Volume 16 Number 1 T997 a Journal of Taxonomic and Evolutionary Botany
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Volume 16 Number 1 t997 ALISO A journal of taxonomic and evolutionary botany Rancho Santa Ana Botanic Garden, Claremont, California ISSN: oo65'6275 Aliso. 16(l), pp. 1-71 O 1997. by The Rancho SantaAna Botanic Garden, Claremonr,CA 917ll-3 157 THE EUPHORBIACEAE OF SONORA. MEXICO VrcroR W. Srr,rNnrRNN Rancho Santa Ana Botanic Garden I500 North College Avenue Claremont, Calfornia 9 I 7I 1 and Universitl, of Ariz.ona Herbarium l l3 Shantz Building Tucson, Ariutna 8572 1 AND RrcsRRnS. Felcrn Dryland.s In.stitute 2509 North Camnbell Avenue #405 Tucson,Arizonct 857I9 AtsSTRAC'I This publication is iln accountofthe Euphorbiaccacin the stateo1'Sonora. M6xico. Ninctccn gcncrt. 143 species,and three additional varictics arc recorclccllirr the state;three spccieserpcctctl within tlrc state are irlstt trcatcd. ()ne specics of Acultltho antl three species and one subsl.rccics<tf I:ultltrtrbiu nre describcd.Dichotomous kcys tirr thc identilication of'genera and spccicsarc providcd. tsibliographic citations, type inlirrnratit)n.syr)onyrns, bricf habit descriptions,tinrcs of rcproduction. habitat prcler enccs as well as clcvationll range within Sonora,gcographical distribution, antl rcpresentativcspggi Irtotlsitre given lbr cach species.When appropriatc,notcs ()lr uscs.tax()nonllc or nornenclaturalprob lcrns. antl othcr points of interestarc cliscusscd. Key words: L,upliorhiaccac.Mi'xico. Sonora. RBSL MF.N Esta publicaci(rncs un estudio dc h tnnrilia liuphorbiaccac cn cl cstado clc Sonora, M6xico. Sc rcportan l9 gdneros,l,{3 cspcciesv -l varicdades;se incluycn aderrristres cspcciesque probablemente estdn prescntcscn Sonora. Se dcscribc una cspccic tlc Atulvplru y trcs especiesy una subespccicdc I')upfutrbiu. Se proporcionan claves para la identihcaci6n de 96neros y espccics. Para cada L-\pceir- \L' proporcionan rel'erencias bibliogrirficas. inlbrnraci6n sobre t:l tipo, sincininros, i'poca dc floracirin y lipo dc vegctaci6n.Se proscnta la distribucitin illtitudinal para Sonorl, la distribuci6n gcogrifica. y Ios cspccitnenesreprcscntados para cadl especie.Para algunasespecies se ap()nan notas s()brcusos, problcmas taxon6micos y nomcnclaturales.y se discutenotros puntos de inter6s. Pallbras clave: Euohorbiaccae.M6xico- Sonora. INrRoDUCrloN Juss., and Euphorbia spp.l. This publication is an ac- count of all the Euphorbiaceae species native or nat- The Euphorbiaceae constitute a large and diverse uralized in the state of Sonora, M6xico (Fig. l). assemblageof 311 genera and about 7,500 species Although a political border is not necessarily an (Webster 1994). The family has a nearly cosmopolitan ecological boundary, it serves the purpose of con- distribution, but the greatest diversity is by far in trop- taining a study. However, the borders of Sonora are, ical and subtropical regions. In addition to its great to varying degrees, biologically significant. Most of floristic importance, there are a number of economi- the western boundary is the sea. The east boundary cally important members. Among these are the Rubber is close to the continental divide. The north boundary Tree LHevea brasiliensis (Willd. ex A. Juss.) Miill. marks a division between the better-known continen- Arg.l, Cassava fManihot esculenta Cranrzf, Castor tal flora of Arizona and the relatively poorly known Bean LRicinus communis L.], and numerous ornamen- flora of northern Sonora. The Sonora-Sinaloa border tals lAcalypha spp., Codiaeum variegatum (L.) A. separates a continuous flora but is far enough south Steinmannand Felger ALISO Sanluls BfoGolorar CabezaPrieta WildlifeRefuge ---*./////.////w7rt7 0 100 Km 200 ElPinacate and-<4i1i111 0rgan-PipeCactus # GranDesierto deAltar.,r""f NationalMonument - AltoGolto de (kao Californiay Delta delRio Colorado Puarto-4\ Rrhia r / SienaSan Luis Pefiasco i^--,- '.- f banJorge \ Jan0s i,''.J,J't -."..,; &visOe ,,i Fl \/,oin j Siena Ana i Jlellas't f'(- 1i buenos 'r.. ii. Laeur$i :i ec SierradeI i Aconchiifrcterrt{i ,"'i:ig i '6 ,..'...j \- "'-.iE PuntaCirio\i.r (SierraBacha)\." /t '!.2 ig ;S / i: i(' l= Ures ii .;6.J{ ii i=\ Sierla.lvlazaldnil i=i sS ;.,. ti iE\ i lslaTibu16n i"'j "i" i! i';\EiE\F lslaSan o --- -----r I r'1 i' i i Esteban ," ji"'^..", '^.^ ^ F:\- i Y6cora"'l 'i"!i SierraLibre Sierra" San"" :';'r Javier/ElAliso SienaEl Aguaje iiSierra i. ElBacatete lslaSan\ t\.j PedroNolasco Guaymas Cd.0brag6n Bahiade Lobos LasBocas Fig. l. Sonora, Mdxico to include the northern limits of the tropical Mexican river systems originate in the state, e.9., the Rio So- flora. noyta and Rio Sonora. The eastern miugin of the state Sonora encompasses 185,43I km2 and is the second is comprised of numerous north-south trending moun- largest state in M6xico after Chihuahua. It is topo- tain ranges forming the western cordillera of the Sierra graphically and biologically diverse. Three major river Madre Occidental. The highest elevation is 2,625 m in systems, the Rfo Colorado, the Rio Yaqui, and the Rio the Sierra de los Ajos in northeastern Sonora. The Si- Mayo, course through the