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Name Changes in Podostemaceae
Abstract
Cook, C. D. K. & Rutishauser, R.: Name changes in Podostemaceae. – Taxon 50: 1163–1167. 2001.‐ISSN 0040–0262.
While preparing a review of the family Podostemaceae , we have found it necessary to change the name of some species. Following rules of priority, Crenias K. P. J. Sprengel replaces Mniopsis Martius. No convincing reasons can be found to maintain the monotypic genera Hydrobryopsis, Malaccotristicha, Synstylis and Torrenticola ; they are merged in their sister genera Zeylanidium, Tristicha, Hydrobryum and Cladopus , respectively. On morphological grounds Polypleurella micranthera is transferred to Hydrobryum and Polypleurum submersa is transferred to Saxicolella.
... J.B. Hall (1971), published three new Podostemaceae, all endemic to Ghana, including Saxicolella amicorum J. B. Hall. A second of his species, described as Polypleurum submersum J.B. Hall was later also transferred to Saxicolella by Cook & Rutishauser (2001). All these species share a flower which is erect in the spathellum, remaining included within it at anthesis, with a single stamen and dyad pollen. ...
... The generic name Aulea, attributed to C. Cusset by Lebrun & Stork (1991), but never validly published, took on a life of its own. Cook & Rutishauser (2001) in discussing Saxicolella and in formally transferring to this genus Polypleurum submersum J.B. Hall, state that "Cusset in Lebrun & Stork (1991) assigned S. amicorum and S. submersa to a supposed new genus "Aulea", which has never validly been published. We assume she considered the presumptive unilocular ovary to be sufficient to distinguish "Aulea" from Saxicolella, which has a bilocular ovary. ...
... Thus Saxicolella, following the concept of Cook & Rutishauser (2001 and Rutishauser et al. (2004) is polyphyletic, with two distinct clades (Koi et al. 2012). ...
Saxicolella Engl., an African genus of the waterfall specialist plant family Podostemaceae, was shown to be polyphyletic as currently delimited. One clade, sampled from species in Ghana, is sister to American Ceratolacis (Tul.) Wedd., Podostemum Michx. and all Old World Podostemoideae (podostemoids). The second clade, sampled from Cameroonian material, was embedded within the major clade of African podostemoids. In this paper the generic nomenclature applied to Saxicolella sensu lato (Saxicolella, Pohliella Engl., Aulea Lebrun & Stork nom. inval.), is reviewed and the morphological support for the two clades and their correct generic names is determined. Pohliella is shown to be the correct name for the first clade (based on Pohliella laciniata Engl., Cameroon) and a synoptic treatment of its three published species is given, one of which is extinct, and two are threatened. However, a fourth, unpublished species exists. The new combinations Pohliella submersa (J.B.Hall) Cheek and Pohliella amicorum (J.B. Hall) Cheek are made for the two published Ghanaian species. The recently described New World genus Cipoia C.T. Philbrick, Novelo & Irgang is revealed as being morphologically identical to Pohliella, but in view of the geographical disjunction, confirmation from molecular evidence is awaited before its two species are also transferred to Pohliella. The correct name for the second clade, embedded in African podostemoids, is Saxicolella (sensu stricto), now with two known species, Saxicolella nana Engl. (type of Saxicolella, Cameroon) and Saxicolella flabellata (G.Taylor) C. Cusset (Nigeria).
... The species of Hydrobryum are also d i v e r s e m o r p h o l o g i c a l l y . A m o n g A s i a n Podostemoideae the genus was traditionally defined by the crustose root, as well as the flattened, ribbed capsules (Cusset 1992;Kato 2004;Cook & Rutishauser 2007). Recent explorations in Phou Khao Khouay have helped to discover or rediscover three species with ribbon-like roots, in addition to four species with crustose roots (Koi & Kato 2012). ...
... (Cusset 1992). Subsequently, the crustose genera Synstylis C. Cusset and Diplobryum C. Cusset were proposed as independent genera, but later merged with Hydrobryum (Cook & Rutishauser 2001;Kato 2004;Koi & Kato 2012). ...
... Holdfasts, special organs with which to adhere to submerged rock surfaces in fast water currents (Rutishauser 1997;Cook & Rutishauser 2007), are present in some species with ribbon-like roots in different forms and degrees. However, holdfasts have not been recorded in crustose species until now. ...
Two new species of Podostemaceae are described from a single site in northern Central Laos. Hydrobryum hapteron is characterised by the many long holdfasts in the basal area of the crustose root and the long stalks of capsules. It shares the prominent holdfasts and stalks of capsules with H. ramosum (C. Cusset) Koi & M. Kato but is distinct from it in the crustose root. Hydrobryum subcylindricoides is similar to H. subcylindricum Koi & M. Kato in the ribbon-like root but differs from it in the wider root, Y-shaped stigmas and fewer ribs on the capsule.
... The aquatic angiosperm family Podostemaceae is classified into three subfamilies with approximately 47 genera and 268 species (Engler 1930;Cook 1996;Kita and Kato 2001). The largest subfamily, Podostemoideae (ca. ...
... In their molecular phylogenetic [Volume 29 SYSTEMATIC BOTANY study, Kita and Kato (2001) showed that this species is nested within the Cladopus clade. Subsequently, Cook and Rutishauser (2001) created the new combination Cladopus queenslandicus. These newly recognized relationships have revealed that Cladopus is distributed widely in the tropics and subtropics, ranging from southern India to eastern New Guinea and northeastern Australia, and north to China and Japan. ...
... Kita and Kato (2001) provided molecular evidence for a very close relationship between S. micranthera and Hydrobryum. Based on these and other data, Cook and Rutishauser (2001) created the new combination H. micrantherum. In Southeast Asia there are two other genera with foliose roots, Diplobryum, with two species in Laos andVietnam (Kato andFukuoka 2002), andHanseniella, endemic to Thai- land (Cusset 1992). ...
