Taxonomic Delimitation Research Articles

An improved method of genome size estimation by flow cytometry in five mucilaginous species of Hyacinthaceae

The family Hyacinthaceae constitutes about 900 species of bulbous geophytes usually characterized by high mucilage content. Taxonomic delimitation of Hyacinthaceae has been controversial since the time of Linnaeus due to the absence of reliable discriminating characters. Pattern of genome size variation can thus be considered as an added character to aid intergeneric and intrageneric relationship of the group. However, reports on genome size estimation by flow cytometric analysis of these plants are rare due to the presence of mucilage, which causes problem with nuclei sample preparation. To overcome this problem five reported nuclei isolation buffers were tested in Drimia indica of which Galbraith's buffer gave comparatively better results and was further modified by increasing pH, detergent concentration, and replacing sodium citrate by citric acid. The modified buffer enabled better sample preparation with increased yield, lesser debris, and improved DNA peak CV. The standardized buffer was used to estimate the 2C values of Drimia indica, Drimia nagarjunae, Drimia wightii, Drimia coromandeliana, and Ledebouria revoluta for the first time by flow cytometric analysis. This study also opens up the scope for further improvement in sample preparation for flow cytometric analysis of mucilaginous plants, which is otherwise problematic due to nuclei clumping and increased viscosity of sample.

A morphometric and taxonomic study of Anthurium augustinum complex (Araceae), endemic to the Brazilian Atlantic Forest

AbstractThe Anthurium augustinum (Araceae) complex (including A. augustinum K. Koch & Lauche, A. hatschbachii E. G. Gonç., A. jureianum Cath. & Olaio, A. laucheanum K. Koch, A. lhotzkyanum Schott, A. lucidum Kunth, A. maximiliani Schott and A. parvum N.E.Br.) is endemic to the Brazilian Atlantic Forest. Some of these taxa are strictly endemic, with only the type population known, and may occur in sympatry. These species share a leaf morphology in which the blade is deflexed at the petiole insertion and is usually cordate, or rarely rounded at the base due to congenital fusion of the basal lobes. Taxonomic delimitation of the species in this group is difficult because of overlap in diagnostic characters such as deflexed leaf blade, cordate, rounded or semi‐oval leaf base and camptodromous venation. The objective of the study was to test whether these taxa could be recognized using leaf morphometrics. Elliptic Fourier analysis was carried out on a sample of 257 individuals in 12 natural populations. The results of multivariate analyses indicated that in various comparisons, leaf shape was not diagnostic due overlap of variation within and between populations of different species. Consequently, we propose that A. laucheanum, A. lhotzkyanum and A. maximiliani should be regarded as synonyms of A. augustinum, and that the following five species be recognized in this complex: A. augustinum, A. hatschbachii, A. jureianum, A. lucidum and A. parvum. We also formally designate two neotypes (A. laucheanum, A. maximiliani), one lectotype (A. augustinum) and one epitype (A. augustinum). (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Genetic and morphological diversity of Sphagnum angustifolium, S. flexuosum and S. fallax in Europe

AbstractMolecular and morphological evolution of species may be decoupled which can lead to contrasting delimitation of taxonomic units based on morphological and genetic characters. The moss genus Sphagnum (peat mosses) provides a good example in which morphological and genetic characters often contradict each other. We investigated morphological and genetic variability within a highly polymorphic and taxonomically controversial species complex of the genus Sphagnum in order to reveal the ultimate causes of discordance between morphology and molecular evolution. Specifically, we aimed at addressing the following questions: (1) Are the three closely related European taxa (S. angustifolium, S. fallax, S. flexuosum) of the S. recurvum group morphologically and genetically distinct entities? (2) Are morphological and genetic groups concordant? (3) Is there any sign of hybridization among taxa that might complicate their morphological delimitation? We show that European specimens of the S. recurvum group form three distinct gene pools based on 11 polymorphic microsatellite markers. Individuals defined as morphotype “fallax” appear to be genetically clearly distinct from both morphotype “angustifolium” and “flexuosum”. However, for the latter two morphotypes, traditionally used morphological and genetic markers provide partly incongruent taxonomic delimitations. We show that in about 13% of the accessions 12 traditionally used morphological characters cannot fully distinguish the genetic groups revealed. Our genetic analysis also reveals that only a low proportion of the specimens (3%) is admixed suggesting that hybridization is unlikely to explain the taxonomical controversies observed. Therefore, we hypothesize that taxonomic controversies are likely due to the extreme phenotypic plasticity of morphological characters rather than to porous species boundaries.

