Nomenclatural changes in Lithospermum (Boraginaceae) and related taxa following a reassessment of phylogenetic relationships 1,2 1 JAMES I. COHEN AND JERROLD I. DAVIS 1 L. H. Bailey Hortorium, Department of Plant Biology, Cornell University, 412 Mann Library Building, Ithaca, NY 14853, USA 2 Author for Correspondence: [email protected] Abstract. Lithospermum (Boraginaceae) comprises approximately 40 species in both the Old and New Worlds, with a center of diversity in the southwestern United States and Mexico. Using ten cpDNA regions, a phylogeny of Lithospermum and related taxa was reconstructed. Lithospermum (including New World and Old World species) and related New World members of Lithospermeae form a monophyletic group, with Macromeria, Onosmodium, Nomosa, Lasiarrhenum, and Psilolaemus nested among species of Lithospermum. New World Lithospermeae also is a monophyletic group, with Eurasian species of Lithospermum sister to this group. Because Lithospermum is not monophyletic without the inclusion of the other New World genera, species from these genera are transferred to Lithospermum, and appropriate nomenclatural changes are made. New combinations are Lithospermum album, Lithospermum barbig- erum, Lithospermum dodrantale, Lithospermum exsertum, Lithospermum hel- leri, Lithospemum leonotis, Lithospermum notatum, Lithospermum oaxacanum, Lithospermum pinetorum, Lithospermum rosei, Lithospermum trinverium, and Lithospermum unicum; new names are Lithospermum chiapense, Lithospermum johnstonii, Lithospermum macromeria, Lithospermum onosmodium, Lithosper- mum rzedowskii, and Lithospermum turneri. Key Words: Lasiarrhenum, Lithospermum, Macromeria, Nomosa, Onosmodium, Perittostema, Psilolaemus, Lithospermeae, Boraginaceae. The genus Lithospermum L. (Boraginaceae) monophyletic, but resolution is lacking within comprises approximately 40 species (Johnston, the tribe and no New World members of 1954a). Although it has a cosmopolitan distri- Lithospermeae were included in the analysis; bution, most species of the genus occur in the therefore, Johnston’s hypothesis that all six New World, from Canada southward to Peru, genera of Lithospermeae endemic to the New with a center of diversity in Mexico and the World (i.e., all New World genera of the tribe southwestern United States. Lithospermum and other than Lithospermum) are closely related to the tribe to which it belongs, Lithospermeae Lithospermum (Johnston, 1954a) has yet to be Dumort., were revised by Ivan Johnston in a tested (but see Thomas et al., 2008). This group series of papers from 1952 to 1954 (1952, includes Macromeria D. Don, Onosmodium 1953a, b, 1954a, b). In these papers, Johnston Michx., Lasiarrhenum I. M. Johnst., Nomosa I. recognized new species within the genus, M. Johnst., Psilolaemus I. M. Johnst., and described new genera, and proposed hypothe- Perittostema I. M. Johnst. Species of these ses concerning evolutionary relationships with- genera occur from Canada to Guatemala, and in the tribe (1952, 1954a, b). A recent as with Lithospermum, the center of diversity phylogeny of Boraginaceae (Langstrom & for the group is in Mexico. Only two of these Chase, 2002) reconstructs Lithospermeae as genera, Macromeria and Onosmodium, include Brittonia, 61(2), 2009, pp. 101–111 ISSUED: 1 June 2009 © 2009, by The New York Botanical Garden Press, Bronx, NY 10458-5126 U.S.A. 102 BRITTONIA [VOL 61 more than one species; Macromeria includes Although both Lehmann and de Candolle 11 species and Onosmodium includes seven. recognized a large, inclusive Lithospermum, Johnston’s generic demarcations within New they also recognized two endemic New World Lithospermeae are primarily based on World genera, Macromeria and Onosmodium floral characters, such as exserted vs. included (as Purshia Lehm. [Lehmann, 1818], non anthers; flattened vs. cylindrical filaments; and Purshia DC. ex Poir. [Rosacaeae]). Species campanulate, urceolate, or long funnelform from these two genera have only rarely been vs. salverform or funnelform corolla shapes included in Lithospermum (e.g., Muhlenberg, (Johnston, 1954a, b). However, phylogenetic 1813). This treatment of species in the New analyses (Cohen, 2007) suggest that the genera World differs from that of many species in the recognized on the basis of these floral features Old World in which it has been common to are not monophyletic. include species from putatively related genera Lithospermum and other New World mem- of Lithospermeae, such as Buglossoides, bers of Lithospermeae share characteristic Lithodora, and Neatostema, in Lithospermum erect, smooth to slightly dimpled, white, (see Johnston, 1953a [but see Johnston, lustrous nutlets with basal attachment, and 1954a, b for taxonomic changes], Flora all have three-celled glands inside the