Catharus arcanus, Halley & Catanach & Klicka & Weckstein, 2023

Halley, Maưhew R., Catanach, Therese A., Klicka, John & Weckstein, Jason D., 2023, Integrative taxonomy reveals hidden diversity in the Catharus fuscater (Passeriformes: Turdidae) complex in Central and South America, Zoological Journal of the Linnean Society 199 (1), pp. 228-262 : 245-247

Catharus arcanus sp.nov.

Darién nightingale-thrush

( Figs 13 , 14 ; formerly Undescribed 1)

urn:lsid:zoobank.org:act:25B3DB71-FE5E-4FBF-A2CE-8D270CBA7250 .

Catharus fuscater Meyer de Schauensee 1964: 317 (in part).

Catharus fuscater fuscater Wetmore et al. 1984: 157 ; Ridgley and Gwynne 1989: 352; Clement 2000: 299 (in part); Collar 2005: 700 (in part); Renjifo et al. 2017.

Catharus fuscater hellmayri Clement 2000: 299 (in part).

Catharus fuscater mirabilis Clement 2000: 299 (in part).

Catharus fuscater subsp.? Phillips 1991: 112.

‘Unnamed-1’ Halley 2021: 132.

Type material

Monotypic species. FMNH 470769 (holotype), study skin, adult male, collected by J. Klicka (preparator), G.M. Spellman, and J.M. DaCosta on Cerro Chucantí, 17 km south-west of Chimán, Panamá province, Panama (8.7958°, –78.4630°, elev. 1200 m), on 16 February 2006 .

Geographic range

Serranía de Majé, Panama, and along the Serranía del Darién from Cerro Azul in the west, to Cerro Tacarcuna in the east (Wetmore et al. 1984, Cuervo 2013, Renjifo et al. 2017).

Adult specimens examined

Catharus arcanus sp. nov. (N = 25): Panama: Panamá (one male, one female): Cerro Chucantí: FMNH 470769 (male) ; NW slope of Cerro Jefe : LSUMZ 164300 (female) ; Darién (14 males, nine females): unspecified locality on Cerro Tacarcuna, eastern slope: AMNH 136159–136165 (males) , AMNH 136166 (female) ; unspecified locality on Cerro Tacarcuna , slope unknown: AMNH 136171 , 811713 , LSUMZ 80201 (males) , AMNH 136167– 136170 , AMNH 811714 (females) ; La Laguna Camp on Cerro Tacarcuna : USNM 469735 (male) , USNM 486474 (female) ; unspecified locality on Cerro Malí : USNM 484791 , USNM 484792 (males), USNM 484793 (female); unspecified locality on ridge west of Cerro Malí: USNM 486473 (male).

246 • Halley et al.

Immature specimens examined

Catharus arcanus sp. nov. (N = 1): Panama: Darién (one male): La Laguna Camp, Cerro Tacarcuna: USNM 486475 (male) .

Audio recordings examined

Catharus arcanus sp. nov. (N = 6): Panama: Darién: Cerro Chucantí : ML 137736401 , XC 2976–2979, 164780 .

Diagnosis

Genetics: In both phylogenetic reconstructions, samples of C. arcanus sp. nov. formed a clade that was sister to C. [f.] mirabilis of Cerro Pirre (mean uncorrected p -distance = 0.04 ± <0.01). In the UCE tree, these taxa were reciprocally monophyletic and formed a clade that was sister to all South American taxa. ABGD and ASAP analyses both identified C. arcanus sp. nov. and C. [f.] mirabilis as independent genetic clusters. The estimated divergence time between C. arcanus sp. nov. and C. [f.] mirabilis was 1.3 Mya (95% HPD = 0.9–1.7).

