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Molecular Systematics of Saxifragaceae Sensu Stricto
Abstract
To circumscribe Saxifragaceae sensu stricto better, as well as to elucidate generic relationships within this group, we sequenced the chloroplast gene rbcL and its 3' flanking region (yielding 1,471 bp) from 19 genera considered to represent core members of Saxifragaceae. In addition, we conducted a restriction site analysis of chloroplast DNA (cpDNA) for 21 core genera using 23 restriction endonucleases. Phylogenetic analyses using both data sets corroborate the results obtained from surveying the distribution of the loss of the intron in the chloroplast gene rp12 in delimiting a well-defined Saxifragaceae sensu stricto. Within the Saxifragaceae s.s. clade, a number of poorly resolved, basal phylogenetic branches supports the hypothesis that Saxifragaceae s.s. radiated rapidly very early in its evolutionary history. Molecular data also indicate the presence of several strongly supported groups of genera, such as the Boykinia group (Boykinia, Suksdorfia, Bolandra, Sullivantia, Jepsonia, and Telesonix), the Heuchera group (Heuchera, Bensoniella, Conimitella, Elmera, Lithophragma, Mitella, Tellima, Tiarella, and Tolmiea) the Leptarrhena/Tanakaea group, and the Darmera group (Darmera, Astilboides, Mukdenia, Bergenia, and Rodgersia). Significantly, molecular data suggest that the very large, taxonomically complex genus Saxifraga may not be monophyletic. DNA data have also helped to resolve the generic relationships of problematic taxa, indicating, for example, that Telesonix and the enigmatic Jepsonia are sister taxa. In addition to its phylogenetic implications, this study provides insight into basic trends in morphological, chemical, and cytological evolution within Saxifragaceae s.s. The molecular-based phylogenies suggest multiple origins and/or losses of several classes of flavonoid compounds, as well as several independent instances of reduction in stamen and petal number, hypanthium-ovary fusion, and aneuploidy. This study also illustrates the ability of rbcL sequence data to resolve generic-level relationships in some taxonomic groups.
... The enormous phylogenetic utility of rbcL sequences has been emphasized and reviewed previously (e.g., Clegg, 1993; Palmer et aI., 1988a; Chase, Soltis, Olmstead et al., 1993; see Chapter 17). At the family level and above, rbcL has, by far, been the preferred gene for inferring phylogeny . ...
... The lower limit of applicability of rbcL sequences typically extends to the generic level, but in some groups reaches the specific levei. Analyses of rbcL sequences have been used to resolve generic relationships within several families of flowering plants (e.g., Morgan et ai., 1994; Xiang et ai., 1993; Conti et ai., 1993; Soltis et ai., 1993; Kim and Jansen, 1996). In a few cases, rbcL sequence analyses have even clarified relationships among congeneric species: in Comus (Xiang et ai., 1993), Saxifraga (Soltis et ai., 1996), and Drosera (Williams et ai., 1994). ...
... This is easily achieved in angiosperms given that the most widely used 3' amplification primer (3' rbcL) is actually located roughly 80 bp downstream of the terminus of rbcL. This region between the terminus of rbcL and the 3' amplification primer has a general rate of base substitution comparable to that of rbcL and can provide additional parsimony-informative sites (e.g., Xiang et ai., 1993; Morgan et ai., 1994; Soltis et ai., 1993, 1996). atpB atpB encodes the 13 subunit of ATP synthase , an enzyme that couples proton translocation across membranes with the synthesis of ATP (Zurawski et ai., 1982; Gatenby et ai., 1989; reviewed in Hoot et ai., 1995a). ...
A diverse array of molecular approaches is now available to the plant systematist for use in phylogenetic inference, including restriction site analysis, comparative sequencing, analysis of DNA rearrangements (e.g., inversions) and gene and intron loss, and various PCR-based techniques. Although these various methodologies present systematists with unparalleled opportunities for elucidating relationships and evolutionary processes, the sheer number of molecular approaches available, as well as the number of proven DNA regions for use in comparative sequencing, may seem overwhelming to those new to the field of molecular systematics. This chapter provides a general review of the various molecular techniques currently available to the plant systematist. Our primary goal is to review the types of molecular data sets that can presently be obtained; we discuss the advantages and disadvantages of each and the most appropriate approach for studying a given taxonomic level or type of evolutionary question. Given the current emphasis on DNA sequence data for phylogeny estimation, we then concentrate on the choice of an appropriate gene for comparative sequencing and also briefly discuss the pros and cons of manual versus automated sequencing. A description of selected PCR- mediated techniques for systematic and population-level studies is presented in Chapter 2.
... Boykinia has B. aconitifolia Nutt. in eastern North America, B. lycoctonifolia (Maxim.) Engl. in eastern Asia, and at least five species in western North America (Gornall & Bohm, 1985;Soltis et al., 1993): B. intermedia (Piper) G.N. Jones, B. major A. Gray, B. occidentalis Torrey & Gray, B. rotundifolia Parry, and B. richardsonii (Hook.) ...
... Within the North American clade, the ITS tree placed B. rotundifolia from western North America sister to a clade containing B. aconitifolia from eastern North America and the remaining western North American species, whereas the cpDNA tree shows a trichotomy among B. aconitifolia, B. rotundifolia, and the clade of the remaining species. Phylogenetic analyses of the Boykinia group as well as of Saxifragaceae s. s. (Soltis et al., 1993(Soltis et al., , 1995(Soltis et al., , 1996 indicate that Boykinia is sister to Bolandra A. Gray and Suksdorfia A. Gray, both from western North America. The center of origin for Boykinia is most likely western North America. ...
This review shows a close biogeographic connection between eastern Asia and western North America from the late Cretaceous to the late Neogene in major lineages of vascular plants (flowering plants, gymnosperms, ferns and lycophytes). Of the eastern Asian–North American disjuncts, conifers exhibit a high proportion of disjuncts between eastern Asia and western North America. Several lineages of ferns also show a recent disjunct pattern in the two areas. In flowering plants, the pattern is commonly shown in temperate elements between northeastern Asia and northwestern North America, as well as elements of the relict boreotropical and Neogene mesophytic and coniferous floras. The many cases of intercontinental biogeographic disjunctions between eastern Asia and western North America in plants supported by recent phylogenetic analyses highlight the importance of the Bering land bridge and/or the plant migrations across the Beringian region from the late Cretaceous to the late Neogene, especially during the Miocene. The Beringian region has permitted the filtering and migration of certain plant taxa since the Pliocene after the opening of the Bering Strait, as many conspecific taxa or closely related species occur on both sides of Beringia.
... Franch. Garden Lithophragma affine A. [U51265] Soltis & Kuzoff (1995) Gray TE buffer (Morgan and Soltis 1993). Direct sequencing of these purified, single-stranded PCR products was conducted using Sequenase version 2.0 (U. S. Biochemical Corp., Cleveland, OH) and 35S dATP. ...
... The double-stranded PCR product was purified by precipitation using 20% PEG/2.5M NaCl solution, followed by washes in 80% and 95% ethanol and resuspension in distilled H20 (Dunn and Blattner 1987; Morgan and Soltis 1993). Purified double-stranded DNA's were then used in cycle sequencing reactions; the PRISM Ready Reaction Dye Deoxy Terminator Cycle Sequencing Kit (Applied Biosystems, Inc.) was employed. ...
To assess whether discord exists between nuclear- and chloroplast-based phylogenetic trees within the Boykinia group (Saxifragaceae), we compared topologies obtained from analyses of ITS sequences with those acquired earlier via analyses of cpDNA restriction sites and matK sequences. We found manual alignment of sequences in the Boykinia group to be extremely difficult; we therefore explored different alignment strategies using CLUSTAL W and assessed the impact of different gap-open and gap-extension weights. To accomodate the multiple alignments possible with our ITS data set, we also employed the "elision" approach. Both cpDNA and matK sequences provide essentially identical topologies for the Boykinia group and differ from the ITS trees only in the placement of Suksdorfia ranunculifolia. The chloroplast trees place S. ranunculifolia as sister to Boykinia; in the ITS trees, S. ranunculifolia appears in a clade with S. violacea and Bolandra, a placement in agreement with morphology. The chloroplast-based and nuclear-based positions for S. ranunculifolia are each strongly supported, having high bootstrap values. This discordance could be the result of ancient hybridization and chloroplast capture between S. ranunculifolia and a species of Boykinia, resulting in chloroplast-based topologies that do not accurately reflect organismal relationships.
... In addition, two species of Chrysosple- 83 nium (C. valdivicum, C. macranthum) occur in Tierra del Fuego 84 (Hara, 1957), and several species of Saxifraga are also found in 85 the Andes (Webb and Gornall, 1989).DeChaine et al., 2013; Johnson and Soltis, 1995; Johnson et al., 108 1994; Kuzoff et al., 1999; Morgan and Soltis, 1993; Prieto et al., 109 2013; Soltis and Soltis, 1997; Soltis et al., 1993; Soltis et al., 110 2001a; Soltis et al., 2001b; Soltis et al., 1996; Vargas, 2000; Xiang 111 et al., 2012; Zhu et al., 2013) Brochmann et al., 1998; 116 Godsoe et al., 2013; Ness et al., 1989; Segraves and Thompson, 117 1999; Soltis and Doyle, 1987; Soltis and 118 Rieseberg, 1986; Soltis and Soltis, 1989; Soltis and Soltis, 1999; 119 Soltis and Soltis, 1988; Soltis and Soltis, 1989; Soltis et al., 1993; 120 Soltis et al., 1992; Soltis et al., 1991; Soltis et al., 1990; Soltis 121 et al., 1989a; Soltis, 1984; Wolf et al., 1990), 122 biogeography/phylogeography (Oliver et al., 2006; Reisch, 2008; 123 Szövényi et al., 2009; Westergaard et al., 2010), and evolution 124 and diversification (Holten et al., 2006; Kuzoff et al., 2001; Kuzoff 125 et al., 1999; Okuyama et al., 2005; Soltis et al., 2001a; Steen 126 et al., 2000; Vargas et al., 1999; Winkler et al., 2012) Increasing amounts of sequence data and wider taxon sampling 147 have yielded better resolution, support, and evolutionary insights 148 throughout the tree of life (Heath et al., 2008; Moore et al., 2007; 149 Parfrey et al., 2010; Soltis et al., 2011), Ribes (Grossulariaceae), and Liquidambar (Altingiaceae) 178 were selected as outgroups based on previous studies (Fishbein 179 et al., 2001; Jian et al., 2008; Soltis et al., 2013; Soltis et al., 2001a). ...
... In addition, two species of Chrysosple- 83 nium (C. valdivicum, C. macranthum) occur in Tierra del Fuego 84 (Hara, 1957), and several species of Saxifraga are also found in 85 the Andes (Webb and Gornall, 1989).DeChaine et al., 2013; Johnson and Soltis, 1995; Johnson et al., 108 1994; Kuzoff et al., 1999; Morgan and Soltis, 1993; Prieto et al., 109 2013; Soltis and Soltis, 1997; Soltis et al., 1993; Soltis et al., 110 2001a; Soltis et al., 2001b; Soltis et al., 1996; Vargas, 2000; Xiang 111 et al., 2012; Zhu et al., 2013) Brochmann et al., 1998; 116 Godsoe et al., 2013; Ness et al., 1989; Segraves and Thompson, 117 1999; Soltis and Doyle, 1987; Soltis and 118 Rieseberg, 1986; Soltis and Soltis, 1989; Soltis and Soltis, 1999; 119 Soltis and Soltis, 1988; Soltis and Soltis, 1989; Soltis et al., 1993; 120 Soltis et al., 1992; Soltis et al., 1991; Soltis et al., 1990; Soltis 121 et al., 1989a; Soltis, 1984; Wolf et al., 1990), 122 biogeography/phylogeography (Oliver et al., 2006; Reisch, 2008; 123 Szövényi et al., 2009; Westergaard et al., 2010), and evolution 124 and diversification (Holten et al., 2006; Kuzoff et al., 2001; Kuzoff 125 et al., 1999; Okuyama et al., 2005; Soltis et al., 2001a; Steen 126 et al., 2000; Vargas et al., 1999; Winkler et al., 2012) Increasing amounts of sequence data and wider taxon sampling 147 have yielded better resolution, support, and evolutionary insights 148 throughout the tree of life (Heath et al., 2008; Moore et al., 2007; 149 Parfrey et al., 2010; Soltis et al., 2011), Ribes (Grossulariaceae), and Liquidambar (Altingiaceae) 178 were selected as outgroups based on previous studies (Fishbein 179 et al., 2001; Jian et al., 2008; Soltis et al., 2013; Soltis et al., 2001a). ...
... Don) Engl. Saxifraga L. is the largest genus in the family Saxifragaceae (Soltis et al. 2001) and consists of about 400 species (Webb 1993;Soltis et al. 1993Soltis et al. , 1996Healy and Gillespie 2004). Engler (1930) reported that Saxifragaceae are morphologically diverse assemblage of annual, biennial and perennial herbs, shrubs, trees and vines. ...
... It comprises 17 subfamilies (Schulze-Menz 1964). In recent attempts to clarify the circumscription and relationships of the morphologically diverse members of Saxifragaceae using molecular systematic tools (18S rDNA and rbcL), Soltis and Soltis (1997) and Soltis et al. (1993Soltis et al. ( , 2001 concluded that Saxifragaceae is a polyphyletic family of the Saxifragales clade, that encompasses the subfamilies of Rosidae, Dilleniidae and Hamamelidae. Soltis and Soltis (1997) suggested that many of the families (Cunoniaceae, Droseraceae, Cephalotaceae, Gunneraceae, Rosaceae and Greyiaceae) traditionally considered close relatives of Saxifragaceae are only distantly related to this narrowly defined family. ...
