTLY, bUT MODESTLY, LARGER, cLOSELY-SET EYES, AND SMALLER HEAD ( TAbLE 2); STATISTIcALLY AND PERcEPTIbLY LARGER TYMPANUM, AND SHORTER HIND LIMbS; cONSPIcUOUSLY LARGE AND ELEVATED TIbIAL GLANDS; AND DISTINcTIVE cOLOR PATTERN ( FIG. 4A View FIGURE 4 , FIG. 4b View FIGURE 4 ).

smaller or larger (↑) states exhibited by congeneric species when compared to B. williamsi .

Bufo (Anaxyrus) williamsi IS THE SMALLEST bUfONID WITHIN THE B. boreas SPEcIES cOMPLEX ( TAbLE 1, TAbLE 2). THIS NEW SPEcIES HAS A STATISTIcALLY, bUT MODESTLY SHORT, NARROW HEAD SIMILAR TO THE SMALL SIZED B. exsul , bUT B. williamsi cAN bE DISTINGUISHED fROM B. exsul bY A SIGNIfIcANTLY, bUT MODESTLY, LONGER RELATIVE SNOUT LENGTH cOMPARAbLE TO THAT B. boreas AND B. nelsoni ( TAbLE 2). Bufo (Anaxyrus) williamsi HAS RELATIVELY LARGE, cLOSELY SET EYES AND PERcEPTIVELY LARGE TYMPANUM, WHIcH DISTINGUISHES THIS TOAD fROM ALL TAXA WITHIN THE B. boreas SPEcIES cOMPLEX. THE PAROTOID GLANDS ARE SLIGHTLY LONGER THAN WIDE, bUT ARE cOMPARATIVELY SHORTER OVERALL THAN PAROTOIDS Of B. boreas ( TAbLE 2). Bufo (Anaxyrus) williamsi HAS HIND LEGS THAT ARE SIMILAR IN RELATIVE SIZE TO B. exsul , bUT SIGNIfIcANTLY AND PERcEPTIbLY SHORTER THAN THOSE Of B. boreas AND B. nelsoni . THE TIbIAL GLANDS EXHIbITED IN B. williamsi ARE cONSPIcUOUS AND APPROXIMATELY THE WIDTH Of THE PAROTOID GLANDS, REGULAR IN SHAPE AND RUST cOLORED WITH LITTLE VARIATION AMONG INDIVIDUALS Of THIS SPEcIES. IN ADDITION TO MORPHOLOGIcAL SHAPE DIffERENcES, B. williamsi EXHIbITS UNIQUE cOLORATION DIffERENT fROM TAXA Of THE B. boreas SPEcIES cOMPLEX. THE DORSAL GROUND cOLOR cONSISTS Of OLIVE SHADES THAT cONTAIN MINUTE bLAck fLEckS, RUST cOLORED WARTS ARE bORDERED bY fINE, bLAck HALOS, AND PROMINENT PAROTOID GLANDS ARE PALE TAN AND bLAck SPEckED. THE VENTER Of B. williamsi IS SIMILAR TO B. exsul , EXHIbITING SHARPLY cONTRASTED bLAck MARbLING AGAINST A WHITE bAckGROUND cOLOR ON THE ANTERIOR SIDES Of THE LIMbS AND bELLY. THE PRESENcE Of A DORSAL STRIPE IS VARIAbLE AMONG INDIVIDUALS Of B. williamsi , AS IS SIMILAR TO THE OTHER MEMbERS Of THE B. boreas cOMPLEX, WITH THE EXcEPTION Of B. exsul .

DISTINcT NUPTIAL PADS DEVELOP ON THE DORSAL SIDE Of THE THUMb IN MALES Of B. williamsi , A TYPIcAL SEcONDARY SEXUAL cHARAcTERISTIc EXHIbITED AMONG MOST bUfONIDS. THIS SPEcIES LAckS AN ADVERTISEMENT cALL, bUT RETAINS A RELEASE cALL THAT SOUNDS LIkE THE WEEPING Of A cHIck ( STEbbINS 2003). THE cALL IS EMITTED WHEN MALES cOME INTO cONTAcT WITH ONE ANOTHER, SIMILAR TO cONGENERS Of THE B. boreas cOMPLEX.

