Cytogenetic studies in the genus Chaetobromus (Poaceae: Arundineae)

Abstract

The genus Chaetobromus consists of four, somewhat ill defined species. Morphological merging and the existence of intermediates render the separation of these species difficult. A basic chromosome number of x = 6 for Chaetobromus is substantiated by the presence of diploid specimens. The genus forms a polyploid complex, ranging from diploid to duodecaploid. Polyploidy occurs in the form of segmental alloploidy and occasionally as alloploidy. Meiotic abnormalities, in the form of univalents during metaphase I and anaphase laggards, were observed in some specimens. A cancerous growth form, involving the merging of different cells and the subsequent fusion of their nuclei, has been observed in two specimens, Spies 3366 and CW1. No apparent explanation could be found for this uncontrolled increase in ploidy level during microsporogenesis. Extensive morphological, anatomical, and cytogenetical variation exists in the genus, indicating hybridization and polyploidization. Numerical analysis of morphological data obtained from the specimens studied indicates two groups. Cytogenetic evidence supports the numerical analysis. In an attempt to resolve the contributor species to this polyploid hybrid swarm, attention should be given to the diploid representatives of the putative progenitor species.Key words: Chaetobromus, hybridization, meiosis, numerical taxonomy, polyploidy.