Two varieties of Saxifraga diversifolia, diversifolia and parnassifolia, collected from the moist alpine slopes around Gauri Kund, 3930 m (Manimahesh Hills, Himachal Pradesh, India), are studied for detailed male meiosis, chiasma frequency and pollen fertility. Both varieties exist at diploid level (based on x = 8), and show a meiotic chromosome count of n = 8 at diakinesis and metaphase-I, and regular chromosome distributions at anaphases-I/II. The meiotic chromosome count of n = 8 ascertained here represents a new aneuploid cytotype, supplementing the earlier report of a diploid cytotype with 2n = 20 from the north-west Himalayas in India and the Nepal Himalayas. Of the two varieties, var. diversifolia showed the presence of multiple chromosomal associations and univalent chromosomes at diakinesis and metaphase-I of meiosis-I. On the other hand, var. parnassifolia does not have multivalent formation but showed only 2–4 univalent chromosomes at diakinesis and metaphase-I. Occurrence of univalents in pollen mother cells of var. diversifolia and parnassifolia reduced the chiasma frequency significantly and also caused some pollen sterility (7–8%). The paper herein discusses for the first time the occurrence of structural heterozygosity and univalent chromosomes and their apparent affect on chiasma frequency and pollen fertility in S. diversifolia.
... Molecular phylogenies in plants are traditionally based on chloroplast DNA (cpDNA) sequence variation (Despres et al., 2003). The low evolutionary rate of these sequences limits the power of cpDNA for the assignment at the genus or species level (Soltis 1993). When both cpDNA and ITS sequencing fail to resolve phylogenies, the AFLP approach has the potential to solve such difficulties, particularly among closely related species, or at the intra-specific level (Koopman et al., 2001). ...
... Willdenowia 46 -2016 Saxifragaceae (J. W. Kadereit) The non-monophyly of Saxifraga L., first shown by Soltis & al. (1993), has been confirmed in several studies (for discussion see Fernández Prieto & al. 2013;Tkach & al. 2015). In particular, a group of 70 -90 species from North America and Eurasia is only very distantly related to the remainder of Saxifraga and has to be treated as the genus Micranthes Haw. ...
The use of DNA sequence data in plant systematics has brought us closer than ever to formulating well-founded hypotheses about phylogenetic relationships, and phylogenetic research keeps on revealing that plant genera as traditionally circumscribed often are not monophyletic. Here, we assess the monophyly of genera documented in Rothmaler's "Exkursionsflora von Deutschland" (Gefäßpflanzen: Grundband, 19th Ed.; Jäger 2005). Using a survey of the phylogenetic literature, we discuss which classifications would be consistent with the phylogenetic relationships found and could be followed, provided monophyly is accepted as the primary criterion for circumscribing taxa. We indicate whether and which names are available when changes in generic assignment are made (but do not present a comprehensive review of the nomenclatural aspects of such names).
Among the 840 genera examined, we identified c. 140 where data quality is sufficiently high to conclude that they are not monophyletic, and an additional c. 20 where monophyly is questionable but where data quality is not yet sufficient to reach convincing conclusions. While it is still fiercely debated how a phylogenetic tree should be translated into a classification, our results could serve as a guide to the likely consequences of systematic research for the taxonomy of the German flora and the floras of neighbouring countries.
... When molecular sequences were not available for the species surveyed for morphology, sequences from close relatives were used instead (names and GenBank accession numbers provided). Numbers in parenthesis indicate the references for molecular data: (1) Zurawski et al. (1986), (2) Albert et al. (1992), (3) Fernando et al. (1993), (4) Soltis et al. (1993), (5) Morgan et al. (1994), (6) Ka¨ss and Wink (1996), (7) Sheahan and Chase (1996), (8) Doyle et al. (1997), (9) Swensen et al. (1998), (10) Thulin et al. (1998), (11) Savolainen et al. (2000), (12) Yokoyama et al. (2000), (13) Kajita et al. (2001), (14) Kita and Kato (2001), (15) Lia et al. (2001), (16) Kamiya et al. (2002), (17) fig. 1) for Atroxima and Carpolobia; Rudall and Bateman (2002) for orchids]. The opposite disposition of the flowers of Polygalaceae and Leguminosae fig. 1) is not the result of resupination as coded here, but by an opposite arrangement of the floral organs 4. Hypanthium (0) absent; (1) present. ...
Relationships between the four families placed in the angiosperm order Fabales (Leguminosae, Polygalaceae, Quillajaceae, Surianaceae) were hitherto poorly resolved. We combine published molecular data for the chloroplast regions matK and rbcL with 66 morphological characters surveyed for 73 ingroup and two outgroup species, and use Parsimony and Bayesian approaches to explore matrices with different missing data. All combined analyses using Parsimony recovered the topology Polygalaceae (Leguminosae (Quillajaceae + Surianaceae)). Bayesian analyses with matched morphological and molecular sampling recover the same topology, but analyses based on other data recover a different Bayesian topology: ((Polygalaceae + Leguminosae) (Quillajaceae + Surianaceae)). We explore the evolution of floral characters in the context of the more consistent topology: Polygalaceae (Leguminosae (Quillajaceae + Surianaceae)). This reveals synapomorphies for (Leguminosae (Quillajaceae + Surianaceae)) as the presence of free filaments and marginal/ventral placentation, for (Quillajaceae + Surianaceae) as pentamery and apocarpy, and for Leguminosae the presence of an abaxial median sepal and unicarpellate gynoecium. An octamerous androecium is synapomorphic for Polygalaceae. The development of papilionate flowers, and the evolutionary context in which these phenotypes appeared in Leguminosae and Polygalaceae, shows that the morphologies are convergent rather than synapomorphic within Fabales.
... A total of 37 morphological characters were scored (Table 1). Because the genus Saxifraga L. is thought to be polyphyletic based on prior molecular analyses ( Soltis et al., 1993Soltis et al., , 1996Soltis et al., , 2001), S. integrifolia W.J. Hooker and S. mertensiana Bongard were coded as for the species. Other extant taxa were coded as for the genus (Table 2). ...
Fossilized flowers and fruits from the Upper Cretaceous (Turonian, ca. 90 million years [my] before present) Raritan Formation of New Jersey are described as the new genus Divisestylus with two species, D. brevistamineus and D. longistamineus. The fossils are fusainized and three-dimensionally preserved. Morphological characteristics suggest affinities with extant Saxifragaceae and Iteaceae, two closely related families in Saxifragales. Similarities include a pentamerous perianth, calyx fused below into a hypanthium with free sepal lobes above, haplostemonous androecium with stamens situated opposite the calyx lobes, inferior ovary, bicarpellate gynoecium, numerous ovules on axile placentas, conspicuous intrastaminal nectary ring, and capsulate fruit opening apically. The unique fusion of the gynoecium, with carpels and stigmas fused but styles free, indicates closer affinities with extant Iteaceae, whereas other characters, such as basifixed anthers in D. brevistamineus, tricolpate and striate pollen grains, and anomocytic stomata, indicate closer affinities to Saxifragaceae. Cladistic analyses utilizing molecular data from a previously published analysis and morphological data as well as morphological data alone demonstrate the fossils share a more recent common ancestor with Iteaceae than Saxifragaceae, thereby making Divisestylus the oldest fossils known with clear affinities to Iteaceae.
Phylogenetic analyses of rbcL sequences were used to address both systematic and evolutionary questions posed by the angiosperm family Hydrangeaceae. Our analyses suggest the presence of a monophyletic Hydrangeaceae most closely allied with Loasaceae, a finding in agreement with other molecular as well as morphological analyses. Molecular data indicate that Hydrangeaceae comprise Decumaria, Pileostegia, Schizophragma, Hydrangea, Dichroa, Broussaisia, Platycrater, Cardiandra, Deinanthe, Carpenteria, Philadelphus, Deutzia, Fendlerella, Whipplea, Fendlera, Jamesia, and the enigmatic Kirengeshoma. A particularly close relationship of Kirengeshoma and Deutzia is indicated. Analysis of rbcL sequences suggests that Fendlera and Jamesia are sister to the remainder of the family, lending support to the hypothesis that at least some Carpenterieae are basal in the family and that Hydrangeaceae may have originated in xeric habitats. If this phylogenetic placement of Jamesia and Fendlera is correct, the rbcL trees also suggest that the level of epigyny has decreased in these genera, as well as in the Fendlerella- Whipplea clade and Carpenteria when compared to the outgroup taxa, which are wholly epigynous. Furthermore, the rbcL trees support proposed evolutionary trends in wood anatomy, suggesting, for example, that upland tropical taxa have evolved longer vessel elements with more numerous bars on scalariform perforation plates. The xerophytic basal members of Hydrangeaceae, like the closely related Loasaceae, have short, narrow vessel elements with scalariform perforation plates bearing few bars. Following Jamesia and Fendlera, the remaining hydrangeoids are divided into two large subclades that closely parallel the traditional division of the family into Philadelpheae and Hydrangeae. Both rbcL sequences and morphological data suggest close relationships between: 1) Fendlerella and Whipplea; 2) Decumaria, Pileostegia, and Schizophragma; 3) Carpenteria and Philadelphus; 4) Deinanthe and Cardiandra; 5) Dichroa, Broussaisia, and Hydrangea macrophylla. Molecular and morphological data also concur in demonstrating that the large genus Hydrangea is not a monophyletic assemblage.
The angiosperm family Rosaceae poses a number of noteworthy systematic problems as well as many questions concerning morphological and chromosomal evolution. Phylogenetic analysis of rbcL gene sequences was performed to address systematic and evolutionary problems of Rosaceae. Both rbcL sequence variation and the presence of duplicated sequences near the 3' end of rbcL were useful in determining phylogenetic relationships in this family. Analyses of rbcL sequences indicate that there are groups of genera within Rosaceae comparable to the subfamilies Maloideae, Amygdaloideae, and Rosoideae, although the composition of each group differs from traditional circumscriptions. According to analysis of rbcL data, Maloideae and Amygdaloideae each include additional taxa not normally associated with them. All members of Rosoideae with x = 9 are phylogenetically well separated from the x = 8 and 7 members of the subfamily. In addition, Spiraeoideae are not monophyletic but appear to consist of several distinct evolutionary lineages. The rbcL-based phylogenies suggest that chromosome numbers are more reliable indicators of some generic alliances than the more commonly used fruit types. Sequence data are also useful in determining the alliances of several problematic genera, suggesting that the capsular and follicular-fruited genera Vauquelinia, Lindleya, and Kageneckia (usually placed in Spiraeoideae) should be included in the pome-fruited subfamily Maloideae, and that Quillaja is not a member of Rosaceae. Molecular data are consistent with several suggestions for the ancestral chromosome numbers and fruit types of Rosaceae, but do not support any one hypothesis for either. This study also suggests that the subfamily Maloideae may have descended from spiraeoid ancestors and that the pome is derived from follicular or capsular fruit types.
The two families of the order Apiales (Apiaceae and Araliaceae) represent a classic example of the difficulty in understanding evolutionary relationships between tropical-temperate family pairs. In Apiales, this problem is further compounded by phylogenetic confusion at almost every taxonomic level, including ordinal, interfamilial, and infrafamilial, due largely to difficulties in understanding trends in morphological evolution. Phylogenetic analyses of rbcL sequences were employed to resolve relationships at the ordinal and familial levels. The results of the ordinal analysis confirm the placement of Apiales in an expanded subclass Asteridae as the sister group to Pittosporaceae, and refute the traditional alliance of Apiales with Cornales and Rosidae. This study has also resolved relationships of a number of enigmatic genera, suggesting, for example, that Melanophylla, Aralidium, Griselinia, and Toricellia are close relatives of Apiales. Clarification of phylogenetic relationships has concomitantly provided insights into trends of morphological evolution, and suggests that the ancestral apialean taxon was probably bicarpellate, simple-leaved, woody, and paleotropical. Phylogenetic analysis at the family level suggests that apiaceous subfamily Hydrocotyloideae, often envisioned as an intermediate group between Apiaceae and Araliaceae, is polyphyletic, with some hydrocotyloids closely allied with Araliaceae rather than Apiaceae. With the exception of some hydrocotyloids, Apiaceae appear to be monophyletic. The relationship between Apiaceae and Araliaceae remains problematic. Although the shortest rbcL trees suggest that Apiaceae are derived from within a paraphyletic Araliaceae, this result is only weakly supported.
We examined the reproductive biology of Tolmeia menziesii and Tellima grandiflora (Saxifragaceae) and barriers to hybridization between these species. Crossing experiments and pollinator observations suggest that Tolmeia is completely self-incompatible, obligately outcrossing, and bumble bee pollinated, whereas Tellima is self-compatible, with a mixed mating system possibly facilitated by rove beetles. Hybrid crosses set seed only when Tellima was the pollen recipient. Observations of pollen-style interactions indicate that self-incompatibility in Tolmeia is late-acting and that pollen tube growth is comparable between reciprocal hybrid pollinations. Seven of 40 progeny from Tolmeia × Tellima crosses were isozymically and morphologically intermediate between Tolmeia and Tellima, and were identical to a naturally occurring hybrid. The remainder were identical to Tellima, the maternal parent in successful hybrid crosses, which we attribute to either intraspecific pollen contamination, or agamospermy. Barriers to hybridization between sympatric Tellima and Tolmeia consist of divergence in floral morphology, pollinator relationships, compatibility, and a series of postzygotic isolating mechanisms including hybrid sterility.
