Chromosome numbers in the genus Mimosa L.: cytotaxonomic and evolutionary implications

Abstract

Chromosome numbers were determined for 125 accessions of 92 taxa of Mimosa from all five of Barneby's (Mem New York Bot Gard 65:1-835, 1991) taxonomic sections. For 69 species, 1 subspecies and 8 varieties, chromosome numbers are presented for the first time, for 6 species and 1 variety previously published data have been confirmed and for 3 species and 2 varieties different numbers were found. Results show that 74% of the accessions were diploid (2n = 2x = 26) and 26% polyploid, these mostly tetraploid (2n = 4x = 52) but with two triploid (2n = 3x = 39). These results double the number of Mimosa species for which the chromosome count is known from less than 10% previously reported to more than 20%, representing an important advance in the cytotaxonomy of this legume genus. These results together with literature data show that ca. 78% of Mimosa species are diploid. Polyploids are present in most of the taxonomic sections and in different lineages across the genus.No particular chromosome number is restricted to a given section or lineage. A possible relation between geography, species distribution, polyploidy and invasiveness was detected, however, further studies based on more accessions, especially from higher latitudes, are required before firm conclusions can be drawn.

Intraspecific and interspecific polyploidy of Brazilian species of the genus Inga (Leguminosae: Mimosoideae)

“…paludosa (Dahmer et al, 2011). The existence of different ploidy levels among populations of the same species generally defines distinct biological species (Freeman and Herron, 2004), or the formation of local races, geographical races, or polyploid complexes.…”

Occurrence and significance of polysomaty in species of Mimosa L.

“…Original chromosome numbers of these accessions had been determined by Dahmer et al (2011). Taxonomic vouchers are kept at the following herbaria: FHO (Oxford University, UK), K (Kew -Royal Botanic Gardens, UK), CEN (Embrapa Recursos Genéticos e Biotecnologia, Brazil), UB (Universidade de Brasília, Brazil), RB (Jardim Botânico do Rio de Janeiro, Brazil), UAMIZ (Universidad Autónoma Metropolitana, México) and ICN (Departamento de Botânica Universidade Federal do Rio Grande do Sul, Brazil).…”

“…Chromosome counts were performed in root-tip cells as described in Dahmer et al (2011): seeds were scarified by a small cut in the testa and germinated in Petri dishes with moist filter paper (Figure 2). When the roots were 1 cm long they were pretreated with a saturated solution of paradichlorobenzene for 24 h at 4°C, fixed in 6:3:1 (ethanol: chloroform: acetic acid) for 24 h and stored in 70% alcohol below 0°C until required.…”

Development and validation of the first SSR markers for Mimosa scabrella Benth.

“…Of the 11 markers, Msc009, Msc041, Msc045, and Msc124 sequences showed significant similarity with chloroplast genomes of some Mimosoideae species and all samples of these markers displayed only one allele per sample and the same allele between mother trees and progenies, revealing maternal inheritance of chloroplast genome for M. scabrella. Msc003 displayed from one to four alleles per sample, showing its tetraploid nature, as described by Dahmer et al (2011). Only identified allele peaks were considered for heterozygote genotype, without considering the allelic dosage for incomplete heterozygotes (Narayan et al, 2015).…”

“…Sobierajski et al (2006) and Moreira et al (2011) investigated mating system using allozyme loci and found mixed mating system, predominantly outcrossing. Dahmer et al (2011) determined tetraploid nature of the species, with chromosome number 2n = 4x = 52. A major challenge for molecular characterization is the lack of sufficient DNA markers specific to M. scabrella.…”