Boletín de la Sociedad Botánica de México 56: 69-76, 1995 DOI: 10.17129/botsci.1465 Bol. Soc. Bot. México 56: 69-76 ( 1995) Systematics of Dasylirion: Taxonomy and molecular phylogeny DA VID J. BOGLER Department of Botany, The University ofTexas, Austin, Texas 78713-7640 Abstract. The results of a systematic study in which Dasylirion was fully monographed are reported. Sixteen species, including four new ones, were recognized. Data from chloroplast DNA restriction site analysis suggest that the species of Dasylirion in southern Mexico are basal in the genus, that Nolina parvif/ora is particularly el ose to both Dasylirion and Beaucarnea, and that Calibanus is closest to Beaucarnea. The phylogeny of Dasylirion and the Agavaceae sensu lato was studied by comparison of cpDNA restriction sites and ITS rDNA sequences. The results strongly indicate that Dasylirion, Noli11a , Beaucarnea, and Calibanus are a monophyletic group that is closer to Maia11themum, Polygonatum, Liriope, Dracaena and Sansevieria than to Yucca and Agave. Hasta and Camassia are at the base of the branch leading to Yucca and Agave. The molecular data indica te that Yucca whipplei is more closely related to Hesperaloe than to other species of Yucca, and thatAgave dasylirioides and A. striata in the «Group Striatae» are basal to the rest of Agave. The resemblance of Aloe and Xa11thorrhoea to the Agavaceae appears to be due to convergen! evolution. Key words : Dasylirion, molecular phylogeny, Mexico, Nolinaceae, Taxonomy. Resumen. Se realizó el estudio monografico del género Dasylirio11. En esta revisión se reconocen 16 especies, incluyendo cuatro especies nuevas. El análisis de sitios de restrición del DNA de los cloroplastos (cpDNA) indica que las especies de Dasylirio11 del sur de Mexico son basales dentro del género, que Nolina parviflora está muy cercana a Dasylirion y Beaucarnea, y que Calibanus esta próximo a Beaucarnea. Se estudiaron las filogenias de Dasylirion y de las Agaváceas mediante comparaciones del cpDNA y secuencias de la región ITS del rDNA. Los resultados indican claramente que Dasylirion, Nolina, Beaucamea y Calibanus se encuentran en un grupo que está más cercano a Maianthemum, Polygonatum, Liriope, Dracaena y Sansevieria que a Yucca y Agave. De la misma forma, Hasta y Camassia son basales a Yucca y Agave. Los datos moleculares indican que Yucca whipplei está mas cercana a Hesperaloe que al resto de las especies de Yucca, y que Agave dasylirioides y A. striata del «G rupo Striatae» son basales a las otras especies de Agave. La semejanza entre Aloe y Xanthorrhoea y las Agaváceas parecen deberse a la convergencia evolutiva. Palabras clave : Dasylirion, filogenia molecular, México, Nolinaceae, Taxonomía. INTRODUCTION study ofthe phylogenetic relationships ofDasylirion and the Agavaceae sensu lato. Dasylirion is a genus of 16 species found in rocky, arid regions ofthe southwestern U.S.A. andMexico. It is dioecious TAXONOMIC HISTORY OF DASYL!R/ON and easily recognized by its dense rosettes of prickly Jeaves The original description of Dasylirion (Zuccarini, 1838) and long, narrow inflorescence stalks. It is commonly known was based on an assortmentofleaf collections, garden specimens as «sotol » and has been u sed forfood, fiber, and thedistillation and species now placed in other genera. The status ofDasylirion of an alcoholic beverage also known as sotol. There have was clarified as more collections became available for study been few detailed studies ofthe taxonomy of Dasylirion and (Zuccarini, 1840). Although there was at one time sorne consequently the identification of collections is often difficult. confusion about the status of Nolina and Beaucarnea (Hemsley, Although it is generally recognized that Dasylirion is closely 1884), the distinctive marginal leaf prickles of Dasylirion related to Nolina, Beaucarnea and Calibanus, it is not clear have made it easy to distinguish. Early efforts to monograph how these are related to Yucca, Agave and other members of Dasylirion were made by Baker (1872, 1881) and Watson the Agavaceae. Our research has focused on the taxonomy (1879). Most of the early descriptions were based on only a of spec ies of Dasylirion and the phylogenetic relationships few specimens and sorne of the characters are now known to of the species and the genus. In this paper we present a be more variable than previously supposed. The most recent simplified overview ofourresults, the details will be published monograph of Dasylirion was made by Trelease (1911), who elsew here. The first part is a general discussion of th e genus recognized 15 species, including thesix species which Trelease with the results of a chloroplast DNA (cpDNA) restriction described. The genus has recently been monographed and the site study of the species of Dasylirion. The second part 16 species of Dasylirion, including four new ones, recognized presents the highlights of a cpDNA and ITS sequencing by Bogler (1994) are presented in Table l. _____________ Bogler DJ. 1995. Systematics of Dasylirion: Taxonomy and molecular phylogeny. Boletín de la Sociedad Botánica de México 56: 69-76. 