The large genus Saxifraga, which consists of 400 morphologically and cytologically diverse species, has long been considered taxonomically complex. Phylogenetic analysis of over 2500 bp of chloroplast sequence data derived from matK and rbcL was employed to examine relationships among sections of Saxifraga, the segregate genera Zahlbrucknera, Saxifragopsis, and Cascadia, and the relationships of these taxa to other Saxifragaceae sensu stricto. Phylogenetic trees resulting from separate analyses of the matK and rbcL sequences were highly congruent; phylogenetic analysis of a combined matK–rbcL data matrix was therefore also conducted. Our analyses indicate that Saxifraga is polyphyletic, comprising two well-differentiated clades. One clade, Saxifraga sensu stricto, is the sister to the remainder of the family and consists of Saxifraga sections Irregulares, Heterisia, Trachyphyllum, Cymbalaria, Mesogyne, Xanthizoon, Porphyrion, Ciliatae, Cotylea, Ligulatae, Saxifraga, and Gymnopera. With the exception of Gymnopera, the species-rich sections of this clade are monophyletic. Also part of this clade is the problematic Zahlbrucknera paradoxa, which is allied with members of section Saxifraga. A second major clade of Saxifraga species, Micranthes sensu lato, comprises the large section Micranthes, as well as the segregate genus Cascadia, and S. tolmiei of section Merkianae. This clade is allied with the Heuchera, Darmera, and Chrysosplenium-Peltoboykinia groups of genera. The segregate genus Saxifragopsis is only distantly related to species of Saxifraga, and is instead the sister to Astilbe. The monotypic Oresitrophe is confirmed as a member of the Darmera group of genera. These results suggest that the floral features used to define Saxifraga may simply be symplesiomorphic in these well-separated Saxifraga lineages. Furthermore, the enormous cytological diversity encompassed by Saxifraga likely represents two independent instances of extensive aneuploidy and polyploidy in Saxifragaceae.
Various factors, including taxon density, sampling error, convergence, and heterogeneity of evolutionary rates, can potentially lead to incongruence between phylogenetic trees based on different genomes. Particularly at the generic level and below, chloroplast capture resulting from hybridization may distort organismal relationships in phylogenetic analyses based on the chloroplast genome, or genes included therein. However, the extent of such discord between chloroplast DNA (cpDNA) trees and those trees based on nuclear genes has rarely been assessed. We therefore used sequences of the internal transcribed spacer regions (ITS-1 and ITS-2) of nuclear ribosomal DNA (rDNA) to reconstruct phylogenetic relationships among members of the Heuchera group of genera (Saxifragaceae). The Heuchera group presents an important model for the analysis of chloroplast capture and its impact on phylogenetic reconstruction because hybridization is well documented within genera (e.g., Heuchera), and intergeneric hybrids involving six of the nine genera have been reported. An earlier study provided a well-resolved phylogenetic hypothesis for the Heuchera group based on cpDNA restriction-site variation. However, trees based on ITS sequences are discordant with the cpDNA-based tree. Evidence from both morphology and nuclear-encoded allozymes is consistent with the ITS trees, rather than the cpDNA tree, and several points of phylogenetic discord can clearly be attributed to chloroplast capture. Comparison of the organellar and ITS trees also raises the strong likelihood that ancient events of chloroplast capture occurred between lineages during the early diversification of the Heuchera group. Thus, despite the many advantages and widespread use of cpDNA data in phylogeny reconstruction, comparison of relationships based on cpDNA and ITS sequences for the Heuchera group underscores the need for caution in the use of organellar variation for retrieving phylogeny at lower taxonomic levels, particularly in groups noted for hybridization.
Differences in habitat, geographical distribution and minor details related to floral and vegetative structures of Petunia spp. have led to many changes in the taxonomy of the genus. In the face of controversy relating to species circumscription in the genus and insufficient variation to identify the evolutionary relationships among Petunia spp. using conventional molecular phylogenetic markers, the purpose of this work was to investigate the potential and limitations of amplified fragment length polymorphism (AFLP) data analyses for delimiting species and inferring evolutionary relationships in a young group, providing the bases for future studies. We analysed 152 individuals distributed randomly across the geographical range of 14 Petunia taxa. AFLP analysis resulted in 1259 polymorphic fragments that proved to be efficient in identifying high numbers of polymorphisms in recently diverged plant species. The phylogenetic approach using AFLP allowed a high level of correct assignment of individuals to their corresponding morphological groups. The results of the genetic clustering analyses were consistent with respect to the main groups and the well-supported relationships in phylogenetic analyses. In this study, we demonstrated the efficiency of AFLP to identify polymorphisms in recently diverged lineages of Petunia. We report that this approach was also valuable in species delimitation for species status of difficult taxa and indicating new species.
By harbouring ca. 3500 native vascular plant species in an area of ca. 170 000 km², the European Alps represent a region of very high species diversity. Using the most recently published flora of the area and phylogenetic literature, I here review which proportion of the endemic flora of the Alps is the result of in situ diversification, i.e., of diversification in the area and (largely) restricted to the area. There exist only very few and mostly species-poor species diversifications in the Alps, accounting for ca. 1.2% of the native and for ca. 9% of the endemic flora of the Alps. In contrast to this, ca. 33% of the endemic species of the Alps belong to lineages widespread in the European Alpine System (EAS), comprising mainly the Pyrenees, Apennines, Carpathians, Dinarids and Balkans, in addition to the Alps. The rarity of Alpine species diversifications is hypothesised to reflect the Quaternary climatic history of the Alps where massive and repeated glaciations prevented the undisturbed evolution of species-rich lineages.
Taxonomy is a systematic classification of living organisms, whereas phylogeny is a theoretical model of the sequence of evolutionary divergence of organisms from their common ancestors. Phylogeny is derived from a combination of Greek words: phylon means stem and genesis means origin. It is the study of evolutionary relationships among organisms. Traditionally, morphology, anatomy, physiology, and paleontology are used to determine the phylogeny (Riley 2009). In Pandanaceae, the morphological characters used to describe species are mainly based on fruit. Further, characterization of the species requires a large set of phenotypic data that are difficult to access statistically and are variable due to environmental effects (Sedra et al. 1993, 1996, 1998). There are a number of DNA-based marker systems available for studying phylogeny. Unlike morphological markers, molecular markers are not prone to environmental influences and do portray the genetic relationship between plant groups (Powell 1992; Gottlieb 1977; Tanksley et al. 1989; McCouch and Tanksley 1991).
The large rbcL analysis published in 1993 (Chase, Soltis, Olmstead et al., 1993) ranks as the largest phylogenetic analysis, molecular or otherwise, ever produced. These data represented over ten years of effort, but significantly the advent of the polymerase chain reaction, PCR, had greatly expanded the numbers of sequences available in the four years just prior to publication. Strategies for production of DNA sequences had become dramatically easier and faster. At the same time that sequencing was becoming more practical, the United States National Science Foundation was approving a large number of molecular systematics proposals, thus making substantial funding available (examine the number of NSF grant numbers listed in the footnotes of the 1993 paper), while Gerard Zurawski (DNAX Corporation) was making available without cost rbcL PCR and internal sequencing primers. Consequently, a large number of laboratories began working on this same plastid locus. To a very large extent and until just recently, protein-coding plastid DNA sequences have been the almost exclusive focus of vascular plant molecular systematists, whereas nearly all published work on other organisms has focused on ribosomal DNA (rDNA; see Chapter 1). By late 1991, the stage had been set for a dramatic increase in the amount of molecular data available on a wide range of seed plants, and this put workers focusing on rbcL in a position to discuss a large-scale analysis. Publication was not necessarily their goal; most simply felt that everyone would benefit from the interaction and that potentially we could use this sort of unpublished, but widely circulated, result as a way to focus better the many individual projects underway.
Chromosome numbers of Micranthes fusca (Maxim.) S. Akiyama & H. Ohba and its related species were determined. The chromosome number for M. fusca was mostly 2n = 30, as in the previous reports. In addition, we found 2n = 45 among population from Kunashiri Island of the Kuril Islands. The chromosome number of Saxifraga purpurascens Kom., 2n = 24, is the first report for this species. The chromosome number 2n = 28 for M. japonka (Boissieu) S. Akiyama & H. Ohba agrees with the previous report.
Evolutionary relationships among the genera of Macaronesian Sempervivoideae, Aeonium, Aichryson, Greenovia, and Monanthes, were studied using sequence variation of the chloroplast DNA trnL (UAA) - trnF (GAA) spacer and the nuclear ribosomal Internal Transcribed Spacer 2 (ITS2). Phylogenetic analysis indicates that the Moroccan Sedum sect. Monanthoidea is the sister taxon of the Macaronesian Sempervivoideae. In combination with the terminal position in the Macaronesian Sempervivoideae of the East African A. leucoblepharum, which has formerly been assumed to be the sister taxon of the other species of Macaronesian Sempervivoideae (i.e. Aichryson and Monanthes), a recent remigration to Africa is suggested. Statistical support for the terminal position of A. leucoblepharum using only spacer sequences is without homoplasy but not high since only single mutations in both the chloroplast and nuclear sequence characterize the clade containing A. leucoblepharum. A. leucoblepharum and the Canarian species with a similar growth-form share 50% of the RAPDs. Within a clade comprising woody species with yellow flowers and a herbaceous rosette, the highest genetic divergence, as determined with RAPDs, is found between A. simsii and the woody Macaronesian and African species. The extremely close genetic ties among the woody and branched (sub)shrubs indicate that, when compared to the other species of the genus, the woody, African Aeonium species are not the sister group of the Macaronesian Sempervivoideae and substantiate the view that an ancestor of A. leucoblepharum recently migrated from the Canary Islands to East Africa and Arabia through long distance dispersal, rather than being a relict of an African Aeonium flora from the Tertiary.
The two families of the order Apiales (Apiaceae and Araliaceae) represent a classic example of the difficulty in understanding evolutionary relationships between tropical-temperate family pairs. In Apiales, this problem is further compounded by phylogenetic confusion at almost every taxonomic level, including ordinal, interfamilial, and infrafamilial, due largely to difficulties in understanding trends in morphological evolution. Phylogenetic analyses of rbcL sequences were employed to resolve relationships at the ordinal and familial levels. The results of the ordinal analysis confirm the placement of Apiales in an expanded subclass Asteridae as the sister group to Pittosporaceae, and refute the traditional alliance of Apiales with Cornales and Rosidae. This study has also resolved relationships of a number of enigmatic genera, suggesting, for example, that Melanophylla, Aralidium, Griselinia, and Toricellia are close relatives of Apiales. Clarification of phylogenetic relationships has concomitantly provided insights into trends of morphological evolution, and suggests that the ancestral apialean taxon was probably bicarpellate, simple-leaved, woody, and paleotropical. Phylogenetic analysis at the family level suggests that apiaceous subfamily Hydrocotyloideae, often envisioned as an intermediate group between Apiaceae and Araliaceae, is polyphyletic, with some hydrocotyloids closely allied with Araliaceae rather than Apiaceae. With the exception of some hydrocotyloids, Apiaceae appear to be monophyletic. The relationship between Apiaceae and Araliaceae remains problematic. Although the shortest rbcL trees suggest that Apiaceae are derived from within a paraphyletic Araliaceae, this result is only weakly supported.
The field of systematic biology has been revitalized and transformed during the last few decades by the confluence of phylogenetic thinking with ready access to the tools of molecular biology. Indeed, the title of this volume and the fact that it is already in its second edition offers ample testimony to the impact that molecular approaches have had on efforts to reconstruct the phylogenetic history of plants. Concomitant with the proliferation of molecular tools has been a growing awareness that reliance on a single data set may often result in insufficient phylogenetic resolution or misleading inferences. Accordingly, it is an increasingly widespread practice to apply multiple data sets to a common group of taxa. One of the consequences of analyzing multiple data sets is that the phylogenies inferred may differ from each other in one or more details. This phylogenetic incongruence is not rare; to the contrary, it is almost the rule rather than the exception, being evident to varying degrees.
Restriction enzyme comparisons of plant genomes have been used widely to address systematic and evolutionary questions during the past 15 years. Most studies have examined variation in chloroplast DNA (cpDNA) or nuclear ribosomal DNA (rDNA) to estimate phylogenetic relationships among species, genera, and in a few cases families of plants (e.g., Jorgensen and Cluster, 1988; Palmer et al., 1988; Olmstead and Palmer, 1994). The restriction site approach also has been used to examine intraspecific variation and genetic diversity among populations (e.g., Neale et al., 1986; Soltis et al., 1989, 1991a, 1997; Whittemore and Schaal, 1991; Fenster and Ritland, 1992; Kim et al., 1992a; Hong et al., 1993; Petit et al., 1993; Byrne and Moran, 1994; Dong and Wagner, 1994; McCauley, 1994; Mason-Gamer et al., 1995; Bain and Jansen, 1996). Restriction site and DNA sequence data have three characteristics that make them especially useful for phylogenetic analyses (Holsinger and Jansen, 1993). First, discrete character states can be scored unambiguously. Second, a large number of characters potentially can be obtained for each taxon. Third, both types of data provide valuable information on the extent and nature of divergence between sequences. None of these features are present in earlier DNA methods, such as DNA—DNA hybridization.
Numerous DNA regions representing the nuclear and both organellar genomes are now available for comparative sequencing in plants (see Chapter 1); in addition, morphological and chemical data can also be obtained for phylogenetic analyses. With such a diversity of potential data sets available and the relative ease with which DNA sequences can be obtained, the acquisition of multiple data sets for the same suite of taxa is straightforward. As a result, the number of groups for which multiple data sets is available is increasing rapidly. Although it is readily apparent that multiple data sets are needed for estimating phylogenetic relationships reliably, it is also recognized that different genes may, in fact, possess different branching histories (see Chapter 10). Consequently, incorporating multiple data sets into phylogenetic studies is not a casual undertaking. Essential tasks in the analysis of multiple data sets include assessing congruence between different phylogenetic trees and data sets, and ascertaining whether multiple data sets should be combined into a single data matrix prior to phylogenetic reconstruction.