Molecular data from Cladopus and Hydrobryum, members of the aquatic angiosperm family Podostemaceae, were analyzed phylogenetically using the chloroplast matK gene and internal transcribed spacer (ITS) regions of the nuclear ribosomal RNA (nrRNA) gene to infer the species relationships and the biogeographic history of the East Asian species. The phylogenies based on matK and ITS were incongruent for relationships in a northern clade of Cladopus, but the pattern of root morphologies (ribbon vs. linear) agreed with the matK phylogeny. The matK phylogeny revealed that all East Asian temperate species of each genus form a monophyletic group that is derived from tropical/subtropical species. A clock-constrained maximum-likelihood tree suggests that the divergence events of the temperate lineages from their tropical sisters occurred coevally in the two genera. Dispersal-vicariance analysis (DIVA) suggests that distribution at the middle latitudes was formed by a wide primary distribution covering tropical and temperate areas and a secondary dispersal event in Cladopus, and by a dispersal event in Hydrobryum. Two KyushLl-Fujian groups are found in Cladopus, one consisting of Japanese C. austro-osumiensis and Chinese C. fukiensis and another consisting of Japanese C. japonicus, C. austrosatsumensis, and C. doianus and Chinese C. chinensis, each of which shows little genetic differentiation between species from Kyushu, southern Japan, and Fujian, China, suggesting parallel biogeographic histories. Disjunct populations of Hydrobryum japonicum from Kyushu in southern Japan and from northern Thailand show little genetic differentiation, whereas a plant from Yunnan, China, diverged earlier than did the Japanese or Thai plants. The DIVA results suggest that the disjunctive distribution of Hydrobryum japonicum was formed by two dispersal events from Kyushu to Yunnan and to northern Thailand.
... Cladopus nymanii H. Möller (1899) was described from West Java as the first record of Podostemaceae in Malesia. North-eastern Australian Torrenticola queenslandica was added as the second species from Papua New Guinea (Van Steenis 1949) and later transferred to Cladopus by Cook & Rutishauser (2001). Dransfield & Whitmore (1970) described Indotristicha malayana from Peninsular Malaysia (Van Steenis 1972), which has later been transferred to Malaccotristicha (Cusset & Cusset 1988a), to Tristicha of a different clade (Cook & Rutishauser 2001), and eventually to Terniopsis including Malaccotristicha (Kato 2006a) (Table 1). ...
... North-eastern Australian Torrenticola queenslandica was added as the second species from Papua New Guinea (Van Steenis 1949) and later transferred to Cladopus by Cook & Rutishauser (2001). Dransfield & Whitmore (1970) described Indotristicha malayana from Peninsular Malaysia (Van Steenis 1972), which has later been transferred to Malaccotristicha (Cusset & Cusset 1988a), to Tristicha of a different clade (Cook & Rutishauser 2001), and eventually to Terniopsis including Malaccotristicha (Kato 2006a) (Table 1). Kato & Hambali (2001) added a fourth species, Cladopus javanicus from West Java. ...
... Samples from the two localities differ in a small degree in the matK sequences, although the two populations are quite similar morphologically (Koi et al. 2008). The species has long been separated as the monotypic genus Torrenticola (Aston 1990), until Cook & Rutishauser (2001) transferred it to Cladopus, based partly on molecular evidence (Kita & Kato 2001). The species is distinct among congeners in the trifid leaves (bracts), but similar to C. javanicus in the monomorphic, long shoot (see above). ...
Two genera and four species of Podostemaceae in Malesia are enumerated and a key to the species is provided. They are morphologically distinct from each other. Cladopus javanicus and C. nymanii are endemic to Java and Malesia, respectively, and C. queenslandicus occurs in eastern Papua New Guinea and north-eastern Australia. Terniopsis malayana, formerly called Malaccotristicha malayana, is distributed in Peninsular Malaysia to Peninsular Thailand. Asian Podostemoideae including Cladopus are a product of secondary diversification following a single migration, while Tristichoideae with Terniopsis show primary diversification in Asia.
... However, the molecular phylogeny of Koi et al. (2012) showed that Saxicolella in this broad sense was polyphyletic, with two clades arising at different points from the family tree. It was shown (Cheek 2020) that these two clades differ from each other in several important characters, sufficient to merit generic separation (Table 1 Cook & Rutishauser (2001;. Characters taken from Koi et al. (2012: 473, table 3), Ameka et al. (2002), Hall (1971), Engler (1926) and Cheek (pers. ...
... Saxicolella has previously been used in a wider sense, to include superficially similar species (Cook & Rutishauser 2001;Ameka et al. 2002). However Koi et al.(2012) showed that, as a result, Saxicolella in that former, wider sense was polyphyletic. ...
The genus Saxicolella Engl. (Podostemaceae) are African rheophytes, restricted to rapids and waterfalls as are all members of the family. Previously, Saxicolella sensu lato was shown to be polyphyletic with two separate clades in the molecular phylogenetic study of Koi et al. (2012). The name Pohliella Engl. was recently resurrected for one clade that is sister to the American genera Ceratolacis (Tul.)Wedd., Podostemum Michx. and all Old World Podostemoideae (podostemoids) (Cheek 2020). Pohliella has distichous phyllotaxy, bilocular ovaries, filiform roots with paired holdfasts, and rootcaps. The second clade, Saxicolella sensu stricto, including the type of the generic name, has spiral phyllotaxy, unilocular ovaries, ribbon-like or crustose roots that lack both holdfasts and rootcaps. Saxicolella sensu stricto, sampled from the type species, S. nana Engl. of Cameroon, is embedded within and near the base of the major clade of African podostemoids and is sister to all other African genera apart from Inversodicraea R.E.Fr. and Monandriella Engl. Recently reduced to three species in Cameroon and S.E. Nigeria by the resurrection of Pohliella (3 to 4 species in Ghana and Nigeria and Cameroon), Saxicolella sensu stricto is expanded to eight species in this monograph by description of five new taxa. Saxicolella futa Cheek and S. deniseae Cheek are newly described from Guinea, S. ijim Cheek from Cameroon, the informally named S. sp. A from Gabon, and S. angola Cheek from Angola. The known geographic range of the genus is thus expanded c. 2,500 km westwards to Guinea from eastern Nigeria and c.1,500 km southeastwards from Cameroon to Cuanza do Sul, Angola. The greatest concentration of species occurs in the Cross Sanaga interval of western Cameroon and eastern Nigeria, with three species. Cameroon (3 species) followed by Nigeria and Guinea (2 species each) are the countries with highest species diversity. The genus can be expected to be found in Sierra Leone, Liberia, Ivory Coast and Congo Republic. A classification is proposed grouping the species into three subgenera (Saxicolella, Butumia (G.Taylor) Cheek comb. et. stat. nov. and Kinkonia Cheek subgen. nov.) based on root morphology and shoot position and morphology. The discovery, morphology, circumscription, distribution, and ecology of Saxicolella is reviewed, an identification key to the species is presented, together with descriptions, synonymy, links to illustrations, and extinction risk assessments for each of the eight species now recognised. All of the species are provisionally assessed as either Endangered or Critically Endangered using the IUCN 2012 standard, making this genus among the most threatened of its size globally. The major threats, above all, are hydro-electric projects. Saxicolella deniseae may already be globally extinct, and two of the four known locations of S. angola appear lost, S. sp. A of Gabon is threatened at at least one of its three locations, while Saxicolella futa is threatened at all three locations, all due to incipient or active hydro electric projects. Contamination of watercourses by increased turbidity from silt-load due anthropic changes and by eutrophication from pollution are also threats for the majority of the species.