Description of holotype. BODY SMALL (SVL = 52.92 MM), RObUST; HEAD NEARLY LONG (17.45 MM) AS WIDE (18.35 MM; 95 % HEAD LENGTH TO HEAD WIDTH). DORSAL OUTLINE Of SNOUT IS MODERATELY TRUNcATE; SNOUT LONG IN LATERAL VIEW (6.61 MM; 1.3 TIMES LONGER THAN EYE DIAMETER). CANTHUS ROSTRALIS DISTINcT, SLIGHTLY cONcAVE AND AbRUPT AT NARES, SLOPING UP TO ANTERIOR MARGIN Of ORbITS. LOREAL REGION MODERATELY cONcAVE. NOSTRILS PROTUbERANT, DIREcTED DORSOLATERALLY AND cLOSER TO ANTERIOR cORNER Of EYE THAN END Of SNOUT. INTERNARIAL DISTANcE 75% Of EYE-TO-NARIS DISTANcE. EYES LARGE (4.94 MM), cLOSE SPAcED (3.83 MM); INTERORbITAL DISTANcE 75% Of EYE DIAMETER. EYES PROMINENT, bREAcHING SNOUT PROfILE IN DORSAL VIEW. TYMPANUM DISTINcT, OVOID, RELATIVELY LARGE (2.89 MM; 58% Of EYE DIAMETER). SUPRATYMPANIc fOLD PRESENT. PAROTOID GLANDS SUb-ELLIPTIcAL, TAPERED AT POSTERIOR MARGIN Of EYE, LONGER (5.56 MM) THAN WIDE (3.90 MM; 77%). PAROTOIDS ELEVATED DORSALLY, SLIGHTLY DIVERGENT AND SEPARATED (9.18 MM); GLAND WIDTH SMALLER THAN EYE DIAMETER (75%). FOREARMS RObUST. FINGERS UNWEbbED; RELATIVE LENGTHS III> VI> I> II; NUPTIAL PADS PRESENT, RAISED ON DORSAL SIDE Of DIGIT I; TIPS ROUNDED, SUbARTIcULAR TUbERcLES MODERATE, ROUND; AccESSORY PALMAR TUbERcLES SMALL AND ROUND. THENAR TUbERcLE RAISED, PROMINENT, AND ROUND. PALMAR TUbERcLE IS DISTINcT, LARGE, SUbOVOID, SEPARATED fROM MEDIAL MARGIN Of LESSER THENAR TUbERcLE. HIND LIMbS SHORT (FML =19.54 MM; TBL =18.75 MM; FTL =33.10 MM), RObUST; fEMUR SLIGHTLY LONGER THAN TIbIA. TARSAL fOLD PRESENT. HIND fEET WEbbED PROXIMALLY. RELATIVE TOE LENGTHS IV> III> V> II> I; TIPS ROUNDED. SUbARTIcULAR TUbERcLES MODERATE, SMALL, ROUND; PLANTAR TUbERcLES SMALL, NUMEROUS. INNER METATARSAL TUbERcLE PRONOUNcED, ELEVATED, AND ELLIPTIcAL. OUTER METATARSAL TUbERcLE SMALLER THAN INNER METATARSAL TUbERcLE, cONSPIcUOUS, OVOID.

LONGITUDINALLY ALONG DORSUM, DORSAL STRIPE bROkEN, WEAkLY PRESENT, ORIGINATING POSTERIOR TO INTERORbITAL SPAcE AND TERMINATING AT SAcRAL HUMP; IRREGULAR, ELEVATED, ScATTERED TUbERcLES PRESENT, INcREASING IN SIZE fROM INTERORbITAL SPAcE TO POSTERIOR MARGIN Of UROSTYLE. SkIN bETWEEN TUbERcLES NEARLY SMOOTH; fOREARMS SMOOTH; HIND LEG TUbERcLES VARY IN SIZE. TIbIAL GLANDS PRESENT ON DORSAL SURfAcE Of LEGS, PROMINENT, EQUIVALENT TO THE WIDTH Of PAROTOID GLAND. SMALL DENSELY cONcENTRATED TUbERcLES PRESENT, ORIGINATING POSTERIOR TO LAbIAL cOMMISSURE, INfERIOR TO TYMPANUM, TERMINATING IN AXILLARY REGION. SMALL, DENSELY cONcENTRATED TUbERcLES PRESENT LONGITUDINALLY ALONG MID AXILLARY LINE, TERMINATING AT ARTIcULATION Of fEMUR. VENTER GRANULAR; SEAT PATcH DARk, cONSPIcUOUS.

Color in life. DORSAL GROUND cOLOR Of THE HOLOTYPE IS cOMPLEX, WITH cHROMATIc HUES Of OLIVE WITH SMALL, DIVERSE AND IRREGULAR bLAck fLEckS, ( FIG. 4A View FIGURE 4 ). FAcE HEAVILY SPEckED. UPPER EYELIDS fLEckED bLAck AGAINST OLIVE bAckGROUND cOLOR. PUPIL bLAck, HORIZONTAL, WITH GOLD-STREAkED IRIS. PAROTOID GLANDS TAN; MINOR bLAck SPOTTING ON cROWN Of GLAND WITH bLAck STREAkS ALONG MARGINS. SMALL, DENSE TUbERcLES OccUR bETWEEN LAbIAL cOMMISSURE AND AXILLARY REGION AND ARE RUST cOLORED. RUST cOLORED TUbERcLES IRREGULARLY DISTRIbUTED AcROSS DORSUM, SMALL bUT VARIAbLE IN SIZE, WITH bLAck MARGINS. TUbERcLES bETWEEN MID-AXILLARY LINE AND ARTIcULATION WITH fEMUR RUST cOLORED, bORDERED bY fINE bLAck HALOS. DORSAL STRIPE cREAM, ORIGINATING AT INTERORbITAL SPAcE, bROkEN jUST POSTERIOR TO TERMINAL MARGIN Of PAROTOID GLANDS, RESUMES ALONG VERTEbRAL REGION, AND TERMINATES AT SAcRAL HUMP. FOREARMS WITH bLAck fLEckS DORSALLY AND MEDIUM TO DARk bROWN OVERLYING OLIVE bAckGROUND. HIND LEGS WITH RUSTY TUbERcLES ARRANGED ATOP DARk bROWN bANDING OVERLYING GROUND OLIVE cOLOR WITH bLAck fLEckING. INfERIOR TO MIDAXILLARY LINE, TUbERcLES DIMINISH IN SIZE UNTIL AbSENT. INfERIOR MID-AXILLARY LINE WITH HEAVY bLAck MOTTLING AGAINST WHITE. SMALL bLAck SPOTS ALONG INfERIOR LOWER LAbIAL MARGIN. ANTERIOR fOREARMS AND HIND LEGS HEAVILY MARbLED bLAck AGAINST THE WHITE bAckGROUND cOLOR. THROAT WHITE, IMMAcULATE. WHITE VENTER HEAVILY MOTTLED IN bLAck; SEAT PATcH cONSPIcUOUS AND DARk bROWN, WITH ROUND, WHITE SPOTTING ( FIG. 4b View FIGURE 4 ). UNDERSIDES Of HANDS AND fEET DARk GRAY. TUbERcLES Of HANDS AND fEET, fINGERS, AND TOES bRIGHT ORANGE.