Plant systematics has been revolutionized during the past decade by the application of molecular techniques to questions of evolutionary patterns and processes. Analysis of variation in the chloroplast genome in particular and, to a lesser extent, in segments of the nuclear genome has vastly improved our understanding of plant phylogeny at all taxonomic levels. The phylogenetic patterns have, in turn, led to inferences of evolutionary processes and spurred hypotheses of adaptive radiation and character evolution. Consequently, systematics has emerged as a vigorous branch of evolutionary biology, providing the requisite historical perspective for comparative biology and the phylogenetic framework for developing hypotheses of evolutionary processes.
The Saxifraga nivalis complex displays significant ecological, morphological and cytological variation. Most European studies suggest that the S. nivalis complex comprises two distinct species: Saxifraga nivalis sensu stricto and Saxifraga tenuis. However, the presence of intermediate morphotypes, inconsistencies in chromosomal counts and variability in morphological keys and descriptions have led to different taxonomic interpretations of the complex in North America. This study investigated the systematics of Canadian Arctic Island members of this complex from 157 specimens using 23 morphological characters. Principal component analysis of the morphological data revealed two adjacent clusters, corresponding to the two taxa and consistent with a close morphological similarity and the presence of hybrids. A preliminary restriction site analysis of five non-coding regions of the chloroplast genome, trnH-trnK, trnT-trnF, trnF-trnV, trnV-rbcL and rbcL-ORF106, was conducted using 21 restriction endonucleases. This analysis indicated a length difference between the trnT-trnF region of S. nivalis and that of S. tenuis, but no difference in restriction sites for any of the assayed regions. These results confirm that in the Canadian Arctic, the S. nivalis complex consists of two closely related, largely sympatric species, with notable morphological variability, and possible hybrids.
This book provides an overview of geographic patterns in the distribution of plant secondary metabolites in natural populations. Examples include most common natural product classes: acetylenic derivatives; alkaloids; carotenoids; cyanogenic glycosides; flavonoids; terpenes of various sizes; as well as other structural types less easily categorized. By comparison, earlier reports in the literature on 'chemical races' focused either on individual classes of compounds, on specific taxa, or on a particular geographic region. Following an introduction that includes definitions of phytochemical and biogeographic ideas, information is presented in five loosely defined geographic trans-oceanic categories: examples within continents; after the ice; intercontinental disjunctions; oceanic islands; and polar disjunctions. It has often been said that natural variation is the essence of evolution. It seems reasonable to suggest that this is as true with plant secondary metabolites as with any other feature that confers an advantage to one set of individuals over antiherbivore or antifungal activity of plants as they colonize new habitats, and thus meet new challenges; or subtle changes in floral pigmentation and patterning that would affect behavior of pollinators. © 2009 Springer Science+Business Media B.V. All rights reserved.
Phylogenetic analyses were conducted for 73 genera of "lower" eudicots (Ranunculidae and "lower" Hamamelididae), magnoliid outgroups, and appropriate representatives for higher taxa within the "higher" eudicot clade (e.g., Rosidae, Dillenidae, Asteridae) based on sequences of three genes: the two chloroplast genes atpB and rbcL and nuclear ribosomal 18S DNA. Based on the partition homogeneity test, the three data sets were relatively congruent (P ≥ 0.13). The data were analyzed using heuristic parsimony searches and bootstrap analyses in three ways: individually, the two chloroplast sequences combined, and all three sequences combined. Both ingroup and outgroup sampling were varied to test the stability of the tree topology. The trees resulting from a combination of the chloroplast data and all three data sets had the best resolution and the strongest branch support. The following higher taxonomic groups were recognized with high bootstrap values (> 90%): Eudicots (including Nelumbo), Ranunculidae (including Euptelea), Papaverales, "core" ranunculids, a clade consisting of "lower" hamamelids and "core" eudicots, "core" eudicots (including caryophyllids, asterids, and rosids), Dilleniaceae, caryophyllids (including Simmondsia), and asterids. All ranuneulid families, including Circaeasteraceae s.l. (including Kingdonia) and Lardizabalaceae s.l. (including Sargentodoxa), formed well-supported monophyletic groups. Other well-supported eudicot clades were Platanus/Proteaceae, Buxaceae/Didymeles, Trochodendraceae/Tetracentraceae, and a group with poor internal resolution that included genera in Hamamelidaceae, various rosids, and Paeonia. Morphology (especially floral features) and other characteristics are described in some detail for well-supported clades determined by the molecular data.
Data from the chloroplast genes rbcL and ndhF, totaling more than 3500 base pairs of DNA sequence, were used to examine the monophyly of the Scrophulariaceae, including several groups that have been suggested to belong to or to be derived from the Scrophulariaceae. Thirty-two taxa representing the Lamiales s.l. and outgroups were sampled and each of the sets of gene sequences was analyzed separately and in combination. Results indicate that two distinct clades composed of elements of the traditional Scrophulariaceae exist and that a monophyletic Scrophulariaceae, even one liberally circumscribed to include several small families, cannot be supported by these data. One group, designated "scroph I," includes Verbascum, Celsia, Selago, Scrophularia, Buddleja, and Nicodemia. A second group, "scroph II," includes Antirrhinum, Digitalis, Veronica, and the Plantaginaceae, Callitrichaceae, and Hippuridaceae. Schlegelia and Paulownia, often assigned either to the Scrophulariaceae or Bignoniaceae, do not appear with either family.
Section Micranthes of the genus Saxifraga (Saxifragaceae) comprises 67 species that are distributed throughout the northern hemisphere. A previous phylogenetic analysis indicates that this section is a lineage distinct from the remainder of Saxifraga. Recent taxonomic treatments have divided section Micranthes into four subsections: Cuneifoliatae, Micranthes, Rotundifoliatae, and Stellares. To investigate the phylogenetic relationships among species in section Micranthes and to test the monophyly of each of the four subsections, we sequenced the chloroplast gene matK for 26 species of section Micranthes. The results of our parsimony analyses suggest that subsections Micranthes and Stellares are each monophyletic. The single taxon of subsection Cuneifoliatae (S. calycina) for which material could be obtained appears within a clade representing subsection Rotundifoliatae; hence Cuneifoliatae may not be distinct from Rotundifoliatae. Within section Micranthes there exists a high diversity of ovary positions, ranging from what has been described as fully superior to greater than one-half inferior. Examination of this character in light of our matK strict consensus tree indicates that the major trend in gynoecial evolution in section Micranthes has been from an ancestor with what has been termed a superior ovary towards greater inferiority. However, gynoecial evolution in subsection Micranthes is complex, with several apparent reversals towards greater superiority.
Comparative sequencing of the maturase-encoding chloroplast gene matK has great potential for reconstructing phylogenetic relationships not only within families, but also within genera of land plants. This gene of 1550 bp is easily amplified due to highly conserved, flanking coding regions that include the trnK exons, rps 16, and psbA. Several available sequencing primers also have wide applicability. Parsimony analysis of 45 matK sequences representing Saxifragaceae sensu stricto provides a level of resolution comparable to that obtained via chloroplast DNA restriction site analysis. Furthermore, this analysis suggests relationships among genera and species that are highly concordant with the results of separate analyses of rbcL sequences and chloroplast DNA restriction sites, and with those of combined analyses of these three chloroplast DNA data sets. Parsimony analysis of 31 matK sequences representing all six sections of Gilia (Polemoniaceae) and 10 allied genera provides strong evidence for the polyphyly of Gilia and suggests relationships among sections of Gilia that are highly concordant with a recent ITS sequence analysis of the Polemoniaceae. Our analyses suggest that matK sequences are not strongly biased toward transitions, and the frequency of mutations at the first and second codon positions approach the frequency of mutations in the third codon position.
The implementation of explicit phylogenetic techniques to the study of relationships among angiosperms has led to the recognition of a major monophyletic group, the eudicot clade, characterized by the production of tricolpate or tricolpate-derived pollen grains. Eudicots comprise nearly 75% of extant angiosperm species (subclasses Hamamelididae, Caryophyllidae. Dilleniidae, Rosidae, and Asteridae, as well as the order Ranunculales in the Magnoliidae sensu Cronquist). Recent phylogenetic analyses, based on both morphological data and molecular sequences, have begun to clarify higher-level phylogenetic relationships within the eudicot clade. The basalmost branch within the eudicots separates a small ranunculid clade, which includes the Ranunculales and Papaverales. The main group within the eudicots, here referred to as the main cudicot clade, is formed by a basal grade of species-poor lineages, mostly of "lower" Hamamelididae, and a large monophyletic group, here referred to as core eudicots, which includes ca. 97% of eudicot species diversity. Within the core eudicots, three distinct groups can be recognized. (1) The caryophyllid clade (ca. 6% of eudicot species diversity) includes the Caryophyllidae as traditionally defined and a few additional taxa previously thought to be of dilleniid and rosid affinity. (2) The rosid clade (ca. 39% of total eudicot species diversity) is composed mostly of taxa previously included in Dilleniidae and Rosidae, and includes a well-supported clade that we term here the core rosids (ca. 24% of total eudicot species diversity). Among the taxa in the core rosid clade are the Fabaceae, Rosaceae, Linales, and Cunoniaceae, as well as some families of Violales, and the "higher" Hamamelididae. (3) The asterid clade (ca. 50% of eudicot species diversity) consists of two large clades composed mostly of taxa previously assigned to Asteridae, and additional members of Rosidae and Dilleniidae. One of these large asterid clades is dominated by the Asterales s.l. (ca. 17% of total eudicot species diversity), while the other corresponds to a broadly defined Lamiidae (ca. 26% of total eudicot species diversity). Paleobotanical data first document the presence of early cudicots ca. 125 million years before the present (Barremian-Aptian boundary, Lower Cretaceous), prior to the major diversification and ecological radiation of angiosperms. Well-preserved floral remains and other fossils provide a minimum age for the origin of eudicot lineages. Sediments of Albian age contain floral remains of Platanaceae and probable Buxaceae, both of which fall within the species-poor lineages at the base of the main eudicot clade. In slightly younger sediments, the taxonomic diversity of eudicots increases considerably. Basal taxa in the core eudicots are represented by Hamamelidaceae and by several flowers of broad saxifragalean affinity in Turonian-Campanian strata. Among taxa within the rosid clade, the Capparales and Myrtales are documented from the Turonian and Santonian-Campanian, respectively. The core rosids are represented by several flowers with affinities to Juglandales, Myricales, and Fagales in the Santonian-Campanian. Flowers with possible affinities to Hydrangeaceae, from the Coniacian-Santonian, represent the basalmost group within the asterid clade, and flowers of broad ericalean affinity (including Actinidiaceae), from the Turonian-Campanian, document the presence of several groups within the ericalean clade. The Asteridae s.l. are not securely represented in the Upper Cretaceous, and, to our knowledge, there is no reliable Cretaceous record for any member of the Lamiidae s.l. Although nearly all of the main eudicot clades are represented by at least one of their included lineages in the Upper Cretaceous, the earliest well-documented records of the Fabaceae, Asteraceae, Lamiales s.l., and Gentianales, which together comprise ca. 45% of total eudicot species diversity, are found in uppermost Cretaceous (Maastrichtian) or Tertiary sediments. The three subfamilies of Fabaceae are well documented by flowers and fruits in the Eocene, although the presence of pollen grains assigned to Caesalpinioideae from Maastrichtian strata suggests that the family extends back into the uppermost Cretaceous. The Asteraceae, Lamiales s.l., and Gentianales are known from the Paleogene based mostly on vegetative remains. The uneven distribution of species diversity among the major clades of eudicots, and the fact that the most species-rich groups are known only from relatively young fossils, suggests that a significant portion of eudicot diversity is the result of relatively recent radiations that occurred during the second half of angiosperm evolutionary history. The evolutionary basis for the explosive diversification of specific eudicot clades-in terms of exceptionally high speciation rates, low extinction rates, or both-remains uncertain.
In the light of recent works of biosystematics on molecular genetics bases, nomenclatural
changes concerning some entities in the Italian flora have been proposed.
The genus Anemone is split in Anemone s.s., Hepatica and Pulsatilla, as well as in Anemonastrum
and Anemonoides; likewise Colymbada, Cheirolophus, Crocodylium, Cyanus and Rhaponticoides are
split from Centaurea s.s. (incl. Cnicus). Tolpis staticifolia is lumped to Crepis, Pseudorlaya to Daucus,
Lomatogonium to Gentianella (which however Gentianopsis results separated from), Hymenolobus and
Pritzelago to Hornungia, Loiseleuria to Kalmia. The genus Ligusticum is divided in Coristospermum,
Mutellina and Pachypleurum; Glaux is united to Lysimachia, Lavatera to Malva. Micranthes is split from
Saxifraga; Cervaria, Holandrea, Imperatoria, Oreoselinum, Pteroselinum, Thyselium, Tommasinia and
Xanthoselinum are isolated from Peucedanum; in the bosom of Orobanche the genus Phelipanche is recognized.
Moreover some statements on entities belonging to Senecio nemorensis group are made.
Lastly new combinations and/or new names are proposed in the genera Anemonoides, Colymbada,
Crepis, Gentianella, Coristospermum, Lysimachia, Malva, Micranthes, Holandrea, Phelipanche and
Senecio.
Appunti di sistematica e tassonomia per la flora italiana. 1.
Alla luce di recenti lavori di biosistematica su base genetico-molecolare vengono proposti alcuni
cambiamenti nomenclaturali realativi a entità della flora italiana.
