Iheringia Série Botânica Jardim Botânico de Porto Alegre Museu de Ciências Naturais ISSN ON-LINE 2446-8231 Karyotype inconsistencies in the taxonomy of the genus Oxalis (Oxalidaceae) Amália Ibiapino Moura1 , Ykaro Richard Oliveira2,* , Paulo Henrique da Silva2 , Yennifer Mata-Sucre1 , Reginaldo de Carvalho3 , Margareth Ferreira de Sales3 , Maria Carolina de Abreu4 1Programa de Pós-Graduação em Biologia Vegetal. Universidade Federal do Pernambuco (UFPE). Laboratório de Evolução e Citogenética Vegetal. CEP: 50670-901, Recife, Pernambuco, Brasil. 2Secretaria do Estado da Educação (SEDUC). CEP: 64600-000, Picos, Piauí, Brasil. 3Programa de Pós-Graduação em Botânica. Universidade Federal Rural de Pernambuco (UFRPE). CEP 52171-900, Recife, Pernambuco, Brasil. 4Laboratório de Botânica. Universidade Federal do Piauí (UFPI), Campus Senador Helvídio Nunes de Barros. CEP: 64600-000, Picos, Piauí, Brasil. *Autor para correspondência: [email protected] Recebido em 05.X.2018 Aceito em 16.I.2020 DOI 10.21826/2446-82312020v75e2020003 ABSTRACT – The family Oxalidaceae consists of six genera, of which Oxalis is the most representative. This genus is subdivided into four subgenera, and its species present great morphological variation, which makes it difficult to identify them. The aim of this study was to make a survey of scientific publications which presented chromosome numbers of species of Oxalis, and to compare the chromosome numbers to the taxonomic classification proposed by Alicia Lourteig. Published chromosome counts were found for 112 species. We infered that there is apparently no relation between the chromosome numbers of the species of Oxalis and the taxonomic classification proposed by Lourteig, as species belonging to a same subgenus did not present a coherent pattern in chromosome numbers. Keywords: chromosome number, cytogenetics, polyploidy RESUMO – Inconsistências cariotípicas na taxonomia do gênero Oxalis (Oxalidaceae). A família Oxalidaceae é constituída por seis gêneros no qual Oxalis é o mais representativo. Esse gênero é subdividido em quatro subgêneros e suas espécies apresentam grande variação nas características morfológicas, o que dificulta a identificação taxonômica das mesmas. Este trabalho teve como objetivo fazer o levantamento de artigos científicos que apresentassem o número cromossômico das espécies do gênero Oxalis e relacionar o número cromossômico com a classificação taxonômica proposta por Alicia Lourteig. Foram encontradas publicações evidenciando o número cromossômico de 112 espécies. A partir deste estudo podemos inferir que não há relações entre o número cromossômicos das espécies de Oxalis e a classificação taxonômica estabelecida por Lourteig, já que espécies pertencentes ao mesmo subgênero não apresentaram padrão no número cromossômico. Palavras-chave: citogenética, número cromossômico, poliploidia INTRODUCTION Oxalis, establishing a relationship among the sections is still difficult due to the high morphological variation The family Oxalidaceae R.Brown is included in the and phenotypic plasticity (Lourteig 1994, 2000, Azkue order Oxalidales and includes six genera and approximately 2000, Emshwiller & Doyle 2002). Phylogenetic studies 770 species distributed mainly in tropical regions (Judd of Oxalis are scarce and the relationships among the 2009, Stevens 2001). Biophytum DC. and Oxalis L. are subgenera and sections are unclear (Abreu et al. 2012). native in Brazil and Averrhoa L. is cultivated in the country In Brazil, some regional works related to the taxonomy of (Fiaschi & Conceição 2005, Abreu et al. 2013). Oxalis is the group can be highlighted, such as the one performed in cosmopolitan and presents about 500 species and can be the Atlantic Forest, in which 63 species are cited (Abreu divided into four subgenera: Monoxalis (Small) Lourt., & Fiaschi 2009); nine species were recorded in the state Trifidus Lourt., Thamnoxys (Endl.) Reiche and Oxalis. It of Pernambuco (Abreu 2007); four species were recorded is believed that South America and Africa are the centers by Souza & Bianchini (2000) in São Paulo and 23 species of dispersion and probably of origin of this genus (Knuth, by Fiaschi & Conceição (2005) and records of 42 species 1930 Denton 1973, Lourteig 1994, 2000, Azkue 2000). in the state of Santa Catarina (Lourteig 1983). Although this subdivision facilitates the complex and Probably the most comprehensive taxonomic studies confusing taxonomy of the South American species of of the genus were performed by Knuth (1930) and Salter Iheringia, Série Botânica, Porto Alegre, 75: e2020003, 2020 Diagramação: www.editoraletra1.com.br 2 MOURA et al. (1944) for South African species and Lourteig (1994, 2000) in greenhouses and root tips or floral buds were used for for South