Nuclear Ribosomal DNA Evidence for a Western North American Origin of Hawaiian and South American Species of Sanicula (Apiaceae)
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Proc. Natl. Acad. Sci. USA Vol. 95, pp. 235–240, January 1998 Evolution Nuclear ribosomal DNA evidence for a western North American origin of Hawaiian and South American species of Sanicula (Apiaceae) PABLO VARGAS†,BRUCE G. BALDWIN‡, AND LINCOLN CONSTANCE Jepson Herbarium and Department of Integrative Biology, University of California, Berkeley, CA 94720-2465 Communicated by Peter H. Raven, Missouri Botanical Garden, St. Louis, MO, November 7, 1997 (received for review July 17, 1997) ABSTRACT Results from phylogenetic analysis of nu- Raillardiopsis) ancestry of the Hawaiian silversword alliance clear rDNA internal transcribed spacer (ITS) sequences from (Argyroxiphium, Dubautia, Wilkesia) provides one unequivocal a worldwide sample of Sanicula indicate that Hawaiian example of such dispersal in the sunflower family (4–6). In this sanicles (Sanicula sect. Sandwicenses) constitute a monophy- paper, we provide phylogenetic evidence from nuclear ribo- letic group that descended from a western North American somal DNA internal transcribed spacer (ITS) sequences for ancestor in Sanicula sect. Sanicoria, a paraphyletic assemblage another example of angiosperm dispersal from the Pacific of mostly Californian species. A monophyletic group compris- coast of temperate western North America to the Hawaiian ing representatives of all 15 species of S. sect. Sanicoria and the Islands involving Sanicula (Apiaceae). In addition, we show three sampled species of S. sect. Sandwicenses was resolved in evidence for two amphitropical dispersals of sanicles from all maximally parsimonious trees, rooted with sequences from temperate western North America to southern South America. species of Astrantia and Eryngium. All sequences sampled from eastern North American, European, and Asian species of MATERIALS AND METHODS Sanicula fell outside the ITS clade comprising S. sect. Sani- coria and S. sect. Sandwicenses. A lineage comprising the We examined DNAs from one to six populations of 23 species Hawaiian taxa and three species endemic to coastal or near- representing all 15 taxa in the western American Sanicula sect. coastal habitats in western North America (Sanicula arcto- Sanicoria, three of four species in the Hawaiian Sanicula sect. poides, Sanicula arguta, and Sanicula laciniata) is diagnosed by Sandwicenses (Sanicula kauaiensis may be extinct), two of six nucleotide substitutions and a 24-bp deletion in ITS2. The species from the Asian Sanicula sect. Pseudopetagnia, and hooked fruits in Sanicula lead us to conclude that the ancestor three of 13 species from the cosmopolitan Sanicula sect. of Hawaiian sanicles arrived from North America by external Sanicla (for taxonomy of Sanicula see refs. 7–10). The only bird dispersal; similar transport has been hypothesized for the section not examined was the Asian Sanicula sect. Tubercula- North American tarweed ancestor of the Hawaiian silversword tae, comprising three species (unavailable to us) regarded by alliance (Asteraceae). Two additional long-distance dispersal Shan and Constance (7) as having ‘‘diverged least from the events involving members of S. sect. Sanicoria can be con- assumed progenitors...ofthegenus.’’ Sampling encompassed cluded from the ITS phylogeny: dispersal of Sanicula crassi- the main continental distribution of the genus (Asia, Europe, caulis and Sanicula graveolens from western North America to North America, and South America) and included a Malaysian southern South America. sample of the only species known from Africa. Populations were sampled widely across the distribution of species repre- The volcanic history, extreme geographic isolation, and dis- sented by multiple DNAs (Table 1). Three species outside harmonic biota of the Hawaiian archipelago demonstrate that Sanicula in subfamily Saniculoideae (Astrantia major, Eryn- terrestrial life in the islands must have arrived by long-distance gium cervantesii, and Eryngium mexicanum) were chosen as dispersal (1). Among plants, the approximately 966 species of outgroups based on morphological and molecular evidence of indigenous Hawaiian angiosperms (89% endemic) have been close relationship to the ingroup (see ref. 11). estimated to stem from 272 to 282 natural introductions to the Total DNAs were extracted from pooled fresh leaf tissue of islands (2). On the basis of comparative floristics, Fosberg (3) 5–10 individuals per population or from dried leaf fragments hypothesized that most natural introductions of Hawaiian of herbarium specimens by using a modification of the hexa- flowering plants were from southeast Asian source areas. decyltrimethylammonium bromide (CTAB) method in Doyle and Doyle (12), with two ethanol precipitations. The 18S–26S Directionality of prevailing air currents, occurrence of inter- nuclear rDNA ITS region (ITS1, 5.8S subunit, and ITS2) was mediary ‘‘stepping-stone’’ islands, and climatic similarities PCR-amplified by using c28kj (59-TTGGACGGAATTTAC- between the Hawaiian archipelago and tropical areas to the CGCCCG-39, designed by K. W. Cullings, San Francisco State west and southwest of the islands accord with Fosberg’s University) and LEU1 (59-GTCCACTGAACCTTATCATT- estimate. TAG-39, designed by L. E. Urbatsch, Louisiana State Univer- A minority (about 18%) of ancestral Hawaiian plant colo- sity) for most samples. The internal primers ITS2, ITS3, ITS4, nists are thought to have dispersed from the Americas (3), and ITS5 (13) were used for sequencing reactions and for PCR despite unfavorable prevailing winds and water currents. Plant dispersal across the unbroken 3,900-km oceanic barrier be- tween temperate western North America and the Hawaiian Abbreviations: ITS, internal transcribed spacer of 18S–26S nuclear Islands appears to have been exceedingly rare. Molecular ribosomal DNA; Ma, million years ago. y Data deposition: The sequences reported in this paper have been phylogenetic evidence of a California tarweed (Madia deposited in the GenBank database (accession nos. AF031960– AF032016). † The publication costs of this article were defrayed in part by page charge Permanent address: Real Jardı´n Bota´nico, Plaza de Murillo, 2, 28014-Madrid, Spain. payment. This article must therefore be hereby marked ‘‘advertisement’’ in ‡To whom reprint requests should be addressed at: Jepson Herbarium accordance with 18 U.S.C. §1734 solely to indicate this fact. and Dept. of Integrative Biology, 1001 Valley Life Sciences Building, © 1998 by The National Academy of Sciences 0027-8424y98y95235-6$2.00y0 no. 2465, University of California, Berkeley, CA 94720-2465. e-mail: PNAS is available online at http:yywww.pnas.org. [email protected]. 