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Research on water exchange in frogs has historically assumed that blood osmotic potential drives water exchange between a frog and its environment, but here we show that the "seat patch" (the primary site of water exchange in many anurans), or other sites of cutaneous water uptake, act as an anatomic "compartment" with a water potential controlled separately from water potential of the blood, and the water potential of that compartment can be the driver of water exchange between the animal and its environment. We studied six frog species (

The northeastern extreme of the Mojave desert tortoise (Gopherus agassizii) distribution near Zion National Park in Utah is contested as a natural range limit because of its suboptimal habitat and known anthropogenic movements of tortoises. In this study, we added microsatellite data from nine tortoises from the Zion area to a previously published population genetic analysis to determine the tortoises' likely origins. Our results suggest that both anthropogenic tortoise movements and descendants of local tortoises make up the individuals found near Zion.

We assessed the potential for microbial interactions influencing a well-documented host-pathogen system. Mycoplasma agassizii is the known etiological agent of upper respiratory tract disease in Mojave desert tortoises (Gopherus agassizii), but disease in wild animals is extremely heterogeneous. For example, a much larger proportion of animals harbor M. agassizii than those that develop disease. With the availability of a new quantitative PCR assay for a microbe that had previously been implicated in disease, Pasteurella testudinis, we tested 389 previously collected samples of nasal microbes from tortoise populations across the Mojave desert. We showed that P. testudinis is a common commensal microbe. However, we did find that its presence was associated with higher levels of M. agassizii among the tortoises positive for this pathogen. The best predictor of P. testudinis prevalence in tortoise populations was average size of tortoises, suggesting that older populations have higher levels of P. testudinis. The prevalence of co-infection in populations was associated with the prevalence of URTD, providing additional evidence for an indirect interaction between the two microbes and inflammatory disease. We showed that URTD, like many chronic, polymicrobial diseases involving mucosal surfaces, shows patterns of a polymicrobial etiology.

Mycoplasma agassizii is a common cause of upper respiratory tract disease in Mojave desert tortoises (Gopherus agassizii). So far, only two strains of this bacterium have been sequenced, and very little is known about its patterns of genetic diversity. Understanding genetic variability of this pathogen is essential to implement conservation programs for their threatened, long-lived hosts. We used next generation sequencing to explore the genomic diversity of 86 cultured samples of M. agassizii collected from mostly healthy Mojave and Sonoran desert tortoises in 2011 and 2012. All samples with enough sequencing coverage exhibited a higher similarity to M. agassizii strain PS6(T) (collected in Las Vegas Valley, Nevada) than to strain 723 (collected in Sanibel Island, Florida). All eight genomes with a sequencing coverage over 2x were subjected to multiple analyses to detect single-nucleotide polymorphisms (SNPs). Strikingly, even though we detected 1373 SNPs between strains PS6(T) and 723, we did not detect any SNP between PS6(T) and our eight samples. Our whole genome analyses reveal that M. agassizii strain PS6(T) may be present across a wide geographic extent in healthy Mojave and Sonoran desert tortoises. US Fish and Wildlife ServiceUS Fish & Wildlife Service [F19AC00070]; Nevada INBRE (National Institute of General Medical Sciences, National Institutes of Health) [P20GM103440]; National Science FoundationNational Science Foundation (NSF) [MCB 1818288] This work was supported by grant F19AC00070 from the US Fish and Wildlife Service, and partially supported by Nevada INBRE (funded by grant P20GM103440 from the National Institute of General Medical Sciences, National Institutes of Health). AL and DAP were also supported by a grant from the National Science Foundation (MCB 1818288). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Pathogens that cause subclinical diseases or exhibit low infection intensities are difficult to quantify in wild populations. Mojave desert tortoises ( Gopherus agassizii ) have been the focus of much research aimed at measuring the presence of upper respiratory disease (URTD) and URTD-associated pathogens, and techniques used to quantify disease in Gopherus species have also been used for disease surveillance in other species of turtles and tortoises of conservation concern. Published surveys of G. agassizii populations have found a relatively low prevalence of URTD, with most URTD-positive animals exhibiting moderate, intermittent signs of morbidity. Therefore, multiple tests have been developed to quantify URTD including genetic detection of the pathogens Mycoplasma agassizii and Mycoplasma testudineum , detection of M. agassizii -specific antibodies, and standardized quantification of clinical signs of URTD and body condition. These diagnostic tests have only been compared in diseased or moribund, semicaptive animals. We compared diagnostic techniques (TaqMan® and SYBR™ Green qPCR, serology, and visible examination) to detect M. agassizii -associated URTD in 126 wild desert tortoises sampled in Nevada and California, US in 2010. All had healthy body condition indices and none exhibited more than mild-to-moderate visual signs of URTD. Pairwise comparisons of diagnostic techniques indicated poor performance in diagnosing disease in individual animals. We found stronger, but inconsistent, statistical associations among diagnostic techniques at the population level. Our findings have implications for quantifying subclinical respiratory disease in tortoises.

We report on a survey of the small mammal communities of Anaho Island and the mainland surrounding Pyramid Lake in the Great Basin of western Nevada. Ten rodent species were detected on the mainland, but only the deer mouse (Peromyscus maniculatus) was detected on Anaho Island. Although the mean abundance of deer mice on the Pyramid Lake mainland was more than double that of Anaho Island (12.5 ± 10.1 individuals per trap grid compared with 5.0 ± 3.4 individuals per trap grid), we did not detect a significant difference between locations. Deer mice on Anaho Island were significantly larger in body size (mean body length = 86 ± 4 mm) than mainland mice (mean = 75 ± 7 mm), but it is unclear what mechanisms might have produced the observed divergence in body size.