American ones. However, this genus presents obtaining the samples for the analysis of the chromosomes. many difficulties of identification, mainly because of the Regarding the methodology used in these researches, use of morphological characteristics that are not very clear the samples were pretreated with 0.2% or 0.5% colchicine (Abreu 2007). For example, Oxalis stem has a variable from 4 to 24 hours or with 8-hydroxyquinoline for 24 hours. morphology in tubers, rhizomes and true bulbs (Vaio et al. Carnoy (ethanol: acetic acid 3: 1) was used as fixative for 2013). Therefore, cytotaxonomy represents an important 24 hours at room temperature. The samples were digested tool for the determination of the taxonomic positioning in enzymatic solutions of 2% pectinase and 20% cellulase of taxa (Stace 1989). Studies on the cytotaxonomy of the at 37 °C for 45 minutes, and were crushed in slide and then genus point to a wide variation in chromosome number immersed in liquid nitrogen to remove of the glass slide. and karyotype. It is a multibasic genus x = 5, 6, 7, 8, 9 and After air-drying, the material was stained, generally in 2% 11, with diverse morphology, acrocentric, submetacentric, Giemsa. The root tips were also stained with 2% acetic telocentric and metacentric chromosomes (Azkue 2000, orcein. In this case, after being removed from the fixative, Azkue & Martinez 1983, 1984, 1988, 1990). the root tips were placed in test tubes with acetic orcein Therefore, the aim of this work was to analyze scientific and HCL, then the mixture was heated and after cooling, studies in which the number of chromosomes of the species the material was placed on the slide and crushed. These belonging to the genus Oxalis were evidenced to establish techniques allowed the chromosomes to be visualized, relations between the chromosome number of these species counted and photographed under an optical microscope. and the taxonomic classification proposed by Lourteig Among the 500 species of Oxalis, 112 were recorded in (1994, 2000). this work as having their chromosomal numbers published (Tab. 1). Numbers n = 5, 6, 7, 9, 11, 12, 14 and 17 were MATERIAL AND METHODS observed from this data. In this study, species with n = 7 are the majority, with 36 representatives. The numbers 2n For the development of this article, studies that = 10, 12, 14, 16, 18, 20, 21, 22, 24, 28, 30, 32, 35, 36, 40, approached cytotaxonomic aspects of species belonging 42, 44, 64 and 72 were recorded; where the mean CN for to the genus Oxalis were investigated. They were obtained the full dataset is 2n = 21.73 ± 12.56 SD and mode 2n = 14 from databases, such as: SciELO (Scientific Eletronic with 32 species and 2n = 12 with 26 species, resulting in a Library Online), ScienceDirect and Web CAPES, using positive skew of data distribution (sk = 0.215). Most of the the keywords: Oxalis, Thamnoxys, chromosome number, data (39–40% of the dataset) were concentrated in seven cytotaxonomy, Oxalidaceae and Oxalidales. In addition, an sections: Articulatae, Cernuae, Corniculatae, Ionoxalis indirect search was performed, observing the bibliographic and Lotoideae (subgroup Oxalis) and Polymorphae and citations, in which mainly the oldest references were Thamnoxys (subgroup Thamnoxys) (Table 2). CNs are requested by the interchange service among libraries. The apparently distributed in different proportions between these collected information was organized into a Microsoft Excel sections and this difference is supported by ANOVA statistic 2010 spreadsheet, following the order, subgenus, section, (F = 2.300, DF = 20, p < 0.01) and linear regresion ( R = species, number n, number 2n and author. Information on 0.06, DF = 125, p = 0.946) (Fig.1), differing significantly subgenera and sections was obtained in Lourteig (1994, among all the 21 considered sections by Lourteig. The 2000). variation of the data for each section is shown in Table 2. In order to test for relationships between the chromosome According to Bedini et al. (2012) and this work, numbers (CN hereafter) and the taxonomic classification by the single chromosome numbers and the quantitative Lourteig (1994, 2000), the following data were calculated studies of CN variation are useful for characterization for the whole dataset and for each section: mean CN and (e.g. distinction) of lineages at the order, family, and, in boxplots, coefficient of variation of CN (CVCN) and CN some instances, the genus level. Regarding the section that profiles by linear regression. ANOVA was used to test each species belonged and its chromosome number, the statistical differences in CN among considered groups, after subgenus Oxalis was registered by species belonging to verification of the normal distribution of the data (Levene the sections: