NUMBER 5 WILLIAMS: THOREAUEA, NEW GENUS OF APOCYNACEAE 47 THOREAUEA (APOCYNACEAE: APOCYNOIDEAE), A NEW GENUS FROM OAXACA, MEXICO Justin K. Williams Department of Biological Sciences, Sam Houston State University, Huntsville, Texas 77341-2116 Abstract: Recent studies of Mexican Apocynaceae have uncovered a new species. The taxon is here viewed as generically distinct and accordingly the name Thoreauea paneroi J. K. Williams, gen. et sp. nov. is proposed. The species is from montane pine-oak cloud forests of the Santiago Juxtlahuaca area of northwestern Oaxaca, Mexico. Its relationship to Thenardia H.B.K. and other genera is discussed. Keywords: Echites, Forsteronia, Laubertia, Parsonsia, Prestonia, Thoreauea, Thenar­ dia, Apocynaceae. Recently, a specimen of Apocynaceae rotatis) et corona corollae praesenti (vice carenti) et from Oaxaca, Mexico was provided to me antheris inclusis (vice exsertis) differt. by one of the collectors, Jose L. Panero, for identification. After close examination, I VINE, twining, latex milky. STEMS te­ determined that the specimen does not key rete, 3-3.5 mm in diameter, light green, gla­ out to any of the genera recognized in a key brous, lenticellate with age; interpetiolar to the Mexican genera of Apocynaceae (J. ridge moderately prominent. LEAVES op­ K. Williams, 1996). This specimen keys out posite to subopposite, petiolate, membra­ most favorably to Thenardia H.B.K., how­ nous; petioles 20-23 mm, with a solitary ever, it possesses novel characters not found bract and 2-4 colleters at base; colleters in Thenardia (e.g., dissected corona at the 0.8-1.0 mm long, linear lanceolate, dark corolla mouth). A cladistic analysis (Fig. 5) brown when dried; leaf blade elliptic, apex based on morphological evidence indicates acuminate with extended tip, base obtuse, that if the new taxon were included in margin entire, glabrous on both surfaces, Thenardia, the genus would become para­ chartaceous when dry, 10.5-14.0 cm long, phyletic, no longer representing a mono­ 4.3-5.0 cm wide, without colleters, dark phyletic lineage delimited by a shared con­ green above, light green below, midrib sensus of characters. Thus, the problematic prominent below, slightly obscure above, specimen is best regarded as representing a lateral secondary veins 5-18, conspicuous, new genus. impressed alternate. INFLORESCENCE an axillary pedunculate, trichotomously­ Thoreauea paneroi J.K. Williams, gen. et branched subumbellate cyme, glabrous; pri­ sp. nov. (Figs. 1 and 2). mary peduncle 23 mm long, 1.0-1.3 mm diameter; secondary and tertiary peduncles TYPE: MEXICO. OAXACA: Mpio. San­ 5-18 mm long; bracts linear-lanceolate, tiago Juxtlahuaca, Dist. San Sebastian Te­ 1.0-4.0 mm long, 0.2-0.4 mm wide, comaxtlahuaca, 1.8 km N of the road Te­ straight; pedicels 7.0-11.0 mm long. comaxtlahuaca-"Coicoyan, de Las Flores" FLOWERS 20-25 per inflorescence, tightly along the road to Escopeta (17° 18' 27.1" clustered, pentamerous, actinomorphic, N, 98° 07' 51.5" W), 4 Mar 1995, J. L. Pa­ perfect. CALYX lobes equal, 0.9-1.0 mm nero with I. Calzada and J. Kuijt 5583 (Ho­ long, separate nearly to the base, triangular, LOTYPE: IZTA!; ISOTYPE: TEX). erect, glabrous; colleters ca. 0.5 mm long, opposite the sepals, solitary, thin, denti­ Thenardia affinis sed corollis urceolatus (vice form. COROLLA fused into a moderately LUNDELLIA 5:47-58. 2002 48 LUNDELLIA DECEMBER, 2002 HUI OTYPE OF: Thoreauea paneroi J. K. Wi 11 iams FLORA DE OAXACA 1\.1cto1steln111 SANTIAGO JUXTLAllUACA San S C' buliin TC'comutlahu au l I! Ian o1I N ,1., 1.. c.lrr<"lt'ra r,.._·onM ~ tl,1,huo -CoKn1 dCl d•· l.<i~ rlor..,, sobrl' !• bred1,1, d E•.,:01w 1~ . 17"111'27 ! ' ' '<. '11!" 07''>1 '>"W. /·11n•1.:l.ldPr.1d!' '.I· c> m,frl.iri;u. wrul,,_ rr..,n• B\""jl,..dt'p1no-..ncmo / mo>Sl'>l1!" Jc 1rwnt~1\.1 2625 111 J<•-.t·I r,.,,,.,,, ~">1n " "' 1 ,u1.wl('.1l;.t1i~ ,. J"b Kt1111 llttb.uio Nu1on.1l d<' Mi~i co (MEXUl M ichi ~an Stal<' Univ,,,ity llC'rb.uium (MSC) FIG. 1. Holotype of Thoreauea paneroi. NUMBER 5 WILLIAMS: THOREAUEA, NEW GENUS OF APOCYNACEAE 49 B. A. FIG. 2. Thoreauea paneroi. A. Flower. B. Longitudinal section of open flower. An = anthers. C = dissected corona around the mouth. F = filaments. Black bar represents 5 mm. erect tube, urceolate, aestivation dextrorse, style-head, forming five separate pollen creamy white; tube 5-6 mm long, 2.7-3.l chambers. PISTIL 3.0-3.5 mm long; ovary mm wide, slightly constricted at the base of two fused carpels united into a common and at the distal four-fifths of tube, gla­ style, superior, ovoid, glabrous, 0.8-1.5 mm brous, mouth of tube surrounded by a long; style head 1.5-2.0 mm, spool-shaped, deeply dissected corona annulus, linear-lan­ slender in the middle and greater in diam­ ceolate, both opposite and alternate the co­ eter at the base, with developed membra­ rolla lobes; lobes 1.0-2.0 mm long, 0.6-0.8 nous collar at base; stigmattic zone located mm at widest point, triangular, erect; limb on underside of style head beneath collar; 3.0-4.0 mm in diameter. STAMENS 5.5-6.0 nectaries five, free, pressed closely together, mm long, included; anther tips slightly be­ tightly surrounding the ovary, as long or low the corolla mouth to occasionally ex­ slightly shorter than the ovary. FRUIT un­ serted ca. 0.2 mm above the rim, filaments known. 