ebook img

MORPHOLOGICAL VARIATION IN MALACOTHAMNUS FASCICULATUS (TORREY & A. GRAY) E. GREENE (MALVACEAE) AND RELATED SPECIES PDF

11 Pages·1999·7.7 MB·English
Save to my drive
Quick download
Download
Most books are stored in the elastic cloud where traffic is expensive. For this reason, we have a limit on daily download.

Preview MORPHOLOGICAL VARIATION IN MALACOTHAMNUS FASCICULATUS (TORREY & A. GRAY) E. GREENE (MALVACEAE) AND RELATED SPECIES

Madrono, Vol. 46, No. 3, pp. 142-152, 1999 MORPHOLOGICAL VARIATION IN MALACOTHAMNUS FASCICULATUS (TORREY & A. GRAY) E. GREENE (MALVACEAE) AND RELATED SPECIES Deborah L. Benesh Oklahoma Biological Survey, University of Oklahoma, Norman, OK 73019 Wayne J. Elisens Department of Botany and Microbiology, University of Oklahoma, OK Norman, 73019 Abstract Character polymorphism is widespread and species delimitation is unresolved among 11 species of Malacothamnus currently recognized in California and Baja California. To evaluate variation among characters used in previous taxonomic treatments and to identify characters most usefulfordiscriminating among four species closely associated with M. fasciculatus, we analyzed 26 morphological characters from 46 exemplarspecimens using cluster, ordination, and statistical analyses. Although many vegetative and reproductive characters exhibited high levels ofvariation among and within OTU's, bractletandcalyx characters demonstrated maximum utility for discriminating among species in principal components and discriminant functions analyses. OTU's representing previously segregated "varieties" ofM.fasciculatus (Torrey & A. Gray) E. Greene did not group together nor did conspecific OTU's, except forthree OTU's representing the San Clemente Island endemic, M. clementinus (Munz & I. M. Johnston) Kearney. The absence ofwell-defined gaps in many characters and intergradation resulting from gene flow and/orrecent divergence from ancestral species impede delimitation at the species and infraspecific levels whether a phenetic or phylogenetic approach is employed. Malacothamnusfasciculatus and M. fremontii A. Gray are particularly variable and difficult to define unambiguously using morphological data. Introduction logically distinct within Malvaceae, species and va- rietal delimitations are problematic because ofchar- Malacothamnus Greene is a genus of woody or acter intergradation and morphological variation suffrutescent perennials with 11 species currently both within and among populations (Kearney recognized in California and Baja California (Bates 1951b; Bates 1963, 1993). The degree oftaxonom- h19a6m3a, C1o9u93n)t.ieDsisitnrinbourttehderfnroCmalMiefonrdnoicaitnooRaonsdarTieo-, siciduenrcienrgtatihnetywiadnedlyinfstlaubcitluiattyinigs envuimdbeentr wohfesnpeccoine-s Baja California Norte, species of Malacothamnus recognized in different treatments. Whereas Greene are primarily associated with chaparral and coastal sage scrub communities. The common names of (1906) recognized nine species, subsequent treat- Malacothamnus, chaparral mallow and bush mal- ments recognized from one (Bates 1963) to twenty- seven (Eastwood 1936) species and a variable num- low, reflect its habit and habitat preferences. Established by E. L. Greene (1906), Malacoth- ber of infraspecific taxa. In the most recent treat- agemdn,uscoismpclheatreacltyeridzeehdisbcyenutniocvaurlpaetles,; unaaspcpeennddian-g rmeecnotgsniozfedthe19Caslpiefcoirensiaansdpesciixesv,arKieetairenseaynd(1M95u1nbz) ovules; and a shrubby habit. Later treatments place and Keck (1968) delimited 18 species, one subspe- Malacothamnus in Tribe Malveae, Subtribe Abutil- cies, and six varieties. In the Jepson Manual (Hick- inae (Kearney 1951a, b). Bates (1968) did not rec- man 1993), Bates recognized ten species without ognize subtribes, but regrouped the Malveae into infraspecific taxa; taxa previously ranked as sub- "alliances" and suggested a Malacothamnus alli- species (Bates 1963) were elevated to species level ance consisting of Malacothamnus (n = 17), Ili- without changes in circumscriptions (Bates, person- amna Greene (n = 33), and Phymosia Desvaux (n al communication). Skinner et al. (1995) noted that = 17). Based on cytological evidence coupled with several Malacothamnus taxa are of "uncertain dis- inference of Tertiary floristic evolution, Bates tinctiveness" and calculated that 75% of the taxa (1967, 1968) suggested that the three genera are in the genus are taxonomically uncertain. derived from a Phymosia-like ancestor. Eastwood Few characters unique to any species have been (1939) proposed that the California Malvastrum identified in previous taxonomic treatments. Gen- {Malacothamnus) was an old genus of previously erally, combinations ofoverlapping characters have greater abundance, but now in decline. Kearney been used to delimit species (Kearney 1951b; Bates (1951b) noted that the lack ofpronounced morpho- 1963, 1993). These recent treatments have em- logical differences among species of Malacotham- ployed type and density of calyx pubescence, nus suggested a recent origin for the genus. length and shape of the calyx lobes, length and Although the genus Malacothamnus is morpho- shape of the bractlets, relative length of the invol- 1999] BENESH AND ELISENS: MALACOTHAMNUS 143 ucel bractlets and calyx lobes, type of