Color in preservative. COLOR IS NOTAbLY DIffERENT AND MUTED ( FIG. 4c View FIGURE 4 , FIG. 4D View FIGURE 4 ) RELATIVE TO LIfE ( FIG. 4A View FIGURE 4 , FIG. 4b View FIGURE 4 ). DISTINcTIVE DIffERENcES INcLUDE NEARLY MONOTONE GROUND cOLOR WHIcH IS DARk GREENISH GRAY, WARTS TO DARk bROWN, DORSAL STRIPE fAINT. PAROTOID GLANDS PALE bROWN AND cONSPIcUOUS, STREAkED, AND SPOTTED A MUTED bLAck cOLOR. IN PRESERVATIVE, THE bRIGHT cOLORATION Of THE SPINOSE TUbERcLES INfERIOR TO TYMPANUM AND TUbERcLES Of HANDS AND fEET fADE TO WHITE. BLAck MOTTLE ON THE VENTER AND LIMbS APPEARS DULLER THAN IN LIfE. TUbERcLES ON fEET AND HANDS ARE WHITE WITH bROWN TIPS.

Morphological results. RESULTS Of STATISTIcAL ANALYSES WERE cONSISTENT fOR bOTH LOG-TRANSfORMED DATA, AND fOR USING REGRESSION Of SVL AGAINST THE MORPHOLOGIcAL VARIAbLES. BOTH ANALYSES DETEcTED SIGNIfIcANT DIffERENcES fOR ALL 14 MORPHOLOGIcAL cHARAcTERS EVALUATED AT THE SPEcIES LEVEL AMONG B. boreas , B. nelsoni , B. exsul , AND B. williamsi ( TAbLE 1, TAbLE 2). Bufo (Anaxyrus) williamsi IS THE SMALLEST Of THIS GROUP (F 3, 376 = 77.9, p <0.0001; F 3, 376 = 63.4, p <0.0001) WITH A RELATIVELY SHORT (F 4, 379 = 903.8, p <0.0001; F 4, 379 = 830.8, p <0.0001; TAbLE 2) AND NARROW HEAD (F 4, 379 =1219.0, p <0.0001; F 4, 379 = 1080.1, p <0.0001; TAbLE 2). THERE WERE SIGNIfIcANT DIffERENcES IN SNOUT LENGTH AMONG SPEcIES (F 4, 379 = 164.9, p <0.0001; F 4, 379 =160.9, p <0.0001), AND IN PAIRWISE cOMPARISONS Of TUkEY HSD POST-HOc TESTS, B. williamsi DIffERED SIGNIfIcANTLY fROM B. exsul bY HAVING A RELATIVELY LONGER SNOUT MORE LIkE LARGER SPEcIES B. boreas AND B. nelsoni , A SIMILARITY DETEcTED IN THE LEAST SQUARES MEANS GENERATED fROM THE MANCOVA ANALYSES AND cORRESPONDING LINEAR REGRESSION THAT NORMALIZE SVL AGAINST THIS cHARAcTER ( TAbLE 2). Bufo (Anaxyrus) williamsi HAS RELATIVELY LARGE EYES (F 4, 379 = 259.9, p <0.0001; F 4, 379 = 240.0, p <0.001) THAT ARE cLOSE TOGETHER (F 4, 379 = 422.5, p <0.0001; F 4, 379 = 371.1, p <0.0001), WHIcH IS DISTINcT fROM B. boreas , AND A LARGER TYMPANUM cOMPARED TO ALL THREE OTHER SPEcIES EXAMINED (F 4, 379 = 231.4, p <0.0001). WHILE THE WIDTH Of THE PAROTOID GLAND IN B. williamsi IS SIMILAR TO B. boreas , THE cOMPARATIVE LENGTH Of THE PAROTOID IS SHORTER ( TAbLE 2). ADDITIONALLY, THE cHARAcTERS THAT DEfINE THE LENGTH Of THE LEG Of B. williamsi ARE SHORT (FL: F 4, 379 = 910.4, p <0.0001; F 4, 379 = 801.0, p <0.0001; TL: F 4, 379 = 1063.8, p <0.0001; F 4, 379 = 909.0, p <0.0001; FTL: F 4, 379 = 571.8, p <0.0001; F 4, 379 = 470.7, p <0.0001), AND DIffER SIGNIfIcANTLY fROM B. boreas (TUkEY HSD POST-HOc PAIRWISE cOMPARISONS, p <0.0001). MANCOVA RESULTS EVALUATING LOG-TRANSfORMED DATA bY POPULATION YIELDED SIMILAR RESULTS WITH SIGNIfIcANT DIffERENcES DETEcTED AMONG LOcALITIES SAMPLED ( FIG. 1A View FIGURE 1 ), AND THIS ANALYSIS cONfIRMED THAT B. williamsi IS THE SMALLEST TOAD AMONG ALL POPULATIONS EXAMINED (F 16, 379 = 34.7, p <0.0001), WITH A cOMPARATIVELY SHORT, NARROW HEAD (HL: F 17,379 = 285.1, p <0.0001; HW: F 17,379 = 353.3, p <0.0001), LONG SNOUT (F 17,379 = 55.1, p <0.0001) AND RELATIVELY THE LARGEST EYES AMONG REGIONAL B. boreas AND cONGENERIc TAXA EXAMINED (F 17,379 = 86.07, p <0.0001). THIS ADDITIONAL ANALYSIS cONfIRMED THAT THE PAROTOID GLANDS Of B. williamsi ARE RELATIVELY SHORTER IN LENGTH (F 17, 379 = 81.1, p <0.0001) cOMPARED TO B. boreas . HOWEVER, THE SIZE Of THE PAROTOIDS AND INTERNARIAL DISTANcE (IND) WERE AMONG THOSE TRAITS THAT WERE SIMILAR IN RELATIVE SIZES TO B. boreas , B exsul , and B. nelsoni . ON THE OTHER HAND, THE TYMPANIc DIAMETER IS RELATIVELY LARGE (F 17, 379 = 82.4, p <0.0001) IN B. williamsi , AND ITS LEGS ARE THE SHORTEST AMONG ALL POPULATIONS SAMPLED (FL: F 17, 379 = 248.9, p <0.0001; TB: F 17, 379 = 312.6, p <0.0001; FTL: F 17, 379 = 139.1, p <0.0001), SIMILAR TO LEG SIZES AMONG B. exsul .

