Cytogeography and morphological characterisation of a taxonomic, polyploid complex of Mimosa (Leguminosae) from subtropical South America

Abstract

Mimosa subseries Dolentes Barneby and Brevipedes Barneby are ecologically and morphologically high-diversified infrageneric taxa of this genus in southern South America. We performed a cytogenetical and morphological analysis of both subseries. Chromosome numbers from accessions throughout the area of distribution were studied. The chromosome numbers 2n=8x=104 for M. dolens subsp. callosa (Benth.) Barneby, M. dolens subsp. acerba varieties acerba (Benth.) Barneby, latifolia (Benth.) Barneby and rudis (Benth.) Barneby, M. dolens subsp. rigida var. rigescens (Benth.) Barneby, var. anisitsii (Lindm.) Barneby and var. foliolosa (Benth.) Barneby; and 2n=4x=52 for M. sceptrum Barneby, M. aff. custodis Barneby and M. dolens var. pangloea Barneby are presented for the first time. Their karyotypes were symmetric, with small chromosomes. There were several areas with taxa growing in sympatry, occasionally with intermediate forms. No diploids were found, which suggests the presence of either a declining polyploid complex or ancient polyploidy in the clade of southernmost representatives of M. series Mimosa, the most derived of the genus. Some vegetative, inflorescence and carpological characters seem to be associated with chromosome duplication. The distribution pattern of the cytotypes suggests events of chromosome duplication in centres of diversity and expansion of octoploids to the southernmost areas of distribution. Our findings support the importance of polyploidy in the morphological diversity, distribution and speciation of this complex.

Early Diverging and Core Bromelioideae (Bromeliaceae) Reveal Contrasting Patterns of Genome Size Evolution and Polyploidy

“…The combination of different genomes in these lineages might have further added towards an adaptive potential ( Barker et al, 2016 ) and supported the survival of the early diverging bromelioids in the arid environments. A similar scenario can be assumed for other polyploid taxa from Cerrado such as Mimosa (Fabaceae; Morales et al, 2018 ) and Eriotheca (Malvaceae; Mendes-Rodrigues et al, 2019 ). However, the abundance of polyploidy and climatic preferences of polyploids in Cerrado and Caatinga remain to be tested across several taxa.…”

Advances in Legume Systematics 14. Classification of Caesalpinioideae. Part 2: Higher-level classification

“…The basic chromosome number in Mimosa is reported to be x = 13 ( Isely 1971 ; Goldblatt 1981b ), with varying sporophytic chromosome counts recorded as 2 n = 26, 2 n = 39, 2 n = 52, 2 n = 104 ( Seijo 1993 , 1999 , 2000 ; Seijo and Fernández 2001 ; Morales et al 2010 , 2011 , 2014a , 2014b , 2015 , 2018 ; Dahmer et al 2011 ), and approximately 20% of species potentially polyploid ( Dahmer et al 2011 ).…”

“…However, almost all of Barneby’s traditional sections and series are not monophyletic ( Bessega et al 2008 ; Simon et al 2011 ) and a new phylogenetically-based classification is needed. Furthermore, the often complex patterns of morphological variation associated with some clades and widespread species alliances, likely further complicated by extensive polyploidy, which prompted Barneby’s extensive reliance on infraspecific taxa, are the focus of detailed studies of particular species complexes (e.g., Grether 2000 ; Morales and Fortunato 2010 ; Morales et al 2010 , 2018 ; Léon de la Luz et al 2015; Borges et al 2017 , 2023 ; Jordão et al 2018 ). The re-assessment of taxon delimitations within species complexes in this group has often resulted in the recognition at the specific rank of taxa that were treated by Barneby as subspecies and varieties.…”

“…Barneby (1991) ; Bessega and Fortunato (2011) ; Bessega et al (2008) ; Borges et al (2023) ; Burkart (1948) ; Dutra et al (2020) ; Grether (1987 ; 2000 ; 2023 ); Grether et al (1996) ; Jordão et al (2020) ; Medina-Acosta et al (2019) ; Morales and Fortunato (2010) ; Morales et al (2010 , 2018 ); Santos-Silva et al (2015) ; Simon et al (2011) ; Villiers (2002) .…”

Como a variação no número cromossômico pode indicar relações evolutivas entre a Caatinga, o Cerrado e a Mata Atlântica?

“…, Asia (e.g. Morales et al 2018) and other regions. But, could cytogeography be applied as an auxiliary to investigate the main evolutionary pathways of an entire flora to infer about the evolutionary history of a biome?…”