A Synopsis of Chromosome Number Variation in the Cyperaceae

Abstract

The Cyperaceae are well known for having a large amount of variation in chromosome numbers both within and among genera. Most of this variation has been previously attributed to agmatoploid or qualitative aneuploid chromosome number change. To date there have been 4,231 reported chromosome number counts in the family. Despite the large number of counts made, they only represent approximately 16% of the species currently recognized. These counts are here presented in an indexed list with standardized nomenclature following a draft copy of the World Checklist of Cyperaceae. Additionally, I explore variation within genera where a significant number of counts have been made. Given the distributions of counts within genera there is evidence for both agmatoploid and polyploid chromosome number changes.

Cytological Studies on Seven Species of Korean <i>Carex</i> (Cyperaceae)

“…The genus exhibits high variance in chromosome numbers ranging from n= 6 to n= 66 with every haploid number between n= 6 and n= 48 (Tanaka 1949, Davies 1956, Roalson 2008). The cytogenetic variance is hypothesized to be due to the non-localized centromeres (holocentric chromosomes), which facilitate chromosome number increases (agmatoploidy) and/or decreases (symploidy) by fission and fusion, respectively (Hoshino 1981, Nishikawa et al 1984, Luceño and Guerra 1996, Chung et al 2011, Hipp et al 2013.…”

Karyotype characterization of four Mexican species ofSchoenoplectus(Cyperaceae) and first report of polyploid mixoploidy for the family

“…Except for the extrapolations of n = 64 (e.g. the reference to 2n = 38 to 2n = 84(-128) for Schoenoplectus in Roalson 2008), no reports have been found of 2n > 84.…”

“…The last line presents a highly asymmetric karyotype with 36 small, dot-shaped + 2 larger chromosomes. The largest pair represent compound chromosomes, each corresponding in 19 Schuyler (1972) S. roylei (Nees) Lye 11 Bir et al 1981, 1986, 1988in Roalson (2008 44 Bir et al 1985in Roalson (2008 11, 44 Bir et al 1990Bir et al , 1991 Roalson (2008) size to about three of the smaller, dot-shaped ones (3.17 versus 1.0 μm, respectively). Dimorphic chromosomes had been also recorded for this species by Hicks (1929), who mentioned one larger chromosome among the n = 20, and for Schuyler (1976), who reported for S. acutus and for the related S. heterochaetus "one meiotic unit which is about three times larger" than the others.…”

“…2n = 104, 110 (Tanaka 1937in Roalson 2008Löve and Löve 1981), whereas Schoenoplectiella has lower numbers, with Schoenoplectus s.s. having, in general terms, intermediate sizes and a higher number of chromosomes ( Figure 3A, B). Already in 1929 Hicks noted that the "Scirpus lacustris group" [Schoenoplectus] had larger chromosomes than the "Scirpus maritimus group" [Bolboschoenus].…”

“…Based on the fact that the groups of species they studied have high and low chromosome numbers with almost equal chromosome sizes, they concluded that the chromosomal evolution in those species has been caused more by polyploidy than by dysploidy (considered by them as aneuploidy). The variation in chromosome number largely distributed around 20 and 40 reported by Roalson (2008) was interpreted by him as a possible indication of polyploidy with subsequent dysploidy (Roalson referred to dysploidy as aneuploidy, which does not occur in groups with holokynetic chromosomes).…”