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Recognition of the genus Thaumatophyllum Schott - formerly Philodendron subg. Meconostigma (Araceae) - based on molecular and morphological evidence.

ABSTRACT: Philodendron subgenus Meconostigma has been a well-circumscribed group since 1829. Members of this group are easily distinguished by diagnostic morphological characters as well as by a distinct ecology and geographical distribution. Based on molecular, morphological and cytological evidence, we propose the recognition of P. subg. Meconostigma as a distinct genus, Thaumatophyllum Schott. We also present the necessary new combinations, an emended key and some nomenclatural and taxonomic corrections regarding 21 names of Thaumatophyllum.

SUBMITTER: Sakuragui CM

PROVIDER: S-EPMC5943393 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Recognition of the genus <i>Thaumatophyllum</i> Schott - formerly Philodendron subg. Meconostigma (Araceae) - based on molecular and morphological evidence.

Sakuragui Cassia Mônica CM Calazans Luana Silva Braucks LSB de Oliveira Leticia Loss LL de Morais Érica Barroso ÉB Benko-Iseppon Ana Maria AM Vasconcelos Santelmo S Schrago Carlos Eduardo Guerra CEG Mayo Simon Joseph SJ

PhytoKeys 20180502 98

Philodendron subgenus Meconostigma has been a well-circumscribed group since 1829. Members of this group are easily distinguished by diagnostic morphological characters as well as by a distinct ecology and geographical distribution. Based on molecular, morphological and cytological evidence, we propose the recognition of P. subg. Meconostigma as a distinct genus, <i>Thaumatophyllum</i> Schott. We also present the necessary new combinations, an emended key and some nomenclatural and taxonomic cor ...[more]

PMID: 29750071

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Project description:Elucidating the evolutionary patterns of flower and inflorescence structure is pivotal to understanding the phylogenetic relationships of Angiosperms as a whole. The inflorescence morphology and anatomy of Philodendron subgenus Meconostigma, belonging to the monocot family Araceae, has been widely studied but the evolutionary relationships of subgenus Meconostigma and the evolution of its flower characters have hitherto remained unclear. This study examines gynoecium evolution in subgenus Meconostigma in the context of an estimated molecular phylogeny for all extant species of subgenus Meconostigma and analysis of ancestral character reconstructions of some gynoecial structures. The phylogenetic reconstructions of all extant Meconostigma species were conducted under a maximum likelihood approach based on the sequences of two chloroplast (trnk and matK) and two nuclear (ETS and 18S) markers. This topology was used to reconstruct the ancestral states of seven floral characters and to elucidate their evolutionary pattern in the Meconostigma lineage. Our phylogeny shows that Meconostigma is composed of two major clades, one comprising two Amazonian species and the other all the species from the Atlantic Forest and Cerrado biomes with one Amazonian species. The common ancestor of the species of subgenus Meconostigma probably possessed short stylar lobes, long stylar canals, a stylar body, a vascular plexus in the gynoecium and druses in the stylar parenchyma but it is uncertain whether raphide inclusions were present in the parenchyma. The ancestral lineage also probably possessed up to 10 ovary locules. The evolution of these characters seems to have occurred independently in some lineages. We propose that the morphological and anatomical diversity observed in the gynoecial structures of subgenus Meconostigma is the result of an ongoing process of fusion of floral structures leading to a reduction of energy wastage and increase in stigmatic surface.

Project description:Background and aimsAraceae species pollinated by nocturnal Cyclocephalini beetles attract their pollinators by inflorescence scents. In Philodendron , despite the intense odour, the osmophores exhibit no definite morphological identity, making them difficult to locate. This may explain why structural studies of the scent-releasing tissue are not available so far.MethodsSeveral approaches were employed for locating and understanding the osmophores of Philodendron adamantinum . A sensory test allowed other analyses to be restricted to fertile and sterile stamens as odour production sites. Stamens were studied under light and electron microscopy. Dynamic headspace and gas chromatography-mass spectrometry were used to collect and analyse scents from different zones of the inflorescence.Key resultsThe epidermal cells of the distal portion of fertile stamens and staminodes are papillose and, similar to the parenchyma cells of this region, have dense cytoplasm and large nuclei. In these cells, the composition of organelles is compatible with secretory activity, especially the great number of mitochondria and plastids. In this portion, lipid droplets that are consumed concomitantly with the release of odour were observed. Quantitative scent analyses revealed that the scent, with a predominance of dihydro-?-ionone, is mainly emitted by the fertile and sterile staminate zones of the spadix. An amorphous substance in the stomata pores indicates that the components are secreted and volatilized outside of the osmophore under thermogenic heat.ConclusionsDespite the difficulty in locating osmophores in the absence of morphological identity and inefficiency of neutral red staining, the osmophores of P. adamantinum have some features expected for these structures. The results indicate a functional link between thermogenesis and volatilization of osmophore secretions to produce olfactory signals for attracting specialized beetle pollinators. These first experimental data about the precise location of osmophores in Philodendron will stimulate studies in related species that will allow future comparison and the establishment of patterns of functional morphology.

Project description:Molecular phylogenetic studies of the six currently accepted species in the genus Echinocactus have partially clarified certain aspects of its phylogeny. Most of the studies lack a complete sampling of Echinocactus and are based only in one source of data. Phylogenetic uncertainties in Echinocactus, such as the recognition of Homalocephala as a different genus from Echinocactus, the exclusion of E.grusonii or the affinities of E.polycephalus, are here resolved. Phylogenetic relationships of Echinocactus were reconstructed with a maximum parsimony, a maximum likelihood and a Bayesian approach including 42 morphological characters, four chloroplast markers (atpB-rbcL, trnH-psbA, trnL-trnF and trnK/matK) and two nuclear genes. The utility of these two nuclear regions related to the betalain cycles (DODA and 5GT) are explored and discussed in relation to their potential as phylogenetic markers. Concatenated analyses with morphological and molecular data sets, plus 13 indels (2847 characters and 26 taxa), show general agreement with previous independent phylogenetic proposals but with strong support in order to propose the recognition of a reduced Echinocactus and the recognition of Homalocephala at the generic level. These results recovered a polyphyletic Echinocactus as currently defined. The here-named HEA clade, recovers the species of Homalocephala, Echinocacuts and Astrophytum as a monophyletic group with strong internal support. The Homalocephala (H.texensis, H.parryi and H.polycephala), was recovered as sister to the Echinocactus clade (E.platyacanthus and E.horizonthalonius), plus the Astrophytum clade. Consequently, we propose here to recognise a monophyletic Echinocactus and a monophyletic Homalocephala as two distinct genera with their own molecular and morphological synapomorphies. The evolution of some morphological characters supporting these clades are discussed, the necessary new taxonomic combinations for Homalocephala are proposed and an identification key for the genera, the species and the subspecies of the HEA clade are presented.

Dataset Information

Recognition of the genus Thaumatophyllum Schott - formerly Philodendron subg. Meconostigma (Araceae) - based on molecular and morphological evidence.

Publications

Recognition of the genus <i>Thaumatophyllum</i> Schott - formerly Philodendron subg. Meconostigma (Araceae) - based on molecular and morphological evidence.

Similar Datasets

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