Porophyllum Pygmaeum (Asteraceae), a Distinctive New Species from Southern Nevada

DAVID J. KEIL Biological Sciences Department, California Polytechnic State University, San Luis Obispo, California 93407

JAMES D. MOREFIELD Rancho Santa Ana Botanic Garden, 1500 N. College Avenue, Claremont, California 91711-3101

ABSTRACT. Porophyllum pygmaeum is a new species from coarse calcareous soils of the Desert National Wildlife Range in Clark Co., Nevada. It has subterete leaves that contain a continuous double layer of palisade mesophyll surrounding a central area of larger, achlorophyllous, polyhedral parenchyma cells and veins. The hollow foliar oil glands lie just below the abaxial epidermis and are deeply invaginated within the parenchyma layers. Porophyllum pygmaeum is a tetraploid (n = 24) perennial herb that apparently is most closely related to P. greggii, a hexaploid herbaceous species of western Texas with much longer and narrower leaves. In its fleshy subterete leaves P. pygmaeum resembles the subshrubby P. tridentatum of Baja California from which it differs by its chromosome number (n = 15 in P. tridentatum), by its dwarf herbaceous habit, by leaves that are always entire and that bear several pairs of submarginal glands, and by much longer achenes. The new species apparently is not closely related to P. gracile, the only other species of Porophyllum that occurs in southern Nevada and adjacent regions of Arizona and California.

Discovery of a single specimen of an un un- mark, Desert Range, 4600 ft [1402 m], 16 known Porophyllum in the RSA herbarium May 1979, T. L. Ackerman 30906 (RSA, UC); prompted the second author to search for living third ridge S of Deadman Canyon, Sheep plants in the field in May and June of i987. On Range, 6800 ft [2073 m], 5 Jul 1979, T. L. his second attempt, a day-long search paid off, Ackerman 30904 (UC); type locality, 22 Apr and a single population was discovered in a 1988 (in bud only; 2n = 2424,,),11 ), D. Keil 20459 remote unnamed valley in Clark Co., Nevada. (OBI, RSA); just W of Alamo Rd. between Our study of specimens collected there concon- road and main drainage of the unnamed firms that these plants represent an undescribed valley between S end of the Desert Range species. and the Sheep Range, 2.5 road mi [4.0 km] N of Hidden Forest Rd. turnoff, 22 Apr 1988

Porophyllum pygmaeum Keil & Morefield, sp. (in bud only; 2n = 2424,,),11 ), D. Keil 20469 (OBI, nov. (fig. l).-TYPE:1).-TYPE: U.S.A., Nevada, Clark RSA). Co., Desert National Wildlife Range, just W of Alamo Rd. between road and main Porophyllum pygmaeum habitu herbaceo, for for- drainage of the unnamed valley between mis magnitudibusque flosculorum, fructium et S end of the Desert Range and the Sheep bractiorum involucri, et numero basico chro chro- Range, 1.4 road mi [2.3 km] N of Hidden mosomatum (x = 12) P. greggii A. Gray simulat, Forest Rd. turnoff, 12.2 air km N, 46°W 46?W of autem foliis crassioribus et multo brevioribus Sheep Peak summit, ca. 56 air km NNW of (10-15 mm adversus 20-80 mm) cum 3-5 pari-pari Las Vegas, T15S R59E, NW %1/4 of SW %1/4 of bus glandium submarginalium contra glandiis Sect. 9 (projected), 1355 m, 4 Jun 1987, J. D. numerosis differt. Foliis crassis subteretibus P. Morefield 4511 & F. Ehrendorfer(holotype: tridentatum Benth. var. tridentatum et var. cras cras- RSA; isotypes: ARIZ, ASC, ASU, BRY, F, sifolium (S. Watson) I. M. Johnston simulat, au au- GH, K, MEXU, MO, NSMC, NY, OBI, POM, terntem habitu herbaceo nano, foliis cum 3-5 par-par TEX, UC, UNLV, US, WU).-PARATYPES: ibus glandium submarginalium et acheniis U.S.A., Nevada, Clark Co., Desert National multo longioribus (7-8 mm longis contra 2.52.5- Wildlife Range, E bajada E of Target bench 3.5 mm), chromosomatum numero (n = 24 ad-

