In some large groups of plants, including dandelions, oaks, and willows, the biological species concept is complicated because the process of _____ allows gene flow to occur between _____ that can be easily distinguished based on appearance.a. hybridization; ecological species
b. polyploidy; evolutionary species
c. allopatric speciation; ring species
d. polyploidy; ring species
e. hybridization; morphospecies