Section 7
Chapter 6,114

Phylogenetic studies on ranunculus cortusifolius ranunculaceae a macaronesian endemic species

Goepfert, D.

Botanical Journal of the Linnean Society 72(3): 161-170


ISSN/ISBN: 0024-4074
Accession: 006113791

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The phyletic position of the Macaronesian Ranunculus species R. cortusifolius was investigated in an analysis of meiotic metaphase I in a series of interspecific hybrids (8 diploid species, 9 genome combinations [R. asiaticus, R. millefoliatus, R. creticus, R. pedatus, R. psilostachys, R. cappadocicus, R. polyanthemas, R. creticus, R. psilostachys], 25 F1's). The exceptionally large size of the R. cortusifolius chromosomes, previously described via cytophotometry, was confirmed and allowed a positive identification of the constituent haploid chromosome sets in all hybrid meiotic preparations studied. MI [mitotic index] was largely univalent-unpaired, with 0 to average 1-2 bivalent-chiasmate pairs (2n = 16), sporadic non-bivalent sticky groupings and occasional (2 hybrids) loose segmental associations (figured). The comparative study of the univalent-bivalent meiotic profiles for the various genome combinations showed that the R. cortusifolius genome has diverged almost as widely from the genomes of species in its own taxonomic group (sect. Pterocarpa Ovcz.) as it has from those of certain morphologically diverse, progressive species from 2 other sections (sect. Xiphocoma, sect. Ranunculus). The morphological conservatism of R. cortusifolius in the face of wide genetic divergence is discussed; an explanation invoking as its most important single cause excessive genome size, on a pre-adaptive model (Waddington et Lewontin), is favored.

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