inflores- and the high level of variability found within spe- cence, and shape and texture ofthe leaves (Kearney cies, there have been no explicit numerical studies 1951b; Bates 1963, 1993). For example, M. fre- ofthe amount and pattern ofvariation nor statistical montii A. Gray and M. davidsonii (Robinson) E. analyses of characters that differentiate species. Greene can be identified by thick, often densely Malacothamnus fasciculatus is morphologically pubescent leafblades, but other species are not eas- and geographically diverse, has been examined at ily distinguished based on leaf characters. Bates the molecular level (Swensen et al. 1995), and in- (1963) provided an example where polymorphism tergrades commonly with other sympatric species, in leaf shape in a single population of about 50 particularly in the southern portion ofits range. The individuals of M. fasciculatus (Torrey & A. Gray) present study focused on variation in morphological E. Greene encompassed almost all the variation characters among five intergrading species: M. cle- found throughout the genus. Differences in habit mentinus (Munz & I. M. Johnston) Kearney, M. among species sometimes may be observed, which davidsonii, M. densiflorus, M. fasciculatus, and M. may result from environmental factors such as wa- fremontii. The primary objectives ofthe study were ter stress, fire, and competition, affecting growth to assess variation among characters used in pre- form (Bates 1963). vious taxonomic treatments, to identify characters The basic floral arrangement within Malacoth- that discriminate among species, and to test hy- amnus is a cyme arranged into terminal heads, potheses of taxonomic delimitation of species and spikes, or open panicles (Bates 1963); variation can varieties. be found in the length, numberofnodes, branching, The five species examined in this study are wide- internode length, and leafiness of the inflorescence spread in southern California and Baja California (Bates 1963). Examples include M. densiflorus (S. Norte, and one species is distributed in northern as Watson) E. Greene, which is distinguished by a well as southern California. Malacothamnusfascic- densely flowered, spikeM-like inflorescence with ulatus as delimited by Kearney (1951b) ranges elongate internodes; and palmeri (S. Watson) E. from Santa Barbara County to Baja California Nor- Greene, which has a densely flowered, head-like or te. Kearney (1951b) recognized five varieties: vars. short, spike-like inflorescence subtended by con- fasciculatus Greene, laxiflorus (Gray) Kearney, and spicuous bracts (Bates 1993). Involucel bractlet and nuttallii (Abrams) Kearney are restricted to main- calyx characters also have been used to delimit spe- land California, whereas var. catalinensis (Eastw.) cies, but exhibit polymorphism within and among Kearney (found on Santa Catalina Island and coast- species (Kearney 1951b; Bates 1963, 1993). Within al Ventura to San Diego Counties) and var. nesi- Malacothamnus, bractlet length ranges from 2.5 to oticus (B. L. Rob.) Kearney (restricted to Santa mm mm 21 and calyx length varies from 5 to 19 Cruz Island) have populations on the California Is- (Bates 1993). A single species, M. densiflorus, en- lands. Also widely distributed are M. fremontii, compasses most of the range for these characters; ranging from Tehama to Riverside Counties and M. mm its bractlets vary from 5 to 15 in length and densiflorus, which is distributed from Riverside its calyces from 6 to 14 mm. Unlike leaf, inflores- County to northern Baja California Norte. The fed- cence, bractlet, and calyx characters, morphology erally and state listed endangered species M. cle- ofthe corolla, pistil, stamen, carpels, and seeds pro- mentinus (Smith & Berg 1988) is endemic to San vide few characters used to segregate species Clemente Island. Populations of M. davidsonii are (Kearney 1951b; Bates 1963). separated by the Transverse Ranges between Los Similar to problems in species delimitation and Angeles County and San Luis Obispo and Monte- identification, infraspecific taxa in M. fasciculatus rey Counties. are notoriously difficult to identify. Although ex- treme morphological forms are evident, intergra- Materials and Methods dation among habit, leaf shape and pubescence, in- florescence structure, and carpel characters is wide- We examined variation among 26 morphological spread. Five varieties of M. fasciculatus were de- characters among five species of Malacothamnus scribed previously by Kearney (1951b) and eight using clustering, ordination, and statistical analyses. subspecies by Bates (1963) in an unpublished dis- Taxonomic identity was determined using keys and sertation. Later, Bates (1993) recognized no infra- descriptions from the Jepson Manual (Hickman specific taxa in M. fasciculatus. In a study of mo- 1993) and, for "varieties" ofM.fasciculatus, Kear- lecular variation in M. fasciculatus, Swensen et al. ney's treatment (1951b) and Munz and Keck (1968) (1995) provided data that indicated var. nesioticus were used. One representative individual from each is genetically distinct from othervarieties ofM.fas- of 46 collections representing natural populations ciculatus. (Table 1, Fig. 1) was selected as an exemplar op- We conducted this study to initiate analyses of erational taxonomic unit (OTU). The OTU's were character variation within and among species of chosen from herbarium specimens or from collec- Malacothamnus. Although previous taxonomic and tions of the first author; they were selected to span floristic treatments (Kearney 1951b; Bates 1963) the geographic and morphological range of each emphasized the lack of constant, unique characters species analyzed (Fig. 1). The widespread species MADRONO 144 [Vol. 46 Table 1. Specimens representing numbered OTU's of Table 1. (Continued). five species of Malacothamnus used in investigations of morphological variation. All locations are in the "var. nuttallii (Abrams) Kearney" state ofCalifornia unless otherwise noted. 