# Interphase nuclei, karyotypes and nuclear DNA amounts in five species of Oenocarpus (Arecaceae)

## TL;DR

This study examines the chromosome structure and DNA content in five species of Oenocarpus, revealing consistent chromosome numbers but varying karyotype features.

## Contribution

The first comprehensive cytogenetic analysis and DNA amount estimates for four Oenocarpus species, including karyotype descriptions.

## Key findings

- All five Oenocarpus species have a consistent chromosome number of 2n = 36.
- Variations in karyotype formulas and secondary constrictions suggest chromosome rearrangements in speciation.
- No significant differences in nuclear DNA amounts were found among the species.

## Abstract

The genus Oenocarpus Martius, 1823 (Arecaceae) includes five species commonly used in Amazonia, especially for their fruits. Little is known about the cytogenetic characteristics and DNA amounts of these species, except for O.bataua (Martius, 1823). This study characterized and compared the types of interphase nuclei, the chromosome sets, and estimated the nuclear DNA amounts of Oenocarpusbacaba (Martius, 1823), O.bataua, O.distichus (Martius, 1823), O.mapora (H. Karsten, 1857) and O.minor (Martius, 1823). Standard cytogenetic analyses and estimates of the nuclear DNA amount by flow cytometry were carried out. These are the first reports of chromosome numbers and DNA amounts, except for O.bataua, as is the description of the chromatin distribution in interphase nuclei and karyotype for all species. All species presented 2n = 36, confirming the previous report for O.bataua. Differences between karyotype formulas and the positioning of secondary constrictions were observed. There were no significant differences for the nuclear DNA amounts among species. The constancy in chromosome number and variations in karyotype formulas suggest the occurrence of chromosome rearrangement as an important mechanism in Oenocarpus speciation.