Chromosomal criteria and their phylogenetic implications in the genus Onobrychis Mill. sect. Lophobrychis (Leguminosae), with special reference to Egyptian species

Abstract

Chromosome numbers and measurements were recorded in 22 individuals from six populations of six species of Onobrychis, including the Egyptian species and most representatives of section Lophobrychis. The basic number of chromosomes was either x = 7 or x = 8 and the chromosomes were medium to medium-small,ranging in length, from c. 1.6 mm to 2.6 mm. Two new ploidy levels were found, 2n = 4x = 28 in O. bobrovii Grossh. and 2n = 4x = 32 in O. pulchella Schrenk. The origin of the chromosome numbers, geographical distribution and evolution of the species were assessed. Comparison of the data with those in the literature revealed that the observed interspecific variability among section Lophobrychis can be useful in taxonomic delimitation and demonstrates a complexity of evolution between the diploid and polyploid species. Section Lophobrychis has a comparatively highly derived organization and can be considered as a heterogeneous unit in the genus Onobrychis.