In PNAS, Devitt et al. (1) present a profoundly interesting and important report of phylogeographic and phylogenetic analyses of a group of salamanders in the genus Eurycea in the Edwards and Trinity aquifers in west-central Texas. These analyses led the authors to extend the scope of their study to analyze important conservation concerns for these salamander species and the ecosystems upon which they depend. These salamanders are mysterious and challenging to those who want to learn about them. An important first step would be to ask how many species are associated with this aquifer system and how are those species distributed in space. However, even this first step is a remarkable challenge insofar as the habitat for the species is within the subterranean interstices of karstic (porous rock) aquifers. These salamanders remind one of the Morlocks in the 19th-century novel by H. G. Wells, The Time Machine (2), because both Morlocks and Eurycea spp. live mostly underground. It would be hard enough to conduct a phylogeographic study of pond-dwelling frogs that can be easily found by listening for their loud breeding calls, but the Morlock-like salamanders do not vocalize and they inhabit parts of the world that are terribly hard to access. Devitt et al. (1) sampled salamanders in caves, water wells, and springs at the recharge and discharge areas of these underground stream systems, yet much of the habitat for these salamanders could not be sampled. Actually, the comprehensive book of standard methods for sampling amphibians (3) offers no guidance on how to sample amphibians within the water table. In fact, sampling these salamanders in their habitat within the water table is likely best accomplished by using water-drilling rigs (Fig. 1), which are not generally the tools of field biologists. Nevertheless, some sampling was done … [↵][1]1Email: dtracy{at}unr.edu. [1]: #xref-corresp-1-1

We describe two new cryptic species of Bufo within the subgenus Anaxyrus discovered in Central Nevada of the western United States. Our analyses revealed that these two localized endemic toads are ...

Five supplementary figures including rarefaction curves, site-level boxplots of OTU richness, and core microbiome information for host species and sampling sites.

Bufo (Anaxyrus) williamsi. sp. nov. DIXIE VALLEY TOAD (FIG. 2b, FIG.4) Holotype. CAS 259271 (CALIfORNIA AcADEMY Of ScIENcE HERPETOLOGY COLLEcTION), ADULT MALE (FIG. 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. 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; TAbLE 1, TAbLE 2), GENETIc EVIDENcE (FIG.3, FIG. 6), AND LOcALIZED DISTRIbUTION (FIG. 2b). 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, FIG. 4b). 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). 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). 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, FIG. 4D) RELATIVE TO LIfE (FIG. 4A, FIG. 4b). 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 F 3, 376 = 63.4, p F 4, 379 = 903.8, p F 4, 379 = 830.8, p F 4, 379 =1219.0, p F 4, 379 = 1080.1, p F 4, 379 = 164.9, p F 4, 379 =160.9, p 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 F 4, 379 = 240.0, p F 4, 379 = 422.5, p F 4, 379 = 371.1, p B. boreas, AND A LARGER TYMPANUM cOMPARED TO ALL THREE OTHER SPEcIES EXAMINED (F 4, 379 = 231.4, p 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 F 4, 379 = 801.0, p F 4, 379 = 1063.8, p F 4, 379 = 909.0, p F 4, 379 = 571.8, p F 4, 379 = 470.7, p B. boreas (TUkEY HSD POST-HOc PAIRWISE cOMPARISONS, p B. williamsi IS THE SMALLEST TOAD AMONG ALL POPULATIONS EXAMINED (F 16, 379 = 34.7, p F 17,379 = 285.1, p F 17,379 = 353.3, p F 17,379 = 55.1, p B. boreas AND cONGENERIc TAXA EXAMINED (F 17,379 = 86.07, p B. williamsi ARE RELATIVELY SHORTER IN LENGTH (F 17, 379 = 81.1, p 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 B. williamsi, AND ITS LEGS ARE THE SHORTEST AMONG ALL POPULATIONS SAMPLED (FL: F 17, 379 = 248.9, p F 17, 379 = 312.6, p F 17, 379 = 139.1, p B. exsul. DIScRIMINANT fUNcTION ANALYSIS (DFA) ILLUSTRATES SIGNIfIcANT MORPHOLOGIcAL DIffERENcES AMONG SPEcIES (F 42, 173 = 2.80, p B. boreas, B. nelsoni AND B. exsul (FIG. 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 F 2 , 29 = 12.2, p Genetic Results. THE cOMbINED DNA ANALYSES Of THE cONTROL REGION SUPPORT THE DIffERENTIATION Of THE NEW SPEcIES, B. williamsi (FIG.3, FIG. 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, FIG. 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, FIG. 3, FIG. 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, FIG. 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). 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). 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, Published as part of 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 in Zootaxa 4290 (1) on pages 127-136, DOI: 10.11646/zootaxa.4290.1.7, http://zenodo.org/record/1012647, {"references":["Stebbins, R. C. (2003) Peterson Field Guide to Western Reptiles and Amphibians. Third Edition. Houghton Mifflin Company, Boston, pp. 208 - 211.","Stephens, M. R. (2001) Phylogeography of the Bufo boreas (Anura, Bufonoidea) Species Complex and the Biogeography of California. MA Thesis. Sonoma State University, CA.","Graybeal, A. (1993) The phylogenetic utility of Cytochrome b: Lessons from bufonid frogs. 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(2010) Reconciling western toad phylogeography with Great Basin prehistory. MS Thesis, University of Nevada, Reno, Nevada.","Trontelj, P & Fiser, C. (2009). Cryptic species diversity should not be trivialized. Systematics and Biodiversity, 7, 1 - 3. https: // doi. org / 10.1017 / S 1477200008002909","IUCN (2015) The IUCN Red List of Threatened Species. Version 2015 - 3. Available from: http: // www. iucnredlist. org (accessed 9 September 2015)","Blaustein, A. R. & Wake, D. B. (1990) Declining amphibian populations: A global phenomenon? Trends in Ecology and Evolution, 5, 203 - 204.","Bull, E. L. & Carey, C. (2008) Breeding frequency of western toads (Bufo boreas) in Northeastern Oregon. Herpetological Conservation and Biology, 3, 282 - 288.","Kats, L. B. & Ferrer, R. P. (2003) Alien predators and amphibian declines: review of two decades of science and the transition to conservation. Diversity and Distributions Journal, 9, 99 - 110. https: // doi. org / 10.1046 / j. 1472 - 4642.2003.00013. x","Muths, E. (2003) Home range and movements of Boreal toads in undisturbed habitat. Copeia, 1, 160 - 165. https: // doi. org / 10.1643 / 0045 - 8511 (2003) 003 [0160: hramob] 2.0. co; 2","Bull, E. L. (2009) Dispersal of newly metamorphosed and juvenile western toads (Anaxyrus boreas) in Northeastern Oregon, USA. Herpetological Conservation and Biology, 4, 236 - 247."]}