... Polypleurum submersum) were described as new species from Ghana in a paper by Hall (1972). The present developmental and morphological studies of the isotype material indicate that this latter species belongs in Saxicolella (Cook & Rutishauser, 2001). ...
... Clearly in Podostemaceae, at least until now, the genus concept is highly artificial (Cook & Rutishauser, 2001). Nevertheless, we are convinced that Saxicolella submersa does not belong in the genus Polypleurum. ...
Saxicolella (six spp.) is a podostemoid genus occurring in tropical west Africa (Cameroon, Ghana, Nigeria). Taxonomically used characters such as root (with holdfasts), pollen (dyads in many Podostemoideae), capsules (with ribs) and seeds are demonstrated and discussed. This paper deals with the structure and development of two species, which are endemic to rivers in southern Ghana: Saxicolella amicorum J.B.Hall and Saxicolella submersa (J.B.Hall) C.D.K.Cook & Rutish. (syn. Polypleurum submersum J.B.Hall).◊Saxicolella amicorum has simple, one-flowered stems up to 3 cm long, whereas S. submersa has branched, many-flowered stems up to 25 cm long. Vegetative shoots can reach 12 cm (S. amicorum) and even 50 cm (S. submersa) in length. The latter species was previously placed in the Asian genus Polypleurum because the long floating axis was misinterpreted as a root which would be typical for Polypleurum. The long floating axis of S. submersa develops exogenous leaves and is actually a stem. Both S. amicorum and S. submersa have various features in common: vegetative parts (roots, stems, leaves) are elongate and very thin (diameter less than 1 mm); prostrate roots are narrow ribbons (twice as wide as thick); endogenous shoots in opposite pairs along the root; leaves usually simple and filiform; leaf bases with two attached ear-like stipules; spathella club-shaped to ellipsoidal; erect flowers with a solitary stamen; ovary ellipsoidal to fusiform, bilocular; capsules nearly isolobous, with three prominent ribs per valve (i.e. eight ribs per capsule including sutural ribs). Evolutionary dynamics of the root structures in African Podostemoideae such as Saxicolella include: formation of green prostrate ribbons as a result of dorsoventral root flattening; reduction of root caps; occurrence of adhesive hairs and exogenous holdfasts which are disk- or finger-like. Structural diversity and developmental patterns in the Ghanaian Saxicolella species are compared with other African Podostemoideae. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 255–273.
... Samples of emergent plants and algae were collected and their morphological features were analyzed for identification. The identification of aquatic plants was carried out with the help of Cook and Rutishauser (2001), and Gamble (2008). The abundance is usually measured by counting the plant species in the sampling quadrate. ...
Aquatic macrophytes are essential to the fish community because they offer food, protection from predators and shelter. The present study deals with the influence of the distribution and abundance of aquatic macrophytes on stream fishes. Twenty-one species of aquatic plants and 13 associated fish species were identified during the study period of January-December 2019. In the study stream, the abundance of aquatic flora positively impacted the fish community. Certain aquatic macrophytes were highly preferred by individual fish species in the area. The Podostemonads formed a major plant group along the stream. Emergent plants, especially Lagenandra toxicaria played an important role in maintaining the composition of the fish community. Hypselobarbus kurali is a known genus of food fish, and they exhibited affinity to the area covered with Lagenandra toxicaria. Hydrilla verticillata, the submerzed plant showed extensive growth during monsoon and supported a large number of Haludaria fasciata.
... Zeylanidium is currently represented by seven species: Z. olivaceum Engl., Z. johnsonii Engl., Z. lichenoides Engl., Z. maheshwarii C.J.Mathew & V.K.Satheesh, Z. sessile (Willis) C.D.K.Cook & Rutish, Z. crustaceum M.Kato and the recently described Z. tailichenoide M. Kato & Koi (Mathew and Satheesh 1996, Cook and Rutishauser 2001, Kato et al. 2015, Kato and Koi 2018. Out of these seven species, the status of Z. johnsonii Engl. is doubtful as it has never been reported by any study after Engler's (1930) description. ...
We present the description of Zeylanidiummanasiae (Podostemaceae), a new species from Kerala, India, which is proposed based on molecular, macro- and micromorphological data. This species is characterised by its ribbon-like dichotomous thallus, floriferous shoots produced along the margins and dichotomy of the thallus, inflorescence with two bracts, unequal stigmatic lobes, ellipsoid fruits and large seeds.
... The type and sole species of Torrenticola, T. queenslandica, from northeastern Queensland and southeastern New Guinea, was treated as Cladopus queenslandicus (Domin) C.D.K.Cook et Rutish. (Cook and Rutishauser, 2001), and Kita and Kato (2001) found it to be nested within the Cladopus clade in a molecular phylogenetic tree, although the two genera differ considerably in vegetative and reproductive characters (Aston, 1990). Cladopus may therefore consist of about 10 species. ...
... About six species (more have been described), South-east and East Asia, New Guinea, north-eastern Australia. Cook and Rutishauser (2001) have sunk Torrenticola into Cladopus (see morphological and molecular data in Kato 2004b Roots thread-like, cylindrical or somewhat flattened, 1-2(-4) mm wide, up to 25 mm long, branched, forming entangled mats, closely attached to rocks by holdfasts associated with root-borne shoots; stems very short, simple, arising along lateral margins of roots, some remaining embedded in root with only the leaves emerging, the others barely emerging and bearing flowers. Leaves scattered in groups along edge of root or 1, 2 or rarely 3 pairs on flowering stems, linear, 2-5 mm long, with thread-or band-like, caducous tips. ...
Annual or perennial, aquatic herbs, often bizarre in form, sometimes resembling lichens, bryophytes, seaweeds, or unlike any
other plants; haptophytes, attached by adhesive hairs to rock or other hard objects in flowing freshwater, mostly in rapids
and waterfalls; roots usually photosynthetic, creeping or partly floating, thread-like, ribbon-shaped, crustose (foliose),
sometimes short-lived or absent. Shoots nearly always arising as endogenous buds from roots; stems reduced or elongate, simple
or branched, sometimes dimorphic, occasionally only present when flowering. Photosynthesis takes place under water, flowers
or even separate floral shoots develop as the water level drops, the vegetative shoots or leaves often shed as plants become
exposed. Phyllotaxis variable, in Podostemoideae usually distichous. Leaves borne on elongate stems or arising fromprostrate,
often disk-like stems, extremely variable in size and shape, from scale-like to well developed and compound; sheaths single
or, in many Podostemoideae, double; sheath lobes sometimes elongated into stipule-like appendages; leaf blades stalked or
sessile, entire, lobed or dissected; blade lobes or segments often bearing photosynthetic filaments and/or additional hairs;
ultimate leaf segments filiform, linear or spathulate. Flowers bisexual, actinomorphic or zygomorphic, solitary, in clusters
or in racemeor cyme-like in florescences; flower buds naked in Weddellinoideae and some Tristichoideae, surrounded by a cupula
(a collar-like vascularised cup) in some Tristichoideae, or completely enclosed in a spathella (a tubular or sack-like cover)
in Podostemoideae; spathellas mostly enclosing a single sessile or pedicellate flower; pedicels often elongating in fruit.
Anthesis takes place in air or flowers cleistogamous under water. Perianth of 1 complete or incomplete whorl of tepals, often
confined to one side of the flower; tepals in Tristichoideae and Weddellinoideae large, 5 or rarely 4 or 6, imbricate and
sepal-like; tepals in Podostemoideae small, 2–20, linear or subulate, usually alternating with stamens, in flowers with only
2 basally fused stamens occasionally an additional tepal borne at top of andropodium (common stalk); stamens 1–40, in 1 or
2 complete whorls, or in 1 incomplete whorl, or confined to one side of flower and consisting of 1–3 free stamens or a Y-shaped
structure consisting of an andropodium carrying 2 stamens; filaments, when in whorls, mostly free or, in Tulasneantha, their bases united to form an androecial tube; anthers dehiscing longitudinally by slits, introrsely to latrorsely or rarely
extrorsely; pollen shed in monads, dyads or (rarely) tetrads, tricolporate in Weddellinoideae, tricolpate to pentacolpate
in Podostemoideae, pantoporate with up to 16 pores in Tristichoideae; ovary superior, 2-or 3-locular or 1-locular in some
Podostemoideae; ovules axile, anatropous, bitegmic, tenuinucellate. Fruit a capsule, smooth or ribbed, with 2 or 3, equal
or unequal valves, sometimes one or more persisting; stigmas 1–3, variable in shape and size. Seeds 2 to very numerous (over
2,000); seed coat usually mucilaginous and sticky; endosperm 0; embryo straight, with 2 cotyledons and a suspensor.
... This association between root branching and shoots is also seen in Cladopus, a species of Polypleurum and Asian members of Podostemoideae, whereas there is no such association in other related species of Polypleurum (S. Koi et al.,Cook and Rutishauser, 2001; Kita and Kato, 2001). This suggests that the foliose roots of Z. olivaceum (Gardn.) ...
Podostemaceae have markedly specialized and diverse roots that are adapted to extreme habitats, such as seasonally submerged or exposed rocks in waterfalls and rapids. This paper describes the developmental anatomy of roots of four species of Zeylanidium, with emphasis on the unusual association between root branching and root-borne adventitious shoots. In Z. subulatum and Z. lichenoides with subcylindrical or ribbon-like roots, the apical meristem distal (exterior) to a shoot that is initiated within the meristem area reduces and loses meristematic activity. This results in a splitting into two meristems that separate the parental root and lateral root (anisotomous dichotomy). In Z. olivaceum with lobed foliose roots, shoots are initiated in the innermost zone of the marginal meristem, and similar, but delayed, meristem reduction usually occurs, producing a parenchyma exterior to shoots located between root lobes. In some extreme cases, due to meristem recovery, root lobing does not occur, so the margin is entire. In Z. maheshwarii with foliose roots, shoots are initiated proximal to the marginal meristem and there is no shoot-root lobe association. Results suggest that during evolution from subcylindrical or ribbon-like roots to foliose roots, reduction of meristem exterior to a shoot was delayed and then arrested as a result of inward shifting of the sites of shoot initiation. The evolutionary reappearance of a protective tissue or root cap in Z. olivaceum and Z. maheshwarii in the Zeylanidium clade is implied, taking into account the reported molecular phylogeny and root-cap development in Hydrobryum.
