Bryophyte phylogeny in terms of chromosome cytology
1986; Taylor & Francis; Volume: 14; Issue: 1 Linguagem: Inglês
10.1179/jbr.1986.14.1.43
ISSN1743-2820
Autores Tópico(s)Lichen and fungal ecology
ResumoCytological interpretation of bryophyte phylogeny is closely concerned with reproductive behaviour. The development of structural sex specific chromosomes differing only in that the Y includes more heterochromatin sensu lato than the X is indicative of monoecism having preceded dioecism in mosses (Bryophyta or Musci) and liverworts (Hepatophyta) at the lowest level of chromosome number now known. Insufficient data preclude similar analysis of the Anthocerotophyta. Evolution within the Musci has involved a significant degree of polyploidy as well as aneuploidy, with dioecy having arisen again at the level of n = 2x, the effects of which are seen in the less widespread evidence of subsequent polyploidy. Numerical change among the chromosomes of the Hepatophyta is almost completely confined to very limited polyploidy and is attributed to the early establishment of dioecy at the level of n = 8, 9 and 10, infrequent sexual reproduction and extensive clonal development. C-, Q-, N- and Hoechst 33258-banding, however, suggest that evolution within liverworts is continuing in hitherto unsuspected ways. Thus, there are pronounced cytological differences between Plagiochila porelloides (n = 9) and P. asplenioides (n = 9) and considerable molecular differences between the constitutive heterochromatin of Pellia epiphylla (n = 9) and P. neesiana (n = 8+X/N). It is also suggested that neither Plagiochila britannica (n = 18) nor Pellia borealis (n = 18) is an autodiploid of recent origin and that at least the former may be an allopolyploid. All these findings are discussed in the context of related groups of green algae and of pteridophytes.
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