Interstitial telomere‐like repeats in the monocot family A raceae

Combining molecular cytogenetics and phylogenetic modelling of chromosome number change can shed light on the types of evolutionary changes that may explain the haploid numbers observed today. Applied to the monocot family A raceae, with chromosome numbers of 2 n  = 8 to 2 n  = 160, this type of approach has suggested that descending dysploidy has played a larger role than polyploidy in the evolution of the current chromosome numbers. To test this, we carried out molecular cytogenetic analyses in 14 species from 11 genera, using probes for telomere repeats, 5S rDNA and 45S rDNA and a plastid phylogenetic tree covering the 118 genera of the family, many with multiple species. We obtained new chromosome counts for six species, modelled chromosome number evolution using all available counts for the family and carried out fluorescence in situ hybridization with three probes ( 5S rDNA , 45S rDNA and A rabidopsis ‐like telomeres) on 14 species with 2 n  = 14 to 2 n  = 60. The ancestral state reconstruction provides support for a large role of descending dysploidy in A raceae, and interstitial telomere repeats ( ITRs ) were detected in A nthurium leuconerum , A . wendlingeri and S pathyphyllum tenerum , all with 2 n  = 30. The number of ITR signals in A nthurium (up to 12) is the highest so far reported in angiosperms, and the large repeats located in the pericentromeric regions of A . wendlingeri are of a type previously reported only from the gymnosperms C ycas and P inus . © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society , 2015, 177 , 15–26.