Species of the genus Saxicolella Engl. (Podostemaceae) are African rheophytes, restricted to rapids and waterfalls as are all members of the family. Previously, Saxicolella sensu lato was shown to be polyphyletic with two separate clades. The name Pohliella Engl. was recently resurrected for one clade that is sister to the American genera Ceratolacis (Tul.) Wedd., Podostemum Michx. and all Old World Podostemoideae. Pohliella has distichous phyllotaxy, bilocular ovaries, filiform roots with paired holdfasts, and rootcaps. The second clade, Saxicolella sensu stricto , including the type of the generic name, has spiral phyllotaxy, unilocular ovaries, ribbon-like or crustose roots that lack both holdfasts and rootcaps. Saxicolella sensu stricto , sampled from the type species, S. nana Engl. of Cameroon, is embedded within and near the base of the major clade of African podostemoids and is sister to all other African genera apart from Inversodicraea R.E.Fr. and Monandriella Engl. Recently reduced to three species in Cameroon and SE Nigeria by the resurrection of Pohliella, Saxicolella sensu stricto is expanded to eight species in this monograph by description of five new taxa. Saxicolella futa Cheek and S. deniseae Cheek are newly described from Guinea, S. ijim Cheek from Cameroon, the informally named S. sp. A from Gabon, and S. angola Cheek from Angola. The known geographic range of the genus is thus expanded c. 2,500 km westwards to Guinea from eastern Nigeria and c.1,500 km southeastwards from near Yaoundé to Cuanza do Sul, Angola. The greatest concentration of species occurs in the Cross-Sanaga interval of western Cameroon and eastern Nigeria, with three species. Cameroon (3 species) followed by Nigeria and Guinea (2 species each) are the countries with highest species diversity. A classification is proposed grouping the species into three subgenera ( Saxicolella, Butumia (G.Taylor) Cheek comb. et stat. nov. and Kinkonia Cheek subgen. nov.) based on root morphology and shoot position and morphology. The discovery, morphology, circumscription, distribution and ecology of Saxicolella is reviewed, an identification key to the species is presented, together with descriptions, synonymy and links to illustrations. All of the species are provisionally assessed as either Endangered or Critically Endangered using the IUCN 2012 Red List Criteria. The major threats, above all, are hydro-electric projects. Saxicolella deniseae may already be globally extinct, and two of the four known locations of S. angola appear lost, S. sp. A of Gabon is threatened at at least one of its three locations, while S. futa is threatened at all three locations. Contamination of watercourses by increased turbidity from silt-load due to anthropic changes and by eutrophication from pollution are also threats for the majority of the species.
In this paper we describe and illustrate two new species, Cladopus yinggelingensis and Terniopsis daoyinensis, both from the Yinggeling National Nature Reserve, Hainan, China. Morphologically, Cladopus yinggelingensis is similar to C. doianus, and Terniopsis daoyinensis is similar to T. ubonensis. For the new taxa, information on its geographic range, habitat, and morphological differences between their known congeneric species are presented.
Rosidae, a clade of ∼ 90 000 species of angiosperms, exhibits remarkable morphological diversity and extraordinary heterogeneity in habitats and life forms. Resolving phylogenetic relationships within Rosidae has been difficult, in large part due to nested radiations and the enormous size of the clade. Current estimates of phylogeny contain areas of poor resolution and/or support, and there have been few attempts to synthesize the available data into a comprehensive view of Rosidae phylogeny. We aim to improve understanding of the phylogeny of Rosidae with a dense sampling scheme using both newly generated sequences and data from GenBank of the chloroplast rbcL, atpB, and matK genes and the mitochondrial matR gene. We combined sequences from 9300 species, representing 2775 genera, 138 families, and 17 orders into a supermatrix. Although 59.26% of the cells in the supermatrix have no data, our results generally agree with previous estimates of Rosidae phylogeny and provide greater resolution and support in several areas of the topology. Several noteworthy phylogenetic relationships are recovered, including some novel relationships. Two families (Euphorbiaceae and Salvadoraceae) and 467 genera are recovered as non-monophyletic in our sampling, suggesting the need for future systematic studies of these groups. Our study demonstrates the value of a botanically informed bioinformatics approach and dense taxonomic sampling for resolving rosid relationships. The resulting tree provides a starting point for large-scale analyses of the evolutionary patterns within Rosidae.
Podostemum ceratophyllum shows peculiar architectural characters that seem to apply to basal members of Podostemoideae. In contrast to more elaborate taxa of this subfamily, P. ceratophyllum fits into the classical root-shoot (CRS) model, with clearly distinguishable thread-like roots (with root caps and endogenous lateral roots), as well as stems and leaves. Root-born endogenous shoots initially develop a series of distichous leaves having one stipular sheath each. Shoot modules are terminated by double-sheathed leaves associated with stem branching and/or flower formation. Double-sheathed leaves of P. ceratophyllum have two boat-shaped stipular sheaths, each one containing a new leaf (as part of a daughter shoot) or a flower bud. Double-sheathed leaves are an evolutionary novelty of Podostemoideae, leading to branching types not known elsewhere in angiosperms. The vegetative architecture of P. ceratophyllum is similar to other American species of Podostemum.
The Podostemaceae of Laos are much less understood than those of adjacent Thailand. Comparative morphology using new materials, together with the latest molecular phylogenetic studies, have revealed a high diversity in subfamily Podostemoideae in Laos. This subfamily comprises five genera and 15 species. The genus Hydrobryum Endl. is enlarged, and found to be remarkably diverse in root and shoot morphology. We describe two species, H. subcylindricum sp. nov. and H. taeniatum sp. nov., with subcylindrical and ribbon-like roots, respectively; H. austrolaoticum sp. nov., H. verrucosum sp. nov. and H. subcrustaceum sp. nov. with crustose roots, and H. takakioides sp. nov. with crustose roots and elongate shoots. Diplobryum C. Cusset, comprising four species and characterised solely by the nearly 20-ribbed capsule, is polyphyletic. Two Lao and a Vietnamese species of Diplobryum are transferred to Hydrobryum: H. ramosum (C. Cusset) Koi & M. Kato comb. nov., with floating subcylindrical roots and anchoring disk-like bases, and H. vientianense (M. Kato & Fukuoka) Koi & M. Kato comb. nov. and H. minutale (C. Cusset) Koi & M. Kato comb. nov. with crustose roots. The rootless D. koyamae M. Kato & Fukuoka was recently combined as Hydrodiscus koyamae (M. Kato & Fukuoka) Koi & M. Kato. Cladopus (sect. Griffithella) pierrei (Lecomte) C. Cusset is not segregated even at a sectional rank. We also describe Polypleurum pluricostatum sp. nov., and add Hydrobryum tardhuangense M. Kato, Paracladopus chiangmaiensis M. Kato and Polypleurum schmidtianum Warm. as new records to Laos, and Polypleurum wallichii (R. Br. ex Griff.) Warm. from new localities in Laos.
