Comparative call characteristics in the anuran subgenus Nenirana
It is important that species descriptions be accurate. This is especially true with threatened and endangered species, where the scientific literature provides context for species identification and management decisions. In 1953, Bragg documented the advertisement calls of both Southern Crawfish Frogs (Lithobates a. areolatus) and Northern Crawfish Frogs (L. a. circulosus) and concluded L. a. areolatus have lower frequency calls. One of us (M.J.L.) has long felt this observation was incorrect, because adult L. a. areolatus are smaller than L. a. circulosus, and anurans with smaller body sizes tend to produce higher, not lower, frequency calls. Bragg’s observations are not only the sole comparative assessment of advertisement call characteristics of L. areolatus in the primary literature, but also represent the only assessment of the advertisement calls of any of the four species comprising the subgenus Nenirana, which consists of threatened and endangered Gopher Frogs (L. capito and L. sevosus) and Pickerel Frogs (L. palustris). Given this dearth of information, the reliability of this information, and the conservation concerns surrounding this group, we felt it was necessary to reassess the advertisement calls of Crawfish Frogs and give them context by describing the calls of the Nenirana species L. capito and L. palustris. Our data revise Bragg’s conclusions, but just as importantly, we show that the call characteristics of L. capito and L. palustris are similar by having long calls with long interpulse intervals, while both subspecies of L. areolatus have shorter calls with less interpulse separation. These results do not align with morphological and phylogenetic clustering within the Nenirana, but are consistent with call character displacement within this group. Additional data will be necessary to test this inference.
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