Cladistically

Hybridization, interbreeding

Due to hybridization, it can be difficult to delineate the two last common ancestors of a given species. Many species are capable of interbreeding for millions of years, during which many branches may have radiated and bred with species from earlier branches of the same grouping. The process of true cladistic bifurcation can thus take extended effort as branchings become more complex. In practice, for recent radiations, cladistically guided findings only give a coarse impression of the complexity. A more detailed account will give details about fractions of introgressions between groupings, and even geographic variations thereof. This has been used as an argument for the use of paraphyletic groupings.