Cecilia Carmen Xifreda

Chromosome contribution to Andean Polyploid Species of Senecio (Asteraceae), from Argentina

Abstract Meiotic chromosome numbers were determined and observations of meiotic behavior were made in six species and two hybrid specimens of Senecio L. (Asteraceae). Two different numbers were found: 2n=4x=40 in S. pogonias Cabr., S. ragonesei Cabr., S. sectilis Griseb. and S. viridis Phil. var. radiatus R. E. Fr. and 2n=8x=80 in S. subulatus D. Don. var. subulatus and in S. uspallatensis Hook. et Arn.; the latter showed the same chromosome number previously reported. The chromosome number of the hybrid individuals was 2n=4x=40, being their putative parents S. ragonesei and S. sectilis. B chromosomes were found in some individuals of S. pogonias, S. sectilis, S. subulatus var. subulatus and S. uspallatensis. Many meiotic irregularities such as bridges, fragments, laggard chromosomes, micronuclei and cellular fusion were observed. The results are analyzed in relation to the persistence and success of these polyploids, and the speciation mechanisms operating within this group are discussed.

Natural hybrids in Senecio (Asteraceae): new records from Argentina

Abstract Hybridisation is very common within Senecio. It is considered a fundamental mechanism of speciation and also a major feature causing systematic complexity. Morphological features are the preliminary characteristics used to identify hybrids; however this approach is usually not sufficient when this is the case chromosome studies represent a valuable tool for reinforcing the observations. Two natural homoploid interspecific hybrids are reported here: Senecio × lulioi M. G. López et Xifreda (S. brasiliensis (Spreng.) Less. × S. grisebachii Baker) and Senecio × piepaloensis M. G. López et Xifreda (S. ragonesei Cabrera × S. sectilis Griseb.). Classic cytogenetic analysis and pollen stainability were performed to evaluate hybrid origins and to designate the putative parents. S. × lulioi presented a low frequency of quadrivalents and heteromorphic bivalents, both strong evidences of hybridisation between closely related species. S. × piepaloensis exhibited a high frequency of meiotic irregularities, and reduced pollen stainability, certain characteristics of hybrids. This analysis is discussed in relation to the role of hybridisation in the evolution of the genus, and its systematic significance.

Chromosome association and basic number in Anredera krapovickasii (Basellaceae)

Abstract The chromosome number of Anredera krapovickasii (Villa Carenzo) Sperling is given (2n=24) and karyotype is reported for the first time: 18 m + 2 m-sm + 4 sm. Meiotic studies reveal chromosome associations with secondarily associated bivalents. The analysis of chromosome pairing suggests a basic number x=6 for the species, and in consequence for the genus and the Basellaceae family. Basic chromosome number also indicates a closer relationship between Basellaceae and Portulacaceae.

Chromosome numbers and meiotic behaviour in South American species of Hybanthus Jacq. and Anchietea A. St.-Hil. (Violaceae)

Abstract Chromosome numbers and meiotic behaviour of 10 species of Hybanthus and one of Anchietea in South America were analysed in the present study. Most of the previous chromosomal data relating to Hybanthus were obtained from Australian species, and chromosomal information relating to Anchietea was not available until now. Three different chromosome numbers were found: 2n = 16 for Anchietea parvifolia Hallier f., Hybanthus bigibbosus (A. St.‐Hil.) Hassl., H. paraguariensis (Chodat) Schulze‐Menz and H. atropurpureus (A. St.‐Hil.) Taub.; 2n = 32 for H. bicolor (A. St.‐Hil.) Baill., H. calceolaria (L.) Oken, H. communis (A. St.‐Hil.) Taub., H. hasslerianus (Chodat) Hassl., H. leucopogon Sparre and H. nanus (A. St.‐Hil.) Paula‐Souza; and 2n = 48 for H. longistylus Schulze‐Menz. These were the first reports for eight species of Hybanthus and the first one for the genus Anchietea. For H. communis and H. atropurpureus, we confirm their chromosome numbers and describe their meiotic behaviour. The presence of B‐chromosomes in H. atropurpureus, H. communis and H. hasslerianus is reported here for the first time in the genus Hybanthus. In the light of these findings, polyploidy likely played an important role during the speciation of this heterogeneous generic assembly.

Deep cytogenetics analysis reveals meiotic recombination depletion in species of Senecio (Asteraceae)

BackgroundSenecio is the largest genus in the Asteraceae family growing in all environments around the world. It displays taxonomic and systematical difficulties. Cytogenetic knowledge of this genus is ancient, scarce and mainly restricted to chromosome number records.ResultsIn this study we analyzed chromosome number, meiotic configuration, bivalent morphology, meiotic behavior and pollen grain stainability on 100 accessions of 27 different polyploid Senecio L. sect Senecio entities. Median, standard deviation and mode were calculated for number and position of chiasmata and meiotic recombination was statistically evaluated. Although high frequency of multivalents and associated meiotic irregularities are expected in high polyploids, bivalents predominance and, consequently, regular meiosis were observed, with normal sporogenesis and high pollen grain stainability.ConclusionDepletion in the total chiasmata was significant only in some species but the terminal position was preferential in all the entities analyzed, indicating significant reduction in recombination. The regular meiosis observed suggest that intra and intergenomic reorganization process occur quickly and efficiently in this genus. Mechanisms of diploidization, common to all polyploids, are reinforced by the strong reduction in crossing-over rushing polyploids stabilization.

