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Whereas there is increasing evidence that some polyploid taxa have multiple independent origins, little attention has been given to the possibility that taxa arising through selective processes without ploidal shifts also may be the products of recurrent evolution. I argue that there are no necessary reasons why ecologically distinct races and species could not arise from separate lineages at different times and in different places. Similarity of the genetic structure of progenitor populations combined with parallel selective pressures would make this possible, as would evolution in the direction of greatest genetic variance. Putative examples of multiple independent origins of single and multiple adaptations are reviewed. The possibility that some taxa are polyphyletic is suggested by the presence of isolated populations in different clades. I also consider the possibility of the recurrent origins of reproductive isolating mechanisms and of species.
Geranium section Brasiliensia (Geraniaceae) consists of three species centered in Southern Brazil: G. arachnoideum,G. brasiliense, and G. glanduligerum. Fruits with “Erodium-type” dispersal have been found in all species of section Brasiliensia, which allows classifying this section within subg. Erodioidea. Diagnostic morphological features are analyzed and compared to other sections of Geranium subg. Erodioidea. No new characters explaining phylogenetic relationships within subg. Erodioidea or supporting its monophyly are found. A new key is provided, as well as new and detailed descriptions. Geranium brasiliense and G. glanduligerum are here illustrated for the first time. Three lectotypes are designated, and a distribution map is presented.
Dillandia (Compositae, Liabeae) is described as new on the basis of three species: D. perfoliata (S. F. Blake) V. A. Funk and H. Rob. (=Liabum perfoliatum), D. chachapoyensis (H. Rob.) V. A. Funk and H. Rob. (=Munnozia chachapoyensis), and D. subumbellata V. A. Funk and H. Rob. Phylogenetic analysis of Liabeae using data from the nuclear ribosomal DNA internal transcribed spacer (Kim et al. unpublished data) places two of the Dillandia species outside the subtribe Munnoziinae and separates them from all other clades in the tribe as well. Irregular spine groupings on the pollen confirm the separation of these species from the Munnoziinae. Morphological analysis suggests that these two and one additional species form a monophyletic group defined by their possession of bullate leaf surfaces and pale anther thecae. This study is an example of how molecular and morphological data, when used together, can lead to a better classification.
Smithatris supraneanae W. J. Kress & K. Larsen, gen. et sp. nov. is described and illustrated. The new taxon was first collected in the limestone hills in the Saraburi Province north of Bangkok, Thailand, and probably ranges into adjacent Burma as well. Smithatris is most closely allied with several genera in the tribe Hedychieae including Curcuma, Stahlianthus, and Hitchenia. It most closely resembles the latter genus sharing the petiolate leaves and long pedunculate inflorescence with congested, pouched bracts, but differing in the deeply split labellum and hood-like structure formed by the lateral staminodes and dorsal corolla lobe that partially encloses the anther. In a separate analysis of the phylogenetic relationships of the genera of the Zingiberaceae based on molecular sequence data, Smithatris forms a nested assemblage with the above three genera thereby supporting recognition of this new taxon at the generic level. Smithatris is commonly used in ceremonies during the Buddhist lent, is sold as a cut flower in local markets in Saraburi, Thailand, and recently has become widespread in commercial nurseries. The fact that this ethnobotanically important plant has remained unknown to taxonomists until now suggests that our knowledge of the flora of tropical Asia is still rudimentary.
Stem and leaf anatomy of Dirachma socotrana, an endemic species from Socotra, is described in detail. The diffuse porous to semi-ring-porous wood is characterized by solitary vessels and vessels in short radial multiples with a tendency for oblique/radial vessel arrangement, simple vessel perforations, vascular tracheids, nonseptate fibers with simple to minutely bordered pits mainly confined to radial walls, axial parenchyma which is scanty paratracheal and in 1–2-seriate marginal bands, and mainly 1–2-seriate heterocellular rays. The inner bark shows stratified fiber groups; the outer bark has flaring rays. The dorsiventral leaves typically have an indumentum of small, unicellular hairs, anomocytic stomata, an adaxial epidermis largely composed of periclinally divided mucilage cells. The petiole and midrib vascular bundle is typically composed of a simple arc-shaped strand. Prismatic crystals are common in the wood, bark, pith, and leaf. The systematic position of the monotypic family Dirachmaceae in a newly defined Rosales sensu Angiosperm Phylogeny Group was established recently on the basis of molecular data and confirmed by ovule and seed characters. Vegetative anatomical features provide additional arguments for a placement of the family within this order, particularly close to the Rhamnaceae.
