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A phylogenetic analysis of species of Didymodon from the Mediterranean area, Macaronesia, and Southwestern and Central Asia is presented. The ITS1, 5.8S rRNA gene, and ITS2 for 30 species have been sequenced, which represent about 25% of the recognized species in the genus. The molecular data confirm the monophyly of Didymodon as clearly separated from Barbula. The transfer of Didymodon giganteus to Geheebia, of D. sinuosus to Oxystegus, and D. australasiae to Trichostomopsis is not supported by the molecular data. The phylogenetic affinities of the species generally do not correspond with the infrageneric classification proposed for the genus based on morphological characteristics. The only monophyletic section is Asteriscium, but only after the inclusion of D. bistratosus.
Nymphaea odorata, Nymphaeaceae, is the most widely distributed water-lily in North America. Disagreement exists on whether this morphologically variable species should be split into two species, N. odorata and N. tuberosa, or treated as one species with two subspecies. Morphological characters and markers from the inter-simple sequence repeats (ISSRs) were examined to assess taxonomic status and elucidate patterns of genetic variation among populations. This study provides evidence against treatment of N. tuberosa at species rank. The principal component analysis of 26 vegetative characters underscores immense variability, but does partially segregate populations of subsp. odorata and subsp. tuberosa. Based on analysis of variance, a new set of morphological characters is proposed to distinguish the two subspecies: mean leaf blade length-to-width ratio, petiole striping, and lobe apex shape. Results from ISSRs show high polymorphism within and among populations. Genetic variation was found largely within geographical regions (89%) rather than among regions. Principal coordinate (PCOA) analyses and minimum spanning tree (MST) analyses based on ISSRs clearly distinguished Nymphaea mexicana and N. odorata. Within N. odorata, samples of subsp. odorata appear to be a distinct entity, whereas samples largely but not completely separated from samples of subsp. tuberosa. PCOA and MST showed linkage between most samples of subsp. odorata whereas this was less evident in UPGMA.
Sequence data from the nuclear internal transcribed spacer (ITS) and the plastid trnL-trnF regions were used to assess relationships among populations of N. odorata across its North American range, and to evaluate whether subsp. odorata and subsp. tuberosa form distinct taxonomic units. Nymphaea mexicana was included because of suspected hybridization with N. odorata. The trnL-trnF region provided a single informative site in N. odorata. In contrast, the ITS region was more variable. Phylogenetic analysis of ITS data supports the monophyly of the two species. Within N. odorata, two clades were resolved largely representing subsp. odorata and subsp. tuberosa, although a few individuals appeared outside the respective clades. Polymorphic sites were detected in ITS, indicating possible hybridization between the subspecies. The geographic location of these hybrids suggests a possible hybrid zone. Overall, molecular evidence supports the segregation of subsp. odorata and subsp. tuberosa, with limited gene flow between them.
The genus Petalolophus (Annonaceae) consists of only one species, P. megalopus, which is characterised by the possession of elaborate perianth wings that extend abaxially from the midrib of the inner petals. Recently published molecular phylogenetic data suggest that Petalolophus is congeneric with Pseuduvaria. Morphological and anatomical characteristics of both genera are critically re-examined and shown to support this conclusion: Petalolophus shares numerous characteristics in common with Pseuduvaria (particularly species from New Guinea) and it is only the autapomorphic possession of extended perianth wings that currently distinguish Petalolophus from Pseuduvaria. Petalolophus megalopus is accordingly formally transferred to Pseuduvaria. Field observations reveal that the flowers of Pseuduvaria megalopus are visited by flies; it is likely that pollination is sapromyophilous, and that the inner petal wings attract flies by mimicking carrion.
