Some examples of dimorphic variation in animals

The top row shows variation in a zooplankton, Daphnia: the morph on the right is produced in the presence of a predator cue. The second row shows an example of dimorphic variation in horn length, which occurs in many species of scarab beetles: the morph on the right (the "minor" male) cannot compete with the "major" male and attempts to sneak copulations. Dimorphic variation in wings in thrips is illustrated on the third row: the winged form on the right can disperse and found new populations, but is less successful in fights with the wingless form, which has larger forelegs. Paeomorphic variation in salamanders frequently occurs as illustrated on the bottom row: the paedomorphic form retains larval characteristics and cannot disperse among ponds, but has a higher fecundity than the "typical" terrestrial morph.