Field metabolic rates (FMR) and water influx rates (WIR) were measured in Gila Monsters (Heloderma suspectum) in the Mojave Desert of southern Nevada. Gila Monsters had rates of energy use that were less than half of those expected for lizards of their size, including species that live in arid habitats. Free-living Gila Monsters also had comparatively low water flux rates. The annual energy requirements of adult Gila Monsters averaged approximately 3,766 kJ, with two-thirds of the total (2,533 kJ) allocated to activity while above ground, and one-third to resting metabolism (1,233 kJ; mostly while below ground). Unusually low rates of resting metabolism caused relative costs of activity to be high: compared to other lizards, Gila Monsters have among the highest proportional use of energy for activity, relative to total energy use. The average annual water expenditure of adults was approximately 775 mL, and lizards achieved positive mass balance by drinking rain water during the late summer monsoon season....

Mitoura thornei, Thorne's hairstreak butterfly, is endemic to a single mountain in southwestern North America. The small geographic range of this species coupled with threats to its host plant, Hesperocyparis forbesii, motivated a study of habitat association and mapping of both butterfly and host distributions. Specifically, the following questions were posed. How much of the range of the host plant is occupied by M. thornei? What biotic and abi- otic features are associated with the presence and abundance of M. thornei? And, how does tree age affect larval performance? These questions were addressed with a combination of field observations and experiments. 2. Hesperocyparis forbesii size and density were found to be the most important factors associated with the presence and absence of M. thornei at the scale of individual sampling plots, whereas H. forbesii density was found to be the most important factor at the scale of host plant stands. Experiments with larvae showed no effect of tree age on survival, but did show a reduction in larval performance for individuals reared on foliage from the oldest trees. 3. From a conservation perspective, our most important result is the widespread occurrence of M. thornei throughout the study area. Ecologically, the distribution of M. thornei points towards much that has yet to be learned about the use of space in a small, locally rare insect. In general, our results illustrate the challenges of understanding habitat association for a geographi- cally restricted species, and the utility of studying different life history stages, both in the field and in the laboratory.

We investigate how a unique dietary specialist, the Gila monster (Heloderma suspectum), uses behavioral thermoregulation to elevate body temperature (Tb) after feeding. Lizards in a laboratory thermal gradient were fed rodent meals of three different sizes (5, 10, or 20% of body mass), or sham fed (meal of 0% body mass), and Tbs were recorded for three days before feeding and seven days after feeding. Gila monsters selected a mean Tb of 25.2 °C while fasting (set-point range 23.6–27.1), and increased Tbs after feeding. The magnitude and duration of post-prandial Tb increases are positively related to meal size, and Gila monsters selected mean Tbs up to 3.0 °C higher and maintain elevated Tbs for 3–6 days after feeding. Selection of Tb does not appear to differ between day and night time periods, and because the lizards are both diurnal and nocturnal (at different times of year), photoperiod may not be an important influence on Tb selection.

Heterogeneity in habitat often influences how organisms traverse the landscape matrix that connects populations. Understanding landscape connectivity is important to determine the ecological processes that influence those movements, which lead to evolutionary change due to gene flow. Here, we used landscape genetics and statistical models to evaluate hypotheses that could explain isolation among locations of the threatened Mojave desert tortoise (Gopherus agassizii). Within a causal modeling framework, we investigated three factors that can influence landscape connectivity: geographic distance, barriers to dispersal, and landscape friction. A statistical model of habitat suitability for the Mojave desert tortoise, based on topography, vegetation, and climate variables, was used as a proxy for landscape friction and barriers to dispersal. We quantified landscape friction with least-cost distances and with resistance distances among sampling locations. A set of diagnostic partial Mantel tests statistically separated the hypotheses of potential causes of genetic isolation. The best-supported model varied depending upon how landscape friction was quantified. Patterns of genetic structure were related to a combination of geographic distance and barriers as defined by least-cost distances, suggesting that mountain ranges and extremely low-elevation valleys influence connectivity at the regional scale beyond the tortoises’ ability to disperse. However, geographic distance was the only influence detected using resistance distances, which we attributed to fundamental differences between the two ways of quantifying friction. Landscape friction, as we measured it, did not influence the observed patterns of genetic distances using either quantification. Barriers and distance may be more valuable predictors of observed population structure for species like the desert tortoise, which has high dispersal capability and a long generation time.

