Pacific Chorus Frog (Pseudacris regilla)
The Pacific Chorus Frog (Pseudacris regilla), also called the Pacific Tree Frog, is an abundant resident of the Richmond Field Station, breeding in poonded areas of seasonal wet meadows. It is the only known frog species at the RFS and one of the two speicies of the Class Amphibia Order Anura (frogs and toads) along with the Western toad (Bufo boreas) a probable but not verified resident of the RFS (Reference Gutstein, Joyce 1989).
Is it a chorus frog or tree frog? The Pseudacris regilla has commonly been called a "tree frog" and a "chorus frog". It turns out there is a difference between the two common names from a scientific phylogenic perspective. However, recently accumulated evidence has resulted in this species being confirmed to be in the chorus frog genus. This is well explained on Michael F. Benard's excellent website, Natural History of the Pacific Chorus Frog Psuedacris regilla at http://www.mister-toad.com/PacificTreeFrog.html#Names(link is external)(link is external):
A note about names: Chorus frog or Tree frog
You may see these frogs referred to as either "Pacific Chorus Frogs" or "Pacific Treefrogs". The appearance of these two names hints at the debate among biologists about the relationship of Pacific Chorus Frogs to other North American frogs. The key question of the debate was whether Pacific Chorus frogs are members of the tree frog group (genus Hyla) or members of the chorus frog group (genus Pseudacris). Members of the genus Hyla include species like the gray treefrog (Hyla versicolor)(link is external)(link is external) and the green treefrog (Hyla cinerea)(link is external)(link is external), whereas members of the genus Pseudacris include species like the spring peeper (Pseudacris crucifer)(link is external)(link is external) and the western chorus frog (Pseudacris triseriata)(link is external)(link is external).
When pacific chorus frogs were first described by Baird and Girard in 1852(link is external)(link is external), they were placed in Hyla. The genus Pseudacris had been described nine years earlier, by Fitzinger in 1843(link is external)(link is external). Through the following decades, the pacific chorus frog continued to be considered a tree frog (Hyla), as shown in Cope's 1889 The Batrachia of North America(link is external)(link is external), and in Stejneger and Barbour's 1917 A Check List of North American Amphibians and Reptiles(link is external)(link is external). Over time, biologists began to note characteristics in which pacific chorus frogs were more similar to Pseudacris than Hyla. A neat example of this comes from Wright & Wright's 1933 Handbook of Frogs and Toads(link is external)(link is external) in which they state "This species reminds the authors of species of Pseudacris." Hedges (1986 Systematic Zoology(link is external)(link is external)) has a nice summary of some of these traits. For example, characteristics of Pseudacrisinclude (1) round testes with a dark membrane, (2) small toepads, and (3) breeding occurring during cold weather (i.e., in winter or early spring). In contrast, Hyla have (1) elogate pale-colored testes, (2) large toepads, and (3) breeding occurring during warm weather (i.e., late spring or summer). Pacific chorus frogs have dark testes and are cold-weather breeders, and their toepads are intermediate in size between other Pseudacrisand Hyla.
Even with the identification of some traits that linked pacific chorus frogs with the genus Pseudacris, it took time for enough evidence to accumulate to convincingly determine the affinity of pacific chorus frogs. The accumulating evidence included morphology, allozymes, nuclear sequence data and others (e.g., Hedges 1986 Systematic Zoology(link is external)(link is external), Cocroft 1994 Herpetologica(link is external)(link is external), Moriarty & Cannatella 2004 MPE(link is external)(link is external), Pyron & Wiens 2011 MPE(link is external)(link is external)). All of these data now convincingly show that Pacific Chorus frogs belong in the genus Pseudacris rather than the genus Hyla. Thus, it is appropriate to refer to them as "pacific chorus frogs" instead of "pacific tree frogs."