3.0-3.3 mm long, bending inward, and Thoreauea is a member of the subfam­ closely encircling the style head, pubescent; ily Apocynoideae as evidenced by its an­ anthers 2.5-3.0 mm long, yellow, base sag­ thers agglutinated to the style head, dex­ ittate, fertile in the upper part, the lower trorse aestivation of the corolla bud, and part enlarged, sterile and equipped with triporate pollen grains. Within the Apocy­ sclerenchymatic guide rails on the ventral noideae Thoreauea belongs to the tribe face firmly agglutinated to the style-head se­ Echiteae, as delineated by Endress and cretions by thick brushes of hairs, forming Bruyns (2000). Members of the Echiteae are a pseudo-gynostegum, in addition thecae characterized by the thecae agglutinated to agglutinated to the upper slopes of the the style head at two levels and by the 50 LUNDELLIA DECEMBER, 2002 spool-shaped style head that is slender in Heads & de Lange; P. purpurascens J. B. the middle and greater in diameter at the Williams) have been added to the study in base. order to represent better the diversity of DISTRIBUTION AND ECOLOGY: Tho­ Parsonsia (a genus with many superficial reauea paneroi is a moderately sized liana similarities to Thenardia). Morphological known only from the type collection from data for the three species of Parsonsia were the cloud forests of the district of Santiago obtained from literature descriptions (J. B. Juxtlahuaca area of northwestern Oaxaca, Williams, 1996; Heads & de Lange, 1998) Mexico. The species is found in a meso­ SELECTION OF CHARACTERS. Forty­ phytic habitat of montane pine-oak forest five characters and 119 character states (Ta­ at 2625 m elevation. Flowers were collected ble 1) were utilized in this study. Informa­ in March but its phenology is unknown. tive character states were selected from Thoreauea was included, together with those utilized in previous studies (Endress 24 additional genera, in an unpublished et al. 1996; Sennblad et al. 1998; Struwe et morphological cladistic analysis of the Apo­ al. 1994; Potgieter and Albert, 2001). New cynoideae (Williams, 1999). A portion of characters not included in the above works, this analysis (Fig. 5) is discussed below. Be­ but uncovered during the course of this cause additional results of the analysis are study were also included. A discussion of outside the scope of this paper, the full tree the characters utilized in this study is pro­ is not included or discussed. vided in Williams (1999). Table 2 lists the characters and character states for each of METHODS the taxa shown in this analysis. CLADISTIC ANALYSIS. The characters COLLECTION OF DATA. With the ex­ and character states (Table 2) used in the ception of selected species of Parsonsia (see analysis were entered into a data matrix us­ below), a representative specimen is depos­ ing MacClade 3.0 (Maddison & Maddison, ited at the Plant Resources Center for each 1992). A phylogenetic analysis was then of the species examined in the morpholog­ performed in PAUP 3.1 (Swofford, 1993). ical cladistic analysis. Observations and data A heuristic search by stepwise addition of were collected from material borrowed random trees was performed with 100 ran­ from or observed at the following herbaria: dom addition sequences. The heuristic BM, BRIT, CHAPA, F, FLAS, G, GH, K, search was performed with the ACCTRAN, MA, METPEC, MEXU, MO, NY, P, SHST, MULPARS and TBR options in effect. Taxa TAMU, TEX, US, WIS. with multi-state characters were recognized The pollen of all genera was studied us­ as polymorphic for those characters. Char­ ing a light microscope as well as a scanning acters were treated as unordered and of electron microscope (Philips 515). All gen­ equal weight. At the end of the analysis the era were examined and measured under the stored trees were rooted, with both the out­ SEM at the Cell Research Center of the group and ingroup directed as monophy­ University of Texas at Austin. letic. A majority rule consensus tree of the A total of 37 taxa, representing 25 gen­ stored trees was then produced. Bootstrap era, were included in the original cladistic values were calculated using 100 replica­ analysis (Williams, 1999).