Cladopus (with 12 or less species) is an Asian and Australian genus of Podostemaceae–Podostemoideae. They are haptophytes that grow in rivers. The developmental morphology and anatomy of Cladopus austro-osumiensis Y.Kadono & N.Usui, C. austrosatsumensis Koidzumi, C. chinensis Chao, C. japonicus Imamura and C. queenslandicus [Domin] C.D.K. Cook & Rutish. (syn. Torrenticola queenslandica [Domin] Domin ex Steenis) are studied by scanning electron microscope and microtome. The architecture of the examined species fits with the bauplan known from other Asian Podostemoideae. Rosulate shoots arise in zigzag patterns or as opposite pairs from narrow or broad green ribbons which may be interpreted as adhesive creeping roots. Cladopus is the only podostemaceous genus known with both endogenous and exogenous lateral roots along the mother root. Exogenous lobes (which may develop into daughter roots) are next to the sites of root-borne shoots which, finally, give rise to terminal flowers. Cladopus species have the following features (synapomorphies) in common: (1) leaves on older and reproductive shoots with one or two median, long filaments (caducous) and 1–4 lateral short lobes (persistent) on either side of the leaf, which are called stipules; (2) spathella (i.e. mantle-like flower cover) with an apical two-tipped papilla; (3) spathella splitting more or less circumscissilely; (4) capsules globose or nearly so, smooth or with three faint ribs per valve.
The systematic relationship of Tristicha australis C.Cusset & G.Cusset in northern Australia was investigated by comparative morphology and molecular phylogeny. Both lines of evidence show that it is most closely related to Malaccotristicha malayana (J.Dransf. & Whitmore) C.Cusset & G.Cusset and distinct from Tristicha trifaria (Bory ex Willd.) Sprengel and consequently the nomenclatural combination of Malaccotristicha australis is made. It is suggested that M. australis rapidly gained its characteristic morphology that is distinct from Malaccotristicha and resembles Tristicha. Phylogeographically, Australian Podostemaceae with two species, M. australis and Cladopus queenslandicus (Domin) C.D.K. Cook & Rutishauser, are probably derived, compared with the tropical Asian sisters. A key is provided to the species of Tristichoideae to distinguish M. australis and the other species.
New World Podostemaceae (riverweeds) comprise approximately 135 species in 21 genera, most of which are of tropical distribution, shed pollen in monads, and belong to subfamily Podostemoideae. We undertook a phylogenetic study of Neotropical Podostemoideae using molecular (ITS, rbcL, trnL) and morphological data, to assess the monophyly of genera and their interrelationships. Extensive taxon sampling (38 taxa in 15 genera) revealed that the large genera Apinagia and Marathrum are not monophyletic as currently circumscribed, although several species of the former comprised a clade that could be delimited morphologically by the shared character of upright stems (i.e. anchored to the substrate only basally). Marathrum species were split geographically, with Central and South American taxa resolving in different clades. Oserya also comprised two geographically disparate clades, with the type species belonging to the South American clade. To establish the monophyly of Oserya, we erected a new genus Noveloa to accommodate the Central American species N. coulteriana and N. longifolia. The Central American Marathrum clade included the monotypic Vanroyenella, which we transferred to that genus as Marathrum plumosum. The genera Castelnavia and Rhyncholacis were monophyletic in our analyses; C. multipartita f. pendulosa was elevated to species rank as Castelnavia pendulosa. The monotypic Lonchostephus resolved within Mourera, with which it shares a number of morphological features that are found also in Tulasneantha (also monotypic), but which otherwise are unique in Podostemaceae. We recommend that Lonchostephus and Tulasneantha be merged with Mourera and provide the new combination Mourera monadelpha for the latter. Finally, an unexpected clade of morphologically diverse genera, including members of Apinagia, Jenmaniella, Lophogyne, Marathrum, and Monostylis, resolved with strong support but uncertain morphological integrity, as sister to all ingroup taxa except Mourera. However, nomenclatural changes in this group have not been made, pending additional taxon sampling and procurement of further molecular and morphological evidence.
Portuguese
As Podostemaceae (flor-da-cachoeira) do Novo Mundo compreendem cerca de 135 espécies em 21 gêneros, a maioria de distribuição tropical, com pólen em mônades, pertencentes à subfamília Podostemoideae. Realizamos o estudo filogenético de Podostemaceae Neotropicais utilizando dados moleculares (ITS, rbcL, trnL) e morfológicos, a fim de avaliar o monofiletismo dos gêneros e suas relações filogenéticas. Uma extensa amostragem de táxons (38 táxons de 15 gêneros) revelou que os amplos gêneros Apinagia e Marathrum, não são monofiléticos com a atual circunscrição, embora diversas espécies do primeiro, formem um clado que pode ser delimitado morfologicamente por compartilhar o caráter presença de caule ereto (i.e.ancorado ao substrato apenas na base). Espécies de Marathrum foram separadas geograficamente, com os táxons da América Central e do Sul agrupadas em clados diferentes. Oserya também compreende dois clados distintos geograficamente, com a espécie tipo pertencente ao clado da América do Sul. Com o intuito de estabelecer o monofiletismo em Oserya, nós elegemos um novo gênero (Noveloa) para acomodar as espécies da América Central (N. coulteriana e N. longifolia). O clado Marathrum da América Central, incluiu o gênero monotípico Vanroyenella, que nós transferimos para aquele gênero como Marathrum plumosum. Os gêneros Castelnavia e Rhyncholacis são monofiléticos em nossa análise; C. multipartita f. pendulosa foi elevada à posição de espécie como Castelnavia pendulosa. O gênero monotípico Lonchostephus foi incluído em Mourera, com o qual compartilha diversos caracteres morfológicos também encontrados em Tulasneantha (também monotípico), que, no entanto, são únicos em Podostemaceae. Recomendamos que Lonchostephus e Tulasneantha sejam unidos com Mourera e propomos a nova combinação: Mourera monadelpha para esta última. Finalmente, um clado inesperado de gêneros morfologicamente distintos, incluindo membros de Apinagia, Jenmaniella, Lophogyne, Marathrum e Monostylis, uniram-se com forte suporte, mas de integridade morfológica incerta, como grupo irmão de todo o grupo interno, exceto Mourera. Entretanto, mudanças nomenclaturais neste grupo não foram realizadas, dependendo de uma amostragem de táxons adicionais e maiores evidências moleculares e morfológicas.
