during the past 3 - 4 million years
||Butterfly Limenitis spp.
||Frentiu FD, Briscoe AD. A butterfly eye's view of birds. Bioessays. 2008 Nov30(11-12):1151-62. doi: 10.1002/bies.20828 p.1154 right columnPubMed ID18937365
|| Mullen SP. Wing pattern evolution and the origins of mimicry among North American admiral butterflies (Nymphalidae: Limenitis). Mol Phylogenet Evol. 2006 Jun39(3):747-58 DOI: 10.1016/j.ympev.2006.01.021PubMed ID16500119
||Primary source abstract: "Here [investigator] present[s] a robust species-level phylogeny of Limenitis based on 1911 bp of two mitochondrial genes (COI and COII) and 904 bp of EF1-alpha for all five of the Nearctic species/wing pattern races, the majority of the Palearctic species, and three outgroup genera: Athyma, Moduza (Limenitidini), and Neptis (Limenitidinae: Neptini). Maximum-likelihood and Bayesian analyses indicate that the North American species are a well-supported, monophyletic lineage that is most closely related to the widespread, Palearctic, Poplar admiral (L. populi)."
||P.1154 right column: "A particularly striking example of how positive selection may generate spectral diversity among closely related species comes from the butterfly genus Limenitis, members of which have radiated across the North American continent from a European ancestor during the past 3–4 million years (primary source)."