A Mojave Desert shrub community was experimentally burned to understand changes in seed bank of desert annual plant species in response to wildfire. Seed mortality ranged from 55 to 80%, and fire caused significant losses of native and alien annual seeds. Schismus arabicus, Schismus barbatus, Bromus madritensis, Bromus tectorum, Erodium cicutarium and Plantago spp. made up >95% of the seed bank. Bromus spp. and Plantago spp. had proportionately greater mortality of seeds than did Schismus spp. and E. cicutarium. Schismus spp. can be lodged into soil cracks thus avoiding lethal temperatures. E. cicutarium has a self-drilling mechanism that places the seeds at greater depth in the soil. Greater seed mortality occurred beneath shrub canopies than interspaces for most species (Plantago, spp., Bromus spp., and E. cicutarium), but microsite had little effect on Schismus spp. Fire reduced the perennial Ambrosia dumosa densities under canopies. Fire reduced the mean number of species found in samples by about one species per plot and no species was extirpated on experimental plots. The relative abundances of common species did not change dramatically as a result of fire or microsite, however; seed densities varied by treatment and affected interpretations of species compositions.

We used highly variable microsatellite markers to identify population structure, movement, and biological boundaries for populations of the desert tortoise, Gopherus agassizii, in the Mojave and Colorado Deserts of the southwestern United States. The Mojave desert tortoise (listed as “threatened” by the U.S. Fish and Wildlife Service) has a large geographic range, long generation time, low population densities, and little above-ground activity. Additionally, the dispersal patterns of individual tortoises are virtually unknown, making indirect methods to assess movement among populations valuable. Using Bayesian assignment tests, we detected hierarchical structuring within the Mojave desert tortoise. Three basal groups were identified, and these corresponded to the mitochondrial DNA haplotypes reported in 1989. Additional population structure was evident within each basal unit, and this structure corresponds with major geographic barriers. Our analyses suggest that gene flow among populations was historically high because levels of population differentiation were low across the range. Geographic distance explained a large proportion of variation in genetic distance (68%), which pinpoints that dispersal is limited only on a regional scale. In light of these new analyses of the genetic population structure of the Mojave desert tortoise, we make new recommendations for the number and locations of recovery units for conservation of this species.

We quantified the severity of upper respiratory tract disease (URTD) and immunological metrics (differential white blood cell counts and bacteria‐killing ability of blood plasma) in relation to climatic variables in 20 populations of Mojave desert tortoise (Gopherus agassizii). Prevalence and infection intensity of Mycoplasma agassizii, an etiological agent of URTD, have previously been quantified for these populations (Weitzman et al.). Immunological variables were reduced by principal component analyses and separated into cells involved in inflammation (PC1) and cellular functions mediated by lymphocytes and basophils (PC2). In population‐level models, the mean number of lymphocytes per individual was associated with mean annual number of days below freezing. Lymphocytes were also positively associated with mean infection intensity of M. agassizii. Additionally, prevalence of URTD was closely associated with PC1 (cells associated with inflammation). This suggests that at least two immunological strategies are involved in responding to M. agassizii, one that involves primarily lymphocytes and one that involves inflammatory mechanisms. Recent studies on immunology in Testudines suggest that a large proportion of lymphocytes in this taxon are similar to B‐1 lymphocytes of mammals and have phagocytic properties. Controlled experiments are needed to understand the disease mitigation of these lymphocytes in desert tortoises.

We used simulations from a biophysical model that integrates interlinked exchanges of energy and water between frogs and their environments to address questions about the limits to thermoregulation and about adaptations for arboreality. Body size and cutaneous resistance (Rc) both significantly affected body temperature (Tb) and the time to desiccate to 70% of standard mass (an ecologically relevant metric of desiccation). Cutaneous resistances < 25 s/cm allow basking frogs to elevate their Tb several degrees above ambient, but Rc above 25 had little additional effect on Tb. Small frogs (

Post-fire changes in desert vegetation patterns are known, but the mechanisms are poorly understood. Theory suggests that pulse dynamics of resource availability confer advantages to invasive annual species, and that pulse timing can influence survival and competition among species. Precipitation patterns in the American Southwest are predicted to shift toward a drier climate, potentially altering post-fire resource availability and consequent vegetation dynamics. We quantified post-fire inorganic N dynamics and determined how annual plants respond to soil inorganic nitrogen variability following experimental fires in a Mojave Desert shrub community. Soil inorganic N, soil net N mineralization, and production of annual plants were measured beneath shrubs and in interspaces during 6 months following fire. Soil inorganic N pools in burned plots were up to 1 g m(-2) greater than unburned plots for several weeks and increased under shrubs (0.5-1.0 g m(-2)) more than interspaces (0.1-0.2 g m(-2)). Soil NO(3) (-)-N (nitrate-N) increased more and persisted longer than soil NH(4) (+)-N (ammonium-N). Laboratory incubations simulating low soil moisture conditions, and consistent with field moisture during the study, suggest that soil net ammonification and net nitrification were low and mostly unaffected by shrub canopy or burning. After late season rains, and where soil inorganic N pools were elevated after fire, productivity of the predominant invasive Schismus spp. increased and native annuals declined. Results suggest that increased N availability following wildfire can favor invasive annuals over natives. Whether the short-term success of invasive species following fire will direct long-term species composition changes remains to be seen, yet predicted changes in precipitation variability will likely interact with N cycling to affect invasive annual plant dominance following wildfire.

