See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/234100590 Phyletic and evolutionary relationships of Brachyscome lineariloba (Compositae). Article in Plant Systematics and Evolution · January 1987 CITATIONS READS 3 91 1 author: Kuniaki Watanabe Kobe University 79 PUBLICATIONS 1,586 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: The control of diploid-like meiosis in polyploid taxa of Chrysanthemum. View project All content following this page was uploaded by Kuniaki Watanabe on 10 December 2016. The user has requested enhancement of the downloaded file. -Plant-.--­ SystematIcs PI. Syst. EvoI. 157, 121-141 (1987) and Evolution © by Springer-Verlag 1987 Phyletic and evolutionary relationships of Brachyscome lineariloba (Compositae) 1 K. WATANABE and S. SMITH-WHITE Received March 14, 1986 Key words: Angiosperms, Compositae, Asteroideae, Brachyscome (= Brachycome) lineari­ loba, B. breviscapis. - Life pattern, annual inbreeding, ascending dysploidy, amphidiploidy, karyotype, hybridization, meiotic pairing. - Flora of Australia. Abstract: A comparison of karyotypes of Brachyscome breviscapis (2 n = 8), B. lineariloba cytodemes E (2n = 10), B (2n = 12) and C (2n = 16) suggests that these species have a homoelogous basic set of four chromosome pairs, two large pairs and two small, and that the B. lineariloba cytodemes E, Band C are related to B. breviscapis by successive additions of small chromosomes. A pronounced asynchrony of chromosome condensation between these large and small chromosomes has been observed. In the artificial hybrids between B. dichromosomatica (2 n = 4) x B. breviscapis, and the B. lineariloba cytodemes, the B. dichromosomatica chromosomes are similar in size and condensation behaviour to the small chromosomes of B. breviscapis and of B. lineariloba cytodemes E, Band C. Meiotic pairing in these hybrids also demonstrates the strong affinities between these chromosomes. It is suggested that B. breviscapis may be of amphidiploid origin between a species with two large early condensing chromosome pairs and another, B. dichromosomatica-like species with two small late condensing pairs. It seems most likely that the additional small and late condensing chromosomes in B. lineariloba cytodemes E, Band C are derived from the B. dichromosomatica-like parent, and that each addition increases vigour, fecundity and drought tolerance, allowing these cytodemes to colonize more open and arid environments. Transmission of the univa1ents in the quasidip10id B. lineariloba cytodeme E was verified as being via the pollen, and not via the embryo sacs. The Brachyscome lineariloba complex, recognized by DAVIS (1948) as a single species, has been found to include five "races", cytodemes or species, designated as A, B, C, D and E by SMITH-WHITE & CARTER (1970) and CARTER & al. (1974). Two of these, race A, with 2 n = 4, and race D, with 2 n = 8, have been raised to specific rank by CARTER (1978 a), as, respectively, B. dichromosomatica C. R. CARTER and B. breviscapis C. R. CARTER. The other three races which remain within B. lineariloba (DC.) DRUCE are the cytodemes B with 2n = 12, C with 2n = 16, and E with 2 n = 10. The latter is a quasidiploid with four chromosome pairs and two univalents. All these cytodemes and taxa A - E do not constitute a 1 The cytology of Brachyscome lineariloba (Compositae, Asteroidae), 10. 122 K. WATANABE & S. SMITH-WHITE: polyploid series. CARTER'S (1978 a) taxonomic revision, although fully justified, does not alter the close evolutionary and phyletic relationships of the members of the complex. For convenience in this paper, the "race" symbols A, B, C, D and E will be frequently used to refer to the several species and cytodemes. KYHOS & al. (1977) proposed a phyletic scheme of relationship for the members of the complex which was based on a number of criteria: plant size and vigour, growth form, (small) morphological differences, chromosome number and mor­ phology, chromosome association in putative hybrids and geographical distribu­ tion. Obviously, natural hybrids can only occur in regions of species overlap, and KYHOS & al. (1977) give a list of localities where mixed populations are found. Sympatry is not known for the important pairs A and E, A and D, C and E, C and D, and Band D. The species and cytodemes are not internally homogeneous. B. dichromosomatica exists in two geographically disjunct taxonomic varieties, var. alba C. R. CARTER formerly named A3, and var. dichromosomatica C. R. CARTER which is made up of three cytodemes, Ab A2 and A4. The four forms are related to one another by chromosome interchanges, by differences in chromatin condensation patterns at meiotic first prophase, and by suppression or loss of the nucleolar organizer (WA­ TANABE & al. 1975). Also, in about 10% of AI, A2 and A3 plants, one, two, or three B-chromosomes are present (CARTER & SMITH-WHITE 1972, CARTER 1978, SMITH-WHITE & CARTER 1981). Within cytodeme C two subdemes, CI and C2, occur, and even these show considerable heterogeneity for chromosomal variants (WATANABE & al. 1985). Chromosomal variants are also known to occur in cy­ todemes Band E, and in B. breviscapis. The study of artificially produced hybrids overcomes some of the difficulties which were imposed upon KYHOS & al. (1977). Such hybrid material has precisely known parentage, and the range of hybrid material is not geographically restricted. The present study comprises the artificial hybrids D x E, D X A3, D X Ab E X Ab Al X E, B X Ab B X A3 and C I x AI' Throughout this paper, crosses are always indicated with the pistillate or seed parent to be left. The hybridization E x D was attempted, but was unsuccessful. Cytodeme D, which is B. breviscapis, has minute flower heads and produces very little pollen. Materials and methods The geographical sources of the species and cytodemes used in this hybridization work are: B. dichromosomatica var. 15 km north of Simmondston, S. Australia dichromosomatica A I B. dichromosomatica 70 km south-east of Willcannia, adjacent to var. alba A3 the Barrier Highway, N. S. Wales B. breviscapis D Laura Bay, S. Australia B. lineariloba E Laura Bay, S. Australia B. lineariloba B Hookina, north of Hawker, S. Australia B. lineariloba CI 11.2km west of Broken Hill, N. S. Wales The cytological, hybridization and germination techniques used were identical to those described by WATANABE & al. (1975). Cytology of Brachyscome lineariloba 123 1•• 111 JIIIII 10 203040 10203040 1B 2B 3B 4B 5B 6B 1B2B3B4BSB 6B 1E 2E 3E 4E 5E 6E 1E 2E3E 4E 5E 6E 1C 2C 3C 4C 5C 6C 7C BC 1C 2C 3C 4C 5C 6C7C 8C M (3,41 (1,10) ~~ ~':I'.l ~5,11\l (.~ (Ill (1.01 (3,41 (1,10) ~~ (lIP) ~5,11\l (5.e) (\Ol Figs. 1-4. Idiograms of the haploid chromosome set at metaphase (left) and prometaphase (right) of the Brachyscome lineariloba complex; early condensing chromatin in prometaphase dotted, late condensing white. - Fig. 1. B. breviscapis D; n = 4. - Fig. 2. B. lineariloba E; n = 5, chromosomes 5 E and 6 E are univalents. - Fig. 3. B. lineariloba B; n = 6. - Fig. 4. B. lineariloba C; n = 8. Idiograms are drawn from Figs. 5 - 11 and Fig. 4a in WATANABE & al. (1985). Scale = 1O)lm Results Parental karyotypes. Following KYHOS & al. (1977) the haploid set of chromosomes of B. breviscapis D have been arranged in order of size, and are numbered ac­ cordingly (Fig. I). The four chromosomes are all quite characteristic. The corre­ sponding chromosomes of B. lineariloba cytodemes E, Band C have been given the same numbers (Figs. 2 - 4). The implication is that they are homologous, or at least essential homeologous, in the four taxa. The univalent chromosomes of cy­ todeme E have been numbered 5 E and 6 E, and are comparable in size and form with 5 Band 6 B of cytodeme B, and with 5 C and 6 C of cytodeme C. Cytodeme C then has the additional pairs 7 C and 8 C. This numbering system is different from that adopted by WATANABE & al. (1985), where the complete somatic chro­ mosome set had to be ranked in order of size regardless of homeologies. For reference that former rank order for CI is given in parenthesis in Fig. 4. The homeologous ranking, size and form of the chromosomes of the cytodemes D, E, Band C is in general agreement with that given by KYHOS & al. (1977), with the difference that 5 Band 6 B, and 7 C and 8 C are distinctly larger. The chro­ mosomes of B. dichromosomatica Al and A3 have been described by WATANABE ,..... Table 1. Karyotype data of Brachyscome breviscapis D, B.lineariloba E, Band C 1 (length in /lm). L, S Long arm length, short arm length, Ttotal tv .j::>. length, L/S arm ratio, long arm/short arm. Measurements from Figs. 5 - 8. Chromosomes of B. lineariloba E, B, C 1 are arranged in correspondence to the length and arm ratio of those of B. breviscapis. Relative lengths, normalized to 1.00 for chromosome 1 in parentheses. The numbers in the bottomline of C 1 give the chromosome arrangement as used by WATANABE & al. (1985) Species or cytodeme Chromosome 1 2 3 4 5 6 7 8 D L,S 9.4, 7.5 7.6, 2.5 4.7, 3.3 3.7,2.3 T 16.9 (1.00) 11.1 (0.66) 8.0 (0.47) 6.0 (0.36) LIS 1.3 3.0 1.4 1.6 E L, S 8.2,6.3 7.1, 1.5 3.8,2.7 3.3,2.0 3.7,2.0 3.7,2.0 T 14.5 (1.00) 8.6 (0.59) 6.5 (0.45) 5.3 (0.37) 5.7 (0.39) 5.7 (0.39) LIS 1.3 4.7 1.4 1.7 1.9 1.9 B L, S 9.0, 6.8 8.0, 1.8 4.8,3.0 4.3,2.7 5.3, 3.2 5.1,2.7 T 15.8 (1.00) 9.8 (0.62) 7.8 (0.49) 7.0 (0.44) 8.5 (0.54) 7.9 (0.50) LIS 1.3 4.4 1.6 1.6 1.7 1.9 C] L, S 8.2,6.3 7.9, 1.5 3.8,2.7 3.3,2.2 3.7,2.2 3.5, 1.8 3.5, 3.4 4.8,2.0 T 14.5 (1.00) 9.4 (0.65) 6.5 (0.45) 5.5 (0.38) 5.9 (0.41) 5.3 (0.37) 6.9 (0.48) 6.8 (0.47) ~ LIS 1.3 5.3 1.4 1.5 1.7 1.9 1.0 2.4 (1.2) (3.4) (9.10) (13.14) (11.12) (15.16) (5.6) (7.8) ~ >-l)- ~ 1:0 tIl ~ en en 3: ::j :r: ~ :r: ::j tIl Cytology of Brachyscome lineariloba 125 Table 2.