A novel indicator of karyotype evolution in the tribe Leucocoryneae (Allioideae, Amaryllidaceae)

Abstract

The tribe Leucocoryneae is taxonomically andcytogenetically complex, mainly due to its extraordinarymorphological and karyological variation. Robertsoniantranslocations had long been recognized as a central factorcontributing to karyotype diversity within the Leucocoryneae,but so far no major tendency prevailing on theobserved complexity of karyotype formula among specieshas been identified. The assessment of nuclear DNAcontents by flow cytometry using propidium iodide in 23species, representing all genera within the tribe, showed amonoploid genome size variation of 1Cx = 9.07?30.46 pgdenoting a threefolds fluctuation. A highly significant linearassociation between the average DNA content per chromosomearm (2C/FN) and the monoploid genome size (1Cx)is reported for the first time and identified as a novel indicatorof a trend governing karyotype diversity within Leucocoryneae.This trend shows that a reduction in DNA contentper chromosome arm is influencing and has shaped karyotypeevolution of different monophyletic groups within thetribe despite the complex karyotype diversity and apparentlycontrasting patterns of genome sizes.