Il genere Anemone viene diviso, oltre che in Anemone s.s., Hepatica e Pulsatilla, anche in
Anemonastrum e Anemonoides; analogamente da Centaurea s.s. (incl. Cnicus) viene separata
Colymbada, oltre a Cheirolophus, Crocodylium, Cyanus e Rhaponticoides. Tolpis staticifolia è unita a
Crepis, Pseudorlaya a Daucus, Lomatogonium a Gentianella (dalla quale risulta tuttavia separata
Gentianopsis), Hymenolobus e Pritzelago a Hornungia, Loiseleuria a Kalmia. Il genere Ligusticum
viene suddiviso in Coristospermum, Mutellina e Pachypleurum; Glaux è riunita a Lysimachia,
Lavatera a Malva. Da Saxifraga viene separata Micranthes, da Peucedanum vengono isolati Cervaria,
Holandrea, Imperatoria, Oreoselinum, Pteroselinum, Thyselium, Tommasinia e Xanthoselinum; in
seno a Orobanche viene riconosciuto il genere Phelipanche. Inoltre vengono fatte alcune considerazioni
sulle entità del gruppo di Senecio nemorensis.
Infine vengono proposte nuove combinazioni e/o nuovi nomi nei generi Anemonoides,
Colymbada, Crepis, Gentianella, Coristospermum, Lysimachia, Malva, Micranthes, Holandrea,
Phelipanche e Senecio.
Phylogenetic analyses of rbcL sequences were used to address both systematic and evolutionary questions posed by the angiosperm family Hydrangeaceae. Our analyses suggest the presence of a monophyletic Hydrangeaceae most closely allied with Loasaceae, a finding in agreement with other molecular as well as morphological analyses. Molecular data indicate that Hydrangeaceae comprise Decumaria, Pileostegia, Schizophragma, Hydrangea, Dichroa, Broussaisia, Platycrater, Cardiandra, Deinanthe, Carpenteria, Philadelphus, Deutzia, Fendlerella, Whipplea, Fendlera, Jamesia, and the enigmatic Kirengeshoma. A particularly close relationship of Kirengeshoma and Deutzia is indicated. Analysis of rbcL sequences suggests that Fendlera and Jamesia are sister to the remainder of the family, lending support to the hypothesis that at least some Carpenterieae are basal in the family and that Hydrangeaceae may have originated in xeric habitats. If this phylogenetic placement of Jamesia and Fendlera is correct, the rbcL trees also suggest that the level of epigyny has decreased in these genera, as well as in the Fendlerella- Whipplea clade and Carpenteria when compared to the outgroup taxa, which are wholly epigynous. Furthermore, the rbcL trees support proposed evolutionary trends in wood anatomy, suggesting, for example, that upland tropical taxa have evolved longer vessel elements with more numerous bars on scalariform perforation plates. The xerophytic basal members of Hydrangeaceae, like the closely related Loasaceae, have short, narrow vessel elements with scalariform perforation plates bearing few bars. Following Jamesia and Fendlera, the remaining hydrangeoids are divided into two large subclades that closely parallel the traditional division of the family into Philadelpheae and Hydrangeae. Both rbcL sequences and morphological data suggest close relationships between: 1) Fendlerella and Whipplea; 2) Decumaria, Pileostegia, and Schizophragma; 3) Carpenteria and Philadelphus; 4) Deinanthe and Cardiandra; 5) Dichroa, Broussaisia, and Hydrangea macrophylla. Molecular and morphological data also concur in demonstrating that the large genus Hydrangea is not a monophyletic assemblage.
To elucidate relationships at deep levels within Saxifragaceae we analyzed phylogenetically a data set of sequences for six DNA regions, four representing the chloroplast genome (rbcL, matK, trnL-trnF, psbA-trnH) and two from the nuclear genome (ITS and expansion segments of the 26S rDNA). A total of 6676 bp was aligned per taxon, 4559 bp and 1878 bp from the chloroplast and nuclear genomes, respectively. Chloroplast and nuclear trees agreed closely, prompting analysis of a combined, six-gene data set. Application of both parsimony and maximum likelihood methods yielded similar topologies. The use of different ITS alignments and the exclusion of hard-to-align ITS regions had little impact on either the final nuclear-based topology, or the shortest trees from the analysis of six genes. The affinities of two monotypic genera (Saxifragella and Saxifragodes) endemic to Tierra del Fuego were elucidated. Saxifragella is an early branching member of the North Temperate genus Saxifranga s. str.; Saxifragodes is sister to Cascadia, a genus endemic to Oregon and Washington. Long-distance dispersal from east Asia or western North America to South America may have played an important role in forming these and ether similar disjunctions in the family. A number of well-supported clades are present, including Saxifroga s. str., Micranthes, Saxifragopsis/Astilbe, Chrysosplenium/ Peltoboykinia, and the Boykinia and Heuchera groups. The use of additional characters has provided greatly increased resolution and internal support at deep levels. Saxifragaceae comprise two major lineages: Saxifroga s. str. (including Saxifragella) and all other genera of the family (the heucheroids). This major split is accompanied by general biogeographical and morphological differences. Whereas Saxifraga s. str. is largely arctic to alpine in occurrence, the heucheroid clade is largely temperate in distribution. Saxifraga s. str. has a relatively uniform floral morphology (generally actinomorphic; 5 sepals, 5 petals, 10 stamens, 2 carpels), whereas the heucheroid clade encompasses actinomorphic and zygomorphic forms, as well as variation in the number of sepals, petals, stamens, and carpels. Deep-level relationships within both Saxifraga s. str. and the heucheroid clade are well resolved and supported. A phylogenetic classification of the family is provided.
A phylogenetic analysis of 589 plastid rbcL gene sequences representing nearly all eudicot families (a total of 308 families; seven photosynthetic and four parasitic families are missing) was performed, and bootstrap re-sampling was used to assess support for clades. Based on these data, the ordinal classification of eudicots is revised following the previous classification of angiosperms by the Angiosperm Phylogeny Group (APG). Putative additional orders are discussed (e.g. Dilleniales, Escalloniales, Vitales), and several additional families are assigned to orders for future updates of the APG classification. The use of rbcL alone in such a large matrix was found to be practical in discovering and providing bootstrap support for most orders. Combination of these data with other matrices for the rest of the angiosperms should provide the framework for a complete phylogeny to be used in macro-evolutionary studies.
Phylogenetic relationships between the European species of the genus Gentiana L. (Gentianaceae) were inferred from chloroplast trnL, (UAA) intron sequence data. The phylogeny obtained is largely in accordance with the classification of species into sections Gentiana, Megalanthe and Calathianae. Few synapomorphies support the branching of the main lineages and thus could suggest a rapid radiation following the colonization of Europe. Within section Gentiana, our results are highly congruent with the previous distinction of G. montserratii Vivant from G. lutea L. Section Megalanthe is divided into two well separated lineages, both of which comprise calcicole and calcifuge species. The ‘star phylogeny’ obtained in section Calathianae suggests that most of the taxa speciated almost simultaneously. Relative‐rate tests between two lineages suggested that section Chondropliyllae displays higher mutation rates than the rest of the genus Gentiana and that cpDNA can violate assumptions of rate constancy at lower taxonomic level.
We use a comprehensive subset of Canarian angiosperms corresponding to 23 families, 35 genera, and 60 Canarian endemic taxa to test if this flora is suitable to taxonomic identification with the two proposed plant DNA barcode sequences, and if these sequences may reveal the existence of cryptic species overlooked by morphology. The rate of discrimination success between the insular congeneric samples using the rbcL+ matK combination and a "character-based" approach (where we use only the combination of nucleotide positions in an alignment that allows unambiguous species identification) is higher (82.29%) than that obtained with the "distance-based" approach (80.20%) used by the CBOL Plant Working Group in 2009, and also when compared with tests conducted in other floras. This suggests that the molecular identification of the Canarian endemic flora can be achieved as successfully as in other floras where the incidence of radiation is not as relevant. The facts that (i) a distance-based criterion was unable to discriminate between congeneric and conspecific comparisons, and (ii) only the character-based discrimination criterion resolved cases that the distance-based criterion did not, further support the use of a character discrimination approach for a more efficient DNA barcoding of floras from oceanic islands like the Canaries. Thus, a barcoding gap seems not to be necessary for the correct molecular characterization of the Canarian flora. DNA barcodes also suggestthe possible existence of cryptic taxa to be further investigated by morphology, and suggest that the current taxonomic status of some of the taxa analyzed may need revision. This article is protected by copyright. All rights reserved.
We examined the reproductive biology of Tolmeia menziesii and Tellima grandiflora (Saxifragaceae) and barriers to hybridization between these species. Crossing experiments and pollinator observations suggest that Tolmeia is completely self-incompatible, obligately outcrossing, and bumble bee pollinated, whereas Tellima is self-compatible, with a mixed mating system possibly facilitated by rove beetles. Hybrid crosses set seed only when Tellima was the pollen recipient. Observations of pollen style interactions indicate that self-incompatibility in Tolmeia is late-acting and that pollen tube growth is comparable between reciprocal hybrid pollinations. Seven of 40 progeny from Tolmeia x Tellima crosses were isozymically and morphologically intermediate between Tolmeia and Tellima, and were identical to a naturally occurring hybrid. The remainder were identical to Tellima, the maternal parent in successful hybrid crosses, which we attribute to either intraspecific pollen contamination, or agamospermy. Barriers to hybridization between sympatric Tellima and Tolmeia consist of divergence in floral morphology, pollinator relationships, compatibility, and a series of postzygotic isolating mechanisms including hybrid sterility.
Thesis (Ph. D.)--Indiana University, 1980. Vita. Includes bibliographical references.
We explore phylogenetic relationships in Lithophragma through parsimony and maximum likelihood estimation analyses of internal transcribed spacer sequences of 18S-26S ribosomal DNA. Results based on internal transcribed spacer sequences are compared with those from previous studies based on chloroplast DNA restriction site, morphological and flavonoid variation. Phylogenetic analysis of internal transcribed spacer sequences produces a highly reserved topology with six main clades. These results suggest that three previously described species of Lithophragma are not monophyletic. Based on this topology and previous findings, two species not recognized in the most recent monograph L. thompsonii and tetraploid L, bolanderi, are hypothesized to have arisen through hybridization and allopolyploidy, respectively. flowers of Lithophragma exhibit a diverse array of ovary positions ranging from what has been described as superior to deeply inferior. Analysis of ovary position in light of our phylogenetic results reveals a complex pattern of diversification in Lithophragma. This pattern is explored through character mapping and correlation analyses and is found to be inconsistent with either an active or a passive trend toward greater inferiority. A weak relationship between variation in ovary position and the topological position of each taxon suggests homoplastic tendencies toward greater inferiority in some clades and greater superiority in others.
Various factors, including taxon density, sampling error, convergence, and heterogeneity of evolutionary rates, can potentially lead to incongruence between phylogenetic trees based on different genomes. Particularly at the generic level and below, chloroplast capture resulting from hybridization may distort organismal relationships in phylogenetic analyses based on the chloroplast genome, or genes included therein. However, the extent of such discord between chloroplast DNA (cpDNA) trees and those trees based on nuclear genes has rarely been assessed. We therefore used sequences of the internal transcribed spacer regions (ITS-1 and ITS-2) of nuclear ribosomal DNA (rDNA) to reconstruct phylogenetic relationships among members of the Heuchera group of genera (Saxifragaceae). The Heuchera group presents an important model for the analysis of chloroplast capture and its impact on phylogenetic reconstruction because hybridization is well documented within genera (e.g., Heuchera), and intergeneric hybrids involving six of the nine genera have been reported. An earlier study provided a well-resolved phylogenetic hypothesis for the Heuchera group based on cpDNA restriction-site variation. However, trees based on ITS sequences are discordant with the cpDNA-based tree. Evidence from both morphology and nuclear-encoded allozymes is consistent with the ITS trees, rather than the cpDNA tree, and several points of phylogenetic discord can clearly be attributed to chloroplast capture. Comparison of the organellar and ITS trees also raises the strong likelihood that ancient events of chloroplast capture occurred between lineages during the early diversification of the Heuchera group. Thus, despite the many advantages and widespread use of cpDNA data in phylogeny reconstruction, comparison of relationships based on cpDNA and ITS sequences for the Heuchera group underscores the need for caution in the use of organellar variation for retrieving phylogeny at lower taxonomic levels, particularly in groups noted for hybridization.
Phylogenetic analysis of actinorhizal plant families is now possible due to the availability of numerous angiosperm sequences of the plastid gene rbcL. A sampling of a 100 rbcL sequences, including representatives of all eight actinorhizal families, was conducted to estimate their phylogenetic relationships. The phylogeny was estimated by neighbor-joining analysis of a matrix of pairwise substitution rates. Bootstrap and double-bootstrap values were estimated. In order to assess the divergent hypotheses of unique or recurrent evolution of actinorhizal symbiosis, character state changes were traced along the branches of the phylogenetic consensus trees obtained, and the number of character changes for each of the two scenarios was calculated. The most parsimonious scenario favored the recurrent evolution of actinorhizal symbiosis. This scenario is supported by the morphophysiological diversity of actinorhizal symbioses and by the relaxed coevolutionary relationships between the host plants and the microsymbiont.
