Different karyotype patterns among allopatric <i>Pinus nigra</i> (Pinaceae) populations revealed by molecular cytogenetics

<jats:title>Abstract</jats:title><jats:p>To examine variation and taxonomic recognition of <jats:italic>Pinus nigra</jats:italic> (European black pine) at the intraspecific level, chromosomal distribution of 5S and 18S‐5.8S‐26S rDNA loci revealed by fluorescent <jats:italic>in situ</jats:italic> hybridisation (FISH) and fluorochrome banding with chromomycin A<jats:sub>3</jats:sub> and DAPI were analysed among allopatric populations belonging to different subspecies. Despite prevalent opinion on predominantly conserved and homogenous conifer karyotypes, several patterns were observed. Surprisingly, interstitial 18S rDNA loci and DAPI heterochromatin staining after FISH showed variations in distribution and localisation. Three subspecies shared a pattern with nine 18S rDNA loci (ssp. <jats:italic>nigra</jats:italic>, <jats:italic>pallasiana</jats:italic> and <jats:italic>laricio</jats:italic>) while ssp. <jats:italic>dalmatica</jats:italic> and <jats:italic>salzmannii</jats:italic> had eight rDNA loci. DAPI banding displayed two patterns, one with a high number of signals (ssp. <jats:italic>nigra</jats:italic>, <jats:italic>pallasiana</jats:italic> and <jats:italic>dalmatica</jats:italic>) and the other with a lower number of signals (ssp. <jats:italic>salzmannii</jats:italic> and <jats:italic>laricio</jats:italic>). We conclude that our results cannot provide proof for either classification scheme for the <jats:italic>P. nigra</jats:italic> complex, but rather demonstrate the variability of different heterochromatin fractions at the intraspecific level.</jats:p>