Genetic Evidence for Allopolyploidy in the Neotropical Fern Hemionitis pinnatifida (Adiantaceae) and the Reconstruction of an Ancestral Genome Author(s): Thomas A. Ranker, Christopher H. Haufler, Pamela S. Soltis, Douglas E. Soltis Source: Systematic Botany, Vol. 14, No. 4 (Oct. - Dec., 1989), pp. 439-447 Published by: American Society of Plant Taxonomists Stable URL: http://www.jstor.org/stable/2418989 Accessed: 16/05/2010 14:49 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. 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Copyright 1989 by the American Society of Plant Taxonomists Genetic Evidence for Allopolyploidy in the Neotropical Fern Hemionitis pinnatifida (Adiantaceae) and the Reconstruction of an Ancestral Genome THOMAS A. RANKER1and CHRISTOPHERH. HAUFLER Department of Botany, University of Kansas, Lawrence, Kansas66045 Present address:Ifawaiian EvolutionaryBiology Program, University of Hawaii, Honolulu, Hawaii 96822 PAMELA S. SOLTIS and DOUGLAS E. SOLTIS Department of Botany, Washington State University, Pullman, Washington 99164 ABSTRACT. Genetic evidence from enzyme electrophoresisand restrictionsite analyses of cpDNA was employed to explore the origin of the tetraploidHemionitis pinnatifida by determining the role of diploid species of Hemionitisin contributingto the tetraploidgenome. The resultsclearly supported the hypothesis that H. pinnatifidais an allotetraploidwith H. palmataas one of its diploid progenitors. The other diploid parent was not identified among the existing species of Hemionitisand is either extinct or exceedingly rare. Genetic identity analyses compared the extant diploid genomes with the divergent diploid genomes combined in tetraploids.One of these divergent genomes was shown to be a good approximationof that of H. palmata,and the other is a reconstructionof that of the missing diploid parent.These analyses demonstratedthat the missing ancestorwas genetically more similar to H. palmatathan either of these species is to the other diploid species surveyed. Such greater genetic similarity may have been important in allowing hybridization between the two diploid progenitors of H. pinnatifida.The data also suggest that tetraploid individuals may have been synthesized de novo at least five times among the three populations surveyed. Many species of homosporous ferns are al- pear "fixed" in all individuals of a given pop lotetraploid in origin, having arisen through ulation or species (Roose and Gottlieb 1976). chromosome doubling preceding or following Fixation of heterozygosity is maintained by di- hybridization between two distinct diploid pro- somic inheritance resulting from preferential genitors (e.g., Manton 1950; Shivas 1961a, 1961b; pairing of homologous chromosomes from each Wagner 1954; Wagner and Wagner 1980; Walk- parental taxon (Manton 1950). er 1979). Such hybrids usually can be recog- Hemionitis pinnatifidaBaker is a tetraploid (2n nized by their morphological intermediacy for = 60 11;Ranker, unpubl. data; Smith and Mickel characters at which two known diploids are di- 1977) distributed from southern Mexico to Cos- vergent. Recent studies have employed enzyme ta Rica. Smith and Mickel (1977) suggested that electrophoresis to test hypotheses of allopoly- H. pinnatifida arose as a cross between diploid ploidy and reticulate relationships in several H. palmata L. (2n = 30 II; Ranker, unpubl. data; genera of ferns, including Asplenium (Gastony Smith and Mickel 1977; Walker 1966, 1985) and 1986; Werth et al. 1985a, 1985b), Cystopteris an undiscovered diploid form of H. pinnatifida. (Haufler 1985b), Polypodium (Bryan and Soltis Evidence for this was based on meiotic pairing 1987), and Polystichum (Soltis et al. 1987). These behavior in a naturally occurring triploid hy- studies have shown that diploid taxa often have brid (H. palmata x pinnatifida), which was re- unique alleles that distinguish them from con- ported as 2n = 30 II + 30 I, with putatively generic relatives. The combination of marker homologous chromosomes from the H. palmata alleles in hybrid-derived species provides strong genome forming bivalents (Smith and Mickel evidence for ascertaining the parentage of such 1977). Subsequent observations of leaf and rhi- taxa. In allopolyploids, diploid genomic marker zome macromorphology, SEM analyses of leaf alleles typically are combined to produce het- trichomes (Ranker 1987, unpubl. data), and SEM erozygous isozymic patterns. These usually ap- analyses of spore