Species relationships in the genus Tulipa

The relationships of diploid and polyploid species belonging to the sub-section Eriostemones of the genus Tulipa have been investigated from the point of view of chromosome morphology, relative DNA values, and meiotic pairing properties. Karyotype morphology is basically the same for all species and eight principal chromosome classes can be distinguished. The range of DNA values obtained by Feulgen cytophotometry for the diploid species is relatively small and provides little assistance in ascertaining the pattern of ploidy involved in the evolution of the group. Partial asynapsis and reverse loop pairing in several of the diploids at pachytene reveals a degree of structural differentiation which may be the outcome of hybridity between species. Significantly, these anomalies are rarely encountered at the equivalent tetraploid levels and a scheme is proposed to account for this behaviour.