University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Transactions of the Nebraska Academy of Sciences and Affiliated Societies Nebraska Academy of Sciences 1977 Chromosome Analysis Of Bidens Polylepis And Bidens Coronata (Compositae) Merlin G. Butler Chadron State College Ronald R. Weedon Chadron State College Follow this and additional works at: https://digitalcommons.unl.edu/tnas Butler, Merlin G. and Weedon, Ronald R., "Chromosome Analysis Of Bidens Polylepis And Bidens Coronata (Compositae)" (1977). Transactions of the Nebraska Academy of Sciences and Affiliated Societies. 430. https://digitalcommons.unl.edu/tnas/430 This Article is brought to you for free and open access by the Nebraska Academy of Sciences at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Transactions of the Nebraska Academy of Sciences and Affiliated Societiesy b an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. CHROMOSOME ANALYSIS OF BIDENS POLYLEPIS AND BIDENS CORONATA (Compositae) MERLIN G. BUTLER* and RONALD R. WEEDON Department of Biology Chadron State College, Chadron, Nebraska 69337 The closely related species Bidens coronata (L.) Britt. and has been reported to be 24 (Weedon, 1973). Also, the three B. polylepis Blake are morphologically similar and may hybridize awn fOnTIS of B. polylepis, known as varieties by some (B. readily. Sympatric eastward, the species are allopatric in Nebraska-and polylepis "polylepis," B. polylepis "antrorsa," and B. poly­ adjacent states. Karyotype analysis of the two species revealed not lepis "retrorsa"), have been reported to be 24 (Weedon, only a number of sinJilarities but also some significant differences. Orromosomal analysis of the awn forms of B. polylepis (designated as 1973). The haploid number for each of these species is n=12 varieties by some) revealed no significant differences, indicating, along (Weedon, et aI., 1974; Weedon and Butler, 1976). Thus, to with morphological evidence, that B. polylepis is- a single taxonomic classify the plants on the basis of chromosome analysis, one entity, although phenotypically highly plastic-. must turn to possible differences in chromosome morphology. t t t MATERIALS AND METHODS INTRODUCTION Mature achenes from greenhouse progeny of plants The primary objectives of this study were: (A) to pro­ collected in the Great Plains region (voucher specimens at vide a karyotypic nomenclature by describing quantitatively CSCN) were placed in tap water and allowed to germinate. the chromosomes of Bidens coronata (L.) Britt. and B. poly­ These achenes were harvested from specimens having a pollen lepis make; and (B) to define chromosomal similarities and grain viability of approximately 98%, as confirmed by the differences between the karyotypes of these two plant species. Buffalo black staining technique of Jackson (1973). Actively growing root tips were placed in saturated 8-hydroxyquinoline The species-sometimes called "Beggarticks," "Stick­ at room temperature for 3 hours, transferred to a fixative tights," or "Tickseed Sunflowers" -are morphologically simi­ consisting of 100% ethanol and acetic acid (3:1) for at least lar and are often difficult to identify. B. coronata, a native 3 hours, and stored until used in 70% ethanol at 40 C by of eastern North America, displays the distributional pattern techniques similar to those used by Merritt and Burns (1974). of an arc northward and westward around the southern half of the Great Plains, by occurring in east to north-central Microscope slides were prepared by transferring the root Iowa and east-central Minnesota, disjunct then to the Sand tips to 10% HCl and hydrolyzing for 8 minutes at 60oC. The Hills and adjacent areas of Nebraska and South Dakota. terminal one millimeter portions of the root tips were placed B. polylepis continentally is an interior species entering the on clean microscope slides and stained with acetocarmine Great Plains from the east. Hall (1967) speculated that these for a few minutes. The cover slips were put in place, and species and other North American representatives of the then, by the use of a pencil eraser, the cells were flattened by Section Meduseae were fragmented by Pleistocene events the squash technique. Finally, the slides were heated for into four ecogeographically isolated populations, perhaps one to three seconds over a low-flame Bunsen burner to aid from a single, original, pre-Pleistocene ancestral species. He in spreading the chromosomes. further speculated that the situation may very possibly break down again due to secondary contacts brought on recently Slides were scanned by using a phase-contrast micro­ by white man to create a single variable entity. On the other scope with a built-in camera. Suitable metaphase chromosome hand, Figures 1 and 2 indicate that the Sand Hills of Nebraska spreads with attached satellites were photographed at l000x may act as a refuge for B. coronata, both because its western magnification. The film used was 4 x 5 inch Kodak, Koda­ limit of distribution is distinctly separate from that of B. lith,Ortho Film, Type 3. Karyotypes were prepared from the polylepis, and because B. polylepis may not be able to become 8 x 10 inch enlargements by cutting out the individual chro­ established in the unique habitats of the Sand Hills. The mosomes, pairing apparently homologous chromosomes, and establishment of a karyotype for each of the two species Would, thus, be very helpful in determinng the potentiality of secondary merger in the evolution of these two species. *Present address: 'The University of Nebraska Medical Center, The diploid (2n) chromosome number of B. coronata Omaha, Nebraska 68105. 