Aliso: A Journal of Systematic and Floristic Botany Aliso: A Journal of Systematic and Floristic Botany Karyotypes and Idiograms of Some Western North American Karyotypes and Idiograms of Some Western North American Species of Lotus (Fabaceae) Species of Lotus (Fabaceae)

Karyotypes and idiograms are presented for 12 species (L. argophyllus var. argophyllus. L. cras sifolius, L. dendroideus var. dendroideus. L. grandifiorus, L. humistratus, L. oblongifolius var. oblon gifolius. 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 chro mosome morphology alone is not sufficient to separate the North


INTRODUCTION
Of the chromosome numbers reported for the 30 indigenous North American species and 12 varieties of Lotus (Grant 1995), karyotypes have been published for only five species (Zandstra and Grant 1968). Karyotype analyses and idiograms are presented here for an additional 12 species and 3 varieties. The somatic chromosome number is 14 for all the species with the exception of L. humistratus and L. wrangelianus for which the somatic chromosome number is 12.

MATERIALS AND METHODS
The taxa studied and their taxonomic groupings are listed in Table 1. The source of the taxa are given in Table 2. Herbarium specimens are deposited in the herbarium of the Canada Department of Agriculture Ottawa (DAO).
Several plants were raised from seeds for each accession. Root tips were pretreated with 0.002 M 8-hydroxyquinoline for 1 h (Tjio and Levan 1950) and fixed in 3: 1 95% ethanol:glacial acetic acid. The chromosomes were stained employing the Feulgen method (Darlington and LaCour 1976). Root tips were prepared for maceration by immersion in 4% pectinase (to facilitate spreading of the cells) for 1.0 to 2.0 h and stored in 70% ethanol. Temporary slides were pre-pared by squashing the root-tip meristems in 45% acetic acid on a microscope slide and sealing the coverslips with clear fingernail polish or rubber cement. Temporary mounts could be kept for a minimum of two weeks by placing them on a wet filter paper in a covered petri dish, which was stored in a refrigerator to prevent dehydration. With the aid of a Zeiss drawing apparatus, karyotypes of the somatic chromosomes were prepared for each taxon.
For the construction of idiograms, measurement were made of the entire chromosome complements (Zandstra and Grant 1968). Measurements from the drawings of the chromosomes were made using calipers. The average length of each set (chromosome pair), percent chromosome and arm lengths and centromere characteristics, were calculated, and the idiograms drawn, by using the chromosome analysis package CHROMPAC III (Green et al. 1984). The chromosomes were drawn as percentage of total complement length (vertical axis) and are arranged in order by decreasing length.

RESULTS AND DISCUSSION
Measurements from the karyotypes for the different taxa are given in Table 3. Idiograms of the taxa are presented in Fig. 1-15. With the exception of L. humistratus and L. wrangelianus which have somatic chromosome numbers of 12, all of the other taxa are 2n = 14 (Grant 1995). This is the first chromosome number report for L. dendroideus var. dendroideus (2n = 14).
In contrast to European species in which both diploid and tetraploid chromosome numbers are known, all of the North American species are diploid (Grant 1991). However, a single root tip of L. grandiflorus in an otherwise diploid plant had tetraploid cells (2n = 28) (Fig. 16). A similar observation was made in root tips of the European species L. gebelia Vent. (Grant 1965).
As a result of pretreatment of the root tips with 0.002 M 8-hydroxyquinoline (for ease in counting) the chromosomes were uniformly contracted so that the measurements for the total length of the somatic chromosomes is considered to be somewhat shorter than would have been the case without pretreatment (Tjio and Levan 1950).
Chromosome number differences between the species in group V (Microlotus) conform to the taxonomic arrangement by Isely (1981) separating the species into those with n = 6 and those with n = 7.
As may be seen from the idiograms, similarities in chromosome morphology exist among the chromosomes for all groups. The species in group III (Hosackia ) on the average have the greatest total complement length (TCL averages 28.41 j.Lm). The average TCL for the other groups averages 19.35 j.Lm. No correlation was found for chromosome length between annuals and perennials. One species, L. grandiflorus (group IV, Simpeteria) has the greatest TCL of all the species. However, this species exceeds the TCL of L.  I  I  I  I  I  I  I  I  I 10%  15%  20%  0%  5%  10%  15%  20%  I  I  I  I  I  I  I  wranglianus. Arrangement of chromosomes as described in Fig. 1-6. tween 0.9% and 6.2%. The average percentage length difference between the first and second chromosome is similar for each taxonomic group.
For several species, the chromosome length is the same for two or more chromosomes in the same spe-cies and morphologically the chromosomes can not be told apart. Such chromosomes may be distinguished by chromosome banding. In L. uliginosus (L. pedunculatus), the two shortest chromosomes of the complement are almost identical morphologically but were    Grant 1976). A comparison of the idiograms for the five western North American species of Lotus studied by Zandstra and Grant (1968) [group III, L. pinnatus Hook., L. formosissimus Greene; group IV, L. micranthus Benth., L. purshianus (now L. unifoliatus (Hook.) Benth., L. denticulatus (E. Drew) Greene] with those taxa in this study show that the overall chromosome morphology is very similar. Thus, chromosome morphology alone is not sufficient to separate the North American species into different taxonomic groupings.
Preliminary studies using chromatography showed that L. pinnatus and L. formosissimus (group III) were more closely related to each other than to the other three taxa in group V, and that L. denticulatus (group V), the only species studied with a chromosome number of n = 6, showed lower coefficients of association with the n = 7 species (Grant and Zandstra (1968).
Thus, other experimental methods must be used in addition to cytology to aid in resolving taxonomic affinities in Lotus.