Comments: Recuero et al. (2006) examined patterns of mtDNA variation (including new samples and additional samples presented by Ripplinger and Wagner 2004) and reviewed available allozyme data for Pseudacris regilla (sensu lato). They concluded that P. regilla should be partitioned into three species, P. regilla, P. sierra, and P. hypochondriaca (the original proposal included different names based on taxonomic errors that were subsequently corrected). The authors did not provide detailed maps or descriptions of the ranges of the three proposed species and did not describe the contact zones between P. sierra and the other two species.

This species formerly was included in the genus Hyla; it was transferred to the genus Pseudacris by Hedges (1986), based on allozyme data (see also Highton 1991). Cocroft (1994) analyzed morphological and biochemical data and concluded that the Hyla regilla-Hyla cadaverina clade does not arise within the clade containing Pseudacris (traditional sense), P. ocularis, and P. crucifer; he suggested that the most conservation approach may be to leave regilla and cadaverina in the genus Hyla until their relationships are more clearly resolved. da Silva (1997) recommended that for now Hedges' (1986) definition of Pseudacris should be maintained.

Highton (2000) reviewed available allozyme data from Case et al. (1975) and concluded that P. regilla likely encompasses more than one species but that further range-wide study is needed to clarify the situation.

A molecular phylogeny of Pseudacris based on mtDNA data (Moriarty and Cannatella 2004) revealed four strongly supported clades within Pseudacris: (1) A West Coast Clade containing regilla and cadaverina, (2) a Fat Frog Clade including ornata, streckeri, and illinoensis, (3) a Crucifer Clade consisting of crucifer and ocularis, and (4) a Trilling Frog Clade containing all other Pseudacris. Within the Trilling Frog Clade, brimleyi and brachyphona form the sister group to the Nigrita Clade: nigrita, feriarum, triseriata, kalmi, clarkii, and maculata. The Nigrita Clade shows geographic division into three clades: (1) populations of maculata and triseriata west of the Mississippi River and Canadian populations, (2) southeastern United States populations of feriarum and nigrita, and (3) northeastern United States populations of feriarum, kalmi, and triseriata. Current taxonomy does not reflect the phylogenetic relationships among populations of the Nigrita Clade (Moriarty and Canatella 2004). For example, the molecular data appear to indicate that triseriata, maculata, and clarkii in the western United States are conspecific, but the authors indicated that further sampling and analysis of the Trilling Frog Clade are needed before their relationships can be determined and an appropriate taxonomy established. Moriarty and Cannatella (2004) found that subspecific epithets for crucifer (crucifer and bartramiana) and nigrita (nigrita and verrucosa) are uninformative, and they therefore discouraged recognition of these subspecies. They concluded that further study is needed to determine if illinoensis warrants status as a distinct species. Molecular data were consistent with retention of regilla, cadaverina, ocularis, and crucifer in the genus Pseudacris.