3. Santa Barbara Co., upper Cachuma Dam area, Smith M. clementinus (Munz & Johnston) Kearney 4ta9i4n0s,, SHBoBwGe.241.64L,osSADn.ge2l5e.sSCaon.t,aSaBnatrabaMroaniCco.a,MSoaunnt-a 13. San BernardinoCo.,Victorville,NorthVerdeRanch, Barbara, Benesh 63, OKL. 26. Ventura Co., Lake Cas- Raven 16625, CAS. 14. Los Angeles Co., SanClemente itas, near East Casitas Pass, Benesh 64, OKL. 43. Santa Island, Lemon Tank, Beauchamp & Douglas 3236, SD. Barbara Co., Gaviota Pass, Abrams 5030, UC. y1o5.n,LMoosrAanng,elBeesauCcoh.,amSpa,n&CleOmbeenrtbeauIesrlan2d2,69C7h,inUaC.Can- M.fremontii (Torr. ex Gray) Torr. ex Greene 1. Santa Barbara Co., Vandenburg AFB, Nichols 664, M. davidsonii (B. L. Rob.) Greene JER 2. Sutter Co., North Butte, Ewan & Ewan 9597, 11. San Luis Obispo Co., Bee Rock, Hardham s.n., JER 8. Madera Co., Oakhurst, Wolf2433, SBBG. 28. CAS. 12. Los Angeles Co., San Fernando Wash, David- Los Angeles Co., Pine Canyon, Hoffman s.n., SBBG. son s.n., CAS. 16. Los Angeles Co., Big Tujunga, Lyon 29. Ventura Co., Lockwood Valley, unknown s.n., s.n., CAS. 17. Monterey Co., Lake San Antonio,Jensen SBBG. 38. San Bernardino Co., Baldwin Lake, Tilforth 45, UC. & Wisura 2107, RSA. 42. Riverside Co., San Jacinto Mtn., Purer 6472, CAS. M. densiflorus (S. Watson) Greene 9. Mexico, Baja, Valle Redondo, Fosberg 8368, UC. 10. RiversideCo., SantaAnaMtns., aboveGlen Ivy,Howell 1056, UC. 18. San Diego Co., Barrett Lake, Benesh & M. fasciculatus and M. fremontii were dispropor- Anderson 35, OKL. 39. San Diego Co., Ramona, Bran- tionately represented in their southern range where degee s.n., UC. 46. Mexico, Baja, San Pedro Martir they and other species are sympatric. Mtn., Robertson 55, UC. Eleven quantitative and 15 qualitative characters M.fasciculatus (Nutt. ex Torr. & Gray) Greene were chosen to represent vegetative and reproduc- "var. catalinensis (Eastwood) Kearney" tive structures (Table 2). Characters were selected 5. Los Angeles Co., Santa Catalina Island, Middle based on their inclusion as diagnostic features in Ranch Dam, Fosberg 54770, UC. 6. Orange Co., La- previous taxonomic treatments (Kearney 1951b; guna, Peirson 4662, SD. 19. Los Angeles Co., Santa Munz and Keck 1968; Bates 1963, 1993). For each Catalina Island; Black Jack Mtn., Thome 36518, OTU, we obtained a minimum of 10 measurements SBBG. 21. Ventura Co., Santa Monica Mtns. beyond for each character whenever possible. Several mea- Hidden Valley on Sherwood Rd., Holbrook s.n., surements ofbractlet, calyx, and leaf length and/or SBBG. width were converted to a ratio (characters 2, 7, 17, "var.fasciculatus (Nutt. ex Torr. & Gray) Greene" 18; Table 2) to describe shape and relative dimen- 20. San Diego Co., 2 mi EofSan Ysidro on Otay Mesa, sions rather than absolute size. Lack of sufficient Gander 219.13, SD. 31. Riverside Co., El Toro Peak, suitable material on herbarium specimensprecluded San Jacinto Mtns., SantaRosaRange, Hall 765, UC. 32. the use of leaf size, carpel characters, and seed San Diego Co., Fallbrook; ca. 6 mi NE, Benesh & An- characters in our analysis. Preliminary analyses dArebroslointo3s9,,TOhKoLm.e &33.ChMaerxlitcoon,58B6aj8a5,, PRuSnAt.a3B4a.nMdeaxinceoa,r also revealed that several characters not included in Baja, Rancho Estela, Moran 24380, SD. 35. Mexico, our analysis were either variable on a single indi- Baja, El Condor, Sierra Juarez, Moran 13578, SD. 37. vidual, too subjective to be coded accurately, or San Mateo Co., Spring Valley, Cougdon s.n., JEPS. 40. difficult to detect (e.g., leaflobing, leafmargin, leaf Mexico, Baja, Upper Arroyo Copal, Sierra San Pedro apex, leaf thickness, pubescence color, inflores- Martir, Moran 15499, SD. 41. Mexico, Baja, Santa cence type, and bractlet shape). Rosa, Moran & Thome 14427, RSA. 44. San Bernar- Analyses were performed using NTSYS-pc dino Co., San Bernardino Mtns., State Hwy 18 ca 0.5 (Rohlf 1993) and SYSTAT (SPSS Inc. 1997). A mi above Waterman Canyon Road, Raven & Beeks standardized data matrix was used to compute a H1o67n5d9o,),UCT.hom45e.,MWeixsiucroa,, BPaejtae,rsoSno,cor&roAnWnaasbhle(5A8r0r1o1y,o dissimilarity matrix using the average taxonomic RSA. distance coefficient and acophenetic correlation co- efficient. A clustering phenogram was generated "var. laxiflorus (Gray) Kearney" using the UPGMA (unweighted pair-group method 22. Los Angeles Co., Altadena, Ramsey & Ramsey using arithmetic averages) method. A Principal 3084, RSA. 23. Orange Co., Crystal Cove State Park, Components Analysis (PCA) was performed by El Moro Canyon, Benesh 57, OKL. 24. San Bernardino computing a correlation matrix, calculating eigen- CRPoio.vi,netrsCiMadjueognuCo,.P,aVssGa,anrdBneeerrnweiVseahrlle&5y3,,MTuOirKlfpLoh.rethy27&.78,WVieSsnuBtruBarGa.19C1o36.0,., OveTcUt'orssofnotrotthheefcirosmtptohnreenetsa.xes, and projecting the RSA. 36. San Diego Co., Camp Pendleton, Horno Can- Using the SYSTAT software package (SPSS Inc. yon, Beauchamp & Swickard 1518, SD. 1997), discriminant functions analysis was used to determine which combination ofcharacters provid- "var. nesioticus (B. L. Rob.) Greene" ed maximum discrimination amongrecognized spe- 71.888S,antUaC.Barbara Co., Santa Cruz Island, Brandegee cies and "varieties" of M. fasciculatus. Because this method does not allow missing data, seven of 1999] 145 Fig. 1. Collection localities for46 specimens offive species ofMalacothamnus analyzed formorphological variation. Solid symbols represent species described in The Jepson Manual (Hickman 1993; Bates 1993). Shaded symbols rep- resent "varieties" ofM.fasciculatus as delimited by Kearney (1951b; Munz & Keck 1968). 1288 entries (0.54%) from the data matrix were es- Results tsiammaetedspbecyieuss.inSgtathnedaarvderaangde ojfacoktkhneirfeOdTUc'lasssoiffitchae- The UPGMA phenogram (Fig. 2) had four major tions were produced to test group relationships. In clusters and a cophenetic correlation value of othfeliskteantdaaxradwparsocceodmupruet,edth,eacnednttrhoeindeoafcheaOcThUgrwoausp f0r.e8m4o0n.tiCliuastnedraInwOasTUcormepporseesedntoifngtwMo.OfTasUc'iscuolfatMu.s "var.fasciculatus" ofunusual appearance from the esixmailmairn.edWhtoendettehremiOnTeUtowwahsichmogsrtouspimiitlwarastomotshte southern limits of its range in Baja California Nor- group representing that taxon, it was scored as a tpeh.eCnlougsrtaerm,IIawnadsctoheulmdosbtecfoumrpthleerxsgurboduipviindgedinitnhteo correct identification. When it was most similar to three groups, excluding the outlying "var.fascicu- a group representing another taxon, it was scored latus" (OTU 37) from San Mateo County. With the calsasasinfiicantcioornr,ecatncOlaTssUifiwcaatsionr.emFoovredt,hethjeacckeknntirfoeidd rtewporesaefnotrienmgenMt.ionfeadsciecxucleapttuisonsw,eraell footuhnedr OwTitUh'isn recalculated, and the OTU identified as to which cluster II along with OTU's of three other species. group it was most similar. This was repeated for Cluster Ha consisted of 10 OTU's representing M. each OTU, producing a less biased number of cor- fremontii, M. davidsonii, and three "varieties" of rect classifications. Three discriminant functions M. fasciculatus. The closest phenetic similarity analyses were performed: species level only, spe- among all OTU's was in this cluster between M. cies and all "varieties" ofM.fasciculatus, and spe- davidsonii and M. fasciculatus "var. laxiflorus" cies and "varieties" ofM.fasciculatus except "var. (OTU's 17 and 24). Cluster lib comprised OTU's nesioticus". The latter analysis was performed be- representing all five "varieties" of M. fasciculatus cause "var. nesioticus" was represented by only a as well as one OTU of M. davidsonii from Los single OTU, which confounded thejackknifed clas- Angeles County. The OTU representing the Santa sification. Cruz Island endemic M. fasciculatus "var. nesioti- MADRONO 146 [Vol. 46 Table 2. Morphological characters examined among five species of Malacothamnus and purported varieties of M. fasciculatus. Characters useful for differentiating among species in principal components analysis (PCA) are indicated by an asterisk (*). Characters useful fordifferentiating species in discriminantfunctions analysis are indicated by a plus sign (+). 1. stem pubescence type: loose (0), appressed (1) 2. leafblade length/width 3. leafbase: cordate (0), truncate (1) * + 4. bractlet length * 5. bractlets concolorous throughout: absent (0), present (1) * 6. bractlet concolorous with calyx: absent (0), present (1) * + 7. bractlet length/calyx length 8. calyx length from base to tip oflobe * 9. calyx outer pubescence type: rigid (0), soft or pliant (1) * + 10. sepal lobes in bud recurved at margins: absent (0), present (1) * 11. sepal lobes in bud: divergent (0), connivent (1) 12. sepal lobe shape: triangular (0), ovate (1) 13. sepal lobe apex: acute (0), acuminate (1) * 14. sepal lobe constricted at base: absent (0), present (1) * 15. sepal lobe length 16. sepal lobe width at base 17. sepal length/width 18. sepal lobe length/calyx tube length 19. sepal lobes obscured by pubescence: absent (0), present (1) +20. sepal pubescence: short-stalked (0), long-stalked (1) 21. sepal pubescence: number of arms * 22. sepal pubescence: length of arms 23. sepal lobe pubescence type within: glabrous (0), tomentose (1), pilose (2), hispid (3) 24. inflorescence: unbranched (0), branched (1) 25. flower clusters: dense (0), open (1) 26. length of staminal column cms" clustered most closely with "var. nuttallii" fasciculatus. As in the UPGMA phenogram, the from Los Angeles County, whereas OTU's of "var. PCA model placed M. davidsonii within theM.fas- catalinensis"\ including two from Santa Catalina ciculatus complex. Island, did not group together. Discriminant functions analysis identified four Only M. densiflorus and M. fasciculatus OTU's characters as most useful for classifying species: 4, were contained in Cluster He, which included spec- 7, 10, and 20 (Table 2). The OTU's were correctly imens from south-central Riverside County to the