Robert B. Faden

Phylogenetic Studies in the Commelinaceae Subfamily Commelinoideae Inferred from Nuclear Ribosomal and Chloroplast DNA Sequences

Abstract The Commelinaceae are a pantropical family of monocotyledonous herbs. Previous phylogenies in Commelinaceae have emphasized sampling among genera. We extended this previous work by sampling multiple species within some of the largest genera of Commelinaceae (especially Commelina and Tradescantia, and also including Callisia, Cyanotis, Gibasis, and Murdannia), and by sequencing noncoding regions both of the nuclear ribosomal DNA region, 5S NTS, and the chloroplast region, trnL-trnF. We generated a phylogenetic hypothesis for 68 Commelinaceae that partially tests previous morphological, taxonomic classifications. We found little evidence for conflict between nuclear and chloroplast regions for Tradescantia, Murdannia, and Callisia, and some evidence for conflict between the two regions for Commelina, though conflicting regions of the phylogeny were only weakly supported by bootstrap analyses. We found subtribe Tradescantieae to be paraphyletic, consistent with an rbcL study, though with a different topology than that produced by rbcL. In addition, subtribe Commelineae was monophyletic with strong support. We found Callisia to be polyphyletic, consistent with some previous molecular phylogenetic studies, and we found Tradescantia, Gibasis, Cyanotis, Commelina, and Murdannia, to be monophyletic. The molecular phylogenies presented here generally supported previous taxonomic classifications.

Plowmanianthus, a New Genus of Commelinaceae with Five New Species from Tropical America

Abstract A new Neotropical genus of Commelinaceae, Plowmanianthus, is described with five new species. Karyological and morphological data, as well as results of phylogenetic studies, support its inclusion in the subtribe Dichorisandrinae (tribe Tradescantieae) with four other genera (Cochliostema, Dichorisandra, Geogenanthus, and Siderasis). The occurrence of moniliform hairs along the distal margins of the petals is evidence of an even closer relationship with Cochliostema and Geogenanthus, this character being restricted in the family to these three genera. Plowmanianthus may be uniquely characterized as comprising small, perennial rosette herbs with usually one-cymed, axillary inflorescences borne among the lower leaves, an androecium reduced to three fertile stamens, annular, papillate stigmas, and uniseriate to partially biseriate seeds. Plants of the genus are shallowly rooted, the roots not penetrating deeper than the leaf-litter or humus-rich layers of their primary rainforest habitats. Plowmanianthus is also distinctive among the Commelinaceae in the unusually high frequency of cleistogamy in the genus, with some species for which only cleistogamous flowers are known. As currently understood, two species (P. panamensis and P. dressleri) are restricted to the Isthmus of Panama, whereas the remaining four taxa (P. grandifolius subsp. grandifolius, P. grandifolius subsp. robustus, P. perforans, and P. peruvianus) are restricted to lowland Amazonia.

Floral organogenesis and the developmental basis for pollinator deception in the asiatic dayflower, Commelina communis (Commelinaceae)

The upper half of flowers in Commelina communis deceptively lures potential pollinators with its showy petals and staminodes on the false promise of abundant pollen. This paper presents evidence that staminodization in the upper half is associated with a severe retardation of the entire upper floral hemisphere early in development. Possible consequences of this developmental retardation are seen also in the gynoecium, where the upper carpel of the three-carpellate ovary is underdeveloped and sterile at maturity. Only late in development do the upper petals and staminodes expand and acquire pigments necessary for their attractive function. We surmise that retardations of this severity are unlikely to be found for functionally fertile organs such as stamens and ovule-producing carpels, because key preparatory events preceding sporogenesis might otherwise be disrupted. Such differential growth about the floral apex resembles that known in some eudicots to be regulated by the TCP gene family; thus, future molecular developmental studies in Commelina may help to extend our understanding of the evolutionary genetics of floral monosymmetry to monocots.

Four new species of Dichorisandra (Commelinaceae) endemic from Bahia State, Brazil

The four new species described here occur in the Brazilian state of Bahia. Dichorisandra marantoides can be distinguished from other species of the genus by its chartaceous longitudinally ribbed leaves, flowers with five stamens and anthers opening introrsely by slits (being functionally poricidal). Dichorisandra bahiensis is similar to D. tejucensis due to the habit and leaf and flower morphology. However, the two species can be distinguished by the inflorescence, which in D. bahiensis is always positioned at the apex of the stems, perforating the sheath of the lowermost leaf of the lateral branch. Dichorisandra saxatilis resembles D. glaziovii by the morphology and color of anthers, but differs by presence of six stamens, the leaves regularly dispersed along the stem, their laminas glabrous on both sides, with the adaxial surface always green, never with white stripes. Dichorisandra leucosepala also can be distinguished from other species of the genus by white (rarely purplish at the apex), carnose sepals, six stamens with anthers opening by a single pore with purplish pollen sacs. Illustrations of the species, comparisons with similar species, discussions of diagnostic characters and conservation status of the new species are presented.

