Juan Domingo Urdampilleta

Karyotype evolution and phylogenetic analyses in the genus Cardiospermum L. (Paullinieae, Sapindaceae)

Cardiospermum L. belongs to the Paullinieae tribe (Sapindaceae) and comprises 16 species. Of these, 12 species are present in South America and all occur in Brazil. Cardiospermum shows the most variable chromosome number of the tribe. Phylogenetic relationships within the genus Cardiospermum, especially with other species of the tribe, are poorly understood. This research focuses on characterisation of the karyotypic features of Cardiospermum using conventional cytogenetic methods, CMA/DAPI chromosome banding and fluorescence in situ hybridisation (FISH). To elucidate the phylogeny of the genus, the nuclear markers ITS1 and ITS2 were sequenced and analysed using maximum parsimony and Bayesian inference. Cardiospermum shows important diversity in basic numbers, with x = 7, 9, 10, 11 and 12. All species studied have metacentric and submetacentric chromosomes, some species have subtelocentric chromosomes, while telocentric chromosomes are absent. The interphase nuclei differentiate the Cardiospermum species into two groups. The CMA(3) /DAPI chromosome banding revealed the presence of an AT-rich terminal region in C. corindum, C. grandiflorum and C. urvilleoides, whereas GC-rich regions were found in C. grandiflorum, C. halicacabum var. halicacabum, C. halicacabum var. microcarpum, C. heringeri and C. integerrimum. FISH revealed syntenic and non-syntenic distribution of the 18-5.8-26S and 5S rDNA. The syntenic distribution always occurred in the short arms of the same chromosome in all of the species. The phylogenetic relationships reveal, in part, the taxonomic arrangement of the genus Cardiospermum.

Cardiospermum cristobaliae (Sapindaceae, Paullinieae), una nueva especie de Minas Gerais, Brasil

ResumenLa especie nueva Cardiospermum cristobaliae (Sapindaceae, Paullinieae), de la región norte del estado de Minas Gerais, Brasil, es descrita, ilustrada y comparada con la especie más próxima, C. urvilleoides. Adicionalmente se describen caracteres de epidermis foliar y de polen. Se reporta el número cromosómico somático 2n = 24. La especie nueva pertenece a la sección Cardiospermum, se presenta un cuadro comparativo con la especie afín y una clave de las especies sudamericanas de esta sección.AbstractA new species, Cardiospermum cristobaliae (Sapindaceae, Paullinieae), from northern Minas Gerais, Brazil, is described, illustrated, and compared to its putative closest relative, C. urvilleoides. The new species belongs to section Cardiospermum. Also, characters of the foliar epidermis and pollen grains are described. The somatic chromosome number 2n = 24 is reported. A key to the South American species of the section is provided.

Distribution of rDNA and polyploidy in Deschampsia antarctica E. Desv. in Antarctic and Patagonic populations

Unlike the Arctic flora, with many flowering plant species offering opportunities to study evolutionary processes, the Antarctic flora offers only two. One of them is the Antarctic grass Deschampsia antarctica E. Desv., whose distribution spans from northern Patagonia (ca. 38°S) down to Alamode Island (ca. 68°S), in the west side of the Antarctic Peninsula. While some aspects of Antarctic plants have been extensively studied (e.g., anatomy, physiology, genetics), little is known about the related Patagonian populations. Particularly in cytogenetics, no single study has focused on continental populations and its relationships with the Antarctic plants. The combination of traditional fluorescent in situ hybridization (FISH) with a phylogenetic framework highlights the importance of cytogenetics in plant evolutionary studies, by allowing comparison of chromosome characters in phylogenetically related individuals. Most used characters for this purpose are the chromosome number, karyotype morphology and patterns of repetitive DNA. These were used to compare distant populations of D. antarctica in a phylogenetic framework, to obtain a first view of the cytogenetic structure of the species along its distribution. Patagonian populations have greater variability in the chromosomal and molecular characters, while Antarctic populations are very alike, hinting at a South American origin hypothesis. A polyploid population is reported for the first time, located on Central Patagonia populations, close to the northern limit of distribution range. Cytogenetic characteristics suggest that hybridization processes could have played an important role in the evolution of the genome of D. antarctica.

Cytogenetic studies in South American species of Serjania (Sapindaceae: Paullinieae)

Abstract Serjania Mill. (Paullinieae) is considered the most important neotropical genus of Sapindaceae due to species number and its widespread distribution. In this study, 14 species belonging to three sections were analyzed using conventional staining, C/CMA/DAPI banding, and fluorescence in situ hybridization (FISH) with a 18S-5.8S-26S rDNA probe. New chromosome counts are reported for Serjania crassifolia, Serjania platycarpa, and Serjania regnellii, all with 2n = 24, which is remarkably constant for Serjania. The karyotypes are moderately asymmetric, and variations observed in A1 and A2 indices show resemblances between S. platycarpa, Serjania hebecarpa, and S. crassifolia, and between Serjania communis, Serjania gracilis, and S. regnellii. The banding pattern was homogeneous in Serjania. C/DAPI bands (AT-rich sites) were not clearly evidenced, but changes in the number and position of GC-rich sites (CMA bands) were observed. These segments were associated with 18S-5.8S-26S rDNA sites. The significance of the results is discussed in relation to chromosomal data available for the genus and in regard to the infrageneric treatment of Serjania.