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E D ~~~~BB cC FIG. 1. Porophyllum pygmaeum. Drawn from Morefield 4511. A. Habit. B. Leaf (abaxial surface). C. Leaf (adaxial(adaxial surface).surface). D. Achene with pappus. E. Phyllary. F. Anthers. G. Corolla. H. Style. B-H drawn toto samesame scale.scale. versus n = 15), 15), etet a var. tridentatatridentatafoliis foliis sempersemper diam., thethe glands becoming rusty brown upon integrisintegris differt. drying. HeadsHeads solitary,solitary, terminal;terminal; peduncle stout,stout, Perennial herb fromfrom aa slender slender woody rootroot- fistulose,fistulose, 5-155-15 mm long.long. InvolucreInvolucre cylindricalcylindrical stockstock toto more thanthan 1515 cmcm longlong andand 6 6 mm inin atat anthesisanthesis toto campanulate campanulate inin ageage oror when diam.;diam.; herbageherbage stronglystrongly scented.scented. StemsStems I-many,1-many, pressed;pressed; phyllariesphyllaries 5-8,5-8, oblong,oblong, 8-118-11 mmmm long,long, 5-155-15 cmcm tall,tall, simplesimple oror few-branched,few-branched, veryvery lealea- 2-42-4 mmmm wide, wide, persistentpersistent andand spreadingspreading toto rere- fy,fy, purplishpurplish nearnear thethe soilsoil surface, surface, greengreen above,above, flexedflexed inin age, age, thethe apexapex obtuseobtuse toto subacute,subacute, mimi- ±? striate,striate, glabrous.glabrous. LeavesLeaves subteretesubterete withwith anan nutelynutely erose-ciliolate,erose-ciliolate, thethe marginmargin narrowlynarrowly adaxialadaxial groove,groove, 10-1510-15 mmmm long,long, ca.ca. 22 mmmm inin hyalinehyaline //scarious, scarious, thethe abaxialabaxial surfacesurface broadlybroadly diam.,diam., reducedreduced andand scalelikescalelike atat stemstem base,base, notnot rounded,rounded, dotteddotted withwith severalseveral toto manymany oblongoblong much-reducedmuch-reduced belowbelow heads, heads, entire,entire, 3-nerved3-nerved butbut pellucidpellucid oiloil glandsglands 0.5-1.50.5-1.5 mmmm long.long. FloretsFlorets 2525- thethe veinsveins andand veinletsveinlets visiblevisible onlyonly inin clearedcleared 75;75; corollascorollas 7-87-8 mmmm long,long, palepale yellow, yellow, oftenoften oror sectionedsectioned leaves;leaves; apexapex mucronate;mucronate; surfacesurface greenishgreenish oror reddishreddish tinged,tinged, thethe veinsveins darker,darker, glabrous,glabrous, punctatepunctate withwith aa pairpair ofof subterminalsubterminal thethe tube tube 4-4.54-4.5 mmmm long, long, thethe throat throat 2.5-52.5-5 mmmm pellucidpellucid oiloil glands glands andand 3-53-5 pairspairs ofof ellipsoidellipsoid toto long,long, thethe lobes lobes short-triangular,short-triangular, 0.50.5 mmmm long,long, sphericalspherical submarginalsubmarginal glandsglands 0.3-0.70.3-0.7 mmmm inin sometimessometimes reddish;reddish; anthersanthers ±? 33 mmmm long;long; pol-pol- 1989] KEIL & MOREFIELD: POROPHYLLUM 585 len bright yellow, 28-36 ,m~m in diam.; style in-in over an area of at least 0.2 square km. The site cluded or slightly exserted, the terminal ap-ap represented by Keil 20469 may be a continuation pendages narrowly conical, acute, coiled in age. of the same population. These populations are Achenes narrowly cylindrical, 7-8 mm long, directly downgrade from the population rep-rep black, hirtellous with ascending bicellular tri-tri resented by Ackerman 30904. The extent of the chomes 0.1-0.2 mm long; pappus bristles 50-50 latter population is unknown at present. Be-Be 60, tawny, barbellate, unequal in length and cause of insufficient label data, we have been diameter, up to 6 or 7 mm long. n = 24. unable to determine whether the type locality and the collection site for Ackerman 30906 are Distribution, Habitat, and Phenology. the same; if they are not, we are confident that Porophyllumpygmaeum is known only from the they are close. southern portion of the broad dry valley be-be Based upon our observations of the known tween the Desert Range and the Sheep Range localities of P. pygmaeum, we