Assessing the recovery of the federally listed Mojave population of desert tortoises Gopherus agassizii requires detecting subtle changes in population size over a period of many years. The methods that have been employed by the US Fish and Wildlife Service to estimate population density of desert tortoises are inadequate for detecting modest trends in population density, partly due to a hidden variance in a parameter (g0) that corrects for the proportion of tortoises that are inactive and thus unavailable for sampling when population density is being assessed. We used small dataloggers to record the activity of tortoises throughout their active season, and derived daily esti- mates of g0, which we compared with the 2004 estimate published by the US Fish and Wildlife Ser- vice. Due to the substantial variation in animal activity that we found within and among days during the active season, we used a daily method to estimate density. We found that this method, while pro- viding a more accurate assessment of g0, translates into estimates of density with coefficients of vari- ation that are 4" larger than previously reported due to the variation in g0 and n (number of animals encountered). This discrepancy could adversely influence managers' perceptions of population recovery for desert tortoises, and could undermine any ability to monitor the efficacy of recovery actions for populations.

The relationships between Mycoplasma agassizii, a causative agent of upper respiratory disease (URTD), and desert tortoise (Gopherus agassizii), generally illustrate the complexities of disease dynamics in wild vertebrate populations. In this review, we summarize current understanding of URTD in Mojave desert tortoise populations, we illustrate how inadequate knowledge of tortoise immune systems may obfuscate assessment of disease, and we suggest approaches to future management of URTD in desert tortoise populations. We challenge the view that M. agassizii causes consistent levels of morbidity and/or mortality across the Mojave desert. Instead, URTD may be described more accurately as a context-dependent disease. In addition, new evidence for relatively high levels of natural antibodies to M. agassizii in desert tortoises suggests possible problems in conventional diagnostic tests of disease in tortoises as well as a possible tortoise immune mechanism to protect against M. agassizii. Partly because of the problems in diagnostic testing, we recommend abandoning policies to euthanize tortoises that test positive for an immune response to M. agassizii. Based on this review, we question management strategies aimed solely at reducing Mycoplasma spp. in desert tortoise populations, and advocate a more careful consideration of extrinsic factors as a cause of symptomatic disease.

Mycoplasma agassizi has been identified as a cause of upper respiratory tract disease (URTD) in the threatened Mojave population of the desert tortoise (Gopherus agassizii), and anti-M. agassizii antibodies have been found by ELISA in as many as 15% of these animals across their geographic range. Here we report that a cohort of 16 egg-reared desert tortoises never exposed to M. agassizii had ELISA antibody titers to this organism that overlapped with titers obtained from some M. agassizii-infected tortoises. These natural antibodies were predominantly of the IgM class. Western blots of plasma from these non-infected tortoises produced a characteristic banding pattern against M. agassizii antigens. A group of 38 wild-caught desert tortoises was tested by ELISA, and although some of these tortoises had antibody titers significantly higher than the non-infected tortoises, there was considerable overlap at the lower titer levels. However, Western blot analysis revealed distinct banding patterns that could readily distinguish between the non-infected tortoises and tortoises with acquired antibodies, regardless of ELISA antibody titers. We conclude that desert tortoises have natural antibodies to M. agassizii that can compromise the determination of infection status by ELISA. However, the Western blot technique can distinguish between natural and acquired antibody patterns and can be used to confirm the diagnosis of M. agassizii infections in the desert tortoise.

Although the skin of most amphibians measured to date offers no resistance to evaporative water loss (EWL), some species, primarily arboreal frogs, produce skin secretions that increase resistance to EWL. At high air temperatures, it may be advantageous for amphibians to increase EWL as a means to decrease body temperature. In Australian hylid frogs, most species do not decrease their resistance at high air temperature, but some species with moderate resistance (at moderate air temperatures) gradually decrease resistance with increasing air temperature, and some species with high resistance (at moderate air temperatures) abruptly decrease resistance at high air temperatures. Lower skin resistance at high air temperatures decreases the time to desiccation, but the lower body temperatures allow the species to avoid their critical thermal maximum (CT(Max)) body temperatures. The body temperatures of species with low to moderate resistances to EWL that do not adjust resistance at high air temperatures do not warm to their CT(Max), although for some species, this is because they have high CT(Max) values. As has been reported previously for resistance to EWL generally, the response pattern of change of EWL at high air temperatures has apparently evolved independently among Australian hylids. The mechanisms involved in causing resistance and changes in resistance are unknown.

We report on ecological interactions between the Gila monster (Heloderma suspectum) and the desert tortoise (Gopherus agassizii) in the Mojave Desert of southern Nevada. Eggs of desert tortoises are an important source of food for Gila monsters, and although tortoises are not always successful, they vigorously defend their nests from predation by Gila monsters. Shelters were co-occupied by these two species only during the nesting season for desert tortoises, and Gila monsters occupied shelters almost exclusively with female tortoises, probably because these shelters were nesting sites.

