Diversification of Luzula sect. Luzula (Juncaceae) on the Balkan Peninsula – a cytogenetic approach

Abstract

Luzula sect. Luzula is one of the taxonomically most intricate groups of angiosperms, where diversification is mostly driven by true polyploidy and agmatoploidy (fission of chromosomes) leading to three different karyotypes (whole chromosomes – AL, half-sized chromosomes – BL and quarter-sized chromosomes – CL). Morphologically, the taxa are often difficult to distinguish, and genome size data coupled with karyological investigations are currently the most reliable means for their identification. For the Balkan Peninsula, one of the botanically least studied areas of Europe, ten taxa from this section have been reported, but little is known about their distribution. We here estimated the nuclear DNA amount (genome size, GS) using interphase-peak DNA image cytometry and counted the chromosomes for 33 populations of five species of Luzula sect. Luzula mostly from mountainous areas of the Balkan Peninsula and the adjacent southeastern Alps. Five taxa have been confirmed, of which L. divulgatiformis is new for Croatia and L. exspectata for Macedonia and Serbia. The most common species in the Dinaric mountains appears to be diploid (2n = 12 AL) L. taurica, for which the GS (2C = 0.83 pg DNA, fitting well in the range of previously determined values of diploid taxa) has been determined for the first time. The GS and karyotypes of other taxa (L. campestris, L. divulgatiformis, L. exspectata, L. multiflora subsp. multiflora) correspond well to previously published values. An identification key for the Balkan taxa of Luzula sect. Luzula is also included.