DIScRIMINANT fUNcTION ANALYSIS (DFA) ILLUSTRATES SIGNIfIcANT MORPHOLOGIcAL DIffERENcES AMONG SPEcIES (F 42, 173 = 2.80, p <0.0001; FIG. 5 View FIGURE 5 ). THE DFA cORREcTLY cLASSIfIED 77.3 % Of PREDIcTED SPEcIES, WITH SOME MORPHOLOGIcAL OVERLAP DETEcTED AMONG B. boreas , B. nelsoni AND B. exsul ( FIG. 5 View FIGURE 5 ). THE MORPHOLOGIcAL cHARAcTERS WERE AccURATE PREDIcTORS Of B. williamsi IN ALL THIRTY PREDIcTIONS. THE fIRST cANONIcAL AXIS EXPLAINED 60% Of THE VARIATION IN THE DFA WITH TIbIAL LENGTH LOADING MOST HEAVILY, WHILE THE SEcOND cANONIcAL AXIS AccOUNTED fOR 24 % Of THE VARIATION WITH HEAD WIDTH LOADING MORE HEAVILY THAN OTHER cHARAcTERS.

THERE WAS NO SEXUAL DIMORPHISM DETEcTED IN SVL Of B. williamsi (F 1, 28 = 0.09, p> 0.05). HOWEVER, MALES EXHIbITED 3 % LARGER EYES (F 2, 29 = 4.9, p <0.014) AND LONGER fEET THAN fEMALES (F 2, 29 = 12.2, p <0.0002 fOR 5.2% LONGER FTL). THE UNADjUSTED RAW DATA cOLLEcTED fOR THE fOUR SPEcIES EXAMINED fOR ALL fOURTEEN cHARAcTERS ARE PRESENTED IN TAbLE 1.

