Pseudacris collinsorum, Ospina & Tieu & Apodaca & Lemmon, 2020

Ospina, Oscar E., Tieu, Lynee, Apodaca, Joseph J. & Lemmon, Emily Moriarty, 2020, Hidden Diversity in the Mountain Chorus Frog (Pseudacris brachyphona) and the Diagnosis of a New Species of Chorus Frog in the Southeastern United States, Copeia 108 (4), pp. 778-795 : 12-15

Pseudacris collinsorum , new species urn:lsid:zoobank.org:act:E063C1D5-54CD-4D17-987B-6552CE3BDE50

Collinses’ Mountain Chorus Frog

Figures 10–12

Holotype.— UF 190162 (field number: ECM7533; Fig. 10 ), adult male, USA, Alabama, Hale County, side of County Road 49 near intersection with State Road 25, 32.909028N, 87.443128W, Emily Moriarty Lemmon , 3 March 2011.

Paratypes.— UF 190163–190171 (field numbers: ECM7534– ECM7542), collected on the same date as the holotype; UAHC 15645 (field number: JA-06-01), collected on January 2006. All paratypes collected from two sites at the holotype’s locality separated by ~ 300 m.

Diagnosis.— Advertisement call of P. collinsorum shows a faster pulse rate (mean ¼ 88.5 pulses/s) and higher peak dominant frequency (mean ¼ 2,716.3 Hz) than its sister species P. brachyphona (mean ¼ 84.2 pulses/s and mean ¼ 2,456.3 Hz, respectively; Fig. 9 ). Both species ranges are mostly defined by Appalachian Mountains; however, P. collinsorum is separated from P. brachyphona by the Tennessee River and the southern portion of the Blue Ridge Mountains. The geographic separation is supported by genetic data showing P. collinsorum as a divergent lineage with respect to P. brachyphona ( Figs. 2–4 ). Anecdotal evidence suggests that external color pattern is more variable in P. collinsorum compared to P. brachyphona ; the former species may possess the ‘‘inverted parentheses’’ dorsal stripe pattern commonly seen in P. brachyphona , but it frequently exhibits broken stripes or even lacks dorsal pattern altogether (EML, pers. obs.; Figs. 10 , 11 ).

Description of holotype.— Adult male, SVL ¼ 23.54 mm; snout is rounded in dorsal and ventral views with HL ¼ 8.08 mm and HW ¼ 9.15 mm. Eye to nostril distances (SL ¼ 2.84) form an almost equilateral triangle with separation between eyes. Eye width and tympanum diameter are 2.79 and 2.01 mm, respectively. Forelimbs and hindlimbs are thin, but the latter are long with FL ¼ 12.26 mm and TL ¼ 14.07 mm. Hindlimb fingers are slender, and feet are long with FoL ¼ 12.07 mm. Ventral coloration is light, with darker pigmentation under the vocal sac area. Pigmentation is also visible under feet and hands. The preserved specimen shows a uniform gray background coloration, with brown transverse stripes on the hindlimbs. Smaller, discontinuous bands are present on the forelimbs. Brown spots create patches along the canthus rostralis. Spots also create lines between the eyes and posteriorly creating a ‘‘T’’ shape. Two broad, spotted, and irregular stripes merge anteriorly and run separate posteriorly resembling an inverted ‘‘U.’’ A solid brown band runs from each tympanum towards the snout where they merge.

Distribution and ecology.— Pseudacris collinsorum inhabits the southernmost portion of the Appalachian Mountains on the Piedmont, Ridge and Valley, Plateau regions, and adjacent northern Coastal Plain. The species does not occur further north than the southern portion of the Blue Ridge Mountains and the Tennessee River. The distribution of P. collinsorum includes the northern half of the state of Alabama, south to the Tennessee River, northeast corner of Mississippi, northwest Georgia, and southwestern corner of North Carolina. Compared to P. brachyphona , this species inhabits lower elevations with species distribution models indicating the highest suitability as low as 100 masl. According to the SDMs, P. collinsorum is associated with habitats such as those in the Southern Piedmont dry pine forest, East Gulf dry upland hardwood forest, and southern Ridge and Valley/Cumberland dry calcareous forest (Supplemental Table 5; see Data Accessibility). These habitats contain dry to dry-mesic forests primarily dominated by pine and oak species. Pseudacris collinsorum is associated with areas where precipitation during the driest season is relatively high (~ 260–500 mm), which probably allows for their survival in predominantly drier habitats. Suitable habitat for P. brachyphona is generally richer in tree diversity and deciduous species are common ( Quercus , Carya , and Acer spp. ). Those forests are more mesic than in the habitat of P. collinsorum and fall into the South-Central Interior mesophytic, Eastern cool temperate ruderal, and Northern-Central hardwood and conifer forest types (Supplemental Table 5; see Data Accessibility). Compared to P. brachyphona , temperatures in suitable habitats for P. collinsorum are warmer during the driest season ( P. collinsorum : 20–238C vs. P. brachyphona : ~ 08C), but colder during the wettest season ( P. collinsorum : 0–108C vs. P. brachyphona : 18–218C).

