Updating the list of chromosome numbers for Philodendron (Araceae)

Abstract

Aiming for a better understanding of karyotype evolution within Philodendron, we report chromosome counts for 23 species of the genus, of which 19 are being reported for the fi rst time, thus increasing to 84 (ca. 17 % of the genus) the total number of species with available chromosome counts. Th e diploid numbers 2n = 32 and 2n = 34 were the most common, with 10 and 11 species, respectively, whereas only two species presented diff erent chromosome numbers (P. giganteum with 2n = 30 and P. adamantinum with 2n = 36). Th e results are discussed in the context of previous analyses of karyotypes of Philodendron spp., taking into account bidirectional dysploidy as the main mechanism of chromosome number evolution within the genus.

Karyotype heterogeneity in Philodendron s.l. (Araceae) revealed by chromosome mapping of rDNA loci

“…hederaceum [ 18 ]. Chromosome numbers are all in accordance with previously published data [ 9 ]. The results revealed an enormous karyotypic variability in relation to the distribution of the 35S rDNA in Philodendron s.l., opposed to a high stability in number and position of the 5S rDNA sites.…”

“…It is suggested that x = 16 is the basic number for Philodendron s.l. (including Thaumatophyllum ) and that the karyotype evolution of the group has been driven by both ascending and descending dysploidy events, since no polyploidy was reported so far [ 8 , 9 ].…”

“…Thus, based on the chromosome number and genome size variation previously mentioned for Philodendron and Thaumatophyllum [ 8 , 9 , 20 ], we have addressed the following questions: (I) Is the distribution of rDNA sites in Philodendron and the sister genus Thaumatophyllum conserved? (II) Does the distribution pattern of rDNA sites agree with the available phylogenetic data?…”