Pollination by water (hydrophily) is a highly specialized mechanism that occurs rarely among aquatic angiosperms, which mainly retain the reproductive systems reminiscent of their terrestrial ancestors. Hydrophily is abiotic and typically associated with unisexual flowers, factors that predictably would promote xenogamy and outcrossing. Yet, there have been few reports of hybridization involving waterpollinated plants (hydrophiles), with no firm evidence of natural interspecific hybridization. The genus Najas comprises about 40 species of submersed aquatic plants, all characterized by subsurface hydrophily. Hybridization in this genus has been suspected, but verified previously only among infraspecific taxa. In this study we document the first instance of interspecific hybridization in Najas using genetic evidence from three populations that were identifiable as N. guadalupensis but yielded polymorphic DNA sequence profiles. To facilitate our analysis we first conducted a phylogenetic survey of New World Najas taxa using nuclear and chloroplast markers. Alleles cloned from a biparentally-inherited locus (ITS) in these aberrant populations associated with two distinct but phylogenetically sister species (N. guadalupensis subsp. olivacea and N. flexilis) thus confirming their hybrid origin. In all cases the chloroplast markers associated with N. guadalupensis subsp. olivacea, implicating it as the maternal parent. The hybrid Najas plants occur at the edge of the sympatric range of the parental species. They possess no readily distinctive morphological features and require genetic analysis for confident detection. One population grows aggressively, raising concerns that at least some hybrid Najas plants represent a potential conservation threat. The possible hybrid ancestry of the endemic N. guadalupensis subsp. muenscheri also was assessed, but could not be confirmed or refuted by the data evaluated.
Podostemaceae, uma família botânica restrita a ambientes de corredeiras e cachoeiras, é amplamente reportada como de espécies com alto grau de endemismo local. Testamos esta hipótese para os representantes neotropicais da família, utilizando os dados históricos da literatura, material depositado em herbário, coletas empreendidas pelos autores e uma análise através do sistema de informação geográfica. Em contraste com a estimativa de endemismo referenciada nos estudos de P. van Royen (66%), reportamos 15%–37% de espécies endêmicas, baseadas na taxonomia atual. Exemplos de endemismo regional, suportados pela amplitude de ocorrência e de maior eixo geográfico são discutidos para um subgrupo de espécies. Grandes regiões hidrográficas (Bacia do rio Amazonas, Bacia do rio Paraná) e grandes áreas (sudeste do Brasil), demonstraram possuir uma ampla e distinta flora de Podostemaceae. Propomos rios e bacias como a unidade mais apropriada para acessar o endemismo de Podostemaceae, considerando endêmicas de um-rio e de dois-rios como distribuição restrita. Limitações no conhecimento taxonômico atual são discutidas com relação ao estabelecimento de uma estimativa significativa de endemismo local de espécies. Aplicamos provisoriamente o estado de conservação de espécies neotropicais de Podostemaceae de acordo com as categorias da IUCN, reportando que aproximadamente um terço das espécies se encaixa em uma das seguintes categorias: Dados Insuficientes (DD), Não Ameaçada (LC) e Vulneráveis (VU). Dez espécies estão Críticamente Ameaçadas (CR). As espécies de Podostemaceae são restritas a ambientes que têm sofrido os maiores impactos antrópicos—os rios tropicais. Grandes reservatórios tornam grandes extensões dos rios inabitáveis. A expansão do uso de energia proveniente de hidrelétricas na América Latina irão exacerbar este problema.
The scope of morphological plasticity of vegetative structures among Podostemoideae (Podostemaceae) is documented for Crenias weddelliana, a neotropical species, Maferria indica, a palaeotropical species, and Sphaerothylax abyssinica, from Kenya, and compared with related taxa. The study highlights intrinsic characters of the widely enigmatic plant body of many species of the subfamily Podostemoideae. These include dorsiventrality of shoots occurring irrespective of gravity, incurvate distichy and one-sided spirodistichy correlated with shoot dorsiventrality, asymmetric leaves, and several types of positioning of the two prophylls and inflorescence structures. The homogeneity of hairs of the ‘Zeylanidium olivaceum type’ established on the subulate leaves of some Indian species is of taxonomic value. The latter also applies to the stipella (not stipule) on the asymmetric compound leaf in New World species. The morphological data represent a framework of features consistent for the subfamily. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 138, 63–84.
Zeylanidium olivaceum (Podostemaceae-Podostemoideae) is the only crustose-rooted species of the genus that still develops prominent primary shoots from the seedling in addition to the secondary (root-borne) shoots forming the clonal plant body. The primary shoots are articulated into an up to 8.5 cm long and 4 mm thick stalk (hypocotyl) and a copiously foliated paint-brush-like shoot which is sympodially branched in the form of a helicoid cyme. The helicoid branching pattern indicates a transversal prophyll position, typical of the dicotyledons, but replaced in most other Podostemoideae by a median prophyll position. The short stems within the leafy head do not separate, but are fused to a dense aggregate (coenosome). Branches are mainly vegetative with a rosette of about 20 elongate subulate leaves. The primary shoots branch in the vegetative stage and thus differ from other Podostemoideae where ramification is confined to the floriferous shoots. The leaves adhere together at the base, forming an apical furrow-like hollow surrounding the shoot tip. The tiny shoot apex is one-layered, radially symmetrical, and develops leaf primordia in a decussate pattern. The erect primary shoots thus differ from the distichously foliated plagiotropic secondary shoots by the decussate phyllotaxis, and by the presence of more than 20 leaves on a shoot as compared to the about six leaves on the vegetative and floriferous secondary shoots. The features observed in the primary shoots are interpreted as primitive as compared to those of the secondary shoots. Z. olivaceum is thus characterised by heterobathmy, i.e., the occurrence of plesiomorphic (primary shoots) and apomorphic features (secondary shoots). The primary shoots exhibit primitive features that apparently have been lost in secondary and primary shoots of most other members of subfamily Podostemoideae.
