Coleman 2009

Coleman, A.W. 2009. Is there a molecular key to the level of "biological species" in eukaryotes? A DNA guide. Molecular Phylogenetics and Evolution. 50(1): 197-203.

This paper focuses on the second Internal Transcribed Spacer of the nuclear ribosomal gene cistron (ITS2).

Objectives:

1) to explore information content of ITS2 region (concentration is on characteristics that accompany seperation of clades into two or more sexually isolated subclades)

2) to evaluate predictive powers of ITS2 for discriminating interbreeders

3) to derive a simplified sequence-based technique for its application to evaluate biological species

-where multiple taxonomic species/genera are capable of gamete interaction, their ITS2 sequences are extremely similar
-where one species encompasses more than one interbreeding group, their ITS2 sequences contain considerable variation
-as ITS2 differences between potential mates increase, sexual compatibility and zygote productivity decrease
-organisms that differ by even one compensatory base change in the ITS2 region are completely unable to cross. There has been no exception yet to this rule. However, this paper does not use a whole lot of animal examples in their table so there could be many exceptions. Who knows.