Aponogeton is an important genus whose species are cultivated widely as ornamental aquatic plants. Although a fairly recent monograph has been published, the genus remains poorly studied systematically. We conducted a phylogenetic survey of Aponogeton that focused on relationships among the nine native Australian species as well as their relationship to other members of the genus. Our analyses included a phylogenetic assessment of morphological characters and molecular data obtained both from chloroplast (trnK 5′ intron, matK) and nuclear DNA (nrITS) loci. Molecular data provided evidence of hybridization and polyploidy as well as an informative overview of interspecific relationships in the genus. Two potentially new Australian species also were identified by the molecular data. Combined molecular data produced a well-resolved cladogram that enabled us to evaluate previous phylogenetic hypotheses based on non-explicit methods as well as the soundness of the existing classification of the genus. We conclude that Aponogetonaceae originated in Australia and subsequently radiated into Africa, Madagascar, and Asia, from which a secondary Australian diversification occurred resulting in a biphyletic origin of the native Australian species. A pattern of morphological distinctiveness coupled with low molecular divergence indicates relatively recent and rapid speciation of Aponogeton in Australia. Our results also demonstrate that in this group, morphological data are extremely unreliable taxonomically due to their extensive homoplasy. The phylogenetic relationships elucidated by this study provide evidence to support the establishment of two additional sections, Flavida and Viridis, which are described.
Although known to European botanists since 1876, the genus Ptychococcus (Arecaceae: Arecoideae: Ptychospermatinae) of New Guinea has remained one of the most poorly known genera of the Ptychospermatinae. The present study, based on examinations of plants in the field, in herbaria, and in cultivation, reduces the number of species to two and presents a historical overview of this misunderstood genus, along with a taxonomic revision, a key, descriptions and synonymies of the two species. A neotype is designated for Ptychococcus paradoxus.
Paspalum vallsii, a new species in Paspalum sect. Pectinata from cerrado areas of central Brazil, is described and illustrated. It is most similar to P. reticulinerve, from which it differs by having solitary, longer spikelets with the upper glume and the lower lemma glabrous. It differs also from P. imbricatum and P. aspidiotes by having a narrower rachis. A key to the species of Paspalum sect. Pectinata is provided.
Geranium section Dissecta (Geraniaceae) consists of four species centered in Eurasia, between the Mediterranean region and the Himalaya Mountains. In contrast to the current literature, we consider G. chelikii, and G. davisianum to be synonyms of G. sintenisii, and G. pallens to be a synonym of G. asphodeloides. We also accept G. dissectum and G. crenophilum, the latter sometimes considered as subspecies of G. asphodeloides. A multivariate morphometric study showed that some quantitative characters such as deeply divided leaves, shorter and narrower petals, and shorter filaments clearly distinguished the annual G. dissectum. The characters contributing most to separation of the three remaining perennial species were petal width and the length of glandular hairs of stem and pedicels. In G. asphodeloides and G. dissectum the rootstock and stem base has a very starch-rich parenchyma in the cortex, while in G. sintenisii and G. crenophilum the starch-rich parenchyma is mainly developed in the pith. A new key is provided, as well as new and detailed descriptions. Geranium crenophilum and G. sintenisii are here illustrated for the first time. Nine lectotypes and a neotype are designated, and distribution maps are presented. Analyses of the plastid trnL-trnF spacer, nuclear ITS sequences, and morphological data reveal that sect. Dissecta is strongly supported as monophyletic. In these analyses G. dissectum appeared as sister group to the rest of the species.
In this paper we present a revision of Charianthus, which represents the first genus in the Miconieae (Melastomataceae) to be the subject of a combined molecular and morphological cladistic analysis. Charianthus is a morphologically well-characterized clade of six species of hummingbird pollinated shrubs and small trees found in the tropical montane rain forests and elfin forests of the Lesser Antilles. Analysis of the internal transcribed spacer (ITS) region, combined with morphological data, resulted in a strongly supported Charianthus clade. Charianthus fadyenii was placed in the Tetrazygia clade where its position as sister to T. bicolor is strongly supported. Inclusion of C. fadyenii in Charianthus renders both Charianthus and Tetrazygia non-monophyletic, therefore, this species has been transferred to Tetrazygia. Charianthus purpureus, as defined by earlier taxonomists, is a polyphyletic species because of the inclusion of morphologically distinctive populations on the islands of Dominica and Grenada; thus, two new species, C. dominicensis and C. grenadensis, have been described, based on the results presented herein. The revised circumscription of Charianthus renders it the only vascular plant genus endemic to the Lesser Antilles.