Genetic Results. THE cOMbINED DNA ANALYSES Of THE cONTROL REGION SUPPORT THE DIffERENTIATION Of THE NEW SPEcIES, B. williamsi ( FIG.3 View FIGURE 3 , FIG. 6 View FIGURE 6 ). THREE MAjOR GEOGRAPHIc cLADES WERE IDENTIfIED AS OREGON-NW NEVADA (ONV), HUMbOLDT-LAHONTAN (HL) AND MOjAVE (M) AND GENETIc RELATIONSHIPS ARE ILLUSTRATED IN THE B. boreas TCS HAPLOTYPE NETWORk ( FIG. 1b View FIGURE 1 , FIG. 3 View FIGURE 3 ), cONfIRMING THE DIffERENTIATION Of B. williamsi fROM NEIGHbORING POPULATIONS Of B. boreas IDENTIfIED UNDER THE HL cLADE AND NORTHERN POPULATIONS Of B. canorus . THE TCS NETWORk HIGHLIGHTS THE fAcT THAT B. boreas fROM NORTHERN NEVADA ARE LESS DIVERGENT fROM EAcH OTHER, A RESULT cOMMON WITHIN THE cLADES IDENTIfIED HERE, bUT ILLUSTRATES THAT EAcH ARE DIScONNEcTED fROM EAcH OTHER, SUPPORTING THE STRONG GEOGRAPHIc SIGNAL WITHIN THE GREAT BASIN ( FIG. 1b View FIGURE 1 , FIG. 3 View FIGURE 3 , FIG. 6 View FIGURE 6 ). Of THE THREE, THE SOUTHERN cLADE (M) IS MORE DIVERSE, WHIcH INcLUDES HAPLOTYPES Of B. boreas , THE LOcALIZED ENDEMIc, B. nelsoni , AND SOUTHERN POPULATIONS Of B. canorus ( FIG. 1b View FIGURE 1 , FIG. 3 View FIGURE 3 ). THIS PATTERN IS A cONSISTENT RESULT Of PREVIOUS STUDIES ( STEPHENS 2001; GOEbEL et al. 2009). THERE ARE MINOR DIffERENcES IN THE TOPOLOGIES Of OUR PHYLOGENETIc ANALYSES, YET THE DIffERENTIATION Of B. williamsi AS A UNIQUE AND SISTER LINEAGE TO bOTH THE HL GROUP Of B. boreas AND NORTHERN B. canorus IS A cONSISTENT RESULT ( FIG. 6 View FIGURE 6 ). PAIRWISE cOMPARISONS Of NUcLEOTIDE DIVERSITY REVEALED THAT B. williamsi IS cOMPARAbLY DIffERENTIATED AS ARE OTHER SPEcIES IN THE boreas SPEcIES cOMPLEX WITH AN AVERAGE GENETIc DISTANcE Of 2.1 %, INDIcATING REcENT DIVERGENcE fROM B. boreas , A cONSISTENT RESULT fROM PREVIOUS STUDIES EXAMINING boreas DIVERSITY WITHIN THE SPEcIES cOMPLEX ( GRAYbEAL 1993; SHAffER et al. 2000; STEPHENS 2001; PAULY et al. 2004; GOEbEL et al. 2009; TAbLE 3).

Etymology. THE SPEcIfIc EPITHET IS IN TRIbUTE TO RObERT WILLIAMS, fORMER FIELD SUPERVISOR Of THE U.S. FISH AND WILDLIfE, WHOSE HERcULEAN EffORTS ON bEHALf Of THE fAUNA Of NEVADA AND CALIfORNIA WERE cRITIcALLY IMPORTANT IN DIScOVERING ADDITIONAL bIODIVERSITY Of ANURANS IN THE GREAT BASIN, AND IN fOcUSING ON THE NEEDS TO PROVIDE PROTEcTION TO THE RARE AND IMPERILED fAUNA, AND THE EcOSYSTEMS UPON WHIcH THEY DEPEND, IN NEVADA AND CALIfORNIA. THE DIXIE VALLEY TOAD WOULD NOT HAVE bEEN DIScOVERED WITHOUT THE EffORTS Of THIS cOURAGEOUS PUbLIc SERVANT.

Distribution. Bufo (Anaxyrus) williamsi IS fOUND ONLY WITHIN WETLANDS Of LIMITED EXTENT fED fROM ARTESIAN SPRINGS ON THE WESTERN EDGE Of THE DIXIE VALLEY PLAYA, EAST Of THE STILLWATER RANGE IN DIXIE VALLEY, NV ( FIG. 2b View FIGURE 2 ). VERY ISOLATED AND RESTRIcTED IN SIZE, THE ENTIRE ESTIMATED GEOGRAPHIc RANGE IS APPROXIMATELY 6 kM2, WITH NO USAbLE cORRIDORS TO OTHER TOAD HAbITAT OUTSIDE DIXIE VALLEY. FOUR SPRING DIScHARGE SITES AND THE MARSH HAbITAT DOWNSTREAM Of THE SPRINGS ARE SEPARATED fROM EAcH OTHER AND INTERRUPTED bY SAGEbRUSH STEPPE DOMINATED bY bIG SAGEbRUSH ( Artemisia tridentata SSP. tridentata ), GREASEWOOD ( Sarcobatus vermiculatus ), RUbbER RAbbITbRUSH ( Ericameria nauseosa ) AND SALTbUSH ( Atriplex SPP.) ( BLM 2011). THE SPRING-fED WETLANDS SUPPORT MARSH VEGETATION SUcH AS SPIkERUSH ( Eleocharis SPP.), kNOTWEED ( Polygonum SPP.), cANARYGRASS ( Phalaris SPP.), DUckWEED ( Lemna SP.), VARIOUS SPEcIES Of RUSH ( Juncus SP.), cOMMON REED ( Phragmites australis ), AND cATTAIL ( Typha SPP.) ( BLM 2011), AND TOADS ARE TYPIcALLY fOUND IN SHALLOW WATER OR ASSOcIATED WITH MOIST SOILS WITHIN THE IMMEDIATE PERIMETER Of THE RIPARIAN AREAS THAT bORDER SAGEbRUSH HAbITAT.