The systematic position of the river-weed family Podostemaceae remains enigmatic due to taxonomic difficulties imposed by the radically altered morphology of these alga-like an-giosperms. Although previous workers have placed this group phylogenetically among a wide variety of monocotyledons and dicotyledons, most contemporary authors have proposed that fiver-weeds are closely related to members of the dicotyledonous order Rosales. A diversity of opinion also exists as to whether the Hyclrostachyaceae are related to Podostemaceae. We have investigated the phylogeny of fiver-weeds by comparing DNA sequences of the chloroplast encoded rbcL gene for eight river-weed genera together with 84 other angiosperm and 11 non-flowering seed plant taxa. The high level of sequence divergence in rbcL that exists between fiver-weeds, Hydrostachyaceae and other angiosperms presents systematic problems that parallel those associated with the highly divergent morphology of these groups. Rooting rbcL sequences with distant non-flowering plant outgroups results in a topology where Podostemaceae comprise a basal angiosperm clade, but in which other renditions of angiosperm family relationships are depicted unreasonably. Restricting the comparison of river-weed sequences entirely with an-giosperms places the group as a sister clade to the Hydrostachyaceae as some authors had anticipated, but this result is only weakly supported. The high level of both morphological and molecular divergence in the river-weed clade confounds efforts to correctly ascertain their phylogenetic relationships. A tentative hypothesis from rbcL data is that the Hydrostachyaceae and Podostemaceae are sister taxa whose closest relatives are the rosid families Crassulaceae and Haloragaceae.
The two families of the order Apiales (Apiaceae and Araliaceae) represent a classic example of the difficulty in understanding evolutionary relationships between tropical-temperate family pairs. In Apiales, this problem is further compounded by phylogenetic confusion at almost every taxonomic level, including ordinal, interfamilial, and infrafamilial, due largely to difficulties in understanding trends in morphological evolution. Phylogenetic analyses of rbcL sequences were employed to resolve relationships at the ordinal and familial levels. The results of the ordinal analysis confirm the placement of Apiales in an expanded subclass Asteridae as the sister group to Pittosporaceae, and refute the traditional alliance of Apiales with Cornales and Rosidae. This study has also resolved relationships of a number of enigmatic genera, suggesting, for example, that Melanophylla, Aralidium, Griselinia, and Toricellia are close relatives of Apiales. Clarification of phylogenetic relationships has concomitantly provided insights into trends of morphological evolution, and suggests that the ancestral apialean taxon was probably bicarpellate, simple-leaved, woody, and paleotropical. Phylogenetic analysis at the family level suggests that apiaceous subfamily Hydrocotyloideae, often envisioned as an intermediate group between Apiaceae and Araliaceae, is polyphyletic, with some hydrocotyloids closely allied with Araliaceae rather than Apiaceae. With the exception of some hydrocotyloids, Apiaceae appear to be monophyletic. The relationship between Apiaceae and Araliaceae remains problematic. Although the shortest rbcL trees suggest that Apiaceae are derived from within a paraphyletic Araliaceae, this result is only weakly supported.
The angiosperm family Rosaceae poses a number of noteworthy systematic problems as well as many questions concerning morphological and chromosomal evolution. Phylogenetic analysis of rbcL gene sequences was performed to address systematic and evolutionary problems of Rosaceae. Both rbcL sequence variation and the presence of duplicated sequences near the 3' end of rbcL were useful in determining phylogenetic relationships in this family. Analyses of rbcL sequences indicate that there are groups of genera within Rosaceae comparable to the subfamilies Maloideae, Amygdaloideae, and Rosoideae, although the composition of each group differs from traditional circumscriptions. According to analysis of rbcL data, Maloideae and Amygdaloideae each include additional taxa not normally associated with them. All members of Rosoideae with x = 9 are phylogenetically well separated from the x = 8 and 7 members of the subfamily. In addition, Spiraeoideae are not monophyletic but appear to consist of several distinct evolutionary lineages. The rbcl-based phylogenies suggest that chromosome numbers are more reliable indicators of some generic alliances than the more commonly used fruit types. Sequence data are also useful in determining the alliances of several problematic genera, suggesting that the capsular and follicular-fruited genera Vauquelinia, Lindleya, and Kageneckia (usually placed in Spiraeoideae) should be included in the pome-fruited subfamily Maloideae, and that Quillaja is not a member of Rosaceae. Molecular data are consistent with several suggestions for the ancestral chromosome numbers and fruit types of Rosaceae, but do not support any one hypothesis for either. This study also suggests that the subfamily Maloideae may have descended from spiraeoid ancestors and that the pome is derived from follicular or capsular fruit types.
The Ericaceae, Epacridaceae, and Empetraceae are usually recognized as closely related families of woody plants that share a preference for acidic soils, anthers that invert in development, and the presence of endosperm haustoria, among other characteristics. The Empetraceae are recognized as distinctive because of their often unisexual and wind-pollinated flowers. Epacridaceae are distinguished from Ericaceae by anthers that open by slits rather than pores and a primarily Australian distribution. Phylogenetic relationships of these related families are investigated using nucleotide sequences of the plastid gene rbcL. Parsimony analyses indicate a monophyletic, broadly defined Ericaceae that includes Empetraceae and Epacridaceae.
The evolutionary relationships among the seven tribes of Onagraceae, the most intensively studied family of intermediate size, have been examined from morphological and molecular perspectives. Previous cladistic analyses of chloroplast (cp) and nuclear ribosomal (nr) DNA restriction sites, nuclear-encoded rbcS amino acid sequences, nrRNA nucleotide sequences, and morphological characters, produced trees that agree in defining the tribe Jussiaeeae as the sister group to the rest of the family. However, the relationships among the rest of the tribes are not completely resolved by these analyses. Cladistic analyses of sequence data from the chloroplast encoded rbcL gene produced results that bear on two major issues: (i) intertribal relationships within Onagraceae, and (ii) congruence with other cladistic analyses. Sequences of rbcL were obtained from all tribes of Onagraceae and from three families that have been proposed as sister taxa of Onagraceae on the basis of other molecular and morphological evidence (Lythraceae, Punicaceae, Trapaceae). Phylogenetic analysis of rbcL sequence data produced a single most parsimonious tree, both Fitch and weighted, that defines three strongly supported monophyletic groups within the family: all tribes except Jussiaeeae; Onagreae and Epilobieae; and, most interestingly, Fuchsieae and Circaeeae. The formation of this last clade corroborates the results of the cpDNA restriction site and of the nrRNA sequence data. The data also indicate an apparent slowdown in the rate of rbcL sequence divergence in the woody Fuchsia lineage relative to the herbaceous Circaea lineage. The placements of monogeneric tribes Lopezieae and Hauyeae are not strongly supported. The topology of the rbcL tree basically confirms that of the cpDNA restriction site tree. Among the other cladistic analyses, the nrRNA sequence survey produced the tree closest to the rbcL tree, followed in order by the rbcS amino acid sequence tree, the nrDNA restriction site tree, and the morphological tree.
A parsimony analysis of 57 angiosperm rbcL sequences was conducted to test the monophyly of the Asteridae and to identify major lineages within the Asteridae. Three major clades, the Caryophyllidae, the Rosidae plus Dilleniidae, and the Asteridae sensu lato, emerge from an unresolved radiation in the "higher" dicots. The Asteridae sens. lat. include the Ericales, Cornales, and Apiales in addition to the Asteridae sens. str. Two major lineages within the Asteridae sens. lat. are identified: the Dipsacales, Apiales, Asterales, and Campanulales in one, and the Gentianales, Scrophulariales, Lamiales, Boraginales, and Solanales in the other. This analysis demonstrates the utility of molecular phylogenies to help place problematic taxa, such as the Menyanthaceae, Oleaceae, and Callitrichaceae, within the Asteridae. Implications from this phylogenetic analysis and evidence from the fossil record lead to the suggestion that the origin and diversification of the major higher-dicot lineages occurred during a relatively short period of time about 80-95 million years ago.
Critical review of the distribution of flavonoids in the angiosperms, combined with considerations of their biosynthesis has led to a reappraisal of existing dicta on the phylogenetic status of the various structural types. Caution is necessary when attempting evolutionary interpretations because there seem to be two trends operating within the angiosperms. The major one involves reduction in structural complexity, following a reverse direction down the biosynthetic pathway. Reduction in the actual number of flavonoid structures produced is also part of the trend. A secondary trend, often superimposed on the first, involves diversification whereby the flavonoid nucleus undergoes progressive elaboration (extra oxygenation, 0-methylation, etc.). The complications engendered by these two trends require the recognition of at least three evolutionary grades: primitive, advanced and highly advanced. It is very difficult to distinguish between the primitive and highly advanced conditions because in many cases the flavonoid phenotype is identical: in the first case the simplicity is primary and in the second it is secondary by reduction. Correlations in distribution of the different flavonoid structures can not only be interpreted in phylogenetic terms but also in terms of adaptive complexes. Many structures and groups of structures have never been reported from nature -- are these ill-adaptive? On the other hand, there are several combinations which do appear regularly and it is suggested that they contribute to adaptive peaks. These flavonoid combinations are shown, within the limits of their definition, to characterize many orders and superorders (with increased precision of definition, the
combinations can also be used to characterize families and lower taxa). The flavonoid profiles of the orders show a remarkable correlation with the occurrences of other secondary metabolites such as benzyl isoquinoline alkaloids, tannins, iridoids, sesquiterpenes and polyacetylenes. It is possible that flavonoids are not independent in their efficiency of action but rather act in functional consort not only with other metabolites and physiological processes, but also with morphological and anatomical defenses.
Restriction site variation in chloroplast DNAs (cpDNAs) of Coreopsis section Coreopsis was employed to assess divergence and phylogenetic relationships among the nine species of the section. A total of fourteen restriction site mutations and one length mutation was detected. Cladistic analysis of the cpDNA data produced a phylogeny that is different in several respects from previous hypotheses. CpDNA mutations divide the section into two groups, with the two perennial species C. auriculata and C. pubescens lacking any derived restriction site changes. The other seven species are united by five synapomorphic restriction site mutations and the one length mutation. These seven species fall into three unresolved clades consisting of 1) the remaining three perennial species, C. grandiflora, C. intermedia, and C. lanceolata; 2) three annual species, C. basalis, C. nuecensoides, and C. nuecensis; and 3) the remaining annual, C. wrightii. The cpDNA data suggest that, although the perennial habit is primitive within the section, the annual species of section Coreopsis have likely not originated from an extant perennial species. The estimated proportion of nucleotide differences per site (given as 100p) for the cpDNAs of species in the section ranges from 0.00 to 0.20, which is comparable to or lower than values reported for other congeneric species. The low level of cpDNA divergence is concordant with other data, including cross compatibility, interfertility and allozymes, in suggesting that species of the section are not highly divergent genetically.
The floral anatomy and morphology of 26 species from the Saxifragoideae and three from the Iteoideae are described and compared. The flowers of the Saxifragoideae are predominantly actinomorphic, partially epigynous and/or perigynous, and pentamerous, with two carpels which bear numerous ovules. There is usually some degree of independence between carpels, and the normally separate styles possess both a canal and transmitting tissue. Generally, staminodia are absent and nectariferous tissue, which is not vascularized, is present. The subfamily is characterized by large multicellular trichomes with globular, often glandular, heads. Placentation may be parietal, axile, or transitional between the two; parietal appears to be a derived condition in the subfamily. The vascular cylinder in the pedicel generally consists of several to many discrete bundles from which diverge ten compound traces at the base of the receptacle, leaving an inner cylinder of vascular strands that coalesce at a higher level into either as many ventral bundles as carpels or twice that number. In the former case, each ventral bundle consists of one-half of the vascular supply to each adjacent carpel and separates into individual ventral strands in the distal half of the ovary. The ventral bundles provide vascular traces to the ovules and, along with the dorsals, extend up the style to the stigma. Each trace diverging in a sepal plane typically supplies one or more carpel-wall bundles, a median sepal bundle, and a stamen bundle. Each petal-plane trace usually provides one or more carpel-wall bundles, a lateral trace to each adjacent sepal, a petal bundle and, in flowers with ten stamens, a stamen bundle. Dorsal carpel bundles are usually recognizable and may originate from traces in either perianth plane. While the position of Ribes remains problematical, its floral structure does not easily exclude it from the Saxifragoideae. Floral structure in the Iteoideae is remarkably similar to that in the Saxifragoideae, the main differences being a lesser degree of independence between carpels, generally narrower placentae with somewhat fewer ovules, and the presence of only unicellular, acutely pointed epidermal hairs as opposed to the relatively complex, multicellular trichomes prevalent in the Saxifragoideae.
The recently-developed statistical method known as the "bootstrap" can be used to place confidence intervals on phylogenies. It involves resampling points from one's own data, with replacement, to create a series of bootstrap samples of the same size as the original data. Each of these is analyzed, and the variation among the resulting estimates taken to indicate the size of the error involved in making estimates from the original data. In the case of phylogenies, it is argued that the proper method of resampling is to keep all of the original species while sampling characters with replacement, under the assumption that the characters have been independently drawn by the systematist and have evolved independently. Majority-rule consensus trees can be used to construct a phylogeny showing all of the inferred monophyletic groups that occurred in a majority of the bootstrap samples. If a group shows up 95% of the time or more, the evidence for it is taken to be statistically significant. Existing computer programs can be used to analyze different bootstrap samples by using weights on the characters, the weight of a character being how many times it was drawn in bootstrap sampling. When all characters are perfectly compatible, as envisioned by Hennig, bootstrap sampling becomes unnecessary; the bootstrap method would show significant evidence for a group if it is defined by three or more characters.
Previous studies have shown that in several angiosperms and the liverwort Marchantia the chloroplast gene rpl2, encoding ribosomal protein L2, is interrupted by an intron, but that in spinach (Spinacia oleracea, Caryophyllales) this intron has been lost. We have determined the distribution of the rpl2 intron for 390 species representing 116 angiosperm families. Filter hybridizations reveal that the intron is absent from the chloroplast genomes of all examined families of the Caryophyllales, suggesting that the intron was lost in the common ancestor of the order. Sequencing of the rpl2 gene in five genera of the Caryophyllales and in Rumex (Polygonales) not only confirms the filter hybridization results, but also shows that for all taxa lacking the intron, the rpl2 gene has undergone a precise deletion of the intron. In all cases, it is the original rpl2 gene that has sustained loss of its intron. This implies that in chloroplast DNA, integration of exogenous genes (e.g., a reverse transcript of a spliced mRNA) occurs mainly by homologous, replacement recombination, rather than by illegitimate recombination elsewhere in the genome. Filter hybridizations also reveal that the rpl2 intron was lost independently in the common ancestors of at least five other lineages of dicotyledons: Saxifragaceae (s.s.), Convolvulaceae (including Cuscuta), Menyanthaceae, two genera of Geraniaceae, and one genus of Droseraceae. The molecular and phylogenetic implications of these independent intron losses are discussed.