The structural and developmental diversity of the Podostemaceae is remarkable. A comparison of 19 genera (of 48 genera), and 27 species (of 270 species) is presented, covering both subfamilies, the Podostemoideae (= Pod.) and Tristichoideae (= Trist.). Assuming the Podostemaceae to be derived from a typical cormophytic plant with the classical root-shoot (CRS) model, then evolutionary dynamics of vegetative structures in this family include: formation of green crustaceous structures as a result of dorsiventral flattening of roots, stems or both, reduction and loss of root caps, occurrence of sticking rhizoids and often disk-like holdfasts, and heterotopy of organ formation (from exogenous to endogenous bud formation). Some examples of structural dynamics are unique to certain taxa, e.g. 90° switch of the dorsiventrality plane in leaves of Marathrum, Mourera, and Oserya (Pod.); positional correlation of dithecous leaves (i.e. leaves with two sheaths) and dichotomous shoot branching in Podostemum and genera mentioned above (Pod.); occurrence of unique leaf-shoot mosaics (called ramuli) in Tristicha and allies (Trist.). Thus, the structural categories of typical flowering plants are transcended in the Podostemaceae due to developmental changes and saltational evolution. An overview of reproductive traits in Podostemaceae is given, focussing on characters that are useful in traditional systematics: shape, texture, and dehiscence of spathella (Pod.); presence and shape of cupule (Trist.). Starting with neotropical taxa showing radial flower symmetry (e.g. Rhyncholacis, Marathrum pro parte), most Podostemoideae can be derived by reduction of the number of stamens and basal fusion of the two remaining stamens. Most podostemads are wind-pollinated or autogamous. A few neotropical genera such as Mourera (Pod.) and Weddellina (Trist.) show polyandry, probably as an adaptation to insect-pollination. Other taxonomically used characters such as pollen (dyads in many Pod.), ovules, seeds, and capsules (ribs, dehiscence) are also demonstrated and discussed.
This volume is a reference and identification manual for the vascular plants found in permanent or seasonal fresh water in the subcontinent of India south of the Himalayas. About 660 species are described and the style of the text is accessible both to experts and to those with only a little botanical training. All the plants are illustrated by line drawings showing the diagnostic features. The importance of wetlands to life on Earth is now generally accepted. This is the first such Flora to cover wetland plants for this entire geographical area, replacing and supplementing many local Floras. It will enable scientists and conservationists to identify the plants with accuracy and to build on this information to promote conservation. This is a most valuable contribution to systematic botany by an international recognized scientist.
Leaves and stems of flowering plants have been widely accepted as clearly distinguishable structural categories. Evolution, however, can blur the stem–leaf (axis–appendage) distinction. Compound leaves with apical growth and three-dimensional branching may be seen as developmental mosaics sharing some growth processes with leafy stems (shoots). To cope with fuzzy boundaries between structural categories, fuzzy morphology is proposed as a complementary way of looking at higher plant architecture. Fuzzy morphology treats structural categories (e.g., leaves and stems) as concepts with fuzzy (not sharp) boundaries. The developmental morphology of compound leaves is described comparing Apium repens (Apiaceae) with less typical angiosperms ("misfits") of the rheophyte family Podostemaceae, especially Marathrum rubrum, Mourera fluviatilis, and Tristicha trifaria. In some taxa within the Podostemaceae, typical leaf characteristics may be replaced by new properties, e.g., 90° switch of symmetry plane of the leaf p...
As has been stated in the introduction of the second part, this third part will include the remainder of the American part of the tribe Eupodostemeae of the subfamily Eupodostemoideae which was not treated in part I, viz. the genera Oserya, Devillea, Ceratolacis, Mniopsis, Podostemum and Castelnavia. Included are the dubious genera, and it also contains additions and corrections to part I, latin descriptions of new taxa, a list of collectors’ numbers in this part, new references to the literature, and a general index to the third part. The attention of the reader is drawn to a publication of SZAFER (1952) in which a fossil Podostemacea from Europe has been described. As I have not seen the material it is at present impossible to judge the value of the discovery though it seems highly improbable that Podostemaceae ever lived in Europe.
The developmental morphology and anatomy of the highly specialized vegetative organs of Malaccotristicha malayana (Podostemaceae, subfamily Tristichoideae) are described. The plant body can be interpreted using the root-shoot model. The prostrate roots have asymmetrical root caps and root hairs over the ventral surface and are much flatter than those of Indotristicha ramosissima and Tristicha trifaria (Tristichoideae), the least specialized taxa in Podostemaceae. The lateral roots are initiated endogenously, proximal to the apex in the periphery of the poorly developed vascular cylinder of the parental root. They resemble the pericycle- or endodermis-derived roots of other vascular plants. Roots may also regenerate endogenously at injured parts of roots. The ramuli, interpreted as determinate shoots, arise laterally and endogenously below the subdermis of the root, and their apices have tunica-corpus-like organization. The scaly leaves formed on the ramuli develop tristichously on the ramulus apex. Unlike I. ramosissima and T. trifaria, M. malayana have no ramuli that arise on the root-branched shoots. Rudimentary holdfasts, associated with the ramuli, develop endogenously on the ventral side of the base of ramulus primordia.
The infrafamilial relationships of Podostemaceae were deduced from nucleotide sequences of the chloroplast matK gene. The matK phylogenetic analyses show that Podostemaceae are composed of two major clades that correspond to the subfamily Tristichoideae sensu stricto and Weddellina and the subfamily Podostemoideae. Weddellina, which has long been recognized as a member of the Tristichoideae, is sister to the Podostemoideae, supporting the classification that recognized a third subfamily Weddellinoideae. Malaccotristicha malayana and Terniopsis sessilis form a basal clade in Tristichoideae sensu stricto. Tristichoideae show a high morphological diversity and, surprisingly, a close relationship exists between Dalzellia zeylanica and Indotristicha ramosissima, which remarkably differ in their body plans. A few genera defined by particular characters, such as Synstylis and Torrenticola, merge into clades of other larger genera. The Podostemoideae taxa studied are composed of two American clades, an Asian-Australian clade and a Madagascan clade, and may suggest that the subfamily perhaps originated in America and migrated to the Old World.
PodostemumandCrenias (Podostemaceae) -American river weeds - infrageneric systematic relationships using molecular and morphological methods
- P Moline