Heterochromatin and rDNA patterns in Solanum species of the Morelloid and Dulcamaroid clades (Solanaceae)

Abstract The heterochromatin distribution and the position of 18-5.8-26S, and 5S rDNA loci were determined in 13 species of Solanum of the Morelloid and Dulcamaroid clades. The CMA/DAPI staining and FISH were employed. Two types of constitutive heterochromatin were determined: CMA+/DAPI− associated to NOR and CMA+/DAPI− distributed as terminal bands. In the Morelloid clade, CMA+/DAPI− bands were found in five species while in the Dulcamaroid clade, only S. angustifidum presented this feature. In the Morelloid clade, two to four 18-5.8-26S rDNA loci occupied terminal positions and two rDNA 5S loci were found with variable positions (terminal, intercalary, and centromeric). In the Dulcamaroid clade, two terminal 18-5.8-26S rDNA loci were detected with the exception of S. salicifolium which possessed four such loci and two to four 5S rDNA loci. Solanum crispum is the only species possessing the 5S in synteny with 18-5.8-26S rDNA loci. Karyotype features chromosome banding pattern as well as the location of ribosomal genes which varied among the species, reflecting the chromosome differentiation and evolutionary divergence. The findings obtained contributed to the development of tools that can be used for establishing chromosomic homeologies among species and hence to clarify their taxonomic relationships.

Cytological study of Polystichum (Dryopteridaceae) species from southern South America

Polystichum is one of the most diverse genera of ferns, with 360–400 species distributed worldwide. South America harbors ~40 species, clustered in three centres of diversity, namely, the Northern and Central Andes Center (NCC), the Brazilian Center (BC) and the Southern South America Center (SSC). To increase our understanding of the systematic relationships within Polystichum, mitotic chromosomes and spore features were studied in nine species from Argentina and Chile. All species presented the basic number x = 41, with different ploidy levels (2x, 4x and 8x). In general, chromosomes were homogeneous in size (average length 2.50–5.75 µm) and mostly subtelocentric; centromeres were inconspicuous and secondary constrictions were frequently observed. All species presented 64 spores per sporangium, suggesting normal sexual reproduction. Significant differences in spore size were found among species and it was positively correlated with ploidy level. A relationship between sum total chromosome length and ploidy level was observed. However, there was also a reduction in single-chromosome length in the polyploids, pointing to genome downsizing. Our results agree with previous records, with diploids being frequent among NCC species and absent among SSC species. In addition to sharing very specific morphological characters, SSC species are cytologically characterised by being polyploids (4x and 8x). A literature survey covering 116 species of Polystichum revealed that Australian and New Zealand Polystichum species exhibit similarly high frequencies of polyploidy. In the case of P. tetragonum (2n = 164), endemic to the Juan Fernandez archipelago, our data suggested that it was originated by transoceanic migration from a South American ancestor, probably also tetraploid.

Characterization of some satellite DNA families in Deschampsia antarctica (Poaceae)

Deschampsia antactica E. Desv. is one of the only two native vascular plants of Antarctica, having a disjunct distribution with South America. Its presence in different environmental conditions turns it into an interesting evolution model, particularly for genomic evolutionary studies. The repetitive DNA is a genome component that cause important changes in genome size and chromosome organization, and therefore, its variation is very important in group’s delimitation. Some tandem repetitive DNA sequences, known as satellite DNA (satDNAs) are shared between many groups of Poaceae (e.g., of these are the CON1, CON2, COM1, and COM2 sequences) highlighting its evolutionary component. This study aims to identify, classify, and characterize repetitive elements in the D. antarctica genome by clustering analysis of genome sequences, focusing on the CON1, CON2, COM1, and COM2. Repetitive DNA represented about 73.3% of the D. antarctica genome. All studied populations presented loci for the studied satDNAs but the distribution pattern showed differences that seem to be related to the geographic distribution. The analysis of CON/COM sequences in D. antarctica contributes to the understanding of these elements in Poaceae genomes and highlights the importance of changes in chromosome organization of repetitive DNA in populations with fragmented geographical distribution. The distribution of such chromosome changes may both reflect the process of colonization of D. antarctica in Antarctica and explain some evolutionary processes of differentiation in Deschampsia species complex in the Patagonia, which is still unresolved with other DNA sequences.

Insights into the Andean genera Bridgesia and Guindilia (Sapindaceae): an integrated approach

Sapindaceae s.l. is a moderately large family of trees, shrubs and lianas. The genera Bridgesia and Guindilia belong to the Thouinieae tribe; however, its circumscription to this tribe is in doubt. This work presents a comparative analysis of pollen morphology between species of both genera. They share the basic spherical tricolporate pollen type for the family, but the features studied do not characterize any of them. In addition, the work intends to characterize the karyotype and genome size evolution of both genera, and elucidate the phylogenetic relationships within the family through maximum likelihood and Bayesian analyses of the ITS, trnL and trnL-F sequences. Our results show two different patterns regarding karyotype data: Bridgesia presents 2n = 2x = 28, with metacentric and submetacentric chromosomes; the basic number of the genus, x = 14, is in agreement with the 25% of the chromosome numbers recorded in Sapindaceae. The genus Guindilia exhibits a basic number x = 10; of the three species G. cristata and G. trinervis present metacentric, submetacentric and subtelocentric chromosomes, whereas G. dissecta shows only metacentric and subtelocentric ones. In addition, G. cristata is a polyploid species, with DNA content exactly three-fold that of the diploid species, suggesting a recent event of polyploidization in this species. The infra-familial phylogenetic relationship and circumscription of both genera analysed here evidence that Bridgesia belongs to Paullinia group. The fact that Guindilia is grouped in a different clade encouraged us to propose a new informal tribal group, Guindilia group, in the current infrafamilial arrangement of Sapindaceae.