Foliar Micromorphology in the Classification of South American Hybanthus Species (Violaceae)

The infrageneric classification of Hybanthus subgen. Ionidium (Violaceae) is unclear and needs to be redefined. In the present study, it is proposed to be separated into five clearly distinct sections, based on the leaf micromorphology, according to the presence or absence of different trichomes and papillae. Scanning electron microscopy provided evidence supporting changes in the systematics of Hybanthus subgen. Ionidium. Five well-defined leaf micromorphological types were identified for the South American species studied. Additionally, three new sections are established in this study: Hybanthus sect. Ionidium, Hybanthus sect. Parviflorae and Hybanthus sect. Pombaliae. Hybanthus atropurpureus is designated as the lectotype of Hybanthus sect. Micranthae.

Identity of the Brazilian species Dioscorea pumilio Griseb. and its synonyms

1. Instituto de Botánica Darwinion, Labardén 200, Casilla de Correo 22, San Isidro, Buenos Aires, Argentina 2. Instituto de Botânica, Núcleo de Pesquisa Curadoria do Herbário SP, Av. Miguel Stéfano 3687, 04301-902, São Paulo, SP, Brasil 3. Autor para correspondência: mkirizawa@uol.com.br ABSTRACT (Identity of the Brazilian species Dioscorea pumilio Griseb. and its synonyms). Dioscorea pumilio, a dwarf species, was originally described by Grisebach in 1875 based on staminate material only, which was obtained from a few fl owered and fl oral bud collection made by A. Glaziou. The diagnosis and the drawings with the authorʼs handwriting in the exsiccates deposited at the Göttingen Herbarium (GOET), and the isotypes at the Herbaria of Paris (P), Copenhagen (C) and Berlin (B), are enough to elucidate the identity of the species. Two synonyms of Dioscorea pumilio, D. beyrichii and D. sphaeroidea, are proposed here. All three names were based upon type materials collected at the same site of the “Parque Nacional da Serra dos Órgãos”, Brazil. A brief comment about the systematic implications is also included.

Diversidade florística de Dioscoreaceae na Reserva Biológica do Alto da Serra de Paranapiacaba, Santo André, São Paulo, Brasil

The present study aimed to investigate and analyze the floristic diversity of Dioscoreaceae from Reserva Biologica do Alto da Serra de Paranapiacaba, Santo Andre, in order to increase the knowledge of Dioscoreales flora of this conservation unity and of Sao Paulo State. The field trips were conducted from 1978 until 2014; specimens from herbaria B, BOTU, ESA, IAC, NY, R, RB, SP, SPF, and UEC were consulted. We confirmed the occurrence of eight species ofDioscorea L. from Atlantic Forest of Serra do Mar. Among them, D. sanpaulensis and D. trilinguis are already listed as endangered species in the Brazilian Flora Red Book.Dioscorea torticaulis should now be included in the book as well, as it is endemic and rare in the Reserva Biologica de Paranapiacaba. The identification key, descriptions, illustrations, taxonomic, geographic, and phenology comments are presented.

Senecio ser. Chilenses, a New Name for Senecio ser. Suffruticosi (Asteraceae, Senecioneae) from Southern South America

Abstract.  The name Senecio L. ser. Chilenses DC. ex M. G. López, A. F. Wulff & Xifreda is here validated to replace Senecio ser. Suffruticosi Cabrera, non Senecio sect. Suffruticosi Greenm. Although the epithet Suffruticosi was published at different infrageneric ranks within Senecio (Asteraceae, Senecioneae) for two different taxa from South and North America, respectively, the two epithets are considered homonyms. Series Chilenses was previously published by de Candolle, but without a description.

Nomenclatural and Taxonomic Novelties in Senecio ser. Corymbosi (Asteraceae, Senecioneae) from Southern South America

Abstract The new name, subseries Alcabrerae M. G. López, A. F. Wulff & Xifreda for Senecio L. ser. Corymbosi (Cabrera) Cabrera, is here proposed to replace Senecio subsect. Amplectentes Cabrera. Although the name Amplectentes was published at different subgeneric ranks within the genus Senecio (Asteraceae, Senecioneae), the use of the same epithet is considered homonymy according to the International Code of Botanical Nomenclature, Article 53.4 and Article 21, Note 1. Additionally, S. saucensis Cabrera, one of the five species belonging to Senecio subser. Alcabrerae, is synonymized with S. toroanus Cabrera, formerly assigned to Senecio ser. Hualtatini DC., and S. toroanus is transferred to subseries Alcabrerae. The micromorphology of the cypselae for both species is provided, in support of the synonymy.