The Monopetalae or Sympetalae have been resurrected recently as the Asteridae s.l., a large clade that includes almost all sympetalous angiosperms. Phylogenetic analyses of a large, combined data set of sequences of four genes (18S rDNA, rbcL, ndhF, atpB) have improved our understanding of the evolutionary history of this large clade of angiosperms. Most of the taxa fall within one of four major clades, the Cornales, Ericales, euasterids I (comprising Lamiales, Solanales, Boraginaceae, Gentianales, and Garryales), and euasterids II (comprising Asterales, Apiales, Dipsacales, Escalloniales, and Aquifoliales). We used the phylogenetic tree based on our recent phylogenetic analysis of four genes to elucidate the evolutionary patterns of the ovule and the diversification of iridoid biosynthesis in the asterids. Asterid-specific patterns of character distribution can be seen. Unitegmic-tenuinucellate ovules occur almost universally in the asterid clade. Cellular endosperm is ancestral in the asterids; nuclear endosperm emerged several times. Shedding of tricellular pollen does not seem to be a useful character for higher level taxonomy except for uniting Apiales and Dipsacales. Reversals from nuclear endosperm formation and tricellular pollen are not observed. Iridoids occur in many asterid clades and are probably ancestral. The ability to produce iridoids, however, has been lost frequently. Secoiridoids predominate in the euasterids II, whereas carbocyclic iridoids are most diverse in Lamiales. Although this study showed high correlation of unitegmic-tenuinucellate ovules with iridoid synthesis, several questions remain. Studies of the ontogeny and biosynthesis of these characters can now focus especially on those areas of transition determined in this analysis.
Erythronium populations from the southwestern Olympic Mountains of Washington, U.S.A. are tetraploid (2n = 48) and are morphologically intermediate between two widespread diploid species of this region, the subalpine E. montanum and the low-elevation E. revolutum. The Olympic Mountains populations lie between the geographic and elevational ranges of E. montanum and E. revolutum and exhibit a combination of the isozyme characteristics of these two species, possessing 11 alleles in common with E. montanum and four in common with E. revolutum. The evidence supports their derivation from the above two species through allopolyploid hybridization, and they are described here as the new species Erythroniumquinaultense.
Sequence data for the ITS region of rDNA provide evidence that Linanthus bicolor, an annual species of western North America, is polyphyletic. A previous study identified two sequence types, distinguished by over 50 fixed nucleotide differences, in populations from different geographical regions. Phylogenetic analysis revealed that the two are not sister taxa and, furthermore, that each represents an independent origin of self-fertilization. The morphological similarity of the two taxa, especially in floral traits, is hypothesized to have resulted from convergent evolution in characters associated with self-fertilization. Morphological and genetic data for populations sampled throughout the range of L. bicolor indicate that these distinct genetic types correspond to intraspecific taxa as currently circumscribed. The molecular evidence for polyphyly of L. bicolor, presence of significant morphological differences between the two taxa, and evidence that they are, to a large extent, reproductively isolated provide a strong rationale for distinguishing them at the level of species. We propose that L. bicolor var. minimus be elevated to species status with the designation, L. minimus.
Nuclear ribosomal internal transcribed spacer (ITS) regions were used to address questions about the taxonomy, phylogeny, and biogeography of the hazelnut genus, Corylus (Betulaceae). The ITS phylogeny supports the recognition of two sections within the genus: section Acanthochlamys comprising the basal extant lineage Corylus ferox, and section Corylus consisting of the remainder of the genus. Within section Corylus, recognition of three subsections is supported: subsection Corylus (species with leafy, more or less bell-shaped involucres), subsection Colurnae (tree species with deeply dissected involucres), and subsection Siphonochlamys (species with tubular involucres). The ITS sequence divergence among species within Corylus is low, corresponding with that of most other North Temperate disjunct taxa. A few morphological characters were added to the analysis to boost support for branches. Migration between Asia and North America via the Bering land bridge is suggested by subsection Siphonochlamys while long distance dispersal from Europe to North America during the late Tertiary is suggested by the close relationship and lack of sequence divergence among members of subsection Corylus. A close biogeographic relationship among areas of eastern Asia, the Himalayas, and the Mediterranean region is suggested by the subsection Colurnae clade.
