Meaning of "subspecifically" in the English dictionary

In biological classification, subspecies is either a taxonomic rank subordinate to species, or a taxonomic unit in that rank. A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one. Under the International Code of Zoological Nomenclature, the subspecies is the only taxonomic rank below that of species that can receive a name. Under the International Code of Nomenclature for algae, fungi, and plants, other infraspecific ranks such as variety may be named. In bacteriology, there are recommendations but not strict requirements for recognizing other important infraspecific ranks. A taxonomist decides whether to recognize subspecies or not. A common way to decide is that organisms belonging to different subspecies of the same species are capable of interbreeding and producing fertile offspring, but they do not interbreed in nature due to geographic isolation or other factors. The differences between subspecies are usually less distinct than the differences between species.