suspect that ad-ad in the Desert National Wildlife Range, Clark ditional areas of suitable habitat are present County, Nevada. At the type locality and the along the west slope and bajada of the Sheep site of Keil 20459 (1.1 miles N of the type local-local Range. We plan further fieldwork to circum-circum ity) the species occurs on an open alluvium de-de scribe the range of this apparently rare species. rived from the almost exclusively carbonate rock At least until more populations are located, P. of the adjacent west-draining slope of the Sheep pygmaeum should be considered rare, with at Range. A surface layer of pebble- to cobble-cobble least the type population possibly threatened sized fragments is underlain by rocky soil with by its proximity to a road, though the threat is clay, silt, and sand particles. Rock samples colcol- probably slight at present. We recommend furfur- lected from the soil surface at the type locality ther studies to determine whether official listlist- were determined as dolomite and calcitic do do- ing may be necessary. lomite, some of which had recrystallized as mar-mar Associated Species. At the type locality Po-Po ble. Soil pH at the type locality is approximately rophyllum pygmaeum occurs with the following 8.0 [determined with a Hellige-TruogHellige-Truog soil re re- species (listed in approximate descending order action (pH) tester no. 693]. We have not yet had of abundance): Atriplex confertifolia (Torrey & the opportunity to visit the locality of Ackerman Fremont) S. Watson, Eriogonumtrichopes Torrey, 30904. Lycium shockleyi A. Gray, Ephedra nevadensis S. Porophyllumpygmaeum grows in colonies (per(per- Watson, Krameriaparvifolia Benth., Acamptopap- haps clones connected by underground rootroot- . pus shockleyi A. Gray, Artemisia spinescens D. EaEa- stocks), most of which occupy either shallow ton, Yucca brevifolia.Engelm.brevifoliaEngelm. in S. Watson, MenoMeno- «15(<15 em) cm) depressions in the alluvium, or banks dora spinescens A. Gray, Oenothera caespitosa ~u~t.,Nutt., and benches adjacent to the shallow «50(<50 em) cm) Opuntia basilaris Engelm. & J. Bigelow, ArzstldaAristida drainages. They occur in open areas rather than purpureaNNutt., utt., Astragalus mohavensis S. Watson, in places shaded by larger plants. Amsonia tomentosa Torrey & Fremont, Brickellia Plants of P. pygmaeumare inconspicuous and oblongifolia Nutt., Lepidium montanum Nutt., SalSal- easily overlooked, even at close range, except azaria mexicana Torrey, Oryzopsis hymenoides when they are in flower. On casual inspection (Roemer & Schultes) Ricker, Eriogonum inflatum their vegetative features resemble those of othoth- Torrey & Fremont, Thamnosma montana Torrey er local herbaceous perennials. The stems die & Fremont, Langloisia setosissima (Torrey & A. back well below the soil surface during dordor- Gray) E. Greene, and Blepharidachne kingii (S. mancy. Though local rainfall amounts for 1987 Watson) Hackel. The label for Ackerman 30904 are not known, the area appeared to have rere- lists Coleogyne, Ceanothus, pinyon pine, and juju- ceived spring rainfall far in excess of average. niper as associated taxa. Annuals of large stature were still in profuse bloom at the beginning of June, and the soil LEAF ANATOMY was palpably moist to at least 40 emcm depth. We consider it likelylikely that in in normal or dry years, Methods. Field-collected leaves of P. pygpyg- fewerfewer or smaller individuals of P. pygmaeum maeum were preserved inin Farmer's fixativefixative (3(3 would be in evidence at the type locality locality than ethanol: 1 acetic acid; v:v), embedded, stained, were foundfound inin 1987. and sectioned using standard techniques. Dry At the type locality locality P. pygmaeum isis frequentfrequent leavesleaves of P. pygmaeum, P. greggii, and P. triden- 586586 SYSTEMATICSYSTEMATICBOTANYBOTANY [Volume[Volume14 14

