(1949, 1954) stimulated continued intense debate and field investigations
into evolutionary processes in tropical forests following his proposal
of the Durian Theory. This view of the evolution of tropical forest was
based upon observations of a series of unusual features of tropical plants.
These features were relatively rare in forest plants as a whole, but occurred
across a broad range of plant groups in the tropics.
|Such features included
Put your mouse cursor over the image to see a close up of the Sterculia
fruits with a fleshy aril
fruits displaying distinct black and red colouration
seeds hanging away from the fruit
Corner's description of the observations
which led him to formulate the Durian theory is deceptively simple but
developed as he expanded his hypotheses to encompass a greater range of
phenomena across the tropics. His ability to link a series of apparently
unrelated characters with changes inherent in developmental processes allowed
him to successfully project this onto an evolutionary framework.
Why would such obscure features appear in a number of apparently unrelated
Corner postulated that these were ancestral characters, which remained
as anomalies in present day forest but which, put into an evolutionary
context, could be used to explain the development of complexity and plant
diversity in tropical forests.
||The starting point was a large fruit similar to the durian Durio
zibethinus (Bombacaceae). This possessed a distinct coloured aril surrounding
the seeds, was heavily armoured and massive in structure. The seeds of
such a fruit would be dispersed by a variety of animals attracted by the
nutritious fleshy aril. A massive fruit would require a massive tree on
which to be carried, probably something like the present day palms or cycads.
Thus the durian theory postulated an origin for angiosperms from a cycad/palm
like ancestor rather than the more delicate gymnosperms such as conifers.
Put your mouse cursor over the image to see a close up of the
|This ancestral tree grew from a single axis, as do most
palms today, with terminal leaves and a single terminal inflorescence.
However, this growth form provides little potential for development to
give the variety of form now present in forests. The next evolutionary
development therefore allowed for the production of branches. As
branching systems arose there was an overall reduction in the size of component
parts ie branches, leaves and flowers as the whole plant or tree became
Increase in size and longevity of such trees, in part due to the removal
of the limitations inherent in the possession of terminal inflorescences,
meant that diversity of form also increased. This diversity was accompanied
by an associated increase in animal diversity, as animals diversified to
live in canopy environments as opposed to being ground dwelling, and began
to feed on drier and smaller fruits and seeds.
Over time this ongoing process could give rise to all facets of the
complexity seen in the present day tropical forests, and would also explain
the changes in plant form required to survive outside the tropics in adjacent
seasonal temperate areas.
Although this model cannot be tested it has stimulated much current
research into evolutionary mechanisms in the tropics and remains a significant
milestone in the study of tropical biology.
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