Natural history. Bufo (Anaxyrus) williamsi IS RESTRIcTED TO THE SPRING fED-WETLAND HAbITAT ALONG THE WESTERN EDGE Of THE DIXIE VALLEY PLAYA. SIMILAR TO OTHER TOADS IN THE B. boreas cOMPLEX (EXcEPT PERHAPS B. exsul , WHIcH IS MORE AQUATIc), THE TERRESTRIAL B. williamsi IS TYPIcALLY NOcTURNAL, EMERGING AT DUSk, AND cAN bE fOUND IN MOIST VEGETATION OR IN VERY STILL, SHALLOW WATER WITH VERY LITTLE VEGETATION cANOPY. DIXIE VALLEY EXPERIENcES EXTREME TEMPERATURE fLUcTUATIONS bETWEEN DAY AND NIGHT TEMPERATURES, AS WELL AS SEASON-TO-SEASON EXTREMES, cHARAcTERISTIc Of cOLD DESERT EcOSYSTEMS.

IN AUTUMN, IT IS LIkELY THAT B. williamsi RETREATS TO bURROWS TO HIbERNATE, EMERGING IN SPRING TO bREED. BREEDING OccURS fROM MARcH TO JUNE (FORREST et al. 2013). SEXUALLY MATURE MALES cONGREGATE IN SHALLOW WATER AROUND THE PERIMETER Of WETLAND VEGETATION. Bufo (Anaxyrus) williamsi DOES NOT HAVE AN ADVERTISEMENT VOcALIZATION, bUT RETAINS A RELEASE cALL USED bY MALES WHEN IN cONTAcT WITH OTHER MALES. EGG MASSES AND TADPOLES DEVELOP IN STILL, SHALLOW WATER WITHIN THE MARGINS Of THE MARSH HAbITAT, WHERE THERE ARE ADEQUATE TEMPERATURES fOR DEVELOPMENT AS IS SEEN WITHIN B. boreas ( KARLSTROM 1962; CAREY et al. 2005) . TOADLETS ARE GENERALLY fULLY METAMORPHOSED IN APPROXIMATELY 10 WEEkS (FORREST et al. 2013).

WHILE B. williamsi IS REPORTEDLY AcTIVE THROUGHOUT THE SUMMER (KRIS URQUHART, PERS. cOMM.), LITTLE IS kNOWN REGARDING DISPERSAL AND NON-bREEDING bEHAVIOR Of THIS TOAD. THE OVERALL POPULATION NUMbERS Of THIS TOAD ARE UNkNOWN; HOWEVER, THE cURRENT RANGE IS SEVERELY RESTRIcTED, SUGGESTING THAT THIS SPEcIES’ POPULATION IS LIkELY VERY SMALL.

THE cOLORATION Of THIS TOAD IS STRIkING, bUT WITHIN THE WETLAND VEGETATION, THE DISRUPTED OLIVE AND fLEckING Of B. williamsi IS VERY cRYPTIc cAUSING THEIR DETEcTION TO bE DIffIcULT. THE MAIN STORES Of bUfOTOXIN ARE IN THE PAROTOID GLANDS, WHIcH ARE cONSPIcUOUS IN SHAPE AND TAN cOLOR, WHIcH cONTRASTS WITH THE OLIVE bAckGROUND cOLOR Of THE bODY, AND MAY TRIGGER A WARNING TO POTENTIAL PREDATORS, SUcH AS cOMMON RAVENS ( Corvus corax ) AND cOYOTES ( Canis latrans ). LARGE AND cONSPIcUOUS TIbIAL GLANDS (NOT TYPIcAL Of cONGENERS WITHIN THE B. boreas cOMPLEX) ARE ALSO PRESENT IN B. williamsi AND ARE ADDITIONAL STORES Of bUfOTOXINS.

