Pteronotus alitonus, Colombo & Di Ponzio & Benchimol & Peres & Bobrowiec, 2018

Colombo, Guthieri T., Di Ponzio, Raffaello, Benchimol, Maíra, Peres, Carlos A. & Bobrowiec, Paulo Estefano D., 2018, Geographic variation in a South American clade of mormoopid bats, Pteronotus (Phyllodia), with description of a new species, Journal of Mammalogy 99 (3), pp. 624-645 : 630-634

Pteronotus alitonus sp. nov.

Chilonycteris rubiginosa [rubiginosa ]: Rehn, 1904:200; part.

Chilonycteris rubiginosa rubiginosa: Husson, 1962:74 ; part.

Pteronotus [Phyllodia] parnellii rubiginosus: Smith, 1972:75 ; part.

Pteronotus parnellii: Honacki, Kinman and Koeppl, 1982:150 ; part

Pteronotus sp. 3 : Clare et al., 2013:14.

Pteronotus sp. 1 : Pavan and Marroig, 2016:190.

Holotype. —An adult male ( INPA 6942 ; Fig. 5 ), preserved in alcohol with the skull removed and cleaned, deposited at the collection of the INPA, Amazonas, Brazil. It was collected on 6 September 2014 by Ricardo Rocha (field number PP02) at the Biological Dynamics of Forest Fragments Project (BDFFP) area, 80 km north of Manaus, Brazil (2°20 ′ S, 60°6 ′ W, elevation of 30–125 m). Body, skull, and mandible are in good condition. Tissue is preserved in ethanol and frozen at INPA under the same ID. Sequence of the mitochondrial gene COI is available under the GenBank accession number MH017835 .

Paratypes. — MZUSP 35505 , 35523 ; IEPA 417 , 1847 ; INPA 6947 ; ROM 98128 , 106659 , 117545 ; MHNG 1978.077 , 1978.082 ; AMNH 267851 .

Other material. —The complete list of 82 specimens of P. alitonus analyzed in this study is described in Appendix II.

Distribution. —The new species of Pteronotus is known from several localities in the pristine forests of Guyana, Suriname, French Guiana, and the Brazilian Amazon ( Fig. 1 ; Appendix II).

Etymology. —The specific epithet, alitonus , is composed of the Latin words alius (= different, changed) and tonus (sound, tone), in reference to the distinct echolocation call emitted by this species in comparison to P. rubiginosus .

Nomenclatural statement. —A Life Science Identifier (LSID) number was obtained for the new species Pteronotus alitonus : urn:lsid:zoobank.org:act:4B22D88F-77BA-4021-B031-B54B946DC52D .

