The genus Nicotiana contains over 60 species. Interestingly, the nicotine content of leaves varies widely among species. For instance, a study reported nicotine contents ranging from 0 to >9000 ug/g of leaf tissue in 36 species. If nicotine is necessary to deter herbivores, why don’t all species produce high levels? Briefly provide two evolutionary reasons explaining i why this variation in nicotine concentration may occur. The article by Adler and colleagues (Adler et al., 2012) addresses this interspecific variation and explores some of the evolutionary reasons underpinning it.

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Reason 1 To regulate and select over the cross pollination and self pollinatio... View the full answer