Conservation implications of a morphometric comparison between the Illinois Chorus Frog (Pseudacris streckeri illinoensis) and Strecker’s Chorus Frog (P. s. streckeri) (Anura: Hylidae) from Arkansas, Illinois, Missouri, Oklahoma, and Texas

Abstract

Much uncertainty exists regarding the taxonomic status of the Illinois Chorus Frog (Pseudacris streckeri illinoensis Smith; ICF) relative to Strecker’s Chorus Frog (P. s. streckeri, Wright & Wright; SCF) of the southcentral United States (US). Molecular analyses have been inconsistent in providing taxonomic insight, and no formal morphological comparisons have been previously performed. Each taxon possesses a wide range of background colors. We undertook morphometric analyses to help clarify their taxonomic relationship. Tibia length and mass were compared for live Arkansas (AR) specimens and snout-vent, head and tibia lengths were measured from preserved vouchered specimens. Tibia length and mass were significantly greater for living ICFs versus SCFs in AR. Among preserved specimens, tibia, snoutvent and head lengths were significantly greatly for AR ICFs relative to most intraspecific groups, and Texas (TX) SCFs were significantly smaller than most other groups. Principal components analysis was largely consistent with univariate analyses, although Missouri (MO) ICFs also partitioned distinctly from other sample groups. These data provide morphological evidence of geographic (clinal) variation within a species, but do not provide support for the taxonomic elevation of the ICF to species status. Our data do provide evidence of distinct population segments of P. streckeri. As ICF habitat suitable for reproduction has dramatically declined in Arkansas as have population numbers, we recommend the listing of AR ICFs as a distinct population segment under the Endangered Species Act.