Chromosome number variation and evolution in Neotropical Leguminoseae (Mimosoideae) from northeastern Brazil

Abstract

ABSTRACT. Most members of the subfamily Mimosoideae have pantropical distributions, variable habits, and a basic chromosome number x = 13. We examined karyotypic evolution of 27 species of this subfamily occurring principally in northeastern Brazil by examining chromosomes stained with Giemsa. All of the species had semireticulated interphase nuclei and early condensing segments in the proximal region of both chromosome arms. The basic number x = 13 was the most frequent, with 2n = 2x = 26 in 19 of the species, followed by 2n = 4x = 52 and 2n = 6x = 78. However, the three species of the genus Calliandra had the basic number x = 8, with 2n = 2x = 16, while Mimosa cordistipula had 2n = 4x = 32. The karyotypes were relatively symmetrical, although bimodality was accentuated in some species, some with one or two acrocentric pairs. As a whole, our data support earlier hypotheses that the Mimosoideae subfamily has a basic number of x = 13 and underwent karyotypic evolution by polyploidy. However, x = 13 seems to be a secondary basic number that originated from an ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 11 (3): 2451-2475 (2012 E.C.X.R. Santos et al. 2452 ancestral stock with x 1 = 7, in which polyploidy followed by descending disploidy gave rise to the current lineages with x = 13. Another lineage, including current representatives of Calliandra with x = 8, may have arisen by ascending disploidy directly from an ancestral monoploid stock with x 1 = 7.

Hybrid capture of 964 nuclear genes resolves evolutionary relationships in the mimosoid legumes and reveals the polytomous origins of a large pantropical radiation

“…However, given that paleopolyploidy most likely occurred before the crown group divergence of Caesalpinioideae (Koenen et al, 2020b), and the fact that the mimosoid crown group diverged substantially later than that, paralog copies derived from this WGD are expected to have sufficiently divergent sequences across mimosoids for correct separation of paralogous sequences into separate alignments using the robust orthology assessment pipeline of Yang and Smith (2014) for most of these genes. Paleopolyploidy is also known to have occurred within the mimosoid clade (e.g., Leucaena , Govindarajulu et al, 2011; Mimosa , Dahmer et al, 2011), but chromosome count data suggest that these events were restricted to a few genera (Santos et al, 2012) and that polyploidy is most likely rare in the ingoid clade. Furthermore, this also suggests that a WGD event shared by a larger clade within mimosoids can probably be ruled out.…”

IAPT chromosome data 33

“…MacMill., and D. virgatus (L.) Willd., all counts are 2n = 28 (Turner & Beaman, 1953;Smith-White & al., 1963;Yeh & al., 1986;Kappali & Patil, 1987;. Santos & al. (2012) suggested a secondary basic number for the genus, x 2 = 14, possibly resulting from ascending dysploidy from the primary basic number, x 1 = 13.…”

“…This group is quite representative of caatinga, a biome exclusive to Brazil and characterized by semiarid climate, low average rainfall, rainfall seasonality, and strong endemism (Sampaio, 1995;Queiroz & al., 2009). This subfamily is little known cytologically, and chromosomal data for species endemic to, or occurring in, caatinga are incipient (Biondo & al., 2005;Santos & al., 2012). In this study, 7 of the 10 species analyzed corroborated literature data, while the numbers observed in Senna uniflora, Anadenanthera colubrina, and Piptadenia stipulacea are new records for these taxa.…”

“…Griseb., E. gummiferum (Mart.) J.F.Macbr., and E. timbouva, all with 2n = 26 (Darlington & Wylie, 1955;Tixier, 1965;Bawa, 1973;Bandel, 1974;Gibbs & Ingram, 1982;Huang & al., 1989;Santos & al., 2012), suggesting numerical karyotype stability for the genus and x = 13 as the basic number.…”

“…Of these, only M. candollei presented a polyploid chromosome number (2n = 52), confirming the only previous (Dahmer & al., 2011). The number 2n = 26 observed in M. arenosa, M. ophthalmocentra, and M. tenuiflora confirms previous counts, as well as the basic number x = 13, suggested in the literature for the genus (Dahmer & al., 2011;Santos & al., 2012;Freire & al., 2013;Rodrigues & al., 2017). In turn, the chromosome numbers 2n = 24 and 2n = 18 observed in A. colubrina and P. stipulacea, respectively, differ from the number reported in the literature for these species, 2n = 26 (Gibbs & Ingram, 1982;Alves & Custódio, 1989;Ortolani & al., 2010;Santos, 2017), which may indicate new cytotypes originated from dysploidy processes from x = 13.…”