Zavreliella shidai Cao & Tang, 2017, sp. n.

© 2017 Academia Sinica, Taiwan Open Access Geographic Variation in Cranial Morphology of the Southern Mountain Cavy, Microcavia australis (Rodentia, Caviidae): Taxonomic Implications, with the Description of a New Species Pablo Teta1,*, Ricardo A. Ojeda2, Sergio O. Lucero1, and Guillermo D’Elía3 1División Mastozoología, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, Avenida Ángel Gallardo 470, C1405DJR Buenos Aires, Argentina 2IADIZA CONICET - GiB, Grupo de investigaciones de la biodiversidad; CCT-CONICET Mendoza, Parque San Martín, 5500 Mendoza, Argentina 3Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile (Received 7 April 2017; Accepted 13 September 2017; Published 2 October 2017; Communicated by Jian-Nan Liu) Pablo Teta, Ricardo A. Ojeda, Sergio O. Lucero, and Guillermo D’Elía (2017) We analyzed the geographic variation in cranial morphology of the Southern Mountain Cavy, Microcavia australis, throughout of its distributional range. Our analysis allows us to recognize three geographically allopatric morphotypes. These morphotypes differ in the general size and shape of the skull and discrete morphological traits of the zygomatic arch, palate and mesopterygoid fossa. Based on these results, we restrict the name australis to populations distributed in southern Argentina and west-central Andes and the name maenas to the morphotype of northwestern and central Argentina. The third morphotype occurs in the Dry Chaco ecoregion and is described here as a new species. Key words: Caviomorpha, Cavioidea, Cranial variation, Qualitative morphology, Quantitative morphology. *Correspondence: E-mail: [email protected] BACKGROUND The genus Microcavia H. Gervais and Ameghino, 1880 includes three living and at least four fossil species of small (< 400 g), semifossorial and herbivorous caviomorph rodents endemic to southern South America (Quintana 1996; Ubilla et al. 1999; Dunnum 2015). Among the living forms, M. niata (Thomas, 1898) and M. shiptoni (Thomas, 1925) are restricted to highland areas of northwestern Argentina, southwestern Bolivia and northern Chile, while M. australis (I. Geoffroy and d’Orbigny, 1833) ranges widely from northwestern Argentina to southern Argentinean and Chilean Patagonia (Rood 1970; Tognelli et al. 2001). As for other caviids (e.g., Cavia, Galea), our knowledge about the level and patterns of interand intraspecific morphological variation of Microcavia is limited, resulting in varied taxonomic conclusions (e.g., Dunnum 2015). For instance, Thomas (1921) recognized five subspecies of M. australis, from north to south: maenas Thomas, 1898, salinia Thomas, 1921, joannia Thomas, 1921, nigriana Thomas, 1921, and australis (including kingii Bennett, 1836 in its synonymy). This taxonomic arrangement was followed with some modifications by Ellerman (1940), who distinguished kingii at the subspecies level and included nigriana into the synonymy of australis. Later, Cabrera (1953) hypothesized a simpler scenario, recognizing only three subspecies within australis: maenas, salinia and australis (including joannia, kingii and nigriana as synonyms). Thomas (1921) and Cabrera (1953) each based their taxonomic hypotheses on cranial traits and differences in external coloration of small series of individuals. Zoological Studies 56: 29 (2017) doi:10.6620/ZS.2017.56-29 1 © 2017 Academia Sinica, Taiwan Dunnum (2015), in the most recent treatment of the genus, follows the scheme of Cabrera (1953) and recognized, mostly based on morphological data (see also Tognelli et al. 2001), three subspecies of M. australis. Sassi et al. (2011b), using molecular markers, found high levels of divergence among highland and lowland cavy populations of west-central Argentina, a scenario that suggests that this taxon may encompass more than one form. According to these authors, mean sequence divergence in a fragment of the mitochrondrial genome among populations from different altitudes was around 9%. In agreement with these results, Taraborelli et al. (2007) detected some variation in cranial size along an altitudinal gradient in the same general area. The main purpose of our study is to test prior taxonomic hypotheses by means of cranial and skin morphology analyses among populations currently assigned to M. australis. The study is based on a large sample of specimens, by far the largest yet analyzed, both in terms of specimen number and geographic coverage; it includes holotypes or topotypes of all nominal forms. MATERIALS AND METHODS Specimens examined We examined 272 subadults and adults assigned to Microcavia australis. Specimens document 66 localities (Fig. 1) and include the holotypes of the nominal forms joannia, maenas, nigriana, and salinia. Specimens examined are housed in the following museums and collections: The Natural History Museum (BM, London, UK); Colección Elio Massoia (CEM, acquired by the Fundación de Histora Natural Félix de Azara, Buenos Aires, Argentina); Colección de Mamíferos Fig. 1. A: map of southern South America indicating the collecting localities of the examined specimens of Microcavia. Ellipses shown the groupings of localities that constitute the geographical samples analyzed. See Materials and Methods for an explanation of the acronyms. Different symbols correspond to the three species identified in this work: white circles = M. australis; black circles = M. maenas; black squares = M. jayat n. sp. B. map of southern South America indicating the type localities of names associated with Microcavia australis. (A) (B) page 2 of 18Zoological Studies 56: 29 (2017) © 2017 Academia Sinica, Taiwan del Instituto Argentino de Investigación de Zonas Áridas (CMI, Mendoza, Argentina); Colección de Mamíferos de la Facultad de Ciencias Naturales e Instituto Miguel Lillo (CML, Tucumán, Argentina); Colección de Mamíferos del Centro Nacional Patagónico (CNP, Chubut, Argentina); and Colección Nacional de Mastozoología, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (MACN, Buenos Aires, Argentina. Analyzed specimens and their localities are listed in the Supplementary 1. Cranial measurements Sixteen craniodental measurements were recorded from each specimen by one of the authors (P. Teta) using a digital caliper to the nearest 0.01 mm: total length of the skull (TLS); condylo-incisive length (CIