 This variation provides the basis for a range of studies in what might be called evolutionary cytology.Homoeologous chromosomes are those brought together following inter-species hybridization and allopolyploidization, and whose relationship was completely homologous in an ancestral species.For example, durum wheat is the result of the inter-species hybridization of two diploid grass species "Triticum urartu" and "Aegilops speltoides".