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FIG.FIG.2. 2.Cross Crosssection sectionof leaf of leafof Porophyllum of Porophyllumpygmaeum.pygmaeum. This Thissection sectiondoes doesnot notinclude includeany anyfoliar foliarglands. glands. tatumtatumvar.var. erassifolium crassifoliumwerewere rehydrated rehydratedin a indi a di-Two Twoof theof thesmaller smallerveins veinsare areunbranched unbranchedand and luteluteaqueous aqueousdetergent detergentsolution solutionfrom fromherbar herbar-parallel parallelto the to themidvein. midvein.Occasional Occasionallaterallateral veinsveins iumiumspecimens specimensand andhand-sectioned, hand-sectioned,and anddiverge divergefrom fromthe themidvein midveinat approximatelyat approximatelya a temporarytemporarymounts mountswere werestained stainedwith withphloro phloro-20° 200angle.angle. At theAt theleaf leafapex apexthe themidvein midveinand andmain main glucinol.glucinol. secondarysecondaryveins veinsconverge convergeinto intoa vascularized a vascularized Results.Results.Except Exceptforfor distribution distributionof foliar of foliaroil oil massmasswith withsclereids. sclereids. glandsglandsand andthe thepresence presenceof anof anadaxial adaxialgroove, groove, TheThefoliar foliaroil oilglands glandsdevelop developas nearlyas nearlyspher spher- thetheabaxial abaxialandand adaxial adaxialportionsportions of the of thesubterete subtereteicallysigenous ical lysigenoussecretory secretorycavitiescavities and andare aredeeply deeply leavesleavesof P.of pygmaeumP. pygmaeumappearappear similar. similar.The Theepi epi-invaginated invaginatedinto intothe thepalisade palisademesophyll mesophylland and dermisdermisbears bearsanomocytic anomocyticstomata stomataboth bothab- ab-and andcentral centralparenchyma parenchymalayers.layers. Only Onlythe theepidermis epidermis adaxially.adaxially.The Thecuticle cuticlevaries variesfrom from19 19to 30to 30~m ,umseparates separatesthe theglands glandsfrom fromthe theabaxial abaxialleaf leafsur sur- thick.thick.A continuous A continuousdouble doublecylinder cylinderof palisade of palisadeface. face.The Theglands glandsare arehollow hollowand andare arelined linedby by mesophyllmesophyllsurrounds surroundsa central a centralzone zoneof oflarger largerseveral severallayers layersof offlattened, flattened,presumably presumablysecre secre- polyhedralpolyhedralparenchyma parenchymacellscells (fig. (fig.2). 2).Near Nearthe thetory torycells. cells.The Theglands glandsdo donot notbulge bulgebeyond beyondthe the leafleafbase basethe theabaxial abaxiallayers layersof ofpalisade palisademeso meso-glandless glandlessportions portionsof ofthe theleaf leafsurface. surface.A netA net- phyllphyllare areabsent. absent.The Theouter outercells cellsof theof thecentral centralwork workof smallof smallvein veinletslets surrounds surroundseach eachgland. gland. zonezoneare aretypical typicalisodiametric, isodiametric,chlorenchyma chlorenchyma- LeavesLeavesof P.of greggii P. greggiiandand P. tridentatum P. tridentatumvar.var.eras cras- toustousspongy spongymesophyll mesophyllwith withsmall smallair airspaces spacesat atsifolium sifoliumappearappear internally internallysimilar similarto thoseto thoseof P.of P. thethecell cell"corners." "corners."TheThe innermost innermostcells cellsof ofthe the pygmaeum,pygmaeum,althoughalthough smaller smallerin diam.in diam.Both Bothare are centralcentralparenchymaparenchyma zonezone lack lackboth bothchloroplasts chloroplastssubterete subteretewith withan anadaxial adaxialgroove grooveand andhave havea a andandair airspaces, spaces,and andare aremoderately moderatelyelongated elongateddouble doublecylinder cylinderof palisadeof palisademesophyll, mesophyll,a zone a zone parallelparallelto theto theveins. veins.The Themidvein midveinis centrallyis centrallyof spongyof spongymesophyll, mesophyll,and andan anachlorophyllous achlorophyllous locatedlocatedwithin