Intraspecific Variation and Taxonomic Delimitation of <i>Munronia </i><i>p</i><i>innata</i> (Meliaceae) in Sri Lanka

Munronia pinnata (Wall) The ob (Meliaceae) is a rare, therapeutically important medicinal plant used in traditional and folklore medicine in Sri Lanka. Available species/morphotypes/ecotypes of M. pinnata in different locations exhibit diverse range of variations suggesting the possible revision of current taxonomic status. Present study compares seventy different vegetative and reproductive morphological characters in order to suggest the possible taxonomic delimitation of 13 populations of M. pinnata available in Sri Lanka. A cluster analysis and a Principle Component analysis (PCA) were performed using average taxonomic distance. A single access (sequential), key to sub specific taxa was constructed using stable morphological characters. In the cluster, APRG - 5 populations (Population collected from Ritigala forest) has got separated from all the other populations at a distance of about 100%. Populations collected from the same geographical areas (Gampaha district GPPW - 3, GPWP - 3; Moneragala district MGMG - 9 MGWW - 7; Nuwara Eliya district NEKP - 3, NEMR - 3) have grouped closely either in the dendrogramme or in PCA or both. Based on the results, it could be concluded that population APRG - 5 is distantly related to all others and deserved placing as a sub specific taxon of M. pinnata. Further, populations collected from the same geographical area seem to be closely related with one another. Sequential key prepared using morphological characters could be used for the identification of M. pinnata populations even in the absence of flowers.

Delimiting invasive Myriophyllum aquaticum in Kashmir Himalaya using a molecular phylogenetic approach.

Myriophyllum aquaticum (Vell.) Verdc. (family Haloragaceae) is one of the most invasive and destructive South American aquatic plant species and is present in a wide range of geographic regions, including the Kashmir Himalaya. Confusion regarding the taxonomic delimitation of M. aquaticum in the Himalayan region impedes effective and targeted management. Hence, our goal was improve the identification of M. aquaticum for exclusive delimitation from other related species in the study region using a molecular phylogenetic approach. A maximum parsimony tree recovered from phylogenetic analyses of the internal transcribed spacer sequences of nuclear ribosomal DNA was used to authenticate the identification of M. aquaticum. The results of this study can be used for targeted management of this tropical invader into the temperate Kashmir Himalaya.

Petal venation of a few species of Malvaceae and its possible utility in tracing relationships

Analysis of vein anastomosis of the petals of 13 species of <em>Malvaceae shows</em> that the species differ in respect of frequency and distribution pattern of venation types. Differences are statistically significant. The investigation suggests that the venation anastomosis types may be utilized as additional envidence of taxonomic delimitation.

Phylogenetic reassessment of Hyaloscyphaceae sensu lato (Helotiales, Leotiomycetes) based on multigene analyses

Hyaloscyphaceae is the largest family in Helotiales, Leotiomycetes. It is mainly characterized by minute apothecia with well-differentiated hairs, but its taxonomic delimitation and infrafamilial classification remain ambiguous. This study performed molecular phylogenetic analyses using multiple genes including the ITS-5.8S rDNA, the D1–D2 region of large subunit of rDNA, RNA polymerase II subunit 2, and the mitochondrial small subunit. The primary objective was to evaluate the phylogenetic utility of morphological characters traditionally used in the taxonomy of Hyaloscyphaceae through reassessment of the monophyly of this family and its genera. The phylogenetic analyses inferred Hyaloscyphaceae as being a heterogeneous assemblage of a diverse group of fungi and not supported as monophyletic. Among the three tribes of Hyaloscyphaceae only Lachneae formed a monophyletic lineage. The presence of hairs is rejected as a synapomorphy, since morphologically diversified hairs have originated independently during the evolution of Helotiales. The true- and false-subiculum in Arachnopezizeae are hypothesized to have evolved through different evolutionary processes; the true-subiculum is likely the product of a single evolutionary origin, while the false-subiculum is hypothesized to have originated multiple times. Since Hyaloscyphaceae sensu lato was not resolved as monophyletic, Hyaloscyphaceae sensu stricto is redefined and only applied to the genus Hyaloscypha.

