Karyotypes and Idiograms of Some Western North American Species of Lotus (Fabaceae)

Abstract

Karyotypes and idiograms are presented for 12 species (L. argophyllus var. argophyllus, L. crassifolius, L. dendroideus var. dendroideus, L. grandifiorus, L. humistratus, L. oblongifolius var. oblongifolius, L. stipularis, L. scoparius var. scoparius, L. salsuginosus var. salsuginosus, L. rigidus, L. wrangelianus, L. wrightii) and 3 varieties (L. argophyllus var. argenteus, L. nevadensis var. douglasii, L. scoparius var. brevialatus) of Lotus L. (Fabaceae) belonging to four different groups of the genus (Hosackia, Syrmatium, Microlotus, and Simpteria). The chromosome number for L. dendroideus var. dendroideus (2n = 14) is reported for the first time. Tetraploid cells (2n = 28) were observed in a root tip of L. grandifiorus in an otherwise diploid plant. Chromosome number differences between the species in group V (Microlotus) conform to the taxonomic arrangement by Isely in 1981 separating the species into those with n = 6 and those with n = 7. No correlation was found for chromosome length between annuals and perennials. With the exception of L. crassifolius, the longest chromosome of the complement in the other taxa is clearly distinguished from the second longest chromosome by its greater length averaging a difference of 3.47%. In each taxa, two or more chromosomes have the same length making it impossible to recognize individual chromosomes. It is considered that chromosome morphology alone is not sufficient to separate the North American species into different taxonomic groupings.