withinand andsmaller smallervascular vascularbundlesbundles are arecentral centralparenchyma parenchymaregion regionwith withembedded embedded scatteredscatteredthroughthrough the thecentral centralparenchymaparenchyma zone.zone. veinsveinsand andveinlets. veinlets.The Thecentral centralparenchymaparenchyma zonezone 1989] KEIL & MOREFIELD: POROPHYLLUM 587 is smaller in P. greggii and P. tridentatum var. TABLE 1. Comparison of dimensions and numbers crassifolium than it is in P. pygmaeumand appears of reproductive structures of Porophyllum pygmaeum, to contain fewer veinlets. Foliar glands appear P. greggii, and P. tridentatum vars. tridentatum and crascras- to be of similar structure and origin in all three sifolium.Measurements are in mm. a Heads were obob- species. Glands of P. tridentatum var. crassifolium served that probablycontain more than 50 florets but these were not dissected. differ somewhat from those of P. greggii and P. were dissected. pygmaeum in that they often bulge beyond the P. tridentatum leaf surface. P. P. var. var. Character pgyniaeumpgymaeum greggizgreggil tridentatum crasslfoliumcrasszfolium Phyllary length 8-11 8-14 7-10 6-8 RELATIONSHIPS Phyllary width 2-4 2.5-4.5 1.5-4 2.5-4 Porophyllum pygmaeum is a member of sect. Number of florets 25-75 25-5025-50aa 25-40 25-40 Hunteria as circumscribed by Johnson (1969). In Corolla length 7-8 8-9 5-6 6-7 Johnson's key it most closely approaches P. Pappus length 6-7 9-10 5-6.5 5-6 greggii and P. tridentatum. The former is an unun- Achene length 7-8 5.5-8.5 3-3.5 2.5-3 common species of Trans-Pecos Texas. Poro-Poro phyllum greggii, like P. pygmaeum, is a perennial herb. Both species have a chromosome base number of x = 12; P. greggii is a hexaploid (n = Porophyllum pygmaeum resembles P. tridenta tridenta- 36; Powell and Sikes 1970), and P. pygmaeum is tum of Baja California in having short, thick, a tetraploid (n = 24). Porophyllumgreggii is often subterete leaves that are crowded on the stem. taller than P. pygmaeum (10-30 emcm vs. 5-15 em)cm) Porophyllumtridentatum was treated by Johnson and has a more sparsely leafy stem (internodes as comprising var. tridentatum, with tridentate mostly 8 mm or more vs. mostly 3-7 mm). The leaves and var. crassifolium with entire leaves. leaves of P. greggii are subterete, but are much These taxa were maintained as separate species longer (3-8 em cm long) and somewhat more slenslen- by Wiggins (1964, 1980). Both have a chromochromo- der (ca. 1 mm in diam. when dry) than those of some number of n = 15 (Johnson 1969; Reveal P. pygmaeum (1-1.5 emcm long, 1.5-2 mm or more and Moran 1977) in contrast to the n = 24 of P. in diam.) and have 5-10 pairs of submarginal pygmaeum. Porophyllum pygmaeum differs from glands (3-5 pairs in P. pygmaeum). Internally varieties of P. tridentatum by its herbaceous rathrath- the leaves of the two species are similar. Pe Pe- er than suffruticose habit and by details of leaves duncles of P. greggiigreggiivary vary from 1 to 5 em,cm, whereas and reproductive parts. Leaves of P. pygmaeum those of P. pygmaeum range from 0.5 to 1.5 em.cm. are subterete with an adaxial groove (figs. IB,lB, In size and form the heads and florets of the C, 2) and bear a pair of subterminal oil glands two species are similar (table 1). and 3-5 pairs of submarginal glands 0.3-0.7 mm Although the ranges of P. pygmaeum and P. in diam. or length. Leaves of P. tridentatum are greggii are separated geographically by about internally similar to those of P. pygmaeum but 1300 km, their habitats are probably somewhat have a smaller central parenchyma zone. Those similar. Both occur in arid regions (P. pygmaeum of var. tridentatum are cuneate with three (or in the Mojave Desert; P. greggii in the Chihua Chihua- occasionally more) apiculate-tipped teeth or huan Desert) with calcareous soils (P. greggii also lobes, each bearing a swollen