Phylogeny of the American Amaryllidaceae Based on Nrdna ITS Sequences
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Systematic Botany (2000), 25(4): pp. 708±726 q Copyright 2000 by the American Society of Plant Taxonomists Phylogeny of the American Amaryllidaceae based on nrDNA ITS sequences ALAN W. M EEROW USDA-ARS-SHRS, 13601 Old Cutler Road, Miami, FL 33158 and Fairchild Tropical Garden, 10901 Old Cutler Road, Miami, Florida 33158 CHARLES L. GUY and QIN-BAO LI University of Florida, Department of Environmental Horticulture, 1545 Fi®eld Hall, Gainesville, Florida 32611 SI-LIN YANG University of Florida, Fort Lauderdale Research and Education Center, 3205 College Avenue, Fort Lauderdale, Florida 33314 Communicating Editor: Kathleen A. Kron ABSTRACT. Analysis of three plastid DNA sequences for a broad sampling of Amaryllidaceae resolve the American genera of the Amaryllidaceae as a clade that is sister to the Eurasian genera of the family, but base substitution rates for these genes are too low to resolve much of the intergeneric relationships within the American clade. We obtained ITS rDNA sequences for 76 species of American Amaryllidaceae and analyzed the aligned matrix cladistically, both with and without gaps included, using two species of Pancratium as outgroup taxa. ITS resolves two moderately to strongly supported groups, an Andean tetraploid clade, and a primarily extra-Andean ``hippeastroid'' clade. Within the hippeastroid clade, the tribe Grif®neae is resolved as sister to the rest of Hippeastreae. The genera Rhodophiala and Zephyranthes are resolved as polyphyletic, but the possibility of reticulation within this clade argues against any re-arrangement of these genera without further investigation. Within the Andean subclade, Eustephieae resolves as sister to all other tribes; a distinct petiolate-leafed group is resolved, combining the tribe Eucharideae and the petiolate Stenomesseae; and a distinct Hymenocallideae is supported. These Andean clades are all at least partially supported by plastid sequence data as well. We infer from our data that a great deal of the diversity of the family in the Americas is recent, and that the American Amaryllidaceae may have been reduced to peripheral isolates some time after its initial entry and spread through the Americas. While the sister relationship of the American and Eurasian clades might argue for a Boreotropical origin for the family in America, the cladistic relationships within the American clade based on ITS do not provide any further support for this or any other hypothesis of the family's entry into America. The new tribe Clinantheae is described (four genera: Clinanthus, Pamianthe, Paramongaia, and Pucara), and the lorate-leafed species of Stenomesson are transferred to Clinanthus. Amaryllidaceae J. St.-Hil., a cosmopolitan (pre- for various taxa of tribe Amaryllideae; and Meerow dominantly pantropical) family of petaloid mono- et al. (1999) for the entire family using three plastid cots, represent one of the elements of the Linnaean DNA sequences. Phylogenetic studies for the entire Hexandria monogynia (Linnaeus 1753), the 51 genera family using morphological characters are made of which have been variously classi®ed since as lil- dif®cult by homoplasy for many conspicuous char- iaceous or amaryllidaceous. Meerow et al.(1999) re- acters within this highly canalized group (Meerow viewed the taxonomic history of the family. Despite et al., 2000). a lack of consensus on generic limits and tribal de- The four most recent infrafamilial classi®cations limitations within Amaryllidaceae, cladistic analy- of Amaryllidaceae are those of Traub (1963), Dahl- sis has only rarely been applied to problems in the gren et al. (1985), MuÈ ller-Doblies and MuÈ ller-Dob- family, such as by Nordal and Duncan (1984) for lies (1996) and Meerow and Snijman (1998). Traub's Haemanthus and Scadoxus, two closely related, bac- scheme included Alliaceae, Hemerocallidaceae, and cate-fruited African genera; Meerow (1987, 1989) Ixioliriaceae as subfamilies, following Hutchinson for Eucrosia and Eucharis and Caliphruria respective- (1934, 1959) in part. Within his subfamily Amar- ly; Snijman (1994) and Snijman and Linder (1996) ylloideae, he erected two informal taxa, ``infrafam- 708 2000] MEEROW ET AL.