classified to species an average of 67% (Table 4) southern limits of the North American range in in the standard classification. Whereas M. densiflo- Baja California. Cluster III was composed of two rus was classified correctly 100% of the time, the subclusters ofOTU's representing M.fremontii and lowest value, 56%, resulted when 12 M. fascicu- M. clementinus. The M. clementinus OTU's includ- latus OTU's were misclassified as M. davidsonii ed a (cultivated?) specimen from San Bernardino (10) or M. densiflorus (2). In the jackknifed clas- County. Cluster IV comprised two M. densiflorus sification, a 52% average correct classification was OTU's that are less similar to each other than are obtained. The lowest value, 44%, resulted when 15 most of the other clusters. OTU's of M. fasciculatus were incorrectly classi- The three-dimensional PCA model (Fig. 3) re- fied. vealed groupings similar to those in the UPGMA When "varieties" of M. fasciculatus were in- phenogram. The first three components constituted cluded as taxa, characters 7 and 10 (Table 2) were 49 percent of the total variation: 28%, 11%, and the most useful for discriminating among species 10%, respectively. Characters with high loadings and "varieties" using discriminant functions anal- (Table 3) included characters 4, 7, 11, 15, and 22 ysis. The correct classification percentages were in the first component; 9, 10, and 14 in the second relatively unchanged by the exclusion of the one component; and 5 and 6 in the third component. OTU of "var. nesioticus" The standard classifica- . The PCA model also did not reveal discrete group- tion was correct 43% of the time when "var. nesi- ings corresponding to species boundaries, but in- oticus" was included (Table 4) and 47% when it stead depicted loose groups with considerable over- was removed compared to jackknifed percentages lap among taxa. OTU's representing M. clementin- of 35% when "var. nesioticus" was included and us, M. densiflorus, and M.fremontii were generally 36% when it was excluded. Malacothamnus dav- separated from M. fasciculatus and M. davidsonii idsonii and M. fasciculatus "var. laxiflorus^ were along the first axis. There were no discrete group- consistently classified incorrectly in analyses in- ings among OTU's corresponding to varieties ofM. cluding varieties. For example, OTU's of M. dav- . BENESH AND ELISENS: MALACOTHAMNUS 147 1999] 1 frem 2 frem 41 fasc fasc _~ 3 fasc nutt 25 fasc nutt 44 fasc fasc 26 fasc nutt 11 dav 17 dav ila 24 fasc lax 30 fasc lax 42 frem 12 dav _~ 4 fasc nutt 7 fasc nes 5 fasc cat 36 fasc lax 6 fasc cat 22 fasc lax 21 fasc cat 20 fasc fasc lib 23 fasc lax 27 fasc lax 45 fasc fasc 34 fasc fasc 16 dav 32 fasc fasc 19 fasc cat 43 fasc nutt _ 9 dens 40 fasc fasc 31 fasc fasc 35 fasc fasc lie 39 dens 46 dens 33 fasc fasc _ 37 fasc fasc 8 frem -d 29 frem 38 frem 13 clem 14 clem 15 clem 28 frem 10 dens IV 18 dens 2.0 1.5 1.0 0.5 0.0 AverageTaxonomic (Morphological) Distance Fig. 2. UPGMA phenogram derived from average taxonomic distance coefficients using 26 morphological characters from 46 OTU's of five species ofMalacothamnus. OTU numbers and locations are listed in Table 1. The cophenetic correlation is 0.840. idsonii were classified as "var. nesioticus", "var. levels of variability within species, populations, nuttalliV or "var. laxiflorus" and, even, single individuals. This point often was commented upon to varying degrees by previous Discussion workers (Kearney 1951b; Bates 1963, 1993), but Character variation and life history traits. The there has been no quantification or documentatiWoen diverse taxonomic interpretations within Malacoth- of character variation until the present study. amnus reflect complex patterns of morphological found that most vegetative characters used previ- variation. Our observations and analyses confirm ously to delimit and characterize species, particu- that many characters used previously exhibitedhigh larly those describing the vestiture, lobing, apex, 3 MADRONO 148 [Vol. 46 O M. clementinus A M. densiflorus V M. fremontii M. davidsonii q M. fasciculatus Fig. 3. Three-dimensional model produced in principal components analysis using 26 morphological characters in five species ofMalacothamnus. OTU numbers and locations are listed in Table 1. and margins of leaves, were too variable on spec- whose "coarse" habit, "stout" branches, and imens to code or to describe accurately the phe- "densely" pubescent leaves are readily observable notype ofa collection orOTU. Our study is at least in field populations, but difficult to observe and partially supportive of Bates' (1963) comment that quantify on herbarium specimens. Consequently, some characters are vague or difficult to quantify, only one stem and two leafcharacters were includ- but are apparent to those familiar with the genus. ed in the analyses out of 26 total characters. Ofthe This was particularly noteworthy forM. davidsonii, three vegetative characters identified, none were in- dicated as "useful" for discriminating among spe- cies in our analyses. Table 3. Eigenvalues produced in PCA for 26 mor- Reproductive characters, especially those de- phological CHARACTERS AMONG FIVE SPECIES OF MALA- COTHAMNUS. Character numbers refer to Table 2. Character Component 1 Component 2 Component 3 Table 4. Percentage of taxa correctly classified in discriminant functions analysis of 26 morphological 1 -0.185 -0.233 0.361 characters among five species of malacothamnus. re- 2 -0.070 0.235 0.059 sults are presented for comparisons among species only 3 0.019 0.248 -0.458 and among species and all "varieties" ofM.fasciculatus. 