Advertisement call.— Male Pseudacris collinsorum produce a fast PR call compared to other members of the trilling frog clade within Pseudacris ( Fig. 12 ; Lemmon, 2007; Banker et al., 2020). The PR of this species (mean ¼ 88.5 pulses/s) exceeds that of its sister taxon, P. brachyphona (mean ¼ 84.2 pulses/s). Pseudacris collinsorum also have a higher-pitched call (DFP, mean ¼ 2,716 Hz), than P. brachyphona (mean ¼ 2,456 Hz).

Etymology.— The species is named after husband–wife team Joseph T. and Suzanne L. Collins. Joseph Collins (1939–2012) was a renowned American herpetologist, author of wildlife books, and editor at the Museum of Natural History at the University of Kansas, who made major contributions to the study of U.S. amphibians and reptiles for more than 40 years. Collins was also co-founder of three herpetological organizations (Society for the Study of Amphibians and Reptiles, Center for North American Herpetology, and the Kansas Herpetological Society). Suzanne Collins is a professional wildlife photographer specializing in reptiles and amphibians, who has contributed thousands of photographs to dozens of print and online publications. The decision to name the new species after the Collinses was made after Joseph Collins’ demise in January 2012. Prior to his death, Joe contributed substantially to this paper by making intellectual contributions and coordinating the acquisition of tissue samples and specimens.

Figures

FIG. 10. Dorsal and lateral views of type specimens of P. collinsorum (A– D) and P. brachyphona (E–H). (A–B) Male P. collinsorum from Hale County, Alabama (UF 190162). (C–D) Male P. collinsorum from Hale County, Alabama (UF 190167). (E–F) Female P. brachyphona from Preston County, West Virginia (NCSM 100109). (G–H) Male P. brachyphona from Preston County, West Virginia (NCSM 100110). Black bars equal to 1 cm. For a color version of this figure, please refer to the online version of this article.

FIG. 11. Live specimens of P. collinsorum (left, photo by EML) from Lawrence County, Alabama and P. brachyphona (right, photo by Suzanne Collins) from Harrison County, West Virginia. Specimens of P. collinsorum often lack a distinct dorsal coloration pattern. For a color version of this figure, please refer to the online version of this article.

FIG. 12. Oscillograms (first and second columns), spectrograms (third column), and power spectra (fourth column) of advertisement calls from (A) P. collinsorum (recorded at 10.28C) and (B) P. brachyphona (recorded at 12.68C). The second columns represent a single call extracted from those in the first column. In the case of P. collinsorum (A), two males were recorded while duetting and are identified with numbers.

FIG. 9. Differences in pulse rate (PR), number (PN), and dominant frequency peak (DFP) in acoustic signals recorded in P. brachyphona from Tennessee (TN) and Alabama (AL). Locality-specific distributions of PR, PN, and DFP (A–C). The thick bar in these boxplots represents mean value. Lower and upper edges of each box are 25th and 75th quantile, respectively, and lower and upper whiskers represent the minimum and maximum limits of the interquartile range. Outliers are represented as hollow points. Randomization tests (1,000 reps) were performed for each of these variables (D–E), yielding significant differences for PR and DFP between Tennessee and Alabama, but not for PN.

FIG. 2. Species tree for P. brachyphona as estimated in ASTRAL. Numbers on the branches are local posterior probabilities/boostrap support values from RAxML (A). The identifiers are field numbers, followed by the ‘‘I’’ number (DNA sample identifier, see Table 1). State abbreviation and county where the sample was collected are also shown. The tree shows two well-supported clades, corresponding to P. brachyphona from the Northern and Southern distribution ranges, respectively. Pseudacris brimleyi and P. feriarum were included as outgroups. Branch lengths (B) are shown in the inset tree generated with RAxML.

FIG. 3. Genetic clustering based on 21,702 SNPs from AHE loci for P. brachyphona. (A) The Structure plot shows two genetic clusters: Northern (n ¼ 17, green) and Southern (n ¼ 16, blue) as observed in the map (B). The pie charts correspond to the proportion of admixture as estimated in Structure. A blue arrow marks the samples from Hale County, Alabama. Two individuals assigned to the Northern cluster showed introgression from P. feriarum (‘‘out,’’ gray). (C) The discriminant analysis of principal components (DAPC) required one discriminant function to explain 67.4% of the genetic variance. Lines at the bottom of the distributions represent one individual. The DAPC also shows two clusters in agreement with the Northern and Southern clusters from Structure. The location of the Tennessee River is shown.

FIG. 4. Matrix correlation between pairwise genetic (Nei’s) and geographic distances among individuals of P. brachyphona, after exclusion of hybrid individuals. (A) Mantel correlation test for all P. brachyphona showed significant correlation (r). The two clusters of points represent comparisons within and between genetic clusters (Northern and Southern). (B) Significant correlations were also observed for each cluster separately (Northern ¼ black, Southern ¼ gray).