Abstract
Karyotype analyses in species of the family Marantaceae (550 species, 31 genera) were conducted to shed light on the reported strong variation of chromosome number and size and the occurrence of polyploidy. Special attention was paid to the alterations in basic chromosome numbers, karyotypes and ploidy levels. Taxon sampling covered the whole distribution area of Marantaceae in Africa, Asia and America. We applied mitotic chromosome counting using conventional rapid squash techniques in 43 accessions (39 species, 16 genera), evaluated literature records for 51 species and conducted karyotype analyses. Eleven different somatic chromosome numbers were found (2n = 20, 22, 24, 26, 28, 33, 44, 36, 52, 65, 72). Based on the presumed basic chromosome numbers of x = 9, 10, 11, 12, 13, 14, this may correspond to diploid, triploid, tetraploid, pentaploid and octoploid levels, respectively. Dysploid variation, polyploidy and, to a lesser extend, hybridization may be the main factors in chromosome number evolution of the family. Our results also point to a certain degree of association with species diversification and geographical patterns.
Highlights
Changes in chromosome number and structure are important processes that often reflect speciation events as they can establish crossing barriers between populations (e.g. Lowry and Willis 2010; Ouyang and Zhang 2013; Winterfeld et al 2014, 2016; Baack et al 2015; Wölk et al 2015)
(1) we determined chromosome numbers and made karyotype analyses of 43 accessions, focussing on taxa that were not examined before, in which available information seemed to be doubtful or several different chromosome numbers have been reported; (2) we critically examined the numerical variation in monoploid chromosome sets, checked for different ploidy levels and possible aneuploid forms to explain the enormous variation in somatic chromosome numbers; and (3) we chose taxa from all major tropical regions (Africa, America, Asia) to find out whether there are trends in karyotype evolution that can be associated with the diversification of evolutionary lineages in Marantaceae and/or biogeography
Infrageneric variation in basic chromosome numbers was encountered in Ctenanthe, Goeppertia and Marantochloa
Summary
Changes in chromosome number and structure are important processes that often reflect speciation events as they can establish crossing barriers between populations (e.g. Lowry and Willis 2010; Ouyang and Zhang 2013; Winterfeld et al 2014, 2016; Baack et al 2015; Wölk et al 2015). Lowry and Willis 2010; Ouyang and Zhang 2013; Winterfeld et al 2014, 2016; Baack et al 2015; Wölk et al 2015) Chromosome variations such as polyploidy, hybridization or dysploid change may provide the cytological basis for ecological differentiation, adaptation and isolation. The plants are perennial herbs and lianas from the understorey and gaps of tropical lowland rainforest and are distributed throughout tropical and warm temperate parts of the world (Andersson 1998). Their diversity centre is in the New World, where they are represented by ca. Ca. 50 species in 11 genera are found in Africa including Madagascar and ca. 50 species in 6 genera in Asia (Prince and Kress 2006; Al-Gharaibeh 2017)
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