Evolution in the Proteaceae.
Authors: Johnson LAS , Briggs BG 
Published: December 2005

The sources of evidence bearing on the evolution of the Proteaceae are outlined.
New cytological data are presented for Embothrium (South American), Beauprea
(New Caledonian), and 15 Australian genera which are mostly tropical or subtropical
and with morphological characters considered primitive. Beauprea, Buckinghamia,
Opisthiolepis, Embothrium, Oreocallis, and Strangea have 2n = 22 and this number is
also confirmed for Stenocarpus and Lomatia. Hollandaea, Darlingia, Cardwellia,
Carnarvonia, Helicia, Hicksbeachia, Gevuina, Musgravea, and Austromuellera have
2n = 28. In all these cases the chromosomes are comparable in size with those previously
described in Grevillea and other genera. Placospermum has 2n = 14 and its chromosomes
are many times larger, comparable with those which have been reported in Persoonia.
The palaeobotanical evidence is discussed, but does not throw much light on the
detailed phylogeny or on the origin of the family, although it suggests that Proteaceae
were well developed in the Upper Cretaceous period. From comparative morphology
and cytology, together with considerations of distribution, ecology, and other factors,
the characters of the ancestral "Proto-Proteaceae" are postulated and an evolutionary
scheme of probable relationships of subfamilies, tribes, and genera is put forward, but
formal taxonomic rearrangement is deferred for a later publication. Morphological
features of the ovule and seed and of floral orientation are discussed. The characters
and probable evolutionary trends within each individual group are dealt with in detail
and form the basis of a number of proposed rearrangements in the taxonomic system.
Placospermum is considered to combine many primitive morphological and
cytological features, and it is excluded from both the subfamilies Proteoideae and
Grevilleoideae, being thought to represent an early offshoot before the differentiation
of those groups. The Proteoideae are probably polyphyletic but the Grevilleoideae
represent a more close-knit assemblage.
Within the subfamilies certain groups consist of clearly allied genera and appear
to be monophyletic. These constitute the majority of the formally recognized tribes,
viz. Proteeae (here including Synaphea and Conospermum), Grevilleeae (here restricted
to Finschia, Grevillea, and Hakea), Musgraveeae (Musgravea, Austromuellera), and
Banksieae. The tribe Embothrieae, here restricted to those genera of the Grevilleoideae
with n = 11, shows considerable morphological diversity but is accepted for the present.
It is shown that Strangea should be removed from the Grevilleeae and placed in the
Embothrieae near Stenocarpus, with which it shares distinctive seed and inflorescence
characters.
Some isolated genera, viz. Orites (Grevilleoideae) and in particular Franklandia
(Proteoideae), show marked specialization in many features and may be given tribal
status. The other two tribes recognized, Persoonieae (in the Proteoideae) and
Macadamieae (in the Grevilleoideae), consist of genera which, although advanced in
certain respects, preserve numerous primitive features. Each of these tribes comprises
a number of groups and individual genera which appear to be the result of evolutionary
lines that have been independent from a very early stage. The African genus Brabeium,
formerly placed in Persoonieae, is shown to be related to Macadamia.
There remain certain genera, viz. Dilobeia (Proteoideae) and also Hollandaea,
Knightia, Darlingia, Cardwellia, and Carnarvonia (Grevilleoideae), for which no formal
grouping is at present suggested.
The frequent independence of trends of specialization in individual characters is
stressed, and the relationship of zygomorphy and other floral and inflorescence
specializations to pollination by higher insects and birds is discussed. The primitive
condition of the inflorescence is considered to have been essentially racemose, not a
thyrse as recently suggested. Racemose inflorescences are found in many Proteoideae
but the apparent raceme in Grevilleoideae is thought to be a reduced panicle.The phytogeography of the family is briefly discussed. There is evidence
indicating a tropical origin, and therefore suggestions of southern connections between
Australia and Africa are discounted, though they may have occurred between Australia
and South America.
Stress is placed on the need for an understanding of evolution within the family
as a prerequisite to the development of theories on its position among the Angiosperms
and on its historical phytogeography.