Macroevolutionary trends in the karyotypic evolution of Caesalpinioideae (Leguminosae).

Caesalpinioideae is the most complex subfamily of Leguminosae from taxonomic, phylogenetic, and cytogenetic perspectives. The subfamily comprises 163 genera and 4680 species occurring in ecologically diverse environments, mostly in tropical but reaching temperate zones. It encompasses 11 tribes of which Mimoseae stands out for representing most of the taxonomic diversity of the subfamily with 100 genera and c. 3500 species. We investigated karyotypic evolution of the subfamily through analysing cytogenetic traits in a dated phylogenetic framework using literature and newly generated data. We sampled 471 taxa for chromosome number counting, 216 taxa for genome size, and 98 taxa for heterochromatin analysis. Additionally, we provide new karyotypic analyses for 33 taxa using chromomycin A3 (CMA) and 4′, 6-diamidino-2-phenylindole (DAPI) double staining. The analysed karyotypes exhibited polymorphisms in chromosome number as well as in the number and position of CMA+ bands. Our analyses suggest that the pattern of heterochromatin distribution evolved independently in the subfamily. Our analyses suggest x = 14 as the ancestral number for Caesalpinioideae and revealed distinct trends of descending dysploidy and polyploidy among clades. The smaller genome size and the lower number of heterochromatin bands in Mimoseae in relation to other Caesalpinioideae lineages suggest that diploidized palaeopolyploid genomes arose approximately 45 Mya. This study represents the first large-scale investigation of chromosomal evolution in Caesalpinioideae and revealed that the clade-specific 2n stability contrasts with a dynamic evolution of heterochromatin which may be associated with genomic reshuffling experienced in this legume group.

Project(s)

Priority 4: Accelerated Taxonomy

Funder

Funder name	Awards
Conselho Nacional de Desenvolvimento Científico e Tecnológico, Brazil	CNPq number 04/2021 - Universal 407535/2023-3 - Process no. PQ-305774/2024-7 - Process no. PQ-312855/2021-4
Fundação de Amparo à Pesquisa do Estado da Bahia, Brazil	PIE0023/2016
Fundação de Apoio à Pesquisa do Estado da Paraíba, Brazil
Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco, Brazil	FACEPE-APQ-0970-2.03/15 - BIC-1221-2.02/19
Fundação de Amparo à Pesquisa do Estado de São Paulo, Brazil	2022/05890-3
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil	Postgraduate scholarship (Finance Code 001) - Postdoctoral Internship 88881.119479/2016-01