Mimicry is often the first conclusion
jumped to when two coexisting plants resemble each other, or an organism. In many
cases alternative explanations have not been investigated, and mimicry should
not be established until they have been considered and appropriately excluded (Ruxton and Schaefer, 2011). Alternate hypotheses
concerned with mimicry often exhibit fewer restrictions, and would therefore be
more likely to allow the plant to evolve. Ruxton and Schaefer (2011) argue that the lack of
elimination regarding alternate hypotheses is a massive restriction in current
plant mimicry research. If researchers were to more clearly focus on
deciphering a mechanism or applying the Ockham’s razor principle mimicry might
not always be the hypothesised explanation (Ruxton and Schaefer, 2011). Researchers of plant
adaptations need to consider convergent evolution and exploitations of sensory
biases as alternative hypotheses to mimicry when attempting to explain similar
aspects between plant species (Ruxton and Schaefer, 2011).
Mimicry in plants is also subject
to many evolutionary constraints, and it can be concluded that there will always
be a limit to a plants mimicking ability. One such constraint is the fact that
plants are sessile, which presents multiple limitations (Williamson, 1982). The sessile nature of plants allows pollinators
or herbivores time to assess the mimic and the model, and possibly decipher
differences and learn how to distinguish between them. Another problem is that
the pollinators or herbivores may recall the location that the mimic is in as
being undesirable, the organism may have a bad experience and be deceived by
the plant and learn not to visit that location again; being sessile the plant
cannot change location. Another constraint on plant mimicry is their
aggregation habits (Williamson, 1982). Species tend to clump together, a habit which
can increase a visitor’s likelihood of visiting too many mimic plants and
avoiding the area all together. Aggregation can also occur on the individual
plant, with appendages such as fruit, flowers and leaves as the mimic signal
transmitters; this aggregation having the same negative effect on a visitor as
multiple plants (Williamson, 1982). Some deceptive species, such as the orchids,
have evolved to limit aggregation by only occurring in small numbers and over
wide spatial distances, so visitors are unable to have negative associations
with individual plants. The sessile constraint can sometimes be avoided through
the use of floral or seed mimicry, in which the appendages involved are only
present for a short period of the plants lifespan. Aggregation constraints are
perhaps the largest constraint on plant mimicry because visitor deception is
much more successful and efficient if there are not many mimicking plants
around, so they can never occur in large numbers (Williamson, 1982).