Pollen morphology of Justicia L. (Acanthaceae) from Thailand and its taxonomic value

The acetolysed pollen of 33 species of the genus Justicia in Thailand is investigated using both light and scanning electron microscopy. The pollen of the genus is characterised as being isopolar, bilaterally or radially symmetrical, with mostly prolate or prolate spheroidal shape. Based on characters with high factor loading in the cluster analysis and principal components analysis, the studied species are divided into two major groups; one with 3-colporate with six pseudocolpi and the other with 2-porate or 2–3-colporate with aperture areas. The pollen morphology of each group is described and illustrated. Pollen characters are useful for taxonomic delimitation and relationships among Thai species.

Comparative root anatomy of the species under Sida rhombifolia complex (Malvaceae)

IntroductionAnatomical studies of the root of four Sida species, S. rhombifolia, S. alnifolia, S. scabrida and S. rhomboidea, coming under Sida rhombifolia complex (Malvaceae) were carried out and compared. The genus Sida is the botanical source of the controversial Ayurvedic drug ‘Bala’. Nearly five species of Sida including S .alnifolia are used as Bala. Materials and methodsAfter taxonomic confirmation, observed root morphology, root anatomy and powder microscopy of four Sida species as per standard procedures. ResultsRoots of all the four species are distinct in their morphology as well as anatomical characters such as pattern of bast fibres and medullary rays. ConclusionBased on the anatomical characters, a diagnostic key is prepared which can be used as a supporting tool for taxonomic delimitation of the species coming under the S. rhombifolia complex as well as to ascertain the identity of the drug Bala.

Pliocene intraspecific divergence and Plio‐Pleistocene range expansions within Picea likiangensis (Lijiang spruce), a dominant forest tree of the Qinghai‐Tibet Plateau

A knowledge of intraspecific divergence and range dynamics of dominant forest trees in response to past geological and climate change is of major importance to an understanding of their recent evolution and demography. Such knowledge is informative of how forests were affected by environmental factors in the past and may provide pointers to their response to future environmental change. However, genetic signatures of such historical events are often weak at individual loci due to large effective population sizes and long generation times of forest trees. This problem can be overcome by analysing genetic variation across multiple loci. We used this approach to examine intraspecific divergence and past range dynamics in the conifer Picea likiangensis, a dominant tree of forests occurring in eastern and southern areas of the Qinghai-Tibet Plateau (QTP). We sequenced 13 nuclear loci, two mitochondrial DNA regions and three plastid (chloroplast) DNA regions in 177 individuals sampled from 22 natural populations of this species, and tested the hypothesis that its evolutionary history was markedly affected by Pliocene QTP uplifts and Quaternary climatic oscillations. Consistent with the taxonomic delimitation of the three morphologically divergent varieties examined, all individuals clustered into three genetic groups with intervariety admixture detected in regions of geographical overlap. Divergence between varieties was estimated to have occurred within the Pliocene and ecological niche modelling based on 20 ecological variables suggested that niche differentiation was high. Furthermore, modelling of population-genetic data indicated that two of the varieties (var. rubescens and var. linzhiensis) expanded their population sizes after the largest Quaternary glaciation in the QTP, while expansion of the third variety (var. likiangensis) began prior to this, probably following the Pliocene QTP uplift. These findings point to the importance of geological and climatic changes during the Pliocene and Pleistocene as causes of intraspecific diversification and range shifts of dominant tree species in the QTP biodiversity hot spot region.

Study of the polymorphism of the PatagonianCalceolaria polyrhiza(Calceolariaceae) using decision tree and sequential covering rule induction

Climate and landscape changes that occurred in Patagonia during the Pleistocene presumably led to the ample biodiversity that currently characterizes the region. Many Patagonian species constitute unresolved complexes that may be related to these environmental changes. Accordingly, discriminating among taxonomic entities within an endemic and widely distributed species in Patagonia would enable a better understanding of the diversification processes that occurred in the recent past. We explored the polymorphism of Calceolaria polyrhiza, a widely distributed species for which phylogeographic studies suggest a recent diversification, with the aim of disentangling the morphological variability patterns in this species. We employed quantitative and qualitative floral and vegetative traits, including geometric morphometric variables. We used two clustering algorithms, testing for correspondence between detected clusters and the species previously described for the complex. Finally, we described these clusters using decision trees and sequential covering rule induction. Major clusters were determined, which match the previously described species. Floral traits related to corolla design and shape were the most useful characters for distinguishing groups and the variation patterns in these traits might be associated with historical and ecological factors. The need for conducting plant systematic studies using techniques that ensure objective taxonomic delimitations and descriptions is stressed. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173, 487–500.

