The elusive Juncus minutulus: a failure to separate tetra- and hexaploid individuals of the Juncus bufonius complex in a morphometric comparison of cytometrically defined groups
Abstract
Screening of nuclear genome size revealed, besides the diploid level corresponding to known diploid species, two polyploid cytotypes conforming with the 4x and 6x levels treated by some authors as Juncus minutulus and J. bufonius s. str. The relationship between nuclear DNA content and the number of chromosomes was verified by chromosome counting.
The 2C values of diploid, tetraploid and hexaploid individuals were ca 0.65, 1.18+-2.8% and 1.84+-1.6% pg 2C DNA, respectively. Classificatory discriminant analysis using characters selected by canonical discriminant analysis and stepwise variable selection resulted in a validation error rate of 0.45 after cross-validation.
This provides independent support for the opinion of some previous authors that J. bufonius L. is best treated as a single variable species comprising two cytotypes that are inseparable using hitherto suggested diagnostic characters.