We examined burrow microclimate and cocoon formation of the burrowing frog, Cyclorana australis, from northern Australia, during the dormancy season by monitoring frogs in burrows in the field. At the beginning of the dry season, while the soils were still quite moist, frogs dug shallow burrows, with 2–8 cm of soil above the top of the burrow chamber. The frogs spent 2–3 months underground without cocoons, but they began to form cocoons once the soils dried to water potentials that would dehydrate the frogs (as determined by laboratory experiments on water exchange). Frogs remained underground for up to six months, and then emerged when soil water potentials were great enough to permit water absorption, although it is unclear whether this was the primary cue for emergence. Soil temperatures adjacent to burrows were intermediate to those in full sun and full shade at 10-cm depth and increased throughout the dormancy period. Frogs removed from burrows after 2–4 months underground had a body mass 136% of their standard mass, indicating that burrowed frogs store a considerable amount of water in the bladder while in the burrows in the early weeks of aestivation. Because C. australis absorb water during the first part of aestivation (or at least maintain water they absorbed prior to burrowing), and construct a relatively impermeable cocoon during the latter part of aestivation, when they could lose water, these frogs may never experience water stress, despite being underground in the dry season for 5–6 months.

We present a new, plaster model for measuring operative environmental temperature (Te) and water loss of amphibians with little or no cutaneous resistance to water loss. These models are made from molds of live animals, cast in plaster of Paris, and can be fitted with water reservoirs that allow them to be used for extended periods. Plaster models did not differ significantly in Te or water loss rate from either identically shaped models made of 3% agar and measured in a wind tunnel or from live cane toads (Bufo marinus) measured outdoors in a variety of conditions. Thus, plaster models offer an accurate measure of both Te and water loss across a range of environmental conditions. The plaster models are also relatively simple to make and offer several advantages over other model types, in that they are durable, they do not shrink like agar models, they can be colored to match absorptivity of live animals, and they can be made in postures representative of live animals.

This research examined the onset, duration, and termination of hibernation in Desert Tortoises (Gopherus agassizii) over several years at multiple sites in the northeastern part of their geographic range, and recorded the temperatures experienced by tortoises during winter hibernation. The timing of hibernation by Desert Tortoises differed among sites and years. Environmental cues acting over the short-term did not appear to influence the timing of the hibernation period. Different individual tortoises entered hibernation over as many as 44 days in the fall and emerged from hibernation over as many as 49 days in the spring. This range of variation in the timing of hibernation indicates a weak influence at best of exogenous cues hypothesized to trigger and terminate hibernation. There do appear to be regional trends in hibernation behavior as hibernation tended to begin earlier and continue longer at sites that were higher in elevation and generally cooler. The emergence date was generally more similar among study sites than the date of onset. While the climate and the subsequent timing of hibernation differed among sites, the average temperatures experienced by tortoises while hibernating differed by only about five degrees from the coldest site to the warmest site.

Translocation could be used as a tool in conservation of the threatened Mojave Desert Tortoise ( Gopherus agassizii ) by moving individuals from harm’s way and into areas where they could contribute to conservation of the species. Numerous factors may affect the success of translocations, including the conditions experienced by tortoises in holding facilities while awaiting translocation. The tortoises available for our translocation study had been provided supplemental water during their years spent in a captive holding facility, potentially inducing carelessness in water conservation. In addition to generally investigating the efficacy of translocation, we compared the effects of continuing with the effects of ceasing the holding facility’s water supplementation regimen. After exposure to one of the two water regimens, all tortoises were given the opportunity to hydrate immediately prior to release. We examined behavior, body mass, carapace length, movement, and mortality of tortoises for two activity seasons following release to the wild. Water supplementation was correlated with high rates of carapace growth and distant movements by males after release. Lengthy movements following translocation may be problematic for conservation planning, but this should be evaluated in light of the goals and circumstances of each translocation project. Although the mortality rate was 21.4% in 1997, data suggest that drought conditions at the site rather than the translocation itself negatively affected the tortoises. None of the tortoises died during their second season at the site. Our results indicate that translocation should be considered a useful tool in conservation of the Desert Tortoise.

The federally listed desert tortoise (Gopherus agassizii) is currently monitored using distance sampling to estimate population densities. Distance sampling, as with many other techniques for estimating population density, assumes that it is possible to quantify the proportion of animals available to be counted in any census. Because desert tortoises spend much of their life in burrows, and the proportion of tortoises in burrows at any time can be extremely variable, this assumption is difficult to meet. This proportion of animals available to be counted is used as a correction factor (g0) in distance sampling and has been estimated from daily censuses of small populations of tortoises (6-12 individuals). These censuses are costly and produce imprecise estimates of g0 due to small sample sizes. We used data on tortoise activity from a large (N = 1 50) experimental population to model activity as a function of the biophysical attributes of the environment, but these models did not improve the precision of estimates from the focal populations. Thus, to evaluate how much of the variance in tortoise activity is apparently not predictable, we assessed whether activity on any particular day can predict activity on subsequent days with essentially identical environmental conditions. Tortoise activity was only weakly correlated on consecutive days, indicating that behavior was not repeatable or consistent among days with similar physical environments.

Diet quality and body size affected passage time of 2 diets (higher and lower in fiber) in hatchling and juvenile desert tortoises (Gopherus agassizii). Mean retention time of the liquid fraction of each diet was significantly shorter than that of the solid fraction, and hatchlings had shorter passage times than juveniles. Habitat disturbances that limit access of hatchlings to diets lower in fiber may negatively impact the physiological and behavioral ecology of young desert tortoises.