A chemotaxonomic assessment of four indigenous South African Lippia species using GC–MS and vibrational spectroscopy of the essential oils

Lippia species are widely used as traditional remedies by many South African communities. The identification of Lippia spp. indigenous to South Africa is currently based on the morphology and geographical origin of the specimen. However, morphological similarities are evident and due to sympatric distributions, different species may co-occur in the same natural environment, thereby presenting difficulties in the taxonomic delimitation of these taxa. In this paper, gas chromatography–mass spectrometry (GC–MS) and vibrational spectroscopic analyses were used to investigate the chemotaxonomic differentiation of four Lippia species (L. javanica, L. scaberrima, L. rehmannii and L. wilmsii), based on the essential oil composition. The results demonstrate that multivariate classification of chromatographic data enabled separation of Lippia oils into three distinct clusters representing L. scaberrima, L. rehmannii and L. javanica. With the aid of chemometric algorithms, it was also possible to use both mid infrared (MIR) and near infrared (NIR) spectroscopy for a clear distinction of the Lippia spp., with results comparable to those obtained by GC–MS. Orthogonal projections to latent structures (OPLS) presented a better classification algorithm than principal component analysis (PCA), in both GC–MS and spectroscopy analyses. Chemical variations within the Lippia spp. complex were evident, particularly for L. javanica and L. scaberrima, which exhibited significant intra-species variation.

Micromorfología foliar del género Quercus (Fagaceae) en México

México es el principal centro de diversidad del género Quercus en el Hemisferio Occidental. A pesar de los avances recientes en el conocimiento de los encinos mexicanos, aún existe cierto grado de confusión taxonómica, particularmente dentro de algunos complejos de especies. En este estudio se utilizó microscopía electrónica de barrido para describir las estructuras micromorfológicas foliares (tricomas, ceras epicuticulares y estomas) de ambas superficies foliares (haz y envés) en representantes seleccionados de encinos mexicanos, con el objetivo de evaluar la utilidad taxonómica de estos caracteres. En total se examinaron 27 especies, pertenecientes a las secciones Quercus (encinos blancos) y Lobatae (encinos rojos y negros), incluyendo varios grupos de plantas cercanamente relacionadas con problemas de delimitación taxonómica, así como especies que presentan hibridación. Se encontraron varios tipos de tricomas, tanto los de tipo glandular (simples y bulbosos) como los no glandulares (solitarios, multirradiados, estrellados, estrellados fusionados y fasciculado estipitados). Las ceras epicuticulares se observaron en forma de capas, capas fisuradas, costras, gránulos, placas y placas en rosetas. Los estomas fueron elípticos y se encontraron elevados con respecto a la superficie foliar o al mismo nivel que ésta. Entre los tres tipos de estructuras examinadas, los tricomas fueron los más útiles para propósitos taxonómicos, seguidos por las ceras epicuticulares. Todas las especies tuvieron diferentes combinaciones de estados de carácter para estas estructuras micromorfológicas, lo que permitió la elaboración de claves para identificar a las especies dentro de los grupos problemáticos.

Electrophoretic pattern of seed proteins in <i>Trifolium</i> L. and its taxonomic implications

The taxonomic delimitations of 61 taxa of the genus Trifolium L. belonging to presently accepted five sections, namely Lotoidea, Mistyllus, Vesicaria, Chronosemium and Trifolium are evaluated, based on numerical analysis of their electrophoretic seed protein profiles. The dendrogram, resulted from the hierarchical cluster analysis of SDS-PAGE profiles of seed proteins conform, with some restrictions, to the present splitting of the genus Trifolium into the sections but not into the subsections and series.DOI: http://dx.doi.org/10.3329/bjpt.v20i1.15461Bangladesh J. Plant Taxon. 20(1): 19-26, 2013 (June)