Remarks. THE DIXIE VALLEY TOAD IS THE NEWEST ADDITION TO THE B. boreas SPEcIES cOMPLEX, INcREASING THE REGIONAL DIVERSITY IN THE cOMPLEX TO fIVE SPEcIES ( FROST 2015). THE TAXONOMY WITHIN THE GENUS Bufo REMAINS UNSTAbLE AND cONTROVERSIAL, AND TO PROVIDE cONTINUITY fOR THE NOMENcLATURE UNDER B. boreas AND fOR THE DELIMITATION Of THE DIXIE VALLEY TOAD, WE REcOMMEND THAT B. williamsi RETAINS Bufo , INcREASING THE NEARcTIc bUfONIDS IN THE SUbGENUS Anaxyrus TO 23 SPEcIES (PAULY et al. 2009; FROST 2015). NEW ANURAN DIScOVERIES HAVE bEEN RARE WITHIN THE UNITED STATES, WITH ONLY THREE NEWLY DEScRIbED fROGS (THAT WERE NOT SIMPLY ELEVATED fROM SUbSPEcIES STATUS) SINcE 1985 ( MOLER 1985; LEMMON et al. 2008; FEINbERG et al. 2014). Bufo (Anaxyrus) williamsi REPRESENTS THE fIRST NEWLY DEScRIbED bUfONID SPEcIES TO OccUR NORTH Of MEXIcO SINcE 1968 ( FROST 2015) AND DEMONSTRATES THAT OUR kNOWLEDGE Of NEARcTIc ANURAN DIVERSITY REMAINS INcOMPLETE AND THAT NOVEL DIScOVERIES cONTINUE TO OccUR, EVEN IN UNLIkELY SETTINGS. THE MOST REcENTLY NAMED NEW ANURAN SPEcIES, Rana kauffeldi (FEINbERG et al. 2014) AND Pseudacris fouquettei (LEMMON et al. 2008) REMAINED UNDETEcTED DESPITE OccURRING IN A HIGHLY POPULATED REGION ( R. kauffeldi ) OR HAVING A bROAD DISTRIbUTION ( P. fouquettei ). Rana AND Pseudacris cONTAIN MULTIPLE SPEcIES cOMPLEXES, WHERE THE TAXONOMY REMAINS UNSTAbLE AND cONTROVERSIAL DUE TO cRYPTIc DIVERSITY, ( PLATZ & FORESTER 1988; MORIARTY & CANNATELLA 2004; VREDENbURG et al. 2007; LEMMON et al. 2008; FEINbERG et al. 2014), AN ISSUE HIGHLIGHTED bY NUMEROUS SUbSPEcIES REcLASSIfIcATIONS Of fROGS WITHIN THESE GROUPS (GREEN et al. 1996; LEMMON et al. 2008), AND EVIDENcED bY THE NEWEST SPEcIES DEScRIbED THAT WERE bOTH THEMSELVES cRYPTIc.

THE ARID GREAT BASIN HAS fEW AQUATIc RESOURcES, WITH HIGH ENDEMISM ASSOcIATED WITH WIDELY DISPERSED SPRINGS, SMALL STREAMS AND SEEPS WITHIN THE REGION ( HUbbS & MILLER 1948; SHEPARD 1992, HERSHLER & SADA 2002; SADA & VINYARD 2002; SMITH et al. 2002). DUE TO ISOLATION AND RARITY, SPRINGS AND RESULTING WETLANDS MAY HARbOR cRYPTIc SPEcIES ( SHEPARD 1993). REcENT MOLEcULAR STUDIES INVESTIGATING THE fINE ScALE RELATIONSHIPS WITHIN THE B. boreas SPEcIES cOMPLEX HAVE SUGGESTED THAT THE WESTERN TOAD DIVERSITY AcROSS ITS bROAD GEOGRAPHIc RANGE IS NOT AccURATELY REfLEcTED UNDER THE cURRENT TAXONOMY WITH RESULTS INDIcATING THAT EVEN ADDITIONAL HIDDEN DIVERSITY IS LIkELY ( GOEbEL, 2005; GOEbEL et al., 2009), PARTIcULARLY AROUND THE EDGES Of THE GREAT BASIN (GOEbEL et al. 2009). HOWEVER, SAMPLING WITHIN THE GREAT BASIN HAD bEEN VERY LIMITED OR AbSENT UNTIL THE REcENT LOcALIZED STUDY (TRAcY et al. UNPUbL. DATA) EXAMINING B. boreas DIVERSITY WITHIN THE REGION. THAT STUDY ALSO INDIcATES THAT B. williamsi IS GENETIcALLY DISTINcT fROM B. boreas . EVIDENcE SUGGESTS AQUATIc ISOLATION Of DIXIE VALLEY IS ESTIMATED TO HAVE OccURRED APPROXIMATELY 650KYA WHEN THE cLIMATE SHIfTED (REHEIS et al. 2002; NOLES 2010) WHIcH cOULD HAVE STRANDED AQUATIc ORGANISMS TO THIS ENDORHEIc bASIN. THE UNDETEcTED DIVERSITY IDENTIfIED WITHIN TOADS Of DIXIE VALLEY YIELDED GENETIc DISTANcES ( TAbLE 3) SIMILAR TO THOSE Of THE cLOSELY RELATED SPEcIES WITHIN THE B. boreas SPEcIES cOMPLEX WHEN cOMPARED TO B. boreas . THE NOVEL DIScOVERY Of B. williamsi , WHOSE cONcEALMENT WAS DUE TO ITS OccURRENcE WITHIN THE RANGE Of THE WIDELY DISTRIbUTED B. boreas , IS AN EXAMPLE Of REMARkAbLE RESULTS THROUGH THE cOUPLED USE Of bOTH SYSTEMATIcS AND TAXONOMY, LEADING TO THE IDENTIfIcATION Of HIDDEN DIVERSITY.

Bufo (Anaxyrus) williamsi HAS THE SMALLEST RANGE Of ALL cONGENERS Of THE B. boreas SPEcIES cOMPLEX, AND THESE RESULTS HIGHLIGHT THE IMPORTANcE Of AccURATE TAXONOMY HAVING PROfOUND IMPLIcATIONS fOR THE MANAGEMENT AND cONSERVATION INITIATIVES fOR TAXA (BIckfORD et al. 2006; TRONTELj & FIšER 2009), PARTIcULARLY RARE SPEcIES OccURRING WITHIN THE RANGE Of WIDELY NOMINAL SPEcIES.