4 0.899 0.168 0.117 See text for discussion of results when "var. nesioticus" 5 0.490 -0.068 -0.632 was removed from the analysis. 6 0.256 0.129 -0.750 7 0.802 0.343 0.244 Percent correctly classified 8 0.678 -0.320 -0.223 9 0.426 -0.496 -0.020 Species only Including 10 -0.630 0.483 -0.422 "varieties" -0.780 0.231 -0.370 ofM. 1121 -0.040 0.303 0.177 fasciculatus 13 0.012 0.416 0.088 Stand- Jack- Stand- Jack- 14 0.433 0.563 -0.239 Taxa ard knifed ard knifed 15 0.788 -0.308 -0.327 16 0.152 -0.215 -0.210 M. clementinus 67 67 100 67 1187 00..76811 --00..228278 --00..333224 MM.. ddeanvsiidfsloonriuis 17050 5600 800 800 19 -0.563 -0.395 -0.146 M.fremontii 86 71 29 29 20 0.480 -0.418 0.388 M.fasciculatus 56 44 21 -0.524 -0.365 -0.365 "var. catalinensis" 75 75 22 0.760 0.308 0.217 "var.fasciculatus" 45 36 23 0.092 0.305 -0.273 "var. laxiflorus" 0 0 24 -0.489 -0.436 -0.191 "var. nesioticus"'' 100 0 25 -0.500 -0.385 -0.060 "var. nuttallii" 40 20 26 0.125 -0.211 0.086 Total 67 52 43 35 1999] BENESH AND ELISENS: MALACOTHAMNUS 149 scribing the bractlets and calyx, were more consis- intergradation in Malacothamnus (Loveless and tent within OTU's, were easier to code, made up Hamrick 1984; Briggs and Walters 1985). Addi- the majority of characters subjected to numerical tionally, replenishment of alleles from the soil seed analyses, and comprised all 11 characters that dis- bank may contribute to heterogeneity within and criminated most effectively among species in the among populations (Huenneke 1991). Germination PCA and/or discriminant functions analyses (Table experiments indicate that Malacothamnus seeds re- 2). Other reproductive characters describing the in- main viable for more than 50 years (Bates 1963; florescence and staminal column exhibited little Benesh unpublished data) and germinate rapidly utility for discriminating among species. Three following a fire (Bates 1963). characters exhibited high levels of discrimination among species in both PCA and discriminant func- Taxonomic implicationsandspeciesdelimitation. tions analyses, and represent characters of maxi- Among 46 OTU's included in clustering and ordi- mum taxonomic utility: bractlet length, bractlet nation analyses, only those representing M. clemen- length/calyx length, and the presence or absence of tinus formed a distinct cluster and grouped with rqueacluirtvaitnigveseapnadl tlhorbeeemqauragnitnitsatiinvebucdh.arAancottehrserwfeirvee OspTeUc'iessowfeMr.efirnetmeornmtiiix.edSianmtphleeUdPspGeMciAmepnhseonfoogtrhaemr significant in either PCA or discriminant functions and PCA model. Malacothamnusfasciculatus was analyses: bractlets concolorous with calyx, bractlets the most widely sampled species and encompassed concolorous throughout, outer calyx pubescence the most morphological variation. Similar to the in- texture, divergence ofsepal lobes in bud, sepal lobe terspecific pattern, OTU's representing segregated constriction at base, sepal lobe length, and length "varieties" of M. fasciculatus were completely in- of the arms and stalks of the sepal pubescence. termixed and clustered with those of three other Variation patterns observed among species re- species: M. fremontii, M. davidsonii, and M. den- flect historical factors such as biogeography and sifiorus. The 16 specimens in cluster lib of the phylogeny, and genetic factors such as population phenogram (Fig. 2) formed the most internally con- structure, mating system, reproductive isolation, sistent taxonomic grouping, with one M. davidsonii and seed dispersal (Avise 1994). Populations ofM. in a group of M. fasciculatus OTU's. fasciculatus and related species vary in size from The general lack ofresolution delimiting species few to numerous individuals, consist often of of Malacothamnus using numerous characters and clones because ofreproduction via rhizomes (Bates a phenetic approach indicate polymorphism among 1963; Swensen et al. 1995), and are characterized species was extensive. In our study, multivariate by lack of fertility barriers (Bates 1963). Artificial techniques did not identify any well-defined mor- hybridization experiments revealed widespread phological and geographic clusterwithin Malacoth- cross-compatibilities and interfertilities among spe- amnus. The pattern of morphological and geo- cies (Bates 1963). Natural hybridization between graphical variation was widespread among the five species also has been postulated; Bates (1963) iden- species sampled, and character intergradation was tified four regions of sympatry with interspecific not restricted to particular species pairs or to a few hybrid swarms. Bates (1963) suggested that "ran- areas of sympatry. Conspecific OTU's were gen- dom but recurrent hybridization and isolation of erally spatially separated on the phenogram (e.g., populations has probably been a major factor in the OTU's 16+32+19 and OTU's 17+24+30), except evolution of morphological diversity in Malacoth- forclusterlie where three M. densiflorus specimens amnus.'''' grouped with four OTU's of