Morphology: Adult study skins of C. arcanus sp. nov. are paler on the dorsal surface than similarly-aged skins of C. hellmayri and C. [f.] mirabilis , in both sexes ( Fig. 13 ). Unlike adult females of C. [f.] mirabilis , which had darker crowns than mantles, there was no contrast between the pale crown and mantle of the C. arcanus sp. nov. adult female (LSUMZ 164300), which had an enlarged ovary (11 × 5 mm), 100% pneumatized skull, and no bursa. Ventrally, study skins of C. arcanus sp. nov. and C. [f.] mirabilis were paler than C. hellmayri ( Fig. 13 ). Like C. [f.] mirabilis (and to a lesser extent C. hellmayri , see: Ridgley and Gwynne 1989), C. arcanus sp. nov. has a yellowish wash on the ventral surface in life, that renders the breast ‘olive’ and abdomen ‘pale yellow’ (fide E. Eisenmann, on the label of AMNH 811714). Similar notes were written on the labels of LSUMZ 80201 (‘Yellowish olive instead of grey underneath in fresh specimens’) and AMNH 811713 (‘olive yellowish instead of grey underneath’). This character distinguishes these three taxa from all South American populations, but the yellow wash fades quickly after death. After a few years, museum skins of C. arcanus sp. nov. have no trace of yellow in the ventral plumage and the ‘olive’ fades to cooler than Light Drab (119C). To our knowledge, no fresh (<5 years old) material of C. arcanus sp. nov. or C. [f.] mirabilis exists in any collection.

Voice: Catharus arcanus sp. nov. is distinguished from the South American taxa by its Type 1 punctuation call structure ( Fig. 9 ), and from C. [f.] mirabilis by its ‘tightly spaced’ contact call structure ( Fig. 10 ). Our dataset lacked recordings of blurred calls from C. arcanus sp. nov., and too few recordings were available to adequately determine whether C. arcanus sp. nov. and C. [f.] mirabilis are divergent in song. Notwithstanding, the only triadic song contour (BCA) detected in C. arcanus sp. nov., which accounted for 43% of songs (N = 3/7), was not detected in C. [f.] mirabilis . Of the three tetradic contours detected in C. arcanus sp. nov. (CABD, CDAB, DBAC), only one (CDAB) was detected in C. [f.] mirabilis ( Fig. 12 ).

Description of the holotype

FMNH 470769 weighed 37.9 g before it was prepared. The testes were slightly enlarged (2 × 1 mm) and the skull was completely pneumatized. In 2022, the entire dorsal surface of FMNH 470769 was darker than Sepia (119), with the crown being slightly darker than the back and rump. The undertail coverts were Light Drab (119C) and the flanks were darker and cooler than Vandyke Brown (121). The breast and throat were darker than Light Drab (119C). A fine black line connected the malar regions across the throat.

Etymology

The scientific name is derived from masculine Latin adjective arcanus (mysterious, secret), referring to the retiring nature of the species. The proposed English name references the Serranía del Darién, which encompasses most of its geographic range.

Comments

The sister-species C. arcanus sp. nov. and C. [f.] mirabilis are separated by only 125 km on the Isthmus of Panama and there is no major water barrier between them. The palynological record in lowland Panama, from the Last Glacial Maximum (LGM), includes elements of the montane flora that now occur> 1000 m higher in elevation ( Bush and Colinvaux 1990). Given these facts, and the age of the divergence, it seems likely that these mountain-bound species had opportunities for secondary contact in the Darién lowlands during the LGM, and have already passed historical ‘tests’ of sympatry.

Figures

Figure 9. Taxonomic variation in the structure of ‘punctuation calls’, visualized in RavenPro 1.5 (Cornell University). We recognize three groups based on shared acoustic structure: (Type 1) pulsed/rippling:C. [f.] hellmayri, Undescribed 1, C. [f.] mirabilis; (Type 2) long/sinuous: C. [f.] sanctaemartae, C. [f.] fuscater, C. [f.] berplepschi; (Type 3) short/simple: Undescribed 2, C. [f.] opertaneus, Undescribed 3, C. [f.] mentalis.

Figure 10. Taxonomic variation in the structure of ‘contact calls’, visualized in RavenPro 1.5 (Cornell University). No recording of contact calls in C. [f.] mentalis was available.

Figure 12. Heat map showing frequency distributions of song contours within each population. Dyadic, triadic, and tetradic song contour names follow Fig.5. Single-note songs are shown in the first column (A) and songs with five or six notes were combined into a single category, shown in the last column (FIVESIX). Open (white) circles denote song contours that were not detected in C. [f.] hellmayri, despite it having a much larger sample size than other taxa. Closed (black) circles denote contours that were only detected in one taxon.

Figure 13. Dorsal and ventral views of the adult plumages in C. hellmayri, C. arcanus sp. nov., C. mirabilis, and C. f.sanctaemartae. Photograph by M.R.H.

Figure 14. Side view of the adult plumages in C. arcanus sp. nov.. Photograph by M.R.H.