Two monotypic genera of Mimosoideae from southern South America, Mimozyganthus and Piptadeniopsis, have been particularly difficult to classify and there has been disagreement about their relationships to other legume genera. We undertook a phylogenetic study based on molecular data from the chloroplast and nucleus, and synthesized it with new data from morphology, cytology, and palynology, in order to determine where these genera belong in the mimosoid phylogenetic tree. Mimozyganthus, an enigmatic genus whose unique morphology led workers to consider it transitional between the subfamilies Mimosoideae and Caesalpinioideae, is instead nested among the higher mimosoids on the molecular tree. Careful evaluation of the characters that were considered to be caesalpinioid-like reveals that they are not identical and are independently derived. Piptadeniopsis is most closely related to Prosopidastrum, a primarily Argentinian genus with lomentiform fruits. This is in close agreement with most morphological characters, although the pollen is different in the two genera. Piptadeniopsis, Mimozyganthus, and Prosopidastrum form a monophyletic group on all molecular trees, a result consistent with vegetative and fruiting morphology, but not floral characters. Although the relationship of this group to other taxa is unresolved in the individual molecular analyses, a combined analysis of all molecular data for a subset of the taxa reveals that the three taxa are more closely related to the Leucaena group than to Prosopis. We hypothesize that the unique floral characters of Mimozyganthus may have evolved in response to pollinator selection, and a pollination study is needed to test this hypothesis.
Breadfruit (Artocarpus, Moraceae) is an important staple in Oceania and throughout much of the tropics. Interpretations of species delimitations among breadfruit and its closest relatives have varied from recognition of one to several species. To better understand the systematics and ultimately the origins of breadfruit, we considered evidence from molecular data. Amplified fragment length polymorphism data for 261 individuals of breadfruit, its closest relatives, putative hybrids, and nine outgroup taxa were analyzed using neighbor joining and parsimony analyses. Three species, A. altilis (domesticated breadfruit), A. camansi, and A. mariannensis, are recognized and the existence of hybrids (A. altilis × A. mariannensis) verified. A revised treatment based on the molecular results, as well as morphological and geographical considerations, is presented.
Classification of Rhododendron species based on morphology has led to a consensus taxonomy recognizing the major subgenera Azaleastrum, Hymenanthes, Pentanthera, Rhododendron, Tsutsusi, and three minor ones. To determine whether these subgenera are monophyletic and to infer phylogenetic relationships between Rhododendron sections and species, we carried out a cladistic analysis using molecular data, including all groups within the genus. For this purpose, we sequenced a large part of the nuclear gene RPB2-I, encoding a major RNA Polymerase II subunit, from 87 species and analyzed the data by maximum parsimony, maximum likelihood, and Bayesian methods. The resulting phylogenies show subgenera Azaleastrum and Pentanthera to be polyphyletic and group all Rhododendron species (except the two in section Therorhodion) into three large clades. Based upon these results, modifications in Rhododendron classification are proposed, which consolidate minor subgenera and recognize monophyletic subgenera and sections.
We examined infrageneric relationships within Phacelia subgenus Phacelia based on phylogenetic hypotheses derived from internal transcribed spacers (ITS) and the 5.8S gene of nuclear ribosomal DNA. Maximum parsimony (MP) and maximum likelihood (ML) phylogenies support the monophyly of sects. Euglypta and Miltitzia, previously hypothesized based on seed characters and ecological distribution. Tree branching patterns within the Euglypta/Miltitzia clade indicate three principle lineages: 1) the P. pachyphylla complex, 2) a clade of P. brachyloba and 3) a clade consisting of two sister groups, the P. affinis complex and the P. fremontii complex. An aneuploid increase in chromosome number occurs from the P. pachyphylla complex (n = 11) to P. brachyloba (n = 12) while the pattern within the P. fremontii complex includes both aneuploid increases and decreases. There is high bootstrap support for monophyly of taxa representing both the P. magellanica polyploid complex and the P. humiles species group; the former contains the only known tetraploid taxa in subgenus Phacelia.
