Darwin's
abominable mystery and the fossil record of early flowers
Else Marie Friis (with
Kaj Raunsgaard Pedersen and Peter R. Crane)
Swedish Natural History Museum,
Stockholm, Sweden
Darwin
wrote in a letter to J. D. Hooker dated 22 July 1879: “The rapid development as
far as we can judge of all the higher plants within recent geological times is
an abominable mystery”. Although Darwin
did not specifically mention the flowering plants in this famous quotation his
“abominable mystery” has since then been tightly linked to the
origin and diversification of angiosperms, one of the major biotic upheavals in
the history of life, and still a major puzzle in evolutionary biology. In Darwin’s time angiosperms
were thought to enter the fossil record very sudden and apparently “fully
evolved” in the mid-Cretaceous. Darwin
therefore speculated about a long pre-Cretaceous history for angiosperms in
remote areas that have left no fossil signals. However, an improved
stratigraphic framework developed in the last century together with the
discovery and study of numerous informative angiosperm fossils has greatly
changed our view of early angiosperm evolution. It is now clear that the first
major phylogenetic diversification and ecological radiation of angiosperms took
place in the Early to mid-Cretaceous over a relatively short time interval of
some few million years. Subsequently, angiosperms steadily increased in both
their diversity and abundance, only slowly reaching the levels of systematic
differentiation and diversity they display today. A key remaining issue is the relationship
of angiosperms to other seed plants, which is still unresolved. New fossils are
constantly being added to the fossil record of angiosperms and other seed
plants and these may be relevant to clarifying this aspect of angiosperm
evolution.
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