Many of the threats to the persistence of populations of sensitive species have physiological or pathological mechanisms, and those mechanisms are best understood through the inherently integrative discipline of physiological ecology. The desert tortoise was listed under the Endangered Species Act largely due to a newly recognized upper respiratory disease thought to cause mortality in individuals and severe declines in populations. Numerous hypotheses about the threats to the persistence of desert tortoise populations involve acquisition of nutrients, and its connection to stress and disease. The nutritional wisdom hypothesis posits that animals should forage not for particular food items, but instead, for particular nutrients such as calcium and phosphorus used in building bones. The optimal foraging hypothesis suggests that, in circumstances of resource abundance, tortoises should forage as dietary specialists as a means of maximizing intake of resources. The optimal digestion hypothesis suggests that tortoises should process ingesta in ways that regulate assimilation rate. Finally, the cost-of-switching hypothesis suggests that herbivores, like the desert tortoise, should avoid switching food types to avoid negatively affecting the microbe community responsible for fermenting plants into energy and nutrients. Combining hypotheses into a resource acquisition theory leads to novel predictions that are generally supported by data presented here. Testing hypotheses, and synthesizing test results into a theory, provides a robust scientific alternative to the popular use of untested hypotheses and unanalyzed data to assert the needs of species. The scientific approach should focus on hypotheses concerning anthropogenic modifications of the environment that impact physiological processes ultimately important to population phenomena. We show how measurements of such impacts as nutrient starvation, can cause physiological stress, and that the endocrine mechanisms involved with stress can result in disease. Finally, our new syntheses evince a new hypothesis. Free molecules of the stress hormone corticosterone can inhibit immunity, and the abundance of "free corticosterone" in the blood (thought to be the active form of the hormone) is regulated when the corticosterone molecules combine with binding globulins. The sex hormone, testosterone, combines with the same binding globulin. High levels of testosterone, naturally occurring in the breeding season, may be further enhanced in populations at high densities, and the resulting excess testosterone may compete with binding globulins, thereby releasing corticosterone and reducing immunity to disease. This sequence could result in physiological and pathological phenomena leading to population cycles with a period that would be essentially impossible to observe in desert tortoise. Such cycles could obscure population fluctuations of anthropogenic origin.

The four species that comprise the Bufo boreas group of toads are critically imperiled in all or portions of their geographical ranges. We present data from 16 microsatellite loci isolated from B. boreas that cross-amplify in these four species. These markers have proven useful in the analyses of population structure and conservation genetics, and provide a powerful tool for future researchers who seek to understand the conservation genetics of these rare toad species. Polymorphism was assessed for 339 individuals from seven populations representing the four species. All loci were polymorphic (X = 8, range of four to 19 alleles). Three loci were not in Hardy–Weinberg equilibrium (HWE) in one population, and one of these loci was out of HWE in a second population (P

Animals that are unable to meet their metabolic needs should adopt compensatory behaviors to mitigate their energetic deficits. Voluntary hypothermia is one such energy-saving strategy. Physiological constraints associated with the digestion of plant tissues, however, may limit the thermoregulatory options of herbivorous ectotherms. In this laboratory study, selected body temperatures of Desert Iguanas (Dipsosaurus dorsalis), subjected to two different rations of a carnivorous and a herbivorous diet, were measured in a laboratory thermal gradient. Lizards fed a carnivorous diet and rationed to 50% of their daily energetic requirement selected significantly lower body temperatures than did lizards in the other diet/ration treatments. Lizards fed a herbivorous diet selected higher body temperatures than did the same lizards fed a carnivorous diet regardless of ration. Our study indicates that selected temperatures are influenced by both diet quality and quantity. These results support the hypothesis that herbivorous reptiles require elevated body temperatures to digest plant tissues. Our findings do not fully support the behavioral hypothermia hypothesis, which posits that diurnal lizards will seek cool temperatures at night to reduce their energy expenditure. Thermoregulatory strategies of Desert Iguanas and other herbivorous lizards may be influenced by the need to balance high body temperatures to digest plant material with the high metabolic costs of maintaining high temperatures.

The technique of counting growth rings to estimate age of turtles is widespread in the scientific literature. Review articles to date have provided primarily lists of authors who have found the technique useful or not, but these reviews have failed to evaluate properly how well the technique actually works. In an attempt to examine how well the published literature supports a biologically meaningful relationship between age and number of growth rings, we surveyed 145 scientific papers that have used counts of rings on scutes to estimate age of individual turtles. Of the 145 papers surveyed, the authors of 44 papers, which comprised 49 case studies, presented data testing the use of growth ring counts for a population of turtles. Of these 49 case studies, 6 reported that the use of the technique was reliable for aging their turtle species past sexual maturity, 15 reported its use to be reliable for aging turtles to young adult (i.e., sexual maturity), 8 reported its use to be reliable for aging juvenile turtles, 2 found it to be reliable with no age limit given, and 8 reported its use unreliable as a method for aging their turtles. The remainder of the case studies presented data that were difficult for us to interpret as reliable or unreliable. Although 22 papers addressed the pattern of growth ring deposition, only four case studies had sufficient data to indicate that a consistent number of rings was added each year. In this paper, we illustrate how the wide- spread use of this technique ultimately has led to its acceptance without the rigor of tests of its validity or accuracy. We conclude that (a) studies attempting to calibrate the relationship between growth rings and age are few, (b) a majority of the papers that we surveyed referenced other papers that did not themselves include a test justifying growth ring counts as an estimate of turtle age, (c) aging turtles from counts of growth rings might be feasible in some types of studies, for some species at some locations, but only after calibrating the relationship between ring counts and age for each circumstance, and (d) there is currently no justification for generalizing the use of growth rings to estimate turtle age for many species.

