Cytological data for 188 species in 65 genera of Proteaceae were collated from
the literature. Excluding the occasional infrageneric polyploid, Proteaceae
have seven confirmed character states for chromosome number
(n = 14, 13, 12, 11, 10, 7, 5). Genera of
subfamily Persoonioideae are x = 7, and, on a
cytoevolutionary doctrine of ‘paleo-polyploidy’ in angiosperm
families, these low chromosome number taxa were hypothesised to represent the
ancestral genome of Proteaceae. Chief supporting evidence for this hypothesis
is the ancient origin of Persoonioideae in Proteaceae phylogeny. However all
current genomes in Proteaceae have features that suggest that they are
derived, including those of Persoonioideae with their ‘genomic
obesity’, and by reference to the chromosomes of Bellendenoideae
(n = 5) and the outgroup Platanaceae
(n = 21), quite probably their number is also a
derived character state. Furthermore the high chromosome number genera of
Proteaceae in subfamilies Proteoideae and Grevilleoideae
(n = 14, 13, 12, 11, 10) have genomic lengths
that are far smaller than would be expected from a doubling of the chromosomes
of Persoonioideae, and, so far as any information is available, these genera
are also genetic diploids. This paper questions ‘paleo-polyploidy’
as a general cytogenetic mechanism for plant macroevolution at the levels of
genus, tribe and sub-family in Proteaceae. It is proposed that diploid
cytoevolutionary processes of chromosome number increase and decrease from a
primitive genome of FN = 24, with specific examples of
x = 12 and x = 21,
can explain the cytological phenomena in the family.
Genome size stability despite high chromosome number variation in Carex
gr. laevigata