M. fasciculatus in an Variable compatibility systems may be present area of sympatry and purported hybridization among species of Malacothamnus; M. fasciculatus (Bates 1963). Although found at elevations less and M. palmeri are self-incompatible, whereas self- than 650 meters throughout much of its range compatibility has been observed in M. fremontii (Bates 1963), inland populations ofM.fasciculatus and M. jonesii (Bates 1963). Additionally, Bates in Riverside and San Diego Counties and northern (1963) observed that although the flowers of Ma- Baja California Norte can be found at higher ele- lacothamnus are bisexual and pollen is released vations, resulting in sympatry with M. densiflorus while stigmas are receptive, insects commonly visit (Fig. 4). Bates (1963) recognized this area as a zone the flowers. He concluded that species of Mala- of introgression and suggested that delimitation of cothamnus have a mixed mating system but arepre- M. densiflorus and M. fasciculatus is arbitrary in dominantly outcrossing. However, in an examina- this region. tion of genetic variation within M. fasciculatus, Because comparatively few characters exhibited Swensen et al. (1995) reported a value of isozyme significant taxonomic utility (Table 2), it is useful differentiation among ten populations (G = 0.584) to consider whether a phylogenetic approach to st which is most concordant with that ofa selfing spe- species delimitation (e.g., Nixon and Wheeler 1990, cies (Loveless and Hamrick 1984; Hamrick and Davis and Nixon 1992), based on uniform and Godt 1990). Because of the lack of interspecific unique characters or combinations of characters, is reproductive barriers, gene flow among populations more useful than the phenetic methods used in this and species may be partly responsible for character study. Population (OTU)-based datahave been used MADRONO 150 [Vol. 46 Fig. 4. Collection locations for specimens of five species of Malacothamnus analyzed for morphological variation. Cluster designations correspond to the clusters produced in the UPGMA phenogram (Fig. 2). Only clusters II and III are shown. successfully to identify lineage-defining characters encompass the largest geographical range and mor- in several groups (e.g., Davis and Manos 1991), phological variation among the species investigated and several species of Malacothamnus can be de- and in the genus (Bates 1963). Illustrating the dis- limited using morphological data with this proce- cordant views of species boundaries and the extent dure. For example, M. densiflorus can be defined ofphenotypic variation among these species, Bates by a unique character combination of an unbran- (1993) submerged five and three specific epithets ched, elongated inflorescence, dense flower clus- to synonymy within M. fasciculatus and M. fre- ters, and large bractlet and calyx lengths. Mala- montii, respectively. Other than geographic locality cothamnus clementinus is identified by the associ- (e.g., "var. catalinensis", "var. nesioticus"), vari- ation of isodiametric leaves (similar to M. fascicu- eties of M. fasciculatus were equally difficult to latus) and recurved sepal lobes in bud (similar to characterize and were not recognized in the Jepson M. fremontii). The combination of "stout" branch- Manual (Hickman 1993). Because of complex pat- es and "dense" leaf pubescence of M. davidsonii terns of intergradation among morphological char- also are unique in the genus and are used to define acters, we were not able to identify any unique this species by several workers (Kearney 1951b; character combinations for M. fasciculatus or M. Bates 1963, 1993). However, in M. davidsonii as in fremontii. M. fasciculatus, M. fremontii, and other species in Using molecular data, Swensen et al. (1995) ex- Malacothamnus, lineage-defining characters are of- amined variation among varieties ofM.fasciculatus ten difficult to detect in herbarium specimens, vary to assess the genetic distinctness ofthe two known greatly among and within populations, and are dif- populations of the Santa Cruz Island endemic, M. ficult to divide into discrete character states. The fasciculatus "var. nesioticus". Sampling within M. absence of well-defined gaps in many characters fasciculatus was from six counties and was based and intergradation resulting from gene flow and/or on ten populations in the isozyme studies and seven recent divergence from ancestral species pose se- populations in the RAPD and rDNA analyses. rious problems to species delimitation within Ma- Swensen et al. (1995) concluded that the pattern of lacothamnus whether a phenetic or phylogenetic molecular variation supported Kearney's (1951b) approach is employed. varietal delimitations within M. fasciculatus, and Malacothamnus fasciculatus and M. fremontii that "var. nesioticus" was the most divergent ge- . 