The genus Zygocarpum is described with six species formerly of Ormocarpum. This genus is endemic to the Horn of Africa, the southern end of the Arabian Peninsula, and the island of Socotra. Analysis of combined nuclear ribosomal ITS/5.8S and morphological data reveals that Zygocarpum is strongly supported as monophyletic and the basal-most lineage of a mainly African-Madagascan clade comprising also Ormocarpum, Ormocarpopsis, and Peltiera. A second analysis involving a combination of nuclear ribosomal ITS/5.8S, chloroplast trnL intron, and morphological data reveals some well supported relationships among the species of Zygocarpum. Zygocarpum dhofarense and Z. yemenese, endemic to the Arabian Peninsula, form a sister clade to the central Somalian Z. gillettii. The precise relationships among the other two Somalian species, Zygocarpum rectangulare and Z. somalense, as well as the endemic Socotran Zygocarpum coeruleum, are less certain. The distribution of Zygocarpum, which spans the Gulf of Aden, is considered to be due to a Late Tertiary vicariant event involving the separation of the Arabian Peninsula from continental Africa.
With approximately 2,000 species, Carex is the largest genus in the Cyperaceae and is one of the most widespread genera in the world. Relationships within Carex and among the genera of the Cariceae (Carex, Cymophyllus, Kobresia, Schoenoxiphium, and Uncinia) are unclear. For this reason, a molecular phylogenetic study employing nrDNA ITS and cpDNA trnT-L-F spacer sequences was undertaken. In addition to creating hypotheses of relationship for the Cariceae and testing classifications of this tribe, a primary goal of this study was to assess relationships within Carex section Acrocystis and identify a monophyletic group for more detailed study. These analyses suggest that Cymophyllus, Kobresia, Schoenoxiphium, and Uncinia are nested within Carex. Three primary clades are suggested: a Carex subgenus Vignea clade, a clade including Carex subgenus Primocarex (for the most part) and the other genera of Cariceae, and a clade predominately comprised of Carex subgenera Carex and Indocarex. A large part of Carex section Acrocystis forms a monophyletic group but several Eurasian species are more closely related to other groups rather than to this core clade. Assessment of chromosome number variation across the Cariceae clade suggests that the ancestor of the Cariceae had a moderate to high chromosome number. In addition, these analyses suggest the sister group of the Cariceae is a clade including Scirpus sensu stricto, Amphiscirpus, and Dulichium.
The phylogeny of Isolepis was investigated by cladistic analysis of rbcL and trnL-F sequence data from 69 species in 26 genera of Cyperaceae. The genus Isolepis, as currently circumscribed, is not monophyletic. Three species, I. nodosa, I. Marginata, and I. trolli, are more closely related to Ficinia, whereas the position of I. humillima is uncertain. The remainder of Isolepis is sister to Ficinia and Desmoschoenus and together with Hellmuthia and Scirpoides form a clade sister to Cyperus s.l.; this clade shares the Cyperus-type embryo. Scirpus s.l. is not monophyletic. Scirpus s.s. and other genera with a Fimbristylis-type embryo form a monophyletic clade, whereas Schoenoplectus and other genera with a Schoenoplectus-type embryo form a grade.
