Arturo F. Wulff

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.

Chromosome studies on the Bambusoideae (Gramineae)

Meiotic chromosome numbers and observations were made in eleven species belonging to nine different genera of Bambusoideae. The numbers include counts in eight species that have never been investigated cytologically:Arundinaria aff.amabilis (n=24), Chusquea bambusoides (n=ca. 20),Cryptochloa dressleri (n=11), Olyra ciliatifolia (n=11), Sucrea monophylla (n=11), Raddia brasiliensis (n=11), Strephium distichophyllum (n=11), andPariana aurita (n=22). The generaStrephium andSucrea have not been studied previously with respect to their chromosomes. The significance of these results are discussed in relation to the over 140 published counts in the subfamily, which indicates a preponderance of polyploidy in the woody members, or bamboos, but not in their herbaceous allies. Aneuploidy is rare in the former but frequent in the latter. It is postulated that the herbaceous bambusoids, which flower every year and produce recombinants regularly and in short-time cycles, could have tolerated successive reductions of the linkage groups and their genetic flexibility. These changes would not have been favored in the bamboos, which have more genetic constancy due to the long lapse (often 20–120 years) between flowering generations.

Morphometric and Cytogenetic Studies in Mimosa diversipila (Mimosoideae, Leguminosae) and Their Taxonomic and Evolutionary Inferences

Abstract Here we describe the morphological variability, chromosome number, and chromosome size in Mimosa diversipila. This species comprises two varieties, which are distinguished by the indumentum. However, this character is insufficient for circumscription of these infraspecific taxa. Using multivariate techniques, we found that quantitative characters were useful for identification of the varieties, which also have a different geographic distribution. Cytogenetic studies revealed that these taxa form a polyploid complex and that the polyploidy may contribute to the morphological variability observed.

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.

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.