1999] BENESH AND ELISENS: MALACOTHAMNUS 151 netically among sampled populations with unique Transverse Ranges (Valentine and Lipps 1967, Sor- isozyme and RAPD alleles and rDNA restriction lien 1994). sites. Our morphological analyses indicate a con- The rare species M. davidsonii is disjunct be- clusion similar to Bates (1963, 1993) is warranted. tween the South Coast Ranges and Los Angeles There is extensive morphological intergradation County. The four OTU's representing these disjunct among "varieties" of M. fasciculatus and we are regions did not group together, but exhibited the unable to characterize any variety unambiguously, closest morphological similarity to M. fasciculatus including "var. nesioticus." and, to a lesser extent, M. fremontii. Our data sup- port Bates' (1963, 1993) observation of the inter- Biogeographic implications. Populations of two gradation between M. davidsonii with M. fascicu- species examined in this study, M.fasciculatus and latus. As in this and other examples of character M. clementinus, are considered California Island intergradation between species, this study cannot endemics or island-mainland disjuncts. Whereas M. differentiate between hypotheses of interspecific clementinus is restricted to San Clemente Island, hybridization or primary (and incomplete) diver- previously segregated "varieties" of M. fascicula- gence from ancestral species. Future studies em- tus included a Santa Cruz Island endemic ("var. ploying molecular markers may represent the best nesioticus") and a Santa Catalina Island and main- approach to investigate specific instances of gene land disjunct ("var. catalinensis""1). Our results sup- flow, species delimitations, and interspecific rela- ported the status of the endangered species M. cle- tionships. mentinus as a distinct morphotype in Malacoth- amnus that may be found occurring naturally only Acknowledgments on San Clemente Island. Malacothamnus clemen- tinus forms the most morphologically coherent We thank K. Anderson, A. Fone, andJ. Takara forfield assistance, S. Junak forpermission tocollectat SantaBar- group for any species examined, and its three bara Botanic Garden, and the California Native Plant So- OTU's are most similar morphologically to four ciety and University ofOklahoma Graduate Student Sen- OTU's ofM.fremontii collected at elevations rang- ate for monetary assistance with field work. The Okla- ing from 1160 to 1500 meters in Los Angeles, Ma- homa Biological Survey is acknowledged forgranting use dera, San Bernardino, and Ventura Counties. Our of computing facilities. Dan Hough and Ian Butler pro- analyses included an OTU (P. H. Raven #16625, vided assistance in computer use and computations. Scott annotated by Bates) from San Bernardino County, cRuosmsmeleln,tGsoorndoann eUanrol,ierandrdafJtohofntLhiasDpuapkeer.oAffesrpeedcivaalltuhaabnlke but it was unclear if it was a human-facilitated in- you to David Bates for his clarifications, comments, and troduction. Bates (1963, 1993) previously noted the support. similarities between M. clementinus and M. fre- montii in calyx characters, and suggested that M. clementinus represented a "generalized" form of Literature Cited Malacothamnus that persisted in refugial habitats in Avise, J. C. 1994. Molecular markers, natural history and San Clemente Island (Raven and Axelrod 1978). evolutioMn. Chapman and Hall, New York. Mainland and island OTU's representing M.fas- Bates, D. 1963. The Genus Malacothamnus. Ph.D. ciculatus "var. catalinensis""1 did not group together dissertation. University ofCalifornia, Los Angeles. in our morphological analyses, indicating polymor- . 1967. Chromosome numbers in the Malvales. phism among Santa Catalina Island and mainland Gentes Herbarium 10:39-46. populations formerly placed in "var. catalinensis" . 1968. Generic relationships in the Malvaceae, We present no morphological evidence to charac- trib.e1M9a9l3v.eaPpe.. 7G5en1t-e7s54HeirnbJa.riCu.mHi10c(k2)m:a1n17(-ed1.)3,5.The terize "var. catalinensis" or to support its status as Jepson manual: higher plants of California. Univer- a California Island endemic or island-mainland dis- sity ofCalifornia Press, Berkeley, CA. junct. For M.fasciculatus "var. nesioticus", its co- Briggs, D. and S. M. Walters. 1985. Plant variation and herence as a distinctive morphotype within M.fas- evolution, 2nd ed. Cambridge University Press,Cam- ciculatus and as a Santa Cruz Island endemic could bridge. not be tested because only one OTU was examined. Davis, J. I. and P. S. Manos. 1991. Isozyme variation and Swensen et al. (1993) found that the two known cspoemcpileesxde(lPiomaicteaatei)o:n ainn atphpelicPautcicoinnelolfiathenutpthayllloigaen-a populations of "var. nesioticus" were more dissim- netic species concept. Systematic Botany 16(3):431- ilar genetically to each other than either population 445. was to other "varieties". Our PCA indicated that and K. C. Nixon. 1992. Populations, genetic vari- the Santa Cruz Island OTU was most similar to a ation, and the delimitation of phylogenetic species. collection of M. fasciculatus "var. nuttallii" from Systematic Biology 41(4):421-435. the Santa Monica Mountains in Los Angeles coun- Eastwood, A. 1936. The shrubby Malvastrums of Cali- fornia with descriptions of new species and a key to ty. This morphological grouping is geographically the known species. Leaflets ofWestern Botany 1(18): proximate and also is consistent with the hypothe- 213-220. sized physiographic and geological correspondence . 1939. New California plants. Leaflets ofWestern of the northern California Islands with the western Botany II(10):186-188.

See more

The list of books you might like

Most books are stored in the elastic cloud where traffic is expensive. For this reason, we have a limit on daily download.