More than a quarter of a century has passed since the publication of Zuckerkandl and Pauling’s (1965) seminal article on the evolutionary implications of macromolecular sequence data. Two fundamental suggestions were made in that article: first, Zuckerkandl and Pauling pointed out that molecular change (nucleotide or amino acid substitutions) might occur at a rate that is proportional to clock time (the molecular clock hypothesis); and second, they noted that the topology of evolutionary branchings (phylogenies) could be deduced from the pattern of molecular change. These two related suggestions form the theoretical underpinnings of the science of molecular evolution.
The Leguminosae, with some 650 genera and over 18,000 species, is the third largest family of flowering plants (Polhill et al., 1981). Of the three subfamilies of the Leguminosae, the Papilionoideae is the largest (450 genera, 12,000 species; Polhill, 1981), most diverse, and by far the most important economically. In part because of its size and diversity, and because of reliance on a small number of “key” taxonomic characters, phylogenetic relationships at the subtribal and tribal levels in the subfamily have remained unclear. A concerted effort has been made in recent years to remedy this problem, by identifying new systematic characters, reevaluating traditional characters, and applying rigorous phylogenetic analytical methods to questions at all taxonomic levels in the family. This has resulted in several volumes, some based on international symposia, in which information from a diversity of sources and disciplines has been compiled in an effort to improve our understanding of the family (Summerfield and Bunting, 1980; Polhill and Raven, 1981; Stirton, 1987).
One table includes a statistical summary of flowering-plant taxa: c235 000 species of 12 615 genera, 440 families, and 711 subfamilies and undivided families in 28 superorders, 70 orders, and 75 suborders of Angiospermae. Three other tables summarize the indigenous distribution of the families and subfamilies of Angiospermae about the world. -from Author
Data derived from cleavage points of various restriction endonucleases in all three genomes present in eukaryotes—nuclear, mitochondrial, and chloroplast— have been used for phylogenetic reconstruction in diverse groups of organisms. Mapped restriction sites, which represent a sampling of a whole genome or of any specific sequence, can be considered estimates of homologous characters and their transformations. In this sense, restriction site data are like any other robustly derived systematic data (e.g., morphological). An important difference is that probabilities for character-state transformations within restriction site characters can now be formulated using hypothetical or empirical estimates of sequence evolution (DeBry and Slade, 1985). Such transformational probabilities can be incorporated into phylogenetic reconstruction using parsimony with the application of maximum likelihood character-state weights (Felsenstein, 1981a).
Chloroplast DNA restriction site variation was examined for all 16 species of Microseris, using 22 restriction endonucleases, filter hybridization experiments, and comparative mapping procedures. Mutations were scored relative to other genera of the subtribe Microseridinae, and related genera of the tribe Lactuceae. A total of 115 restriction site mutations was detected, 78 of which were phylogenetically informative. A single most parsimonious cladogram was constructed which indicates three major lines of evolution within the genus. The morphologically distinct annual M. lindleyi was found to be the most divergent and forms the basal lineage within the genus. Forty-three mutations separate annual and perennial species of the genus, whose average sequence divergence is 0.7%. The parentage of the allotetraploid species M. heterocarpa was confirmed, utilizing cpDNA and nuclear ribosomal DNA variation. Evaluation of relative rates of cpDNA evolution indicates that generation time is not responsible for unequal rates of cpDNA in different lineages. The results also suggest that a taxonomic reevaluation of Microseris at the subgeneric level is warranted.
In an attempt to elucidate relationships among the morphologically diverse members of Saxifragaceae sensu lato, phylogenetic analyses of rbcL sequence data were conducted on representative genera of 16 of the 17 subfamilies. Also included were many putatively related families, as well as a diverse array of dicotyledonous flowering plants. Our phylogenetic analyses suggest that taxa of Saxifragaceae sensu lato are allied with at least 10 separate, often distantly related, lineages of several subclasses of flowering plants. Sequence data, in combination with other lines of evidence, suggest that Saxifragaceae sensu stricto should consist only of subfamily Saxifragoideae, a group of about 30 herbaceous genera that form the core of Saxifragaceae sensu lato. These data also suggest that potential close relatives of Saxifragaceae sensu stricto include Iteoideae, Pterostemonoideae, and Ribesoideae and possibly Penthoroideae and Tetracarpaeoideae, all traditional subfamilies of Saxifragaceae sensu lato, as well as Crassulaceae. These members of Saxifragaceae sensu lato, along with Saxifragaceae sensu stricto, Crassulaceae, and several genera from the subclass Hamamelidae, are basal to a large assemblage of taxa, most of which are usually placed in Rosidae. Within this primarily rosid alliance, representatives of four other subfamilies of Saxifragaceae sensu lato (Francooideae, Baueroideae, Parnassioideae, and Lepuropetaloideae) are allied with the rosid families Greyiaceae, Cunoniaceae, and Celastraceae. According to rbcL sequence evidence, Hydrangeoideae and Cornaceae are closely related members of a clade that is basal to a large group of taxa primarily from subclass Asteridae. Representative genera of four subfamilies of Saxifragaceae sensu lato (Phyllonomoideae, Escallonioideae, Montinioideae, and Vahlioideae) are in our results allied with taxa usually included in Asteridae. Significantly, relationships of Saxifragaceae sensu lato suggested by rbcL sequence data are in very close agreement with those supported by several other lines of evidence, especially embryology, serology, and iridoid chemistry.
Chloroplast DNA (cpDNA) restriction site analysis was used to explore evolutionary relationships within a taxonomically difficult group of diploid willows comprising seven taxa (Salix sect. Longifoliae). Forty-five population samples from throughout North America were analyzed with up to 23 restriction endonucleases. Clades revealed by cpDNA data are generally congruent with groups delineated by enzyme electrophoresis. Both sets of molecular data disagree with traditional taxonomic concepts. Morphological characters such as stigma length and pubescence, traditionally viewed as taxonomically important, are not correlated with major genetic divisions in the section. High levels of intraspecific cpDNA variability were detected, mostly representing geographic patterns of divergence. Salix interior, for example, contains six distinct chloroplast genomes, and has a mean sequence divergence of 0.09%. Conversely, S. sessilifolia, S. fluviatilis, and populations of S. exigua from the Pacific Northwest all possess identical chloroplast genomes. Hybridization appears to be an important process in the section. Five cases of hybridization and subsequent cytoplasmic capture were documented. Chloroplast DNA data suggest a southern origin for the section and a northward radiation into geographically isolated montane and arid lowland habitats. The high incidence of cytoplasmic capture and intraspecific cpDNA variability detected in this study underscores the importance of analyzing multiple cpDNA samples of a taxon in combination with nuclear markers in molecular systematic studies.
Parsimony analyses of DNA sequence data from the chloroplast rbcL gene were used to assess the circumscription and phylogenetic position of the Geraniaceae, generic relationships within the family, and the affinities of the families previously assigned to the order Geraniales. The other families placed in the Geraniales in recent higher-order classifications fall into four well separated lineages, none of which appears to be closely related to the Geraniaceae. Only Hypseocharis, often included in the Oxalidaceae, receives strong support as a close relative to the monophyletic Geraniaceae sens. str., as suggested by Boesewinkel on the basis of seed anatomy. Sequence comparisons of rbcL provide the first highly resolved phylogeny of the Geraniaceae, indicating that Pelargonium is a sister group to the remainder of the family, that Erodium and Geranium are probable sister genera, and that Monsonia and Sarcocaulon are either sister genera or are congeneric.
Several features, foremost its conservative mode of evolution, make chloroplast DNA an extremely valuable molecule for phylogenetic studies. Its conservatism is also its only serious drawback, as this can limit the amount of useful DNA variation at the intraspecific level. Comparative restriction site mapping is currently the preferred molecular method for examining interspecific relationships. At this level, one typically encounters less than 5% homoplasy. Furthermore, the predominantly uniparental inheritance of chloroplast DNA provides unique insights into the origin of hybrid and polyploid complexes, as illustrated by examples from the genus Brassica. In many families of angiosperms, such as the Asteraceae and Orchidaceae, restriction site mapping can also be used to determine intergeneric relationships. The greater expense of DNA sequencing makes it most appropriate only at those higher taxonomic levels-above the family level-where restriction site mapping fails. Within angiosperms, the rbcL gene appears to be the chloroplast gene of choice for phylogenetic studies. Twenty-five rbcL sequences have already been accumulated, and several laboratories are making a coordinated effort to sequence this gene widely among angiosperms and gymnosperms. The more conservatively evolving ribosomal RNA genes hold the greatest promise for resolving the deepest branchings of plant evolution and, indeed, have already settled the ultimate question of chloroplast evolution, namely, its endosymbiotic origin. A third approach to extracting phylogenetic information from chloroplast DNA is by analyzing the distribution of major structural rearrangements, such as inversions and the loss or gain of genes and introns. Although such rearrangements are rare relative to point mutations, their great rarity and freedom from homoplasy also make them extremely powerful characters. Examples to be discussed include an inversion defining the most ancient branching in the Asteraceae, rearrangements that mark several major divisions within the Fabaceae, and events that identify the green algal ancestors of land plants.
Heiser (1949) hypothesized that a weedy race of Helianthus bolanderi had originated by the introgression of genes from H. annuus into a serpentine race of H. bolanderi. Although Heiser's investigation of these species is frequently cited as one of the best examples of introgression in plants, definitive evidence of gene exchange is lacking (Heiser, 1973). To determine whether the weedy race of H. bolanderi actually originated via introgression, we analyzed allozyme, chloroplast-DNA (cpDNA), and nuclear-ribosomal-DNA (rDNA) variation. Evidence from enzyme electrophoresis did not support the proposed introgressive origin of weedy H. bolanderi. We detected a total of 37 low-frequency alleles distinguishing the serpentine race of H. bolanderi from H. annuus. Weedy H. bolanderi possessed only four of the 37 marker alleles. Further analysis demonstrated that serpentine H. bolanderi combined seven of the 35 alleles distinguishing H. annuus from weedy H. bolanderi, indicating that serpentine H. bolanderi shares three more marker alleles with H. annuus than does weedy H. bolanderi. These results are similar to expectations for race divergence from a single common ancestor and suggest that, if introgression occurred, the majority of marker alleles were rapidly lost following the initial hybridization event. Even more compelling evidence opposing Heiser's (1949) hypothesis, however, was from restriction-fragment analysis of cpDNA and nuclear rDNA. We detected a total of 17 cpDNA and five rDNA restriction-site mutations among the 19 populations examined. No parallel or back mutations were observed in phylogenetic trees constructed using either cpDNA or rDNA mutations, and both phylogenies were completely congruent regarding the alignment of all three taxa. In addition, the weedy race of H. bolanderi possessed a unique cpDNA, which was outside the range of variation observed among populations of either of the presumed parental species. Mean sequence divergences between the cpDNAs of weedy H. bolanderi and those of serpentine H. bolanderi and H. annuus were 0.30% and 0.35%, respectively. These estimates are comparable to sequence-divergence values observed between closely related species in other plant groups. Given the lack of parallel or convergent mutations in the cpDNA and rDNA phylogenetic trees, the complete congruence of these trees with flavonoid- and allozyme-variation patterns, and the presence of a unique and divergent chloroplast genome in the weedy race of H. bolanderi, we suggest that the weedy race of H. bolanderi was not derived recently through introgression, as hypothesized, but is relatively ancient in origin.
Tiarella comprises three species, T. cordifolia, T. trifoliata, and T. polyphylla, distributed in eastern North America, western North America, and eastern Asia, respectively. Few systematic studies have compared related species displaying this well-known floristic disjunction. The flavonoids and karyotypes of species of Tiarella were therefore compared to determine the extent of differentiation among these apparently long-isolated species. Species of Tiarella possess the same chromosome number (2n = 14) and very similar karyotypes. Tiarella polyphylla exhibits a distinctive secondary constriction and associated heterochromatic band not observed in either T. cordifolia or T. trifoliata. Each species has a distinctive array of flavonoid constituents. Differences in mono- and diglycosides exist between T. cordifolia and T. trifoliata. Triglycosides are absent from T. polyphylla, whereas they are present in T. cordifolia and T. trifoliata; T. polyphylla displays the simplest array of flavonoids.
Fuchsia sect. Skinnera, the only Old World group in the genus, comprises three species in New Zealand and one in Tahiti. These species include a tree, a large shrub, a climbing-scandent shrub, and a creeping, barely woody plant. The section is extremely distinct from the New World species of Fuchsia, and several sharply contrasting models depicting the evolutionary history of these species and the character state changes associated with habit, breeding systems, and chemistry have been proposed. A chloroplast DNA restriction site analysis of sect Skinnera and two outgroup sections was performed, generating a single tree depicting maternal relationships. This tree is congruent with one previously proposed model and demonstrates that the rare F. procumbens of New Zealand is the sister group to all other species in the section, while F. cyrtandroides of Tahiti is the sister taxon of the two remaining New Zealand species. Based on the chloroplast DNA analysis, a critical reevaluation was made of character state changes in the section relating to morphology, breeding systems, and flavonoid compounds.