English

Proteomic evidences can be pivotal to the discovery of new plant proteins and plant relationships, due to the diversity of form it can reveal. Seed storage protein profiles of 20 Fabaceae species: 4 grainlegumes and 16 non-pulses; of 16 genera and 10 tribes were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) to estimate protein content diversity and the possible genetic relatedness. 28.3% similarity and 71.7% proteomic polymorphism was scored for the species. The high variability expressed by the lot reflects the genetic diversity amongst Fabaceae population. Dendrogram based on the proteomic data clustered the species into four groups. Aside two species, Albizia lebbeck and Albizia zygia belonging to the tribe Ingeae and those of the tribe Caesalpinieae , the other species clustered with several other non-traditional cohorts resulting in a rearrangement that showed least semblance with phylogenetic relationships based on traditional morphology taxonomic delimitation. The similarity in profiles can be preliminarily forensic for proteins of importance whether for nutritional, industrial or for improvement of existing crops or for entirely new plants as crops. The protein mix, and the resultant relationship based on seed storage proteins instigates a review of erstwhile taxonomic, agricultural and research perspectives for the Fabaceae. Keywords : Fabaceae, seed protein, polymorphism, genetic diversity, taxonomy, single protein African Journal of Biotechnology Vol. 12(17), pp. 2157-2163

Non-invasive ancient DNA protocol for fluid-preserved specimens and phylogenetic systematics of the genus <i>Orestias</i> (Teleostei: Cyprinodontidae)

Specimens stored in museum collections represent a crucial source of morphological and genetic information, notably for taxonomically problematic groups and extinct taxa. Although fluid-preserved specimens of groups such as teleosts may constitute an almost infinite source of DNA, few ancient DNA protocols have been applied to such material. In this study, we describe a non-invasive Guanidine-based (GuSCN) ancient DNA extraction protocol adapted to fluid-preserved specimens that we use to re-assess the systematics of the genus Orestias (Cyprinodontidae: Teleostei). The latter regroups pupfishes endemic to the inter-Andean basin that have been considered as a 'species flock', and for which the morphology-based taxonomic delimitations have been hotly debated. We extracted DNA from the type specimens of Orestias kept at the Muséum National d'Histoire Naturelle of Paris, France, including the extinct species O. cuvieri. We then built the first molecular (control region [CR] and rhodopsin [RH]) phylogeny including historical and recently collected representatives of all the Orestias complexes as recognized by Parenti (1984a): agassizii, cuvieri, gilsoni and mulleri. Our ancient DNA extraction protocol was validated after PCR amplification through an approach based on fragment-by-fragment chimera detection. After optimization, we were able to amplify < 200 bp fragments from both mitochondrial and nuclear DNA (CR and RH, respectively) from probably formalin-fixed type specimens bathed entirely in the extraction fluid. Most of the individuals exhibited few modifications of their external structures after GuSCN bath. Our approach combining type material and 'fresh' specimens allowed us to taxonomically delineate four clades recovered from the well-resolved CR tree into four redefined complexes: agassizii (sensu stricto, i.e. excluding luteus-like species), luteus, cuvieri and gilsoni. The mulleri complex is polyphyletic. Our phylogenetic analyses based on both mitochondrial and nuclear DNA revealed a main, deep dichotomy within the genus Orestias, separating the agassizii complex from a clade grouped under shallow dichotomies as (luteus, (cuvieri, gilsoni)). This 'deep and shallow' diversification pattern could fit within a scenario of ancient divergence between the agassizii complex and the rest of Orestias, followed by a recent diversification or adaptive radiation within each complex during the Pleistocene, in- and outside the Lake Titicaca. We could not recover the reciprocal monophyly of any of the 15 species or morphotypes that were considered in our analyses, possibly due to incomplete lineage sorting and/or hybridization events. As a consequence, our results starkly question the delineation of a series of diagnostic characters listed in the literature for Orestias. Although not included in our phylogenetic analysis, the syntype of O. jussiei could not be assigned to the agassizii complex as newly defined. The CR sequence of the extinct O. cuvieri was recovered within the cuvieri clade (same haplotype as one representative of O. pentlandii), so the mtDNA of the former species might still be represented in the wild.