A new genus of Icacinaceae, Sleumeria, is described from northern Borneo. The only known species, Sleumeria auriculata, is a large woody scrambler with spirally arranged leaves with entire margins and prominent reticulation, hairs that dry a distinctive yellow-brown, and racemose or compound racemose inflorescences. The habit, leaf arrangement, and inflorescence type place Sleumeria in a group of climbing Icacinaceae near to Sarcostigma, but it is distinguished from that and other closely related genera by the combination of distinctly pedicellate flowers arranged singly or in pairs along the inflorescence rachis, swollen sagittate anther connectives, and a spherical ovary with a distinct filiform style with an unlobed stigma. Investigation of the stem anatomy confirms the relationship with Sarcostigma, especially the presence of successive cambia, but the new genus differs, amongst other anatomical characters, in lacking islands of included phloem within the xylem.
Multivariate and univariate analyses were used to investigate patterns of floral and foliar morphological diversification among the eight taxonomic varieties of Pedicularis bracteosa (Orobanchaceae). Canonical discriminant analysis supported six varieties but not without considerable morphological overlap. Discrimination was most strongly based upon three floral characters: galea shape, throat length, and calyx tip length; and secondarily on three foliar characters: subtending bract width, longest leaflet width, and longest leaflet length. Analysis of variance on the ratio between calyx length and the length of the connate portion of the calyx did not corroborate a taxonomic difference among all varieties. Because galea shape is associated with specific pollination syndromes that promote reproductive isolation in other Pedicularis species, selection by the different pollinating behaviors of queens versus worker castes of the same species of bumblebees may be driving the diversification of floral morphology. While the taxa are largely allopatric and supported by several strong morphological discriminators, the high degree of morphological overlap among them does not justify their re-ranking above variety. Lack of discrimination between varieties siifolia and canbyi argues for their merger into a single taxon. A revised key to the varieties reflecting the results of this study is presented.
Phylogenetic analyses of nuclear ribosomal ITS and ETS sequences yield considerable improvements in our knowledge of relationships, character evolution, and biogeography in Meryta (Araliaceae). This genus comprises ca. 30 species, all of which share simple leaves and a dioecious sexual system, a unique combination in Araliaceae. Meryta is distributed widely across the Pacific, but each of its species is endemic to only one or a few islands. Previous phylogenetic studies have included only a very limited number of exemplars from Meryta, but have suggested that the genus is related to the Southwest Pacific clade of Schefflera within the larger Polyscias-Pseudopanax group of Araliaceae. Our data confirm this previous placement and provide evidence for the monophyly of Meryta. There is no support for the recognition of three segregate genera, Botryomeryta, Schizomeryta, and Strobilopanax. Within Meryta, we have identified two major clades, one that unites the species from Fiji and New Zealand (both of old geological origin), and a second, “Northern Arc clade” comprising the remaining species of Meryta. In this second clade, several subclades of New Caledonian species can be recognized, along with a “Volcanic Islands subclade.” The presence of species in New Caledonia, Fiji, and New Zealand, together with the placements of these species in the phylogenetic trees, is suggestive of an ancient vicariance, whereas the distribution of the members of the Volcanic Islands subclade appears to be best explained by a series of long-distance dispersal events, most likely from New Caledonia.
With ca. 1400 species, Begonia is one of the largest plant genera. To address the evolution of Begonia we have produced maximum parsimony cladograms for nuclear large subunit and internal transcribed spacer sequence data in combination with 34 informative morphological characters. Data were obtained from 64 species of Begonia, the monotypic genus Hillebrandia, and both species of Datisca. The resulting phylogenetic hypotheses supported three main clades within Begonia, two internally resolved clades of African plants, and one unresolved transcontinental clade containing species from southern Africa, America, Asia, and the Socotran archipelago. Morphological characters often support well-resolved molecular clades. Tepal number in the staminate and carpellate flowers and fruit characters are discussed. None of the morphological characters sampled, including traditionally emphasized characters in sectional delimitations such as locule number and number of placental branches, provides a basis for subdividing Begonia into easily circumscribed monophyletic groups. Implications for future sectional classifications of Begonia are discussed.