A phylogeny and revised classification of the flowering plant family Cunoniaceae and related taxa is presented. Parsimony cladistic analyses, including bootstrap and decay analyses, of chloroplast DNA sequences from two loci, trnL-trnF and rbcL, and morphology show that three genera often placed in their own families, Bauera, Davidsonia, and Eucryphia, are nested within Cunoniaceae. Brunellia may be most closely related to the Australian pitcher plant Cephalotus, and Aphanopetalum is in Saxifragales. Within Cunoniaceae, the New Guinean-South Pacific genera Acsmithia and Spiraeanthemum form a sister clade to the rest of family. Within this larger clade is a basal grade in which flowers mature centrifugally on an inflorescence axis, and a clade in which flowers mature synchronously to acropetally on an inflorescence axis. Other conspicuous morphological characters, including stipule position, inflorescence form, petal presence or absence, number of pollen colpi, carpel number, and fruit morphology, are homoplasious among and within clades at the tribal level. The results are used to propose a circumscription of the family, with 26 genera and approximately 300 species. Twenty genera are placed among six tribes (Cunonieae, Codieae, Geissoieae, Caldcluvieae, Schizomerieae, and Spiraeanthemeae), and six poorly resolved genera are not placed into any formally named group. Among outgroups, the Australian endemic family Tremandraceae is nested within Elaeocarpaceae.
Subfamily Chloridoideae has a history of unsettled taxonomic problems at the tribal and generic levels, and phylogenetic relationships within and among its tribes are not well understood. DNA sequences of the plastid gene matK for 74 species representing 56 chloridoid genera and all tribes and subtribes were used to reconstruct a phylogeny for the subfamily. The base of the Chloridoideae clade shows a polytomy among Triraphis schlecteri and three strongly supported clades labeled A, B, and C. Clade A comprises the Pappophoreae, Uniolinae, and three genera of Eragrostideae; clade B includes most representatives of subtribe Sporobolinae, Spartina, Zoysia, and two Eragrostis species; and clade C encompasses the remaining species. The two largest tribes Eragrostideae and Chlorideae appear polyphyletic. The traditional Pappophoreae minus Pappophorum comprise a clade corresponding to the Cotteinae; Pappophorum nests within a sister clade. The Uniolinae, Orcuttieae, and Triodiinae form strongly supported monophyletic entities. Two large genera, Chloris and Eragrostis, do not appear monophyletic. A pattern of segregation of Old World from New World species is evident in several clades. These results provide a framework for further studies at the tribal and generic levels moving toward a comprehensive systematic treatment of the Chloridoideae.
The Portulacaceae, Basellaceae, Cactaceae, and Didiereaceae form a monophyletic group within the Caryophyllales, and evidence exists that the first may be paraphyletic if the latter three are recognized at the familial level. Several taxonomic treatments of the Portulacaceae based on morphological features have failed to produce consensus regarding infrafamilial relationships. The present paper employs sequences of the chloroplast gene ndhF to produce a molecular phylogeny of the portulacaceous cohort, focusing on the relationship among major lineages of the Portulacaceae and the three families potentially derived from within them. Results of this analysis supported two major clades within the monophyletic cohort. The first included Portulaca, Anacampseros and its relatives, much of Talinum, Talinella, and Cactaceae; the second, weakly supported, included the remaining genera of Portulacaceae, Basellaceae, and Didiereaceae. This phylogeny also showed that several generic circumscriptions remain inadequate, particularly that of Talinum sensu lato, which was polyphyletic in this analysis, and that all present classifications of the Portulacaceae include demonstrably non-monophyletic tribes.
Previous studies of the Malvales have shown that the Sterculiaceae are not monophyletic. However, members of four traditionally recognized tribes of Sterculiaceae (Byttnerieae, Theobromeae, Hermannieae, Lasiopetaleae) appear to constitute a clade named Byttnerioideae. Here we analyze sequences of the chloroplast gene ndhF for 37 species of Byttnerioideae. The monophyly of this diverse group of plants is supported with the inclusion of Kleinhovia from a fifth tribe of Sterculiaceae (Helictereae). The Hermannieae is the only tribe that appears to be monophyletic as traditionally circumscribed. Rulingia and Commersonia, two genera formerly placed in the Byttnerieae, are in a clade with all members of the Lasiopetaleae. The remaining Byttnerieae, Theobromeae, and Kleinhovia form two clades at the base of the Byttnerioideae. These results imply that the unusual hooded petals of many Byttnerioideae (e.g., Theobroma cacao) are plesiomorphic for the clade, with subsequent transitions to large, flat petals or small, scale-like petals that lack a distinct hood. Stamen number has traditionally been used to distinguish tribes in the Sterculiaceae. However, our analyses indicate that this character shows extensive homoplasy, with both increases and decreases in stamen number occurring within the Byttnerioideae.