ÐITS IN AMARYLLIDACEAE 709 ilies'' Amarylloidinae and Pancratioidinae, both of several clones for the sequence reactions (Baldwin which were polyphyletic (Meerow 1995). Dahlgren et al. 1995). et al. (1985) dispensed with any subfamilial classi- ITS shows greatest utility for generating gene ®cation above the level of tribe, recognizing eight, phylogenies at the rank of family and below (Bald- and treated as Amaryllidaceae only those genera in win et al. 1995). To date, ITS sequences have been Traub's Amarylloideae. Stenomesseae and Euste- sparingly successful in resolving family-wide phy- phieae were combined. Meerow (1995) resurrected logenies (Fouquieriaceae, Schultheis and Baldwin Eustephieae from Stenomesseae and suggested that 1999; Nothofagaceae, Manos 1993; Winteraceae, Suh two new tribes needed to be recognized, Calostem- et al. 1992), but have been most valuable when ap- mateae and Hymenocallideae. MuÈ ller-Doblies and plied to single genera or at the subfamilial rank; MuÈ ller-Doblies (1996) recognized ten tribes (among e.g., Aquilegia (Ro et al. 1997), Fraxinus (Jeandroz et them Calostemmateae) and nineteen subtribes, al. 1997), Lupinus (Kass and Wink 1997), Saintpaulia many of them monogeneric; Meerow and Snijman (Moeller and Cronk 1997), Adoxaceae: Adoxoideae (1998) recognized 14 tribes, with two subtribes only (Eriksson and Donoghue 1997), Rosaceae subfamily in one of them. These classi®cations are compared Maloideae (Campbell et al. 1995), Orchidaceae sub- in detail in Meerow et al. (1999). tribe Orchidinae (Bateman et al. 1997; Pridgeon et Meerow et al. (1999) presented cladistic analyses al. 1997), Poaceae subfamily Arundinoideae (Hsiao of combined plastid DNA sequences rbcL, trnL gene et al. 1998). and the trnL-F intergenic spacer for 48 genera of In this paper we present cladistic analyses of the Amaryllidaceae and 29 genera of related Aspara- internal transcribed spacer region (ITS) of nuclear gales. Good support was provided for the mono- ribosomal DNA for 76 species of American Amar- phyly of Amaryllidaceae. The infra-familial rela- yllidaceae (representing all but ®ve of the American tionships of Amaryllidaceae were resolved along endemic genera) and discuss our results in the con- text of previous plastid sequence phylogenies (Ito biogeographic lines. Ito et al. (1999) resolved a very et al. 1999; Meerow et al. 1999). We also discuss the similar topology for a more limited sampling of biogeographic implications of these data. Amaryllidaceae and related asparagoids using plastid matK sequences. The most surprising con- clusion from the plastid sequence phylogeny was MATERIALS AND METHODS that the Eurasian and American elements of the Plant Materials. Species used in the sequence family are each monophyletic sister clades. How- analyses, voucher specimens and GenBank acces- ever, there was insuf®cient base substitution among sion numbers for the sequences are listed in Table the American genera to resolve their relationships 1. All genera of the American Amaryllidaceae were suf®ciently with plastid sequences. sampled except Mathieua (presumed extinct), Pla- The 18S and 26S subunits of nuclear ribosomal giolirion (repeated attempts to amplify DNA from a DNA (nrDNA) are separated by two internal tran- recent herbarium specimen failed) and Placea, Pu- scribed spacer regions, ITS1 and ITS2, and a 5.8S cara, and Traubia (material not available). The pres- gene located between the two ITS regions. ITS1 ence of the pantropical Crinum (tribe Amaryllideae) varies in angiosperms from 187±298 bp, and ITS2 in the Americas is understood to represent a dis- from 187±252 bp (Baldwin et al. 1995). The two ITS persal event unrelated to the origins of the endemic regions evolve more rapidly than the coding re- American tribes of Amaryllidaceae (Arroyo and gions they separate. For closely related taxa, rapidly Cutler 1984; Meerow et al. 1999) and no American evolving, non-coding regions of nuclear genes such species of this genus are considered here. as ITS can potentially yield a greater degree of in- DNA Extraction. Genomic DNA was extracted formative sequence variation than the more highly from silica gel dried leaf tissue using a modi®ed conserved coding regions. From a practical stand- CTAB procedure of Doyle and Doyle (1987). point, the small size of the ITS region, and its lo- PCR and Sequencing Protocol. Ampli®cation of cation between highly conserved sequences, make the ribosomal DNA ITS1/5.8S/ITS2 region was ac- the spacers easy to amplify by PCR (Baldwin et al. complished using ¯anking primers (18S, 26S) 1995). Potential problems of paralogous sequences AB101 and AB102 (Douzery et al. 1999), and the due to the multiple copy nature of nrITS can be at original White et al. (1990) primers ITS5, 4, 2 and least partially overcome by sequencing more than 3 to amplify the spacers along with the intervening one clone of each taxon or pooling PCR extracts of 5.8S sequence. Ampli®ed products were puri®ed 710 SYSTEMATIC BOTANY [Volume 25 TABLE 1. Taxa used in the cladistic analyses nrDNA (ITS) sequence. Tribal and generic assignments in Amarylli- daceae follow Meerow and Snijman (1998). All vouchers are deposited at FTG unless otherwise noted. GenBank Taxon Voucher Accession No. Eucharideae Caliphruria korsakof®i (Traub) Meerow Meerow 1096 (FLAS) AF223529 Caliphruria subedentata Bak. Meerow 1109 (FLAS)