variability in such a “complex” may be due to
polymorphisms among different
individuals of the
same species which are
and whose members exhibit high, but not complete, specificity.
Otherwise a complex may be due to the presence of multiple
morphologically similar) species living together
in the same habitat.
The classification of a "complex" species remains problematic.
There are in fact two tendency about how to classify
species : by their differences or by their similarities
depending on personal approach of taxonomists to
recognizing differences or commonalities between
Lumpers & splitters)