235 Downloaded by guest on September 25, 2021 236 Evolution: Vargas et al. Proc. Natl. Acad. Sci. USA 95 (1998) Table 1. Matrix of informative nucleotide sites and insertionsydeletions (indels) from the nuclear rDNA ITS region in Sanicula and outgroups 1111111111111111111111111111 1123344555555566666777788899990011122222233333456667778888 57824727123578912579567804734893726901235901459353464781346 1 TAGGCCCCCGACATCGGGCCCCACACGGCTCGGACTCAACGGACCTCGCATGCAATCTG 2 TAGGCCACCGACGTCGGGCCCCACCTGGCTCGGCCTCAACGGCACTCGCATGCAATTTG 3 TTAGCCACGGACATTGGTCCCCCAGAGGCGCGGCTTCRATTACCACCGCATGTCACTGC 4 TTAGACACCGACGTCGGGCCCCGTTTGATCGGGCTCCGCTACAATTTATATGCCATCCT 5 TTAGACACCGACGTCGGGCTCCGTT-GACCGGGTTCCGCTACAATTTGTATGCTATCCT 6 TTAGACACCGACGTCGGGCCCTGTTCGACCGGGCTCCGCTACAACTTGTATGCCATCCT 7 TTAGATACCGACGTCGGGCCCCATTCGATCAGGCTCCGCTACAATTTGTATGCCATCCT 8 TTAGACACCGATGTCGTGCCCCGTTCGACCGGGCTCCGCTACAATTTGTATGCTATCCT 9 ATAGAAATCGACGTCGGGTTCCGTGCGATCGGGATCCGCTACAATTTATATGCCATCCT 10 ATAGAAATCGACGTCGGGTTCCGTGCGATCGGGATCCGCTACAATTTATATGCCATCCT 11 ATAGAAATCGACGTCGGGTTCCGTGCAATCGGGATCCGCTACAATTTATATGCCATCCT 12 TTAGAAATCAACGTCTGGTCCTGTTCAACCGGGCTCCGCTACAATTTATATGCCATCCT 13 TTAGAGGCCGACGTCGGGTCCCGTTCAACCGGA--CCGCTACAATTTATATGCCATCCT 14 TAAGAA-CCGACGCAGTGTCTCGTTCGACCGGGCTCTTCTACAATTTGTTTTCCATTCT 15 TTAGAAATCGACGTCGGGTCCCGTTCGACCGGGCTCCGCTACAATTTATATGCCATCCT 16 TTAAAATCCGACGTCGGGTCCTGTTCGACCGGCCTCCGCTACAATTTATACGCCACCCT 17 TTAAAATCCGACGTCGGGTCCTGTTCGACCGGCCTCCGCTACAATTTATACGCCACCCT 18 TTAAAATCCGACGTCGGGTCCTGTTCGACCGGCCTCCGCTACAATTTATACGCCACCCT 19 TTAAAATCCGACGTCGGGTCCTGTTCGACCGGCCTCCGCTACAATTTATACGCCACCCT 20 TAAGAGATCGACGTAGTGTCCCGTTCGACCGAGCTCTGCTACAATTCGTTTTTCATT-T 21 TTAGAGACGCCCGTCGTGTCCTGTTCGATCGGTTTCCGCTACAACATGTTTGCTGTACT 22 TTAGAGACGCCCGTCGTGTCCTGTTCGACCGGTTTCCGCTACAACATGTTTGCTGTACT 23 TTAGAGACGCCCGTCATGTCCTGTTTGATCGGTCTCCGCTACAACATGTTTGCTGTACT 24 TAAGAAACCAACGTAGTTTCCCGTTCGACCGGGCTCTGCTACCATTTGTTTTCCATTCT 25 TTAGAGGCCGACGTCGGGTCCYGTACGACCGGGCTCCGCTACAATTTATATGCCATCCT 26 TAAGAA-CCGACGCAGTGTCTCGTTCGACCGGGCTCTTCTACAATTTGTTTTCCATTCT 27 TTAGAGACGCCTGTCATGTCCTGTTCGACCGGTCTCCGCTACAACATGTTTGCTGTACT 28 TTAGAGACGCCCGTCATGTCCTGTTCGACCGGTCTCCGCTACAACATGTTTGTTGTACT 29 TTAGAGACGCCCGTCATGTCCTGTTTGACCGGTCTCCGCT-CAACATGTTTGCTGTACT 30 TAAGAAACCGACATAGTGTCCCGTTCGACCGAACTCTGCTACAATTCGTTTTTCATTCT 31 TAAGAAACCGAMGTAGTGTCCYGTTCGACCGGGCTCTTCTACAATTTGTTTTTCATTCT 22223333333444444444444444444444444444444444444444455555555 00024689999000111111222222233333345566666677788889900134555 25609283789479146789012567801236950303678902306788949265237 1 TCGGGGGGCGC-CCCACTCCTGGTGGTCGTCACGAGGCCGCAGGCCCGCACGTCGGCGC 2 TCGGGGGGCGCCCCCACTCCTTGTGCTCGTCATGAGGCCGCGGGCCCGCACGTCGGCGC 3 CTGGGCGGCGCAACTTTCCACTTGGCTTGCGCGGTGGATGCATGCCAGCACGTCGAC-- 4 TCGGGGGGCGC-ACTATCCTTCCGACTCGCATTGAGGTTGTGGATCAACGTTTTGGCGC 5 CTGGGGGGCGC-ACCATCCTTGCGATTCGCATGGAGGCTGTGGATCAACGTTTCGGCGC 6 CCGGGGGGCGC-ACCATCCTCAGGACTCGCATGGAGGCTGTGGATCAACGTTTCGACGC 7 CCAGAGGGCGC-ACCTTCCTTACGATTCGCATGGAGGCTGTGGATCAACGTTTCGGTGT