Historical background. —In the synonymy presented above (only with 1st use of the names), we tentatively listed authors that implicitly included in their concepts of Chilonycteris rubiginosa or P. parnellii , populations from northern Brazil and the Guianas, which could be assigned to the new species here described. The 2 latter synonyms represent not binomial (and more formal) entries, but refer to specimens whose association to this new species is clear and explicit. Several studies have been published in recent years evidencing the existence of 2 sympatric lineages of common mustached bats in the Amazonian region. Each of these studies has focused on specific questions about the group, but also provided additional sources of information to guide the present study. Based on information from 3 loci, Clare et al. (2013) described the existence of 4 distinct lineages in the continental range of the species formerly known as P. parnellii : 1 in Central America and 3 in South America. Two of these South American lineages, called Pteronotus sp. 3 and Pteronotus sp. 4 , were found in sympatry in Guyana and Suriname. Clare et al. (2013) also described information from acoustics and morphometrics related to the geographic areas of occurrence of these lineages. Thoisy et al. (2014) showed that the 2 sympatric lineages of the P. parnellii complex found by Clare et al. (2013) in Guyana and Suriname were acoustically discernible and increased their ranges to French Guiana and northern Brazil. Thoisy et al. (2014) provided molecular and morphometric evidence indicating that one of these lineages ( Pteronotus sp. 4 ) corresponds to P. parnellii rubiginosus , the taxon already known for that area. Later, Pavan and Marroig (2016) provided a new phylogenetic hypothesis and an updated taxonomic arrangement for the genus Pteronotus . Pavan and Marroig (2016) corroborated the existence of 8 distinct lineages within the P. parnellii complex (subgenus Phyllodia ), 1 in Mexico, 1 in Central America, 3 in South America, and 3 in the Caribbean, linking them to the available names in the group (as subspecies and species names) and showing that one of the sympatric lineages from South America ( Pteronotus sp. 1 —sensu Pavan and Marroig 2016; Pteronotus sp. 3 —sensu Clare et al. 2013) has no name available. Pavan and Marroig (2017) published a dated phylogeny for the genus Pteronotus based on the same molecular data published by Pavan and Marroig (2016). They discussed the historical processes related to the origin and diversification events within the group. López-Baucells et al. (2017) reported the existence of geographic variation in the echolocation calls of these 2 sympatric species of Pteronotus from South America. The study by López-Baucells et al. (2017) is complementary to Thoisy et al. (2014) because it showed that, despite the existence of intraspecific variation, both species are acoustically discernible, i.e., the differences are consistent across geography. They also provided additional information on the distribution of the unnamed lineage of Pteronotus in Central Amazon. We hypothesize that the Pteronotus sp. 3 (sensu Clare et al. 2013) and Pteronotus sp. 1 (sensu Pavan and Marroig 2016), as well as the specimens studied by Thoisy et al. (2014) and López-Baucells et al. (2017), can be confidently recognized as the same biological entity. We advocate this as we included part of their datasets in the present appraisal and carefully compared the results.

Diagnosis.— Pteronotus alitonus is diagnosed as a distinct species by several independent characters including acoustic, molecular, and morphological data, allowing its recognition in the field, laboratory, and in scientific collections. This species can be easily identified in the field by its echolocation calls emitted between 59 and 60 KHz. P. alitonus has also been molecularly characterized, forming a cohesive mitochondrial clade diverging around 5% from its sister group, the species P. rubiginosus ; the polymorphic sites between P. alitonus and P. rubiginosus COI haplotypes are described in Fig. 6 . Cranially, P. alitonus can be distinguished by a unique combination of traits. It has a shorter rostrum, with nasals wider between the frontal and maxillary sutures, more convergent and slightly upturned at the distal part. The maxillary toothrow length (MxTL) is smaller than 9.7 mm and the IB/palatal length (PL) ratio is usually higher than 0.45. The foramina in the pterygoid canal vary from small to indistinct. The tips of upper outer incisors reach half or more of the height of upper inner incisors; they may be separated from the canines by a small gap (particularly noticeable in ventral view of the skull).

Echolocation description.— Pteronotus alitonus has duty cycle signals consisting of a short upward frequency-modulated (FM) initial component, followed by a long CF component and a short downward FM terminal component (CF-FM signal; Supplementary Data SD6). The signal has few or no harmonics and, when present, the 2nd harmonic is the most intense. The echolocation calls have an average FME of 59.2 kHz (58.4– 61.5 kHz) and signal duration of 24.8 ms (7.0–40.0 ms), with great overlap between the localities recorded.

Morphological description and comparisons.— Pteronotus alitonus is a medium-sized species of mustached bat, weighting between 20 and 26 g; the FL varies from 58.8 to 64.5 mm, and the TL varies from 21.7 to 26.4 mm (López-Baucells et al. 2017; this study), usually overlapping with P. rubiginosus (body mass = 23–35 g; FL = 60.2–66.6 mm; TL = 22.9– 27 mm). P. alitonus resembles the remaining species of the subgenus Phyllodia in external morphological characters, such as the shape of the labio-nasal plate, nostrils, tragus, size of pinnae, and patterns of dorsal and ventral fur color ( Smith 1972; Simmons and Conway 2001). The pelage is dense and short (ca. 6 mm), varying from light brown and pale brown to reddish. The rostral tubercle, a dermal projection present in the proximal part of the rostrum, above the nostrils ( Smith 1972; character 89 of Simmons and Conway 2001), is wide and flattened, similar to a triangle in shape. The form of this structure in some individuals from Guyana (MZUSP 35518–35528) suggests that it somehow reflects the shape of nasal bones and, as such, it seems to be wider and more swollen in P. alitonus when compared to P. rubiginosus (Supplementary Data SD7); nevertheless, a more detailed study on the variation of this character is necessary.

The skull of P. alitonus has a robust rostrum and a large and rounded braincase, as wide as half of the total length of the skull. Although similar to P. rubiginosus , it is smaller ( Table 2 , Fig. 7A ) and exhibits a set of features that, in a combined analysis, is diagnostic for this new taxon. The nasal bones form a markedly concave area in the rostrum at the suture of the maxillary and frontal bones. Nasals also taper anteriorly, being wider in their proximal part, close to the maxillary-frontal suture, and narrower and slightly upturned in their anterior part, in the suture with pre-maxillary bones. Comparatively, the nasals in P. rubiginosus are more parallel and flattened throughout their extension ( Fig. 7A , Supplementary Data SD5). The skull of P. alitonus exhibits a rectangular palate that differs from P. rubiginosus for being shortened in its distal portion (from premolars to incisors). The PL in P. alitonus rarely exceeds 10.2 mm (4 out of the 60 specimens analyzed [7%]) and the MxTL is less than 9.7 mm. P. rubiginosus , on the other hand, exhibits a longer rostrum: the PL equals or is larger than 10.3 mm and the MxTL is more than 9.8 mm for specimens in sympatry with P. alitonus . In addition, the interorbital region of P. alitonus is wider than in P. rubiginosus , the later exhibiting a more pronounced constriction ( Table 2 ). Consequently, the estimated ratio between the IB and the PL (IB/PL) is higher in P. alitonus (mean = 0.46 ± 0.0184) than in P. rubiginosus (mean = 0.43 ± 0.0148). Most of the specimens of P. alitonus (88%) show the IB/PL ratio equal or greater than 0.45, whereas 83% of the P. rubiginosus specimens have ratios equal or below 0.44. The BB in P. rubiginosus (10.13–11.45 mm) is very similar to that of P. alitonus (10.08– 11.30 mm) but seems proportionally smaller because of the larger sizes exhibited by P. rubiginosus . Ventrally, the pterygoid canal has a pair of foramina varying from almost indistinct perforations to small pits (less than 1/3 of the foramen ovale) in the new species; alternatively, P. rubiginosus specimens exhibit a large pair of foramina, as large as half of the diameter of the foramen ovale ( Fig. 7D ).

The dental formula is the same as for all other mormoopids, i 2/2 c 1/1 p 2/ 3 m 3/3 = 34. The inner (or central) upper incisors (I1) are bilobed and usually have less than twice the height of the outer (or lateral) incisors (I2); the I1 are proportionally larger in P. rubiginosus than in P. alitonus , with more than twice the height of I2 ( Fig. 7B ). Ventrally, this character is also noticeable, with the margins of the incisors usually forming a continuous arc in P. alitonus , while the margins of the incisors are steeply uneven in P. rubiginosus ( Fig. 7C ), with the central ones forwardly projected. A small gap separating the outer upper incisors from the canines is sometimes present in P. alitonus (e.g., INPA 6942, MHNG 1978.082, AMNH 267851, ROM 106659) and is absent in all specimens of P. rubiginosus . The labial cingulum and the entire labial margin of the 1st upper premolar (P 3 in homology—sensu Simmons and Conway 2001) in P. alitonus exhibits a concave and rounded profile (C-shaped), with deeper notches on the molar toothrow between the canine and the P3 and between the P4 and P3; by contrast, the labial cingulum of the P3 of P. rubiginosus exhibits a less concave, more open profile, with much less noticeable notches between P3 and the adjacent teeth. Moreover, the general shape of the P3 is usually different between species, being more rounded and narrow buccolabially in P. alitonus and more elongated and long buccolabially in P. rubiginosus . The inner lower incisors are trilobed and larger than the outer bilobed incisors in both species but for some individuals of P. alitonus , i1 and i2 crowns are not in contact. The 1st and 3rd lower premolars (p2 and p4) are large and have well-developed labial cingulids; in both species, the p3 is peg-like and compressed between the lingual edges of p2 and p4, although in P. rubiginosus it is usually larger than in P. alitonus .