oil gland; leaves occurs on soils derived from igneous parent mama- of var. crassifolium are entire with a single subsub- terial) at similar elevations (1067-1981 m for P. terminal gland. The diameter of the subterminsubtermin- greggii; 1355-2073 m for P. pygmaeum). Both al gland(s) of P. tridentatum leaves is propor-propor species are exposed to freezing weather in winwin- tionally greater than that of the corresponding ter. Associated species are not listed on the herher- glands of P. pygmaeum and sometimes exceeds barium labels of any of the specimens of P. greggii the diam. of the green portion of the leaf. In P. that we have examined, but several species that tridentatum var. crassifolium the number of sub sub- occur at the type locality of P. pygmaeumare also marginal glands seldom exceeds one or two present in deserts of Trans-Pecos Texas (e.g., pairs. The various reproductive parts of P. pyg-pyg Atriplex confertifolia, Aristida purpurea, Salazaria maeum tend to be larger than those of P. tridentriden- mexicana), and other genera are represented in tatum, although extreme measurements for some the two areas by closely related species. characters overlap (table 1). The most readily 588 SYSTEMATIC BOTANY [Volume 14 apparent difference is achene length; achenes ACKNOWLEDGMENTS. JDM expresses appreciation of P. pygmaeum average two or more times as for the excellent company and assistance of Friedrich long as those of P. tridentatum. Ehrendorfer, Aaron Liston, and Sara Meury in the Habitats of P. pygmaeum and P. tridentatum field, and DJK acknowledges the able fieldwork and appear to have less in common than those of P. companionshipcompanionship of Lawrence Kelly. Lawrence Bal-Bal thaserthaser determined the rock samples gathered from pygmaeumand P. greggii. Porophyllumtridentatum the type locality. Sherwin Carlquist assisted with the occurs in lowland, hot desert habitats along the anatomical studies. The line drawings were prepared eastern coast of Baja California and on adjacent by Joanna Tomassacci. We thank A. Michael Powell islands. Freezing weather seldom or never oc-oc for making specimens of P. greggii available on loan curs in these habitats. from SRSC, and Rhonda Riggins, John Strother, and Porophyllum gracile Benth. is the only other Arnold Tiehm for reviewing our manuscriptmanuscript and for member of the genus known to occur in Ne-Ne their helpful comments. vada, California, and northern Arizona. It reaches its northern limits in Clark and Esme-Esme LITERATURECITED ralda cos., Nevada. It is a slender broom-like JOHNSON,R. R. 1969. Monograph of the plant genus subshrub 20-60 cm tall with thin, linear, bifacial subshrub Porophyllum(Compositae: Helenieae). Univ. Kan-Kan leaves to 5 cm or more in length, narrowly cy-cy sas Sci. Bull. 48:225-267. lindrical heads with 5-30 florets, and white to POWELL, A. M. and S. SIKES. 1970. Chromosome num-num greenish or pale purple corollas. Both species bers of some Chihuahuan Desert Compositae. have strongly scented herbage, but the odor of Southw. Naturalist 15:175-186. P. gracile is strikingly different from that of P. REVEAL, J. L. and R. MORAN. 1977. Miscellaneous pygmaeum.Although P. gracile is also a member chromosome counts of western American plants-plants of sect. Hunteria, it is probably only distantly IV. MadrofioMadroiio 24:227-235. related to P. pygmaeum. No plants of P. gracile WIGGINS,I. L. 1964. Part II. Flora of the Sonoran Desert. Pp. 189-1740 in Vegetation and flora of the were observed at or near the type locality of P. Sonoran Desert, eds. F. Shreve and I. L. Wiggins. pygmaeum.Johnson (1969) indicated that P. gra-gra Stanford, California: Stanford Univ. Press. cile occurs in the coldest areas occupied by any ---. 1980. Flora of Baja California. Stanford: StanStan- species of Porophyllum. It now shares that dis dis- ford Univ. Press. tinction with P. pygmaeum.