wall morphology and ontog- 439 440 SYSTEMATIC BOTANY [Volume 14 TABLE 1. Approximate locations of populations eny (Ranker 1989) supported the hypothesis that sampled. Vouchers of all collections deposited in H. palmata is one of the parents of the tetraploid. KANU and UC. Population abbreviations are in quo- Those data also suggested that the other rec- tation marks. ognized diploid species of Hemionitis [H. levyi Fourn., H. rufa (L.) Sw., and H. tomentosa (Lam.) Hemionitis pinnatifida: Raddi] are not progenitors of H. pinnatifida. MEXICO. Est. Oaxaca: "SG," Hwy 131 ca. 53 km N This study employs genetic evidence from of Hwy 200 at Pto. Escondido, 26 Dec 1983, Ranker enzyme electrophoresis and restriction et al. 728; "ZAN," Hwy 190, between km posts site 78 and 79, E of Santo Domingo Zanatepec, just analyses of chloroplast DNA (cpDNA) to de- W of Gral. Pascual Fuentes, 15 Jul 1985, Ranker termine the role of H. palmata in contributing & Yatskievych809; "TAP," Hwy 190, between km to the origin of the tetraploid, H. pinnatifida. In posts 7 and 8 at bridge E of junction with Hwy addition, we explore the genetic affinities of a 200, 15 Jul 1985, Ranker & Yatskievych 812. missing diploid ancestor by subtracting the iso- Hemionitis palmata: zymic profile of H. palmata from that of the tetraploid and, thus, reconstruct a MEXICO. Est. Oaxaca: "PASG," Hwy 131 ca. 53 km portion of the N of Hwy 200 at Pto. Escondido, 26 Dec 1983, missing genome for use in genetic identity anal- Ranker et al. 727. yses. JAMAICA. Portland Parish: "J845," Rd Bi, 7 km S MATERIALS AND METHODS of Buff Bay, 23 Nov 1985, Ranker& Trapp845. St. Andrew Parish: "J849," 0.3 km S of Gordon Town Enzyme Electrophoresis. Natural popula- on rd to Guava Ridge, 25 Nov 1985, Ranker & tions of Hemionitis pinnatifida, H. palmata, H. le- Trapp849; "J852," ca. 0.4 km upstream from Gor- vyi, and H. rufa were analyzed electrophoreti- don Town on banks of Hope River, 27 Nov 1985, cally [table 1; because the latter two species are Ranker & Trapp 852; "J853," Junction of rd from not likely candidates for parents of the Gordon Town with Yallahs River, 17 Nov 1985, tetra- Ranker & Trapp 853. Clarendon Parish: "J861," ploid, electrophoretic results will not be pre- ca. 2.7 km from Crofts Hill towards Arthur's Seat, sented in detail, but will only be summarized 30 Nov 1985, Ranker & Trapp 861; "J862," ca. 1.2 in the form of genetic identity analyses (Ranker km from Crofts Hill towards Arthur's Seat, 30 1987)]. All populations were surveyed for elec- Nov 1985, Ranker & Trapp 862. trophoretically detectable enzyme variation us- COSTA RICA. Prov. San Jose: "CRRG,"Banks of Rio ing 12.4% to 12.8% starch gels. The extraction General near bridge of Interamerican Hwy (C.R. procedures were as described in Ranker and Hwy #2), 5 Dec 1984, Ranker 778. Prov. Here- Werth (1986). Both sporophytes and laboratory- Arboretum of Finca la dia: "CRLS," Selva, OTS cultured gametophytes were employed in the field station near Pto. Viejo, 11 Dec 1984, Ranker analyses. Enzymes were surveyed using gel and et al. 793c. electrode buffer systems 6, 8, and 11 (Soltis et Hemionitis levyi ("Hele" indicates the summation of al. 1983). System 8 was modified as described both populations): in Haufler (1985a); for system 11, the gel buffer COSTA RICA. Prov. Alajuela: Service road to Planta was prepared at 0.009 M and 0.011 M histidine- de 3 Dec Ranker Hidroelectrica Ntro. Amo, 1984, HCI. The morpholine-citrate buffer system (here & Gomez-P. 777. abbreviated MC) of Odrzykoski and Gottlieb MEXICO. Est. Oaxaca: Hwy 190, between km posts 7 and 8 at bridge E of junction with Hwy 200, 15 (1984) also was employed but at pH 7.5 and pH Jul 1985, Ranker & Yatskievych 813. 8.0 [pH adjusted by titrating with N-(3-amino- propyl)-morpholine]. Two or three different sets Hemionitis rufa ("Heru" indicates the summation of all of electrophoretic conditions were employed for populations): most enzymes to increase the probability of cor- COSTA RICA. Prov. San Jose: Banks of Rio General rectly assessing the identity of alleles at a locus near bridge of Interamerican Hwy (C.R. Hwy #2), 5 Dec 1984, Ranker 779. among species. The following nine enzymes JAMAICA. St. Andrew Parish: Along Hope River, were assayed using staining procedures de- W of Gordon Town near Blue Mtn. Inn, 26 Nov scribed by Werth (1985), except where noted 1985, Ranker & Trapp 850. Clarendon Parish: (enzyme abbreviation and buffer systems in pa- Near Arthur's Seat ca.