Additional comparisons. —We examined the cranial morphology of specimens of the geographically contiguous species P. fuscus and compared them with specimens of P. rubiginosus and P. alitonus from Guyana to provide a few insights on their differentiation. P. fuscus has its easternmost distribution in the highlands of northwestern Guyana ( Clare et al. 2013), near the border with Venezuela, whereas P. rubiginosus and P. alitonus extend northward to central and southeastern Guyana ( Fig. 1 ). So far, these 3 species have not been recorded at the same locality and, therefore, P. fuscus is considered to have a parapatric distribution relative to P. rubiginosus and P. alitonus . In general, specimens of P. fuscus have a skull shape more similar to P. rubiginosus , but size more similar to P. alitonus (Supplementary Data SD8). Comparatively, the skull of P. fuscus has a narrow and delicate rostrum; the nasal bones are parallel and flat. P. fuscus can be easily differentiated from P. rubiginosus based on the smaller size (greatest length of skull [GLS] = 21.4 mm ± 0.36; MxTL = 9.33 mm ± 0.2). When compared to P. alitonus , specimens of P. fuscus have noticeably narrower rostra, which are not slightly upturned in their anterior most part as for P. alitonus . The maxillary bones are less inflated in their suture with nasals; morphometrically, this feature is noticed by the greatest width across the molars (M2– M2), generally <8.0 mm in P. fuscus , and> 8.18 mm in P. alitonus from Guyana.

Natural history. —Little is known about the biology or behavior of this new species, but our data suggest that it forages preferentially in highly cluttered forested areas as there are no reports on the species occurrence in more open areas such as savannas or karstic regions in the Amazon.

Remarks. —As a consequence of the description of P. alitonus , P. rubiginosus needs to be redefined. In the present study, we described several morphological features that allow the identification of P. rubiginosus , including quantitative and qualitative characters (see previous section; see also Table 2 and Fig. 7 ). P. rubiginosus is found in the Amazon and Cerrado biomes of South America. The occurrence of this species has been confirmed by molecular data for Guyana, Suriname, French Guiana, northern and central Brazil (and states of Maranhão and Piauí in northeastern Brazil), and Bolivia (Pavan and Marroig 2016; A. C. Pavan, pers. obs.). There are also records of Pteronotus cf. rubiginosus in the Amazonian regions of Peru, Colombia, and Venezuela but the status of these populations need to be reviewed.

Figures

Fig. 5.—Dorsal, ventral, and lateral views of the skull and ventral and lateral views of the mandible of the holotype of Pteronotus alitonus sp. nov. (INPA 6942). Scale bar = 5 mm. INPA = Instituto Nacional de Pesquisas da Amazônia.

Fig. 1.——Sampling localities of the common mustached bat (Pteronotus cf. rubiginosus) included in the present study.

Fig. 6.—Single nucleotide polymorphisms (SNPs) among observed haplotypes of Pteronotus rubiginosus and P. alitonus sp. nov. in the 651 bp fragment of COI gene analyzed. Four haplotypes of each species (P. rubiginosus: HAP1, 14, 16, 32; P. alitonus: HAP2, 3, 11, 12) are shown. Fixed SNPs between the most frequent haplotype of each species (HAP1 × HAP2) are highlighted in bold.

Fig. 7.—Comparison of the cranial morphology between Pteronotus rubiginosus (MHNG 1978.083) and P. alitonus sp. nov. (MHNG 1978.082) from Grotte Mathilde, French Guiana. A) Dorsal and ventral views of the skull of P. rubiginosus (left) and P. alitonus (right); B) frontal view of the skull, contrasting the sizes of the internal (I1) and external (I2) incisors in the 2 species; C) ventral view of 1st half of the palate, highlighting the form outlined by the incisors and the gap between I2 and canines in P. alitonus; D) ventral view of the basicranial region, with arrows indicating the foramina in the pterygoid canal with different sizes in the 2 species. Scale bar in top right of A = 5 mm. MHNG = Musée d’Histoire Naturelle – Genève.