Molecular phylogenetic relationships among members of the family Phytolaccaceae sensu lato inferred from internal transcribed spacer sequences of nuclear ribosomal DNA

The phylogeny of a phylogenetically poorly known family, Phytolaccaceae sensu lato (s.l.), was constructed for resolving conflicts concerning taxonomic delimitations. Cladistic analyses were made based on 44 sequences of the internal transcribed spacer of nuclear ribosomal DNA from 11 families (Aizoaceae, Basellaceae, Didiereaceae, Molluginaceae, Nyctaginaceae, Phytolaccaceae s.l., Polygonaceae, Portulacaceae, Sarcobataceae, Tamaricaceae, and Nepenthaceae) of the order Caryophyllales. The maximum parsimony tree from the analysis resolved a monophyletic group of the order Caryophyllales; however, the members, Agdestis, Anisomeria, Gallesia, Gisekia, Hilleria, Ledenbergia, Microtea, Monococcus, Petiveria, Phytolacca, Rivinia, Schindleria, Seguieria, Stegnosperma, and Trichostigma, which belong to the family Phytolaccaceae s.l., did not cluster under a single clade, demonstrating that Phytolaccaceae is polyphyletic.

Variation in leaf morphology of the invasive cat's claw creeper Dolichandra unguis-cati (Bignoniaceae)

The invasive liana cat’s claw creeper Dolichandra unguis-cati (L.) L.G. Lohmann (syn. Macfadyena unguis-cati (L.) A.H. Gentry) exhibits intraspecific variation in leaf morphology, but this is rarely noted in the published literature. The present study documents variation in leaf morphology in two forms of the species that occur in Australia (long pod and short pod). Leaf morphology is compared between the two forms and the position of the shoots (trunk and ground) at the only two sites in which they co-occur. Leaves were categorised on the basis of leaflet number and the presence or absence of tendrils. Simple leaves were produced mainly on shoots growing along the ground and were more abundant in the short-pod form. Long-pod plants were dominated by bifoliate leaves with tendrils. Cat’s claw creeper exhibits considerably wider variation in leaf morphology than recorded previously. Variations in leaf morphology may be linked to differences in the genotype, developmental stage and plastic responses of the plants. Understanding these variations may have implications for taxonomic delimitation and improved management, particularly biological control involving leaf-feeding insects.

Phylogenetic analysis of Codium species from Brazil, with the description of the new species C. pernambucensis (Bryopsidales, Chlorophyta)

The genus Codium comprises c. 125 species widely distributed in marine coastal environments throughout the world. Due to morphological plasticity, the taxonomic delimitation of Codium species can be difficult. Sequences of the first exon of the large subunit of RUBISCO (rbcL) have been used in the molecular delimitation of species and for phylogenetic purposes. In the present study, we complement previous morphological work on Brazilian Codium species with molecular systematics. Based on the partial rbcL sequences, seven species are recognized along the Brazilian coast: C. decorticatum, C. intertextum, C. isthmocladum, C. profundum, C. spongiosum, C. taylorii and the new species Codium pernambucensis. Ten unique sequences were obtained among the samples examined, which we used in combination with previously published sequences to infer molecular phylogenies using various methods. The resulting trees showed three principal monophyletic groupings: Clade A with species having a prostrate habit, not branched, and mostly with small, grouped utricles; Clade B primarily consisting of upright species with cylindrical branches and large individual utricles; and Clade C composed of upright species with cylindrical branches that are slightly flattened, and have intermediate-sized individual utricles. The Brazilian species grouped with morphologically similar taxa from other geographic localities, and are present in all three main clades. A new sprawling species, Codium pernambucensis is described based on morphology and molecular analyses.

Leaf anatomy and its contribution to the systematics of Aechmea subgenus Macrochordion (de Vriese) Baker (Bromeliaceae)

The leaf anatomy of the species Aechmea subgenus Macrochordion was analyzed to obtain valuable data on their taxonomic delimitation and to identify anatomical adaptations to their respective habitats and habits. All leaves of these species are hypostomatic, and present: peltate trichomes on both surfaces; stomata sunk in epidermal depressions; small epidermal cells with thick walls and inclusions of silica bodies; a mechanical hypodermis; an aquiferous parenchyma; chlorenchyma with fibrous clusters and air channels; and vascular bundles surrounded by a parenchymatic sheath and a cap of fibers. The results are evaluated within an adaptive and taxonomic context. Variations in hypodermic thickening, amount of water parenchyma, position of the air channels and shape of the cells filling the air channels are useful for delimiting groups of species, strengthening the relationships suggested by their external morphology.