Phylogenetic Analysis of Cestrum Section Habrothamnus (Solanaceae) Based on Plastid and Nuclear DNA Sequences JUAN CARLOS MONTERO-CASTRO, 1,4 ALFONSO DELGADO-SALINAS, 1 EFRAIN DE LUNA, 2 and LUIS E. EGUIARTE 3 1 Instituto de Biologı ´a, UNAM, A. P. 70-367, Me ´xico D. F. 04510, Me ´xico; 2 Instituto de Ecologı ´a A. C., A. P. 63, Xalapa, Veracruz, 91070, Me ´xico; 3 Instituto de Ecologı ´a, UNAM, A. P. 70-275, Me ´xico D. F. 04510, Me ´xico 4 Author for correspondence (jcmc@ibiologia.unam.mx) Communicating Editor: Matt Lavin ABSTRACT. Phylogenetic analysis of DNA sequences from chloroplast regions and nuclear ribosomal ITS was conducted to test the monophyly of Cestrum sect. Habrothamnus and investigate its relationships with other sections of Cestrum. Molecular divergence was very low among the sampled species, suggesting a rapid diversification in Cestrum. Individual and combined analyses of these molecular data sets using maximum parsimony and Bayesian inference reject the monophyly of the traditionally recognized sections of Cestrum, including sect. Habrothamnus. Infrageneric classifications will require significant revision. Nevertheless, the resolved monophyletic clades in this molecular analysis are geographically structured. KEYWORDS: Cestrum, geographic phylogenetic structure, Habrothamnus, molecular phylogeny, Sessea, Solanaceae. The genus Cestrum ranges from southern Florida and northern Mexico to Chile, including the Antilles. However, a few species (e.g., C. noctur- num, C. elegans, and C. parqui) have become naturalized in several regions of the world. Species of Cestrum range from trees, shrubs, to vines with sympodial, polyaxial, and monochasial branching (Bell and Dines 1995). Species of Cestrum are well- known for their ornamental (Beckett 1987), chemi- cal, and pharmacological potential (e.g., Prema and Raghuramulu 1994; Backhouse et al. 1996; Har- aguchi-Mitsue et al. 2000). Attention has recently been brought to Cestrum because of its chromo- somal structural novelties that imply systems of chromosome maintenance unknown in the eudi- cots (Sykorova et al. 2003). Cestrum is easily confused with the Andean genus Sessea. Cestrum has berries with angular seeds, whereas Sessea has capsular fruits with winged seeds (Benı ´tez and D’Arcy 1998; Benı ´tez and D’Arcy 1999; Benı ´tez and Nee 2001; Nee 2001). Nevertheless, Macbride (1962) and Carvalho and Schnnoor (1997) have united the two genera. Also Cestrum and Sessea share distinctive chromosomes (Sykorova et al. 2003), and in a phylogenetic analysis of the Antillean subfamily Goetzeoideae (Santiago-Valen- tı ´n and Olmstead 2003) Cestrum and Sessea were resolved as well-supported sister taxa. The genus Habrothamnus (Schlechtendal 1833; Endlicher 1839) was reduced to a section of Cestrum (Schlechtendal 1847), which has since been followed by other botanists (e.g., Dunal 1852; Francey 1935, 1936; D’Arcy 1973). Urban (1903) proposed sect. Pseudocestrum to include the Hispan- iolan endemic, C. inclusum. According to Nee’s nomenclatural synopsis (Nee, in prep.) three sections are recognized in Cestrum: sections Ces- trum, Habrothamnus, and Pseudocestrum. Section Habrothamnus includes eight species, which con- trasts with Francey’s classification (1935, 1936) where 28 species and eight varieties are included. All species of section Habrothamnus are confined to the mountains of Central Mexico, Chiapas-Guate- mala, Costa Rica-Panama, and Hispaniola, and are morphologically distinguished by inflorescences mostly terminal, club-shaped, bright-red or yellow corolla tube, diurnal flowering, and hummingbird pollination (D’Arcy 1999; Nee 2001; Nee, in prep.). Although species of Cestrum have been included in phylogenetic studies of the family Solanaceae (Marshall 1999; Olmstead and Palmer 1992; Olm- stead et al. 1999; Chase et al. 2003; Santiago- Valentı ´n and Olmstead 2003; Clarkson et al. 2004) the monophyly of Cestrum or the inter-relation- ships of its constituent species have never been addressed. The aim of this paper is to address these issues, with emphasis in the monophyly of Habrothamnus, using nuclear ribosomal 5.8S and ITS DNA sequences and chloroplast DNA se- quences from the regions trnT-trnL, trnL-trnF, and matK-trnK. Likewise, we explore the utility of these sequence data for resolving a species-level phylog- eny for subsequent studies that will include all species of Cestrum. MATERIALS AND METHODS Taxon Sampling. Species considered part of sect. Hab- rothamnus (18 accessions, Appendix 1) primarily were targeted for analysis. Cestrum dasyanthum, the recently described C. milciomejiae (Zanoni 1995), and Cestrum sp. nov. were also included because they have the diagnostic Systematic Botany (2006), 31(4): pp. 843–850 # Copyright 2006 by the American Society of Plant Taxonomists 843