corol- Iranica [Rechinger, 1967], and Flora of las, except for ca. 12 taxa in which glands, China [Zhu et al., 1995]). presumably, have been lost or modified. At present, the most widely accepted Closely related genera of Lithospermeae that taxonomic system for the genus derives from share these features, such as Buglossoides Johnston’s revisionary efforts on the genus Moench and Lithodora Griseb. (Thomas et and tribe during the 1950s, but that treatment al., 2008), have blue or purple corollas, but also contributed additional complexity to the these corolla colors do not occur in Litho- group’s taxonomy. Johnston placed Arnebia spermum or other New World members of and Echioides Fabr. in Lithospermum in Lithospermeae. 1952, but two years later he removed them, The taxonomic history of Lithospermum is noting differences in stamens and pollen. complex, and the complexity arises, in part, Also, he placed some newly described spe- from treatments of the genus in the 1800s. For cies in Lithospermum in 1953, and transferred example, in Plantae e Familia Asperifoliarum them to Arnebia the following year. In his Nuciferae (1818), Lehmann circumscribed a 1952 revision of Lithospermum, Johnston broadly inclusive Lithospermum, which includ- recognized the difficulty of dividing Litho- ed species currently placed in Lithospermum spermum into smaller groups, stating that (Johnston, 1954a) as well as species currently “The genus has great internal coherence. It included in other genera, such as Mertensia is exasperatingly lacking in lines of cleavage” Roth, Buglossoides, Arnebia Forssk., and Lith- (1952, p. 300). odora. A later taxonomic treatment of Lith- Taxonomic questions regarding generic ospermum in the Prodromus Systematis boundaries of Lithospermum still arise, as Naturalis Regni Vegetabilis by A. P. de Can- seen in the treatment of Boraginaceae in the dolle (1846) was, like Lehmann’s treatment, Flora of China (Zhu et al., 1995), in which quite inclusive; however, unlike Lehmann, de Lithospermum is circumscribed as including Candolle divided the genus into three sections. species often placed in Buglossoides. Treating One section, Eulithospermum DC. included Lithospermum in this broad sense is common only species currently included in Lithosper- in Old World literature; however, Buglos- mum (with one exception, L. chinensis Hook. soides is not monophyletic (cf. Langstrom & and Arn., which is a synonym of Heliotropium Chase, 2002; Cohen, unpublished data) and strigosum Willd. [Zhu et al., 1995]). The other may not be sister to Lithospermum. two sections in the treatment, Rhytispermum A recent taxonomic study of Lithospermum Link and Margarospermum Rchb. f., included (Ralston, 1993) included a phylogenetic anal- species that are often included in other genera, ysis of the genus utilizing a total of twenty such as Buglossoides, Lithodora, Neatostema I. morphological, palynological, karyological, M. Johnst., and Moltkia Lehm. and chemical characters. This analysis provid- 2009] COHEN & DAVIS: LITHOSPERUMUM NOMENCLATURE 103 ed support for the recognition of several species Materials and methods groups, but did not resolve relationships among these groups. Recent work on other taxa of TAXON SAMPLING New World Lithospermeae includes Turner’s Twenty-seven species were included in the synopses of Macromeria (1994a), Onosmo- analyses. Twenty-two belong to the ingroup, dium (1995), and Lasiarrhenum (1994b), and and five are outgroup taxa from related Boyd’s (2003) phylogeny of Macromeria genera in Lithospermeae (Table I). The based on morphological characters. ingroup sampling represents the range of The present study was undertaken to variation within Lithospermum, and species examine the phylogenetic relationships from all but one elusive genus of New World among species of Lithospermum and other Lithospermeae, Perittostema, were included. elements of New World Lithospermeae, Perittostema was not included in the analyses with two of the goals being to determine because it is only known from the type, whether the non-monotypic genera Litho- housed in Paris (P), and the type locality is spermum, Macromeria, and Onosmodium unknown; however, Johnston hypothesized constitute monophyletic groups and to re- that it was collected in Oaxaca, Mexico evaluate the taxonomy of New World (Johnston, 1935, 1954a). The majority of the Lithospermeae. taxa were collected from wild populations. TABLE I LIST OF TAXA INCLUDED IN ANALYSES ALONG WITH COLLECTION OR SOURCE DATA. Taxon Collection Location OUTGROUP SPECIES Alkanna tuberculata Greuter 2002 1260-96 Natl. Bot. Gard. Belgium Buglossoides arvense (L.) I. M. Johnst. 19792083 Natl. Bot. Gard. Belgium Echium vulgare L. J. Cohen 212 Cornell Plantations Lithodora diffusa. (Lag.) I. M. Johnst. M. Chase