On Sun, 4 May 1997, Australian Ornithological Services P.L. wrote:
To expand on Philip Maher's comments. I believe there are about 60
Australian members of the family Loranthacae which are aerial stem
parasites and are hence likely to get the common name Mistletoe.
These 60 species seem to vary greatly in host specificity. Some are found
on a wide variety of host species, some are found usually on hosts from a
particular genus or family and a few mistletoe species occur almost always
on a single host species.
If a Mistletoe species' normal host species all have relatively similar
leaves (e.g. it occurs usually on casurinas) then there are obvious
possible adaptive advantages if this species produces similar leaves.
This seems to me to underly the shape of some Australian mistletoe
species' leaves.
However it is not impossible that individuals from a mistletoe species
could match their particular host's leaf shape to some extent. I believe
outside Australia it has been demonstrated that host chemistry can affect
a mistletoe species' growth form. Maybe someone has demonstrated this
doesn't happen for leaf shape, I don't know.
I'm certainly not an expert on any of the above.
Andrew Taylor
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