state and empty into the erra San Luis in the extreme northeastern corner is Gulf of California. In addition, several other minor nearly as high, and another high peak, further south VOLUME I6. NUMBER I Euphorbiaceae of Sonora 3 on the Chihuahua border, near Mesa Tres Rios may be Table l. Number of native gencra and spcciesof Euphorbiaceae equally high. Numerous other ranges, generally de- in Sonora compared with other North and Central American regions. creasing in peak elevations westward, spread across Size Corr the rest of the state, interspersed with broad valleys Nrli\e Nati\e pared uith Region Specie\ Genera Sonora and expansive plains. Sonora includes the northern limits of tropical and Sonora l;10 r8 Calitbrnia subtropical biota as well as some of the most arid des- (Webstcr 1993h) .14 efi regions of North America. The total annual precip- tsaja Califbrnirr (b()th states) '71 itation decreasesfrom south to north, and east to west, (Wiggins1980t t2 0.8 and increases with elevation. The rainfall is largely Arizclna (Kcarncv biseasonalwith summer and winter-spring rainy sea- and Pcchlcs 1960) 78 l3 1.6 Ncw Mcric<r sons, although summer rains generally decreasenorth- {Rr)irl\('n;rrrrl,\llrL.tl I()95t 67 ll l.l ward and westward across the state (Brirquez et al. Tcxas 1992; Turner et al. 199-5).Total annual precipitation (Correllantl Johnstonl97O) l)9 Iu 1.O varies fiom roughly 85 mm or less near the delta of Nucra Cialicia (McVaush.pcls. conrnr..1997) ca. l-10 o.1 the Rfo Colclrado to more than 1000 mm in portions ( iuiltcllralir of southeastern (Felger Sonora and Wilson 1995; Yet- (Stantilcy lrntl Stcvcrrrrarkl9-19) 13.1 1.1 0.6 man et al. 1995). Human p<tpulation in Sonora re- ('osfl Rictr mained low and major roads f'ew until the mid- to late {Burgcr antl Huli 1995t ca. |6o twentieth century. Much diversity and richnessof ba- sically natural habitat remains, but assaultson the en- era and species in Sonora with other areas in North vironment are esculating. and Central Arnerica. While soil moisture is the principal limiting factor in this dry region, freezing temperatures limit the Vegetutiortof' Sottrtru northern distributions of the more tropical or subtrop- ical species(Turnage and Hinckley 1938; Turner et al. The major habitatsor vcgetatit)ntypes in Sonora 1995).Freezing weather is infrequent,especially in the include ntangr()\'esand coastal vegetation.tropical de- (both southern part of the state and at lclw to m<lderateele- ciduous tirrest. thornscrub, desertscrub Sctnoran vations, and many habitats are essentially fiost-fiee. and Chihuahuan).grassland. oak woodland. pine-oak woodland. pine-oak but fieezing becomes mrlre fiequent and severenorth- tirrest, and mixed conif-erfbrest. wurd and at higher elevations. These vegetation types are briefly discussed below, with emphasis on their There is no listing of the total flclra of the state. euphrlrbiaceouscomponents. For more thorough discussiilns although at least 5000 species are probably present the reader is referred to Gentry (1912). Shrevc (195l), Felger and (Felger and Wilson 199-5).Within this rich flora. we Lowe (1916), Rzedowski(1978). Brown (l9tt2), Bfrquez estimate that the Euphorbiaceae are the fburth largest et al. (in press). family, fbllowing the Asteraceae,Fabaceae, and Po- aceae. We list 19 genera, 143 species plus three ad- Coastal 1tess7117i7177.-Mangrovesoccur sporadically ditional varieties of Euphorbiaceae for the state; three along the coastal fiinge of the southern two thirds of additional species (marked by *) are known fiom scr the state but support no members ctf the euphorbia close to the boundary that they are expected to occur tamily. Three species of Euphorbia occur along the in Sonora and are therefbreincluded in this report. We beaches. Eulthorbia ittc'erta is restricted to upper estimate that this representsnearly all the actual di- beaches and the plants are often washed with sea water versity present.Most of the taxa in Sonora are native, during high tides. Euphorbia platy*sperma may extend and we believe that only three species are definitely onto the upper beaches but well above the highest not native. These are Euphorbia hvpericifulia, E. pep- tides. A substantialnumber of speciesoccur on coastal lus, and Ricinis t'onttnttnis. A few other species, e.g., dunes. Euphorbia leucophylla ssp. comcactcorum is es- E. prostrata and .8. serpens, may not be native, but we sentially restricted to coastal dunes and sometimes oc- are uncertain. curs on upper beaches. A number of other euphorb In comparison with adjacent areas to the north and species that occur on coastal dunes are also found far- west (Arizona, Baja California, California, New Mex- ther inland, e.g., Croton califoruicus, Jatropha ciner- ico), the Euphorbiaceae are quite diverse in Sonora. ea, Euphorbia eriantha, E. petrina, E. platysperma, and polycarpa. This is due to the more tropical affinities of the flora. E. As one moves further south in M6xico and Central Tropical deciduous forest (TDF).-The northern arm America, the diversity of Euphorbiaceae continues to of TDR sweeping northward from the tropics, ends in increase.