Conservation Concerns. AMPHIbIANS ARE THE MOST IMPERILED cLADE Of VERTEbRATES WITH DEcLINES AND EXTINcTIONS OccURRING GLObALLY ( IUCN 2015). IN THE UNITED STATES, 31.7 % Of AMPHIbIAN SPEcIES ARE IN DEcLINE (ADAMS et al. 2013) AND 26% Of RARE ENDEMIcS ARE LISTED AS THREATENED ( IUCN 2015). IN THE WESTERN UNITED STATES, POPULATIONS Of B. boreas HAVE EXPERIENcED DEcLINES AcROSS THEIR LARGE GEOGRAPHIc RANGE ( BLAUSTEIN & WAkE 1990; BLAUSTEIN et al. 1994; BULL & CAREY 2008; PILLIOD et al. 2010). WITHIN THE GREAT BASIN, B. boreas OccUPANcY IS DEcLINING bEcAUSE Of HAbITAT LOSS (WENTE et al. 2005), AND ALL THREE ENDEMIcS ARE THREATENED ( IUCN 2015).

THE DIXIE VALLEY TOAD fAcES A STAGGERING NUMbER Of THREATS TO ITS PERSISTENcE WHIcH ARE cOMPOUNDED bY ITS REMARkAbLY SMALL GEOGRAPHIc RANGE . THE MOST URGENT cONcERN IS THE EXPANSION Of GEOTHERMAL ENERGY PRODUcTION, WHIcH cOULD IMPERIL THE fRAGILE MARSH HAbITAT UPON WHIcH THIS RARE TOAD RELIES . DIXIE VALLEY IS THE HOTTEST AND MOST GEOTHERMALLY AcTIVE SYSTEM IN THE BASIN AND RANGE PROVINcE, AND IT IS HOME TO THE LARGEST GEOTHERMAL ENERGY PLANT IN NEVADA, WHIcH HAS bEEN IN OPERATION fOR OVER 20 YEARS (BLAckWELL et al. 2007) . HOWEVER, NEW PROPOSALS fOR GEOTHERMAL, OR SOLAR, ENERGY DEVELOPMENT cOULD REDUcE THE RARE WATER RESOURcES WITHIN THIS VALLEY, DEVASTATING cRITIcAL bREEDING HAbITAT fOR THE SPEcIES.

WHILE B. williamsi View in CoL IS NOT SYMPATRIc WITH B. boreas View in CoL , INTRODUcED NORTH AMERIcAN bULLfROGS ( Rana catesbeiana View in CoL ), ARE PRESENT AT THE SOUTHERN EDGE Of THE DIXIE VALLEY TOAD RANGE. BULLfROGS ARE MUcH LARGER THAN B. williamsi View in CoL (AS ARE METAMORPHS Of THESE bULLfROGS WHIcH ARE LARGER THAN ADULT B. williamsi View in CoL ) AND bULLfROGS ARE kNOWN TO PREY UPON OTHER AMPHIbIANS. IN ADDITION, bULLfROGS ARE A kNOWN VEcTOR fOR DISEASES ( KATS & FERRER 2003; DASZAk et al. 2004) SUcH AS cHYTRIDIOMYcOSIS, A POTENTIALLY LETHAL PATHOGEN THOUGHT TO cAUSE AMPHIbIAN DEcLINES AND EXTIRPATIONS, AND IMPLIcATED IN SOME DEcLINES NOTED AMONG POPULATIONS Of B. boreas View in CoL ( MUTHS 2003; MUTHS et al. 2008; BULL 2009). IN 2012, A SURVEY DID NOT DETEcT cHYTRIDIOMYcOSIS AMONG B. williamsi View in CoL , HOWEVER, THERE WAS AN INcREASE IN THE INfEcTION AMONG bULLfROGS fROM 18 % IN 2011 TO 75 % IN 2012 (FORREST et al. 2013), WHIcH POSES A SERIOUS THREAT TO THE ENDEMIc DIXIE VALLEY TOAD.

THE US FISH AND WILDLIfE SERVIcE AND NEVADA DEPARTMENT Of WILDLIfE HAVE bEEN MONITORING B. williamsi View in CoL SINcE 2008. ALTHOUGH THE SPEcIES RANGE HAS bEEN DEfINED, THE POPULATION SIZE REMAINS UNkNOWN. THIS LIMITED DISTRIbUTION IS STRONG INDIcATOR THAT THE cURRENT POPULATION IS EXcEEDINGLY SMALL, SIMILAR TO RELATED TOADS, B. exsul View in CoL AND B. nelsoni View in CoL , AND WILL SIMILARLY WARRANT STRONG cONSERVATION INITIATIVES TO PROTEcT AND MONITOR THIS NEW SPEcIES. AT SMALLER POPULATION SIZES, HAbITAT LOSS, NONNATIVE SPEcIES, AND DISEASE MAY AcT SYNERGISTIcALLY, NEGATIVELY IMPAcTING THIS INDIGENOUS TOAD.