35 - - - --...... - Figure 1. Bidens coronata (L.) Britt. mounting them on white cardboard in a manner similar to following system was used in the preparation of karyotypes the approach used by Rary, et al. (1968). for this study of B. coronata and B. polylepis. In making the karyotype, the apparently homologous chromosomes Spreads suitable for karyotype analyses were photo­ were placed in three rows of eight. The chromosomes were graphed, and karyotypes were prepared from the prints. placed visually in decreasing order of size with the apparent These spreads included three karyotypes of B. coronata, metacentric chromosomes composing the second and third three of B. polyiepis "polylepis," three of B. polylepis "an­ rows. The first row was composed of chromosomes with trorsa," and two of B. polylepis "retrorsa." All three of these attached satellites and also containing submetacentric and awn forms are often detected in a given population of B. subtelocentric chromosomes to complete the row of eight polylepis (Weedon, 1973). The length of each arm of the in­ chromosomes. The chromosomes were paired visually as dividual chromosome and the total length of the chromosomes homologous or morphologue chromosomes. Due to possible were measured with a vernier caliper, and the chromosomes contraction out of phase for individual chromosomes and the were measured directly from the microscope slide by the use degree of mitotic activity, some chromosomes may appear of an ocular micrometer. Heterochromatic regions of the to have the same shape and appearance, but, actually, a chromosomes of the taxa were studied utilizing techniques chromosome pair may not be homologous. Figures 3,4, 5, of Merritt (1974). and 6 show the arrangement of the chromosomes within the karyotypes studied. RESULTS AND DISCUSSION Numbers were assigned to the chromosomes within. An organized system for karyotypic preparation in plant the rows for the purposes of analysis and measuring. The cytogenetics is needed for the arrangement of chromosomes. homologous pairs of chromosomes were numbered fromi Th.is system would be instrumental in establishing a method one through twelve for the karyotypes of B. coronata and of chromosome identification and quantitative analysis. The the karyotypes of B. polylepis. 36 Figure 2. Bidens polylepis Blake. • awnless to very short awns * awns long, retrorse • awns long, antrorse The long-ann/short-ann ratio, centric index, length of with LIS ratios of 2.02 and 1.72, respectively; and chromo­ the chromosome in percent of total cell chromatin, and the somes of rows 2 and 3 were determined to be near-metacentric chromosome type were calculated for each chromosome (m-type) or metacentric (M-type) with a LIS ratio range of (Tables I, II, III and IV). The system proposed by Levan, et al. 1.34 to 1.00. (1964) for designating individual chromosomes has been used The karyotype of B. coronata shows 4 satellites attached in this karyotypic analysis. The SAT-chromosomes were mea­ to chromosome pairs, numbers 2 and 3. The karyotypes of sured without inc1udinl!' the length of the satellites in the ann each of the three awn forms of B. polylepis (Figs. 4-6) show 6 length. For example, chromosome numbers 3 and 4 of row 1 of satellites attached to three pairs of subtelocentric or submeta­ B. coronata (Fig. 3) would be tenned sub telocentric (st-type) centric chromosomes. Therefore, the major gross difference with LIS ratios of 2.91 and 3.09, respectively; chromosome of the karyotypes of the two species was the number of satel­ numbers 1 and 2 would be termed submetacentric (sm-type) lites present. 37 ... _.- ••• ... ~ .., 'II ,", II II ... 'a'i . I I 2 ) • I 1 '"Z ") • lA II ~I I II "S "6 r- "7 "• U S 6 I- T • II II It II II JlI xII • m , 10 It , It " DI 10 11 Figure 3. Karyotype of B. coronata with the numbers assigned Figure 5. KarYotype of B. polylepis "antrorsa" with the to homologous pairs of chromosomes. Satellites can be numbers assigned to homologous pairs of chromosomes. seen on chromosome pairs 2 and 3. Satellites can be seen on chromosome pairs 1, 2, and 3. • • I. ROW -. •• IJ II Ii &1 IQI I' II II I I 2 1 ) .. 1 2 II 'f II I' 11 II S 6 2aa 7 e , 2Ja 7 , e S " " II " " II Ie IJ II II II m , 10 11 12 l' m 9 10 1 I "12 Figure 4.