70 DA VID J. BOGLER TABLE 1. Species of Dasylirion and new co mbinations recognized by strongly papillate-roughened. The leaves of sorne species Bogler (1994). ha ve a coat of wax, which gives the leaf a blue-green or white aspect. The margins are lined with a row of sharp, usually forward-pointingprickles. The prickles areoccasionally recurved D. serratifolium (Karwinski ex Schultes) Zuccarini or distinctively colored in sorne species. In a few species the D. lucidum Rose prickles are greatly reduced in size or absent. The tip ofthe leaf D. acrotriche (Schiede ex Schultes) Otto occasionally dies back and splits into a mass of fibers. var. parryanum (Trelease) Bogler Inflorescence. The inflorescence is a very distinctive var. occidentalis Bogler feature of Dasylirion. It is a narrow, compound, spike-like D. glaucophyllum Hooker panicle with an elongate, bracteate peduncle that ranges D. berla 11 . :,eri Watson from 1-6 m in length from base to tip. Flowers are borne in var. palaciosii (Rzedowski) Bogler contracted fascicles of finger-like racemes arranged along var. longistylum (MacBride) Bogler the axis. There is a gradual transition from the lea ves to the D. miquihuanensis Bogler sp. nov. bracts of the inflorescence anda gradual reduction in the size D. treleasei Bogler sp. nov. of the bracts up the stalk. In most species the bracts are well D. quadrangulatum Watson [=D. longissimum] separated and stramineous, but are occasionally densely D. simplex Trelease overlapping and green or reddish colored. The fascicles of D. gentryi Bogler sp. nov . flowers are borne in the axils of the large inflorescence D. durangense Trelease bracts. There is generally a more or less elongated central D. sereke Bogler sp. nov. axis with a number of si de branches. The number of branches D. wheeleri Watson ex Rothrock varies with the position on the fascicle on the inflorescence. D. cedrosanum Trelease In sorne species it is much branched while in others there is D. leiophyllum Engelmann ex Trelease a reduction to 3 or fewer branches. var. glaucum (I.M. Johnston) Bogler Flowers. The individual flowers are borne in congested D. texanum Scheele spirals along the branches of the fascicles. Each flower is borne in the axil of a small, membranous laciniate bract. Within this bract there may be one or two smaller bracts. The pistillate flowers are borne on a di stinctly jointed pedicel. The receptacle is generally very small. There are six separate, MORPHOLOGY OF DASYLIRION elliptical or obovate tepals with weakly laciniate tips. The Habit. Ali species of Dasylirion are polycarpic tepals are usually green or purple in color. There are six perennials with rosettes of fibrous leaves from a short or reduced, nonfunctional stamens opposite the tepals. The elongate caudex. Flowering is terminal, with the apical ovary is sharply 3-angled and has only one locule at maturity. meristem developing in to the inflorescence. Growth continues Although there are initially six ovul es, only one or rarely two sympodially from axillary buds near the apex. Branching of ovules mature into seeds. There is a very short style with the rosette occurs if more than one axill ary bud becomes three weakly united stigma lobes. These stigma lobes form active. an open tube which closes shut after pollination takes place. Trunks. Most species of Dasylirion have a woody Variation in the pistillate flowers involves primarily size caudex that increases in length and width. In a few species differences in th e tepals, style and stigma lobes. the caudex does not seem to grow much abo ve ground leve!, The staminate flowers are borne on short, non-jointed while in sorne species it may grow in toan upright trunk 2 m pedicels and have a very short receptacle. There are six in height with a corky periderm. In most species, however, separate obovate tepals with weakly laci ni ate tips. The six the trunk is not very wide or strong, and in older plants the stamens have glabrous filaments with exserted, dorsifixed trunk tends to recline on the ground. The trunks are often and introrsely dehiscent anthers. There appears to be little supported and protected by a skirt of stiff, dead leaves. variation in the staminate flowers of Dasylirion. Roots. The root system is fibrous and spreading. The Fruits. The mature fruit of Dasylirion is hard to roots have a very tough, sclerified endodermis su rrounded categorize. lt is often described as an indehi scent capsule, by a thick cortex of parenchyma cells. Young plants ha ve 2- but because it has only one seed it has also been called a 3 large, fusiform roots that are apparently contractile. Older nutlet (Dahlgren et al., 1985). Since it al so has three wings plants have a densely spreading root system. it has been called a samara. There is substantial variation in Leaves.