We describe a new species of toad from the Great Basin region of northern Nevada belonging to the Bufo (Anaxyrus) boreas species complex. This cryptic species was detected through genetic analyses of toad populations sampled throughout the Great Basin and the morphological evidence was quantified through extensive sampling of live toads within the region. The new species has the smallest body size in the species complex, and can be further diagnosed from other species in the complex by its large tibial glands and unique coloration. The known distribution of the new species is restricted to an area less than 6 km2 in Dixie Valley, Churchill Co., Nevada. The Great Basin is an arid region where aquatic resources are both rare and widely scattered, making habitat suitable for anuran populations highly vulnerable to anthropogenic change. The habitat occupied by this newly described species is threatened by the incipient installation of geothermal and solar power development projects that require the water that defines its habitat.

Upper respiratory tract disease (URTD), caused by Mycoplasma agassizii, has been deemed a threat to populations of Mojave Desert Tortoises, Gopherus agassizii. Previous work on URTD has focused on serology and visual health examinations to determine the extent of this disease in some natural tortoise populations. Here, we present the first range-wide study of the presence of the pathogen, M. agassizii, in Mojave Desert Tortoises. We detected M. agassizii in tortoise populations throughout the Mojave Desert, with notable differences in prevalence of M. agassizii among sampling sites within tortoise genotypes and sampling years. Analyses of three genetic markers in the M. agassizii genome indicated very low nucleotide diversity and no relevant spatial structuring of Mycoplasma haplotypes. We use published lines of evidence to discuss the roles of rare transmission events and long-term mycoplasmal persistence in individual hosts on tortoise URTD dynamics.

Microbiotic crusts are important components of many aridland soils. Research on crusts typically focuses on the increase in soil fertility due to N-fixing micro-organisms, the stabilization of soils against water and wind erosion and the impact of disturbance on N-cycling. The effect of microbiotic crusts on the associated plant community has received little attention. We quantified the influence of crusts on the production, species diversity, nutrient content and water relations of winter annual plant species associated with microbiotic soil crusts in the northeast Mojave Desert. Shoot biomass of winter annuals was 37% greater and plant density was 77% greater on crusts than were biomass and density on soils lacking crust cover (=bare soils). This greater production of annuals on crusts was likely due to enhanced soil conditions including an almost two-fold increase in soil organic matter and inorganic N compared to bare soils. Crusted soils also had 53% greater volumetric water content than bare soils during November and December, the time when winter annuals become established. As plant development progressed into spring, however, soil water availability decreased: More negative plant xylem water potentials were associated with greater plant biomass on crusted soils. Plants associated with microbiotic soil crusts had lower concentrations of N in shoots (mg N g−1 dry mass). However, total shoot N (mg N m−2) was the same in plants growing on the different soil types when biomass production peaked in April. Shoots had similar patterns in their concentration and content of P. Species diversity of annuals was not statistically different between the two soil types. Yet, while native annuals comprised the greatest proportion of shoot biomass on bare soils, exotic forbs and grasses produced more biomass on crusts. Total shoot nutrient content (biomass×concentration) of the two exotic annual species examined was dramatically greater on crusts than bare soils; only one native species had greater shoot content of N and P when growing on crusts than bare soils. Microbiotic crusts appear to increase site fertility in the northeast Mojave Desert, but nutrients and water distributed within a greater biomass of annual plants growing on microbiotic crusts likely resulted in lower concentrations of nutrients in plant tissue and lower xylem pressure potentials than plants growing on bare soils. Exotic annuals growing on crusts appear to respond to the higher N availability by growing faster, potentially outcompeting native annual species.

Ecosystem management is managing areas at various scales in such a way that ecological services and biological resources are conserved while appropriate human uses are sustained. Major ecological services include allocation of productivity (energy flow), maintenance of soil fertility (nutrient cycling), and operation of the hydrologic cycle. Biological resources encompass all natural variation found in genes, species, and communities along with the processes that maintain this variation. The appropriateness and sustainability of human uses are dictated by the constraints imposed by the biological and physical environment and by legal mandates for land use. There are seven critical steps in ecosystem management. These are: (1) delineate (define) the ecosystem to be managed; (2) define strategic management goals; (3) develop a comprehensive understanding of the ecosystem; (4) obtain socioeconomic data; (5) link the socioeconomic and ecological data in an appropriate model; (6) implement experimental management actions; and (7) monitor management results to determine long-term success or failure. The significance of ecosystem management is that it focuses on ecological systems as a whole rather than on just some of their parts, includes public involvement in the goal-setting process, integrates conservation into economic activity, and represents a paradigm shift from `linear comprehensive' management to `cyclic-incremental' or `adaptive' management.

We describe a method for measuring metabolic rates (MRs) of ectotherms using successive measurements of radionuclide body burdens, which may provide an alternative means of measuring field metabolic rate (FMR). Although MRs can be measured in the laboratory, variability in food supply and quality, temperature, activity, and other factors preclude the direct application of such data to field conditions. Recently, the doubly labeled water (DLW) technique has been successfully applied to estimate FMR in a variety of animals, but this method is expensive, requires special equipment, necessitates the sampling of blood or other body fluids, and may be unsuitable for certain species. We compared the rates of elimination of seven radionuclides with estimates of MRs (CO₂ production) from DLW measurements in the desert iguana, Dipsosaurus dorsalis. We observed temperature-dependent elimination for five of the radionuclides, and found a high correlation (r² = 0.93) between the slopes of individual $^{86}Rb$ eliminat...