WHAT IS A SPECIES, AND WHAT IS NOT

I analyze a number of widespread misconceptions concerning species. Th e species category, defined by a concept, denotes the rank of a specie s taxon in the Linnaean hierarchy. Biological species are reproducing isolated from each other, which protects the integrity of their genoty pes. Degree of morphological difference is not an appropriate species definition. Unequal rates of evolution of different characters and lac k of information on the mating potential of isolated populations are t he major difficulties in the demarcation of species taxa.