Investigation into carrion and
faecal mimicry is not the most popular research topic in evolutionary biology. As
mammals, it is ingrained in us to avoid such things because of the potential diseases
and pathogenic microbes that may be harbored within them.
It is proposed that carrion and
faecal mimicry in flowers has evolved to not only attract pollinators, but also
to deter herbivorous mammals (Lev-Yadun and Gutman, 2013). Carrion and faecal mimicry
is also hypothesised to give a false warning to herbivores of nearby predators.
Flowers mimic the scent of carrion which would likely be surrounded by carnivores,
or of predator’s urine or faecal matter to fake the recent passing of a
carnivore. This fear of predation has been known to influence the herbivores behavior
in such a strong way that vegetation structure can be completely changed (Lev-Yadun and Gutman, 2013). Some hypotheses even go as
far as to say that carrion odor may assist plants by attracting large
carnivores, which may then defend them from herbivores (Lev-Yadun et al., 2009).
Research has shown that the mimicking flowers rely heavily on the volatiles
used by flies as cues to locate carrion and faeces (Johnson and Jürgens, 2010). It has been discovered that
the oligosulphides emitted by the Mediterranean Arum flower are identical to those emitted by animal carrion and
trigger the same electrophysiological response in fly antennae (Johnson and Jürgens, 2010). This shows amazing mimicry
of the chemical cues given by carrion to successfully exploit carrion flies.
The primary purpose of the
odorous emissions is a hotly debated topic, for example the Rafflesia genus only emits odours during
its reproductive season, leading to the conclusion that the attraction of
pollinators is the primary function of the chemical emissions (Lev-Yadun et al., 2009).
Despite this conclusion scientists argue as to whether the evolution of odours
was primarily to repel herbivores, or for the attraction of pollinators.
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| Rafflesia spp. adapted from http://liseblog.dk/thailand-2012/ |
Rafflesia is an amazing plant, not only because of its horrendous smell, but because it is one of the largest flowers produced in the world (as far as I’m aware). I’ve never heard of the hypothesis that these plants produce these odours to mimic the presence of predators. That’s really fascinating! Is there any mention of how these plants produce these volatile compounds that so closely mimic carrion and faeces? Great post!
ReplyDeleteJohnson (2010) mentions that they have evolved to develop specific mixes of compounds such as acids, sulphides and various phenol groups. The different scent patterns are still unclear and he urges more research into manipulative experiments to understand which volatile blends are more significant and successful than others.
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