Chiroderma scopaeum Handley, 1966

Garbino, Guilherme S. T., Lim, Burton K. & Tavares, Valéria Da C., 2020, Systematics of big-eyed bats, genus Chiroderma Peters, 1860 (Chiroptera: Phyllostomidae), Zootaxa 4846 (1), pp. 1-93 : 29-31

Chiroderma scopaeum Handley, 1966

Synonyms:

Chiroderma [sp.]: Anderson, 1960: 7.

Chiroderma salvini scopaeum Handley, 1966a:297 ; type locality “ Pueblo Juárez , Colima, México.”

Type Material. The type of C. salvini scopaeum , by original designation, is specimen USNM 338711 , an adult female collected by Alfred L. Gardner (field number ALG 1565) in Pueblo Juaréz , Mexican state of Colima, on August 19, 1960. The specimen was previously stored in the University of Arizona collection, under the number 7952. The material consists of a stuffed skin with skull and mandible separated. The skin is in good condition, and both pairs of facial stripes are visible. The median dorsal stripe is also visible and located immediately posterior to the nape and extending to the posterior extremity of the animal. The auditory bullae have separated from the skull and upper inner incisors are missing. The posterior palatine process is absent.

Distribution and Habitat. We consider C. scopaeum to be restricted to México, west of the isthmus of Tehuantepec ( Fig. 11 ). The species has been recorded in the states of Chihuahua, Sinaloa, Durango, Nayarit, Jalisco, Colima, México, Morelos, Guerrero, Puebla, Veracruz, and Oaxaca ( Anderson 1960; Handley 1966a; Crossin et al. 1973; Alvarez & Alvarez-Castañeda 1996; Valiente-Banuet et al. 1997). Hall (1981) suggests that C. scopaeum would occur from western México to northwestern Costa Rica, and based on this distribution Reid & Langtimm (1993) identified specimen USNM 565812 as C. salvini scopaeum . The morphological characters of the specimen, however, have allowed us to identify it as C. salvini .

Records of C. scopaeum are from areas dominated by tropical and subtropical coniferous forests, dry deciduous forests at higher elevations, and shrubby vegetation at lower elevations. Studies suggest that in the arid areas of western México, the species would be restricted to the more humid areas close to the Pacific coast and adjacent montane forests, and along the riparian forests in the canyons that cut through the Sierra Madre Occidental ( Anderson 1960, 1972; Crossin et al. 1973; García-Mendoza & López-González 2013). All analyzed specimens were collected within the altitudinal range of the species as reported by Handley (1966a), from sea level to 1,722 m.

Description and Comparisons. Dorsal pelage varies from pale brown to dark brown. Most of the 38 specimens examined had pale brown pelage (84.2%, n=32), whereas dark brown pelage was found in 15.8% (n=6). Individually, dorsal hairs are tricolored, with a dark brown base, buff middle band, and light to dark brown tips. The medial dorsal stripe was present in all specimens (n=34), but was weakly developed in 5.8% of the sample (n=2). Usually, the dorsal stripe extends from the interscapular region to the posterior extremity of the body, but in 10 specimens the stripe originated in the region immediately posterior to the nape. Both pairs of facial stripes are bright and wide (interocular stripe> 1.7 mm). The tragus and base of the ears are yellowish, as are the anterior and posterior margins of the ears close to the base. The remainder of the ear is brown. The spear of the noseleaf has a simple tip and is brown, except for the lateral margins of the horseshoe, which are whitish.

The dimensions of the skull of C. scopaeum are similar to those of C. villosum , and there is also some overlap between the large C. scopaeum and the small C. doriae vizottoi and C. salvini ( Tables 7 and 8). In dorsal view, the brain case is round and less massive than in C. salvini . Approximately ⅓ of the length of the nasal notch extends behind the anterior margin of the orbits. The post-orbital constriction is relatively wide ( Table 7); post-orbital processes are small and pointed. A sagittal crest was unambiguously present in 32 of the 38 specimens (84.2%), but not detected in 2 (5.2%), or ambiguous in 4 (10.5%). The posterior palatine process was absent in 32 of the 38 analyzed specimens (83.8%), but small or vestigial in the remaining 6 (16.2%).

Out of 35 specimens, 30 (85.7%) had convergent I1s, with the tips touching each other; whereas, 5 had both incisors separated along their entire length. The P3 is approximately oval in occlusal outline and is not in contact with P4. The M2 has well defined main cusps, but lacks a posterolingual cingulum. The lower canine has a relatively low crown, below the level of the coronoid process in lateral view. The anterior cingulum of the lower canine projects rostro-medially and is visible in lateral view ( Fig. 17 ). The p2 is small, approximately ¼ of the height of p4; and is longer than tall and does not touch p4.

Compared with C. salvini , C. scopaeum can be distinguished by its smaller size, usually paler dorsal pelage (varying from pale brown to dark brown). C. scopaeum has a relatively broader post-orbital constriction ( Fig. 12 ), and rostro-medially projected cingula of lower canines ( Fig. 17 ).

From C. villosum , C. scopaeum can be differentiated by its bicolored noseleaf and spear having a simple tip; paler ear margins; shorter nasal notch (in villosum the notch reaches the post-orbital processes); shorter orbits (in villosum the anterior margin is in line with the middle of P4); I1s with convergent tips (usually parallel in villosum ); relatively short lower canine (in villosum the tip of the lower canine is at approximately the same level as the coronoid process); and absence of a frontal gap when cranium and mandible are in occlusion (in villosum there is a frontal gap delimited by C, I1–2, and i1–2).

