Sentence:  If factors that contribute to a tree-like pattern of the variance–covariance matrix dominate the evolutionary picture over those that tend to destroy it, one can expect <WSD>treeness</WSD> to be reasonably high. Only if this is true, reconstruction of the evolutionary process by tree analysis and a tree representation for descriptive purposes can be useful. 
Meaning of the word marked with <WSD> tags:  The suitability of an evolutionary tree for representing the structure of a population; the degree to which a population structure can be accurately described as a tree of descent, with different branches evolving independently after they split.