Abstract
Philodendron s.l. (Araceae) has been recently focus of taxonomic and phylogenetic studies, but karyotypic data are limited to chromosome numbers and a few published genome sizes. In this work, karyotypes of 34 species of Philodendron s.l. (29 species of Philodendron and five of Thaumatophyllum), ranging from 2n = 28 to 36 chromosomes, were analyzed by fluorescence in situ hybridization (FISH) with rDNA and telomeric probes, aiming to understand the evolution of the karyotype diversity of the group. Philodendron presented a high number variation of 35S rDNA, ranging from two to 16 sites, which were mostly in the terminal region of the short arms, with nine species presenting heteromorphisms. In the case of Thaumatophyllum species, we observed a considerably lower variation, which ranged from two to four terminal sites. The distribution of the 5S rDNA clusters was more conserved, with two sites for most species, being preferably located interstitially in the long chromosome arms. For the telomeric probe, while exclusively terminal sites were observed for P. giganteum (2n = 30) chromosomes, P. callosum (2n = 28) presented an interstitial distribution associated with satellite DNA. rDNA sites of the analyzed species of Philodendron s.l. species were randomly distributed considering the phylogenetic context, probably due to rapid evolution and great diversity of these genomes. The observed heteromorphisms suggest the accumulation of repetitive DNA in the genomes of some species and the occurrence of chromosomal rearrangements along the karyotype evolution of the group.
Highlights
Araceae is a widely distributed monocot family with high ecological diversity, occurring mainly in tropical regions [1, 2]
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? To answer these questions, molecular cytogenetic data were generated for the first time for 29 Philodendron and five Thaumatophyllum species by fluorescence in situ hybridization (FISH) with rDNA and telomeric probes
The lowest number of 35S rDNA sites was observed for seven species: P. annulatum (Fig 3), P. distantilobum (Fig 1F), P. hederaceum (Fig 3), P. inconcinnum (Fig 4), P. krugii (Fig 1G), P. nadruzianum (Fig 1H), and P. fragrantissimum (Fig 1I), which presented only two sites
Summary
Araceae (ca. 3600 species) is a widely distributed monocot family with high ecological diversity, occurring mainly in tropical regions [1, 2]. 3600 species) is a widely distributed monocot family with high ecological diversity, occurring mainly in tropical regions [1, 2]. Philodendron s.l. is the second largest group within the family 500 species), presenting a wide Neotropical distribution, with the Amazon region as its probable center of origin [2,3,4]. Karyotype diversity in Philodendron s.l. and analysis, decision to publish, or preparation of the manuscript
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