Bumblebees pollinate M.lewisii,whereas hummingbirds prefer the red-flowered M.cardinalis.If,by chance,a hummingbird carries M.cardinalis pollen to M.lewisii,the resulting hybrid offspring are viable.M.lewisii and M.cardinalis are different species due to:

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The fact that bumblebees prefer M.lewisii and hummingbirds prefer M.cardinalis suggest that there are pre-zygotic barriers to reproduction, meaning that the two species do not interbreed due to differences in behavior or anatomy that prevent fertilization from occurring. However, the fact that hybrid offspring can still arise if pollen from one species is accidentally transferred to the other species indicates that the barriers are not completely absolute, leading to occasional hybridization.

Bumblebees Pollinate M