Other members of this lineage including the common or clouded sulphur (C. philodice) and C. eriphyle and C. vitabunda, which are often included in C. philodice as subspecies. Hybridization runs rampant between these, making phylogenetic analyses exclusively utilizing one type of data (especially mtDNA sequences) unreliable. Therefore, little more can be said about its relationships, except that it is perhaps closer to C. (p.) eriphyle than generally assumed, strengthening the view that the latter should be considered a valid species.Wheat, Christopher W. & Watt, Ward B. (2008). A mitochondrial-DNA-based phylogeny for some evolutionary-genetic model species of Colias butterflies (Lepidoptera, Pieridae). Mol. Phylogenet. Evol. 47(3):893-902. doi:10.1016/j.ympev.2008.03.013 (HTML abstract, supplement available to subscribers)