New Species of Commelina (Commelinaceae) from East and South-Central Africa

ABSTRACT Commelina lukei Faden (Commelinaceae) is newly described from southeastern Kenya, also distributed in northeastern Tanzania and Madagascar. It is distinguished from C. kotschyi Hasskarl by its larger, less undulate-margined leaves, larger spathes, and different distribution and ecology; from C. imberbis Ehrenberg ex Hasskarl and C. mascarenica C. B. Clarke by its capsule shape, appendaged seeds, and consistently clasping leaf bases; and from all three species by the presence of solely acicular hairs on the adaxial lamina midrib. Commelina milne-redheadii Faden is newly described from Zambia, also in Angola and Democratic Republic of the Congo. It differs from C. scaposa C. B. Clarke by the presence of leaves on the flowering shoots and larger spathes; from C. hockii De Wildeman by its narrower leaves and much smaller, striped spathes; from C. welwitschii C. B. Clarke by its tuberous roots, fewer-veined spathes, and several- to many-flowered upper cincinnus; and from all three species by its blue flowers and seeds with a dorsal ridge.

Lectotypification of two African species of Commelina (Commelinaceae) with the description of new taxa from Madagascar and Tanzania

Commelina scandens C.B. Clarke and Commelinapurpurea C.B. Clarke were typified by syntypes that belong to different species. Accordingly, each species is lectotypified, and the taxonomic consequences of the lectotypifications are discussed. Commelina scandens is lectotypified by a specimen from Angola, with the result that the species is confined to continental Africa. A new subspecies, Commelina diffusa Burm.f. subsp. violacea Faden, is described for the Madagascan element in Clarkes C. scandens. Commelina purpurea is lectotypified by the syntype from Kenya, resulting in C. lugardii Bullock and C. kabarensis De Wild. being placed in synonymy under C. purpurea. The other element in Clarkes C. purpurea is described as a new species C. pseudopurpurea Faden.

A New Species of Commelina (Commelinaceae) from Tanzania

Commelina polhillii Faden & Alford, a new annual species of Commelina with buff-orange flowers, is described from Tanzania. It differs from the similar C. subulata primarily in seed morphology. However, staminode shape, the presence of basal lobes on the medial anther connective, and differences in spathe pubescence also serve to varying extent to distinguish the two taxa. Leaf anatomy reveals one major difference but primarily helps to unite the two species with a group of approximately seven other species. A preliminary chromosome count, 2n = ca. 30, is recorded.

New or Misunderstood Species of Commelina (Commelinaceae) from the Flora of Tropical East Africa and Flora Zambesiaca Areas

Commelina disperma Faden is described from Tanzania and is separated from C. zenkeri and C. macrosperma by its seeds. Commelina kituloensis Faden is described from the southern highlands of Tanzania and the Nyika Plateau of Malawi and Zambia and is distinguished from C. hockii by spathe, floral, capsular, and seed characters. Commelina zenkeri C. B. Clarke is found to be the correct name for a Ugandan species that was thought to be undescribed.

Recircumscription and taxonomic revision of Siderasis, with comments on the systematics of subtribe Dichorisandrinae (Commelinaceae)

Abstract A new circumscription and a total of six microendemic species, four of them new to science, are herein presented for Siderasis, based on field and herbaria studies, and cultivated material. We provide an identification key to the species and a distribution map, description, comments, conservation assessment, and illustration for each species. Also, we present an emended key to the genera of subtribe Dichorisandrinae, and comments on the morphology and systematics of the subtribe.

Taxonomic revision of Neotropical Murdannia Royle (Commelinaceae)

Abstract This study provides a taxonomic revision for the Neotropical species of the genus Murdannia. Six species are recognized as native, including a new species and a new combination, while two Asian species are recognized as invasive. We present an identification key, a table summarizing the morphologic differences among the species, a new synonym, six lectotypifications, a distribution map, and descriptions, comments and photographic plates for each species. We also provide comments on the morphology of the Neotropical species of Murdannia, comparing them with the Paleotropical species, and a discussion of inflorescence architecture in the genus as a whole.