A parsimony analysis of 46 rbcL sequences was performed to evaluate relationships among Cornus and putative relatives, as well as among subgroups within Cornus. Our results indicate that Alangium, nyssoids (Nyssa, Davidia, and Camptotheca), mastixioids (Diplopanax and Mastixia), Curtisia, and genera of Hydrangeaceae are the closest relatives of Cornus. These taxa, plus Cornus, constitute a "cornaceous clade," which differs from all previously proposed Cornus alliances. Within this cornaceous clade, four major lineages were identified; (i) Cornus-Alangium, (ii) nyssoids-mastixioids, (iii) Curtisia, and (iv) hydrangeoids. The relationships among the four major lineages within the cornaceous clade remain unresolved. Sequence data from rbcL also reveal that Corokia, Helwingia, Aucuba, Garrya, and Griselinia, previously placed in Cornaceae by some authors, are only distantly related to Cornus and other members of the cornaceous clade. Four major lineages were identified within Cornus by rbcL sequence data, but relationships among these groups are incompletely resolved.
The analysis of rbcL sequences of representative species of 13 of the 20 genera of the Cupressaceae sens. str. has produced a cladogram that agrees with data derived from other sources. The monophyly of the family is well supported. The cladogram provides support for the recognition of a basically northern subfamily (Cupressoideae) and a southern subfamily (Callitroideae), but the boundary between the subfamilies needs to be realigned by moving Tetraclinis from the Callitroideae to the Cupressoideae. The tribal arrangement of Li is largely artificial: the Libocedreae, Cupresseae, and Thujopsideae are clearly paraphyletic.
Nucleotide data are a restricted character system complex enough to confound phylogenetic analyses yet simple enough to permit establishment of probability models for sequence change and corresponding character-state weighting schemes. We have previously developed a general method for weighting DNA data that is here elaborated for protein-coding sequences. Included in the present model are corrections for (i) multiple substitution events, (ii) transition/transversion bias, and (iii) differential proportions of changes occurring at first, second, and third codon positions. This model is shown to be generally consistent for all phylogenetically useful data. Greater understanding of the properties of equal versus differential character-state weighting comes from consideration of numbers of terminal taxa and lengths of tree segments. With insufficient sampling of taxa, differential weighting attempts to correct for undetected multiple substitution events. Both equal and differential weighting should give the same result if sufficient numbers of terminal taxa permit the detection of historically misleading character-state changes. Nevertheless, spurious attraction of tree segments remains a systematic problem that is not easily resolved either by equal weighting or by our differential weighting model, which acts globally rather than adjusting for different probabilities of character-state change among tree segments. Artifactual segment attraction is best understood in terms of asymmetries in λ (which represents state changes per character during a particular segment interval). We relate the consistency index to numbers of terminal taxa and λ, illustrating its dependence upon numbers of potential tree segments. Prospects for phylogenetic reconstruction from protein-coding nucleotide data are discussed with reference to the robustness of equal weighting (given our own model) with adequate taxonomic sampling.
Restriction site variation of chloroplast DNA (cpDNA) and nuclear rDNA was used to assess phylogenetic relationships among the nine species of the taxonomically complex genus Lithophragma. Chloroplast DNA restriction site data indicate the presence of two well-marked lineages: L. bolanderi, L. heterophyllum, and L. cymbalaria; and L. affine, L. parvifiorum, and L. trifoliatum. A clear alliance between L. glabrum and the latter group is only weakly supported. A tetrachotomy leaves the relationships among the two major lineages and L. campanulatum and L. tenellum unresolved. Nuclear rDNA data further support a close relationship among L. bolanderi, L. heterophytlum, and L. cymbalaria. Relationships based on DNA data agree in part with those based on morphological data, although several important discrepancies also emerged. In contrast, relationships suggested by cpDNA and flavonoid data are in particularly close agreement. Comparison of the DNA-based phylogeny with evidence from morphology suggests that fusion of the hypanthium to the ovary wall has occurred independently several times in the genus or that hypanthium fusion occurred early in the radiation of the genus and was subsequently lost. Similarly, the DNA-based phylogeny suggests that some flavonoid constituents exhibit multiple gains or losses. In addition, a reduction in the total number of flavonoid compounds present has apparently occurred twice within the genus.
Previous studies have shown that in several angiosperms and the liverwort Marchantia the chloroplast gene rpl2, encoding ribosomal protein L2, is interrupted by an intron, but that in spinach (Spinacia oleracea, Caryophyllales) this intron has been lost. We have determined the distribution of the rpl2 intron for 390 species representing 116 angiosperm families. Filter hybridizations reveal that the intron is absent from the chloroplast genomes of all examined families of the Caryophyllales, suggesting that the intron was lost in the common ancestor of the order. Sequencing of the rpl2 gene in five genera of the Caryophyllales and in Rumex (Polygonales) not only confirms the filter hybridization results, but also shows that for all taxa lacking the intron, the rpl2 gene has undergone a precise deletion of the intron. In all cases, it is the original rpl2 gene that has sustained loss of its intron. This implies that in chloroplast DNA, integration of exogenous genes (e.g., a reverse transcript of a spliced mRNA) occurs mainly by homologous, replacement recombination, rather than by illegitimate recombination elsewhere in the genome. Filter hybridizations also reveal that the rpl2 intron was lost independently in the common ancestors of at least five other lineages of dicotyledons: Saxifragaceae (s.s.), Convolvulaceae (including Cuscuta), Menyanthaceae, two genera of Geraniaceae, and one genus of Droseraceae. The molecular and phylogenetic implications of these independent intron losses are discussed.
The flavonoid glycosides of both varieties of Elmera racemosa were isolated and identified. The compounds were the monoglucosides of kaempferol, quercetin and myricetin, the rutinosides
of the same aglycones, and the rhamnosylrutinosides of kaempferol and quercetin. All glycosides were linked at position-3
of the flavonols. The two varieties (var. racemosa and var. puberulenta C. L. Hitchcock) were identical. A comparison of the flavonoid chemistry of Elmera, Heuchera, and Tellima supports the existence of Elmera as a genus. A survey of several collections of Tellima grandiflora, Heuchera micrantha, and H. cylindrica showed only minor quantitative differences in the two-dimensional thin layer chromatograms from collection to collection.
The possible origin of Tellima and Elmera from ancestral stock having Heuchera-like flavonoid chemistry is discussed.
With the exception of Mitella breweri and M. trifida, all North American species of Mitella, Conimitella williamsii, and species of Lithophragma possess essentially identical chromosome morphology. The high degree of karyotypic similarity among genera is further indicated by normal bivalent formation and high pollen stainability in intergeneric hybrids involving Conimitella williamsii and Mitella stauropetala. Conimitella, Lithophragma, and most species of Mitella possess karyotypes that are indistinguishable from those of species of Heuchera, Tolmiea, and Tiarella. Chromosomal data, as well as evidence from morphology, intergeneric hybridization, flavonoid chemistry, and the host preferences of Puccinia rusts, suggest that Conimitella, Lithophragma, Mitella, Heuchera, Tiarella, and Tolmiea form the core of a natural group of genera having x = 7. The monotypic Bensoniella, as well as Elmera and Tellima, differ in chromosome morphology from species of these six genera. Other lines of evidence, including morphology and flavonoid chemistry, indicate, however, that all of these genera are closely allied. A second natural group of genera having x = 7 is composed of Bolandra, Boykinia, Suksdorfia, and Sullivantia. Studies of species throughout Saxifrageae indicate that chromosome morphology is highly conserved in the tribe. Chromosomal data, in conjunction with insights from enzyme electrophoresis, suggest that this group radiated rapidly in North America with little accompanying chromosomal or genetic divergence.
Bolandra, Boykinia, and Suksdorfia are all characterized by x = 7 and have essentially identical Hy-banded patterns and gross morphological karyotypes. Cytological data suggest a close relationship between Boykinia intermedia and B. major, both of which are unusual in possessing 2n = 28. Karyotypes of Bolandra, Boykinia, and Suksdorfia appear to be indistinguishable from those reported earlier for Sullivantia. Peltoboykinia differs from Bolandra, Boykinia, Suksdorfia, as well as Sullivantia, in having x = 11. Peltoboykinia also exhibits a distinctive karyotype that readily differentiates it from these genera. Karyotypic data suggest that Bolandra, Boykinia, Suksdorfia, and Sullivantia form a natural group. These genera are united also by several morphological features, including axile placentation and a monotelic inflorescence. Data from flavonoid chemistry and the host preferences of Puccinia rusts also indicate a close relationship among these four genera. Although Peltoboykinia is clearly allied with Bolandra, Boykinia, Suksdorfia, and Sullivantia, on the basis of cytological evidence its closest affinities may lie elsewhere in Saxifragaceae, perhaps with Saxifraga.
... Detailed result. return to summary results page. Wells EF, Bohm BA. 1980 Chemotaxonomic studies in the Saxifragaceae s. 1. 15. The flavonoids of subsection Villosae section Heuchera in the genus Heuchera . Can. J. Bot. 58. 1459-63. Saxifragaceae, Chemotax ( , 185709471). ...
Flavonoid constituents of diploid (2n = 14) and tetraploid (2n = 28) populations were analyzed throughout the range of Tolmiea menziesii. The species contains kaempferol and quercetin 3-O-mono-, di, and triglycosides, as well as myricetin and isorhamnetin 3-O-mono- and diglycosides. Minor variation in flavonoid constituents was observed among populations, but this was not correlated with ploidy. The qualitative identity in flavonoid constituents between the diploid and tetraploid cytotypes supports the contention that the tetraploid cytotype is of autopolyploid origin. Flavonoid data are therefore m agreement with evidence from gross morphology, karyology, floral ant hocyanins, ribosomal genes, and enzyme electrophoresis, all of which support the hypothesis of autopolyploidy.
A lineage of short-cycled rusts, Puccinia species, is recorded on 10 genera and 86 species of Saxifragaceae, including 10 sections and various subsections of Saxifraga. These rusts can be arranged approximately in evolutionary sequence. From the rust data it is inferred that Saxifragaceae originated in eastern Asia; migrants radiated early in the Himalayan Region and western North America; a return migrant from North America established Saxifraga in or near Japan; migrants from Japan established slightly advanced Saxifraga groups in the Himalayas and western North America; migrants from the Himalayas (related to Melanocentrae) established moderately advanced Saxifraga groups in Europe and North America; finally Himalayan migrants (related to sect. Kabschia) established sect. Trachyphyllum in Beringia and sects. Xanthizoon, Euaizoonia and Porphyrion in the Alps. These last sections probably evolved during the Pleistocene.
A base chromosome number of x = 7 characterizes many genera of the Saxifraginae. A high degree of karyotypic constancy was found among species representing six of these genera (Boykinia, Heuchera, Mitella, Sullivantia, Tiarella, and Tolmiea). Boykinia aconitifolia and six species of Sullivantia are characterized by the same karyotype. Four species of Heuchera, Mitella diphylla, Tiarella cordifolia, and Tolmiea menziesii (the last at the tetraploid level) possess a second karyotype that differs from the first in the position of the centromere of only one chromosome pair. These karyological observations suggest generic relationships that agree with those based on morphology, flavonoid chemistry, and crossability.
The eastern species of Heuchera fall into two natural groups on the basis of phenological, morphological, and breeding data. Three spring-blooming species (H. pubescens, H. richardsonii, and H. longiflora) formerly belonging to section Heruchea are placed in subsection Americanae of section Heuchera with H. americana and H. caroliniana. These species possess striking differences in floral characteristics but are vegetatively quite similar; they do not have genetic barriers to hybridization and several species in this group are only weakly isolated by geographical and ecological barriers. Natural hybridization involving three species (H. americana with H. pubescens and H. richardsonii) is suspected. Among the summer-blooming species H. parviflora is removed from subsection Micranthae to subsection Villosae within section Heuchera. These species are very similar in floral characters but are vegetatively and ecologically distinct; they apparently do not hybridize in the wild, even though artificial hybrids between them are moderately fertile. The first chromosome counts for H. caroliniana and H. longiflora (both n = 7) are reported. The treatment includes descriptions for all taxa and illustrations for all species. A key to the species and varieties as well as distribution maps are provided. All numbered collections examined are listed in an index.
The flavonoid profiles of Astilbe (four taxa studied) and Rodgersia (two taxa studied) are based on simple flavonol glycosides. Astilbe has of kaempferol, quercetin, and myricetin, while Rodgersia has only mono- and diglycosides of kaempferol and quercetin. Astilbe×arendsii was also shown to accumulate dihydrochalcone glycosides. The flavonoid profile of Rodgersia is the simplest recorded so far in the herbaceous Saxifragaceae. The flavonoids of two species of Aruncus were shown to be based upon kaempferol and quercetin . One of the species also exhibited an eriodictyol glycoside. The triglycoside differences were not considered important, but the differences in myricetin occurrences were taken as evidence against derivation of Saxifragaceae from an Aruncus-like ancestor. Should such an event be proposed, however, serious consideration would have to be given to the current pattern of myricetin occurrence in the two families.
Eight species of Saxifraga representing sections Micranthes, Hirculus, Dactyloides and Xanthizoon were studied for their flavonoids (S. california, S. integrifolia, S. michauxii, S. ferruginea, S. eschscholtzii, S. hirculus, S. caespitosa and S. aizoides). The major compounds present in most species were kaempferol and quercetin monogluocosides and galactosides. Glucosides of kaempferol and quercetin predominate in the first four species listed, while galactosides of quercetin and myricetin are dominant in the lastthree. 3-O-Methyl- and 3,3′-di-O-methylquercetin were identified from S. californica and S. integrifolia. Saxifraga caespitosa synthesizes a complex mixture of O-methylated flavonols as well as a novel O-methylated dihydrokaempferol.Species pairs S. michauxii/S. ferruginea and S. californica/S.integrifolia exhibit close flavonoid similarity which may reflect their morphological similarities.