The subspecies C. d. vizottoi differs from C. scopaeum by having pale buff pelage, and larger size ( Table 7). The p2 of C. d. vizottoi is larger, about ½ to ⅔ of the height of p4, while in C. scopaeum , p2 is approximately ¼ the height of p4.

Geographic Variation and Phylogeography. A clade, here identified as scopaeum , contains six specimens of Chiroderma , of which five were analyzed morphologically ( Fig. 16 ). The two specimens from México (TTU 109703 and TTU 110649) are phenotypically similar to the taxon we defined here as Chiroderma scopaeum , whereas specimens from Panamá (LSUMZ 25470), El Salvador (TTU 62462), and Guatemala (ROM 99703) have the diagnostic characters of Chiroderma salvini . The specimens morphologically diagnosed as salvini that nested in the scopaeum clade may represent a case of incomplete lineage sorting (ILS), a relatively common phenomenon in recently-diverged taxa ( Maddison & Knowles 2006). To test the ILS hypothesis between C. salvini and C. scopaeum , we recommend increasing the genetic sample of Chiroderma from western México, and obtaining additional genomic information such as single nucleotide polymorphisms. Also, it is important to note that no specimens, morphologically diagnosed as scopaeum , are nested in the salvini clade, which contains sequences from Central and South American specimens.

Subspecies. C. scopaeum is monotypic.

Remarks. Anderson (1960) mentioned a record of Chiroderma from Chihuahua, western México, that at the time would considerably increase the known distribution of the genus, suggesting an undescribed species for the region. Based on a larger sample size, Handley (1966a) described the subspecies Chiroderma salvini scopaeum , then considered a smaller variant of C. salvini salvini . In this study, we consider the morphological, genetic, and biogeographic evidence as sufficiently strong to treat scopaeum as a species distinct from salvini , instead of as a geographic variant, or subspecies.

Natural History. Information on the diet of C. scopaeum is scarce. In Tahuacán, Puebla, one individual was observed visiting the flowers of the columnar cactus Pachycereus weberi (Pachyceraceae) , but the bat was not covered in pollen ( Valiente-Banuet et al. 1997). In Sinaloa, C. scopaeum was captured in mist nets set under fruiting fig trees. In Jalisco, mist nets over a stream and under a canopy formed by wild figs and other trees also caught C. scopaeum ( Jones et al. 1972; Watkins et al. 1972). Specimens have been captured in altered landscapes, such as cornfields ( Almazán-Catalán et al. 2009).

Summarizing data from the literature, along with the specimens we examined, C. scopaeum appears to be seasonally polyestrous. Pregnancies occurred in January (Sinaloa), February (Jalisco), and June (Jalisco and Nayarit) ( Jones et al. 1972; Watkins et al. 1972). Lactating females have been found in May (Morelos) and June (Nayarit and Jalisco) ( Watkins et al. 1972). Females noted as non-reproductive were recorded in July (Chihuahua; Anderson 1972) and August (Colima; Wilson 1979).

Specimens Examined (N = 35): México: Colima, La Sidra ( TTU 61623 ) , Pueblo Juárez ( USNM 338711 [holotype of scopaeum ]) ; Jalisco, 20 km SW Talpa de Allende ( AMNH 254647 ) , 9.3 km W Chapala ( TTU 38049 ) , 6.4 km NW Autlán de Navarro ( TTU 109703 ) , La Cumbre ( TTU 40987 ) ; Morelos, Oaxtepec ( USNM 559607 ) ; Nayarit, 12.9 km NE San Miguel del Zapote, 51.5 km W Mesa del Nayar ( USNM 559608–559613 ) , 13 km NE San Blas ( TTU 110649 ) , 5 km E El Venado ( USNM 559614 , 559615 ) , 12.9 km E San Blas ( TTU 6122 ) , Arroyo La Taberna ,, 3.2 km W Mesa del Nayar ( USNM 511374–511377 ) , 2.9 km NE (by road), Coapan ( USNM 511380–511382 ) , 2.3 km N (by road), El Tacote ( USNM 508636 ) , 3.2 km E Jalcotoán ( USNM 523258 , 523259 ) , Mesa del Nayar ( USNM 511378 , 511379 ) , Playa Novillero ( USNM 553885 ) ; Oaxaca, 30 km NW Sala de Veja ( AMNH 190006 ) ; Veracruz, Ojo de Agua del Rio Atoyac ( TTU 9996–9999 ) .

Figures

FIGURE 11. Collecting localities of the analyzed specimens of Chiroderma salvini and C. scopaeum. The locality numbers are referenced in the gazetteer (Appendix 1).

FIGURE 12. Dorsal (A) and ventral (C) views of the skull of Chiroderma salvini (USNM 565812—Costa Rica, Guanacaste), and dorsal (B) and ventral (D) views of C. scopaeum (USNM 511379—México, Nayarit).

FIGURE 16. Phylogenetic relationships of Chiroderma salvini and C. scopaeum based on 24 sequences of the cytochrome c oxidase subunit 1 gene. Localities in parentheses are detailed in the gazetteer (Appendix 1). This subtree is a detailed version of the clades named “salvini” and “scopaeum” in figure 4.

FIGURE 17. Lateral view of part of the right dentary of A) Chiroderma salvini (LSUMZ 25649—Panamá, Darién) and B) C. scopaeum (USNM 511378—México, Nayarit). The lower left canine was removed from the image.