Cytogenetics and evolution ofMatricaria and related genera (asteraceae-anthemideae)

Abstract

1. Chromosome numbers resp. karyotypes are established and compared for 18 species of the Anthemideae generaAnthemis, Chamaemelum, Tripleurospermum, Matricaria, Sphaeroclinium, andPentzia (Table 1, Figs. 1–2). 2. Selfing tests demonstrate that various perennial and annual species of these genera are predominantly selfsterile; onlyMatricaria discoidea is an obligate inbreeder (p. 162f.). 3. An experimental crossing programm involving 12 species from 5 genera has resulted in 22 successful F1-combinations which where analysed in regard to morphology, chromosome number, pollen meiotic behaviour, pollen (and partly seed) fertility (Fig. 3), and compared with their parents (Figs. 4–18, Tables 3–17). 4. Karyotype similarities, F1-chromosome pairing and F1-fertility together with morphological, embryological, biochemical and other data contribute to the controversial problem of relationships and systematics of Anthemideae (p. 183–188):Anthemis is rather heterogeneous, its subgen.Cota may deserve generic status, sect.Maruta approachesChamaemelum; Tripleurospermum is coherent; the two latter genera linkAnthemis with the more advancedMatricaria; they all form a related N. Hemisphere group. S. Hemisphere taxa are more remote: “Matricaria” nigellifolia is much closer toCotula and should be placed in the genusSphaeroclinium; the inclusion of other “Matricariae” into the S. African genusPentzia is justified; some form the hitherto unrecognized annualP. globifera group. 5. Cytogenetic results illustrate mechanisms underlying evolutionary differentiation of Anthemideae (p. 188–194): genie and cytoplasmic factors determine color and shape of flowers, presence or absence of paleae, azulene content, etc.; small karyotype changes appear already within species and gradually reduce chromosome pairing affinities in species hybrids; gross translocations and loss of centromeres have led to species divergence and descending dysploidy (2 n=16→12) in thePentzia globifera group; experimental allotetraploids have originated from intergeneric hybridization involving 2x members ofAnthemis, Tripleurospermum, andMatricaria; through unreduced gametes several 3x progenies have been produced; reproductive barriers between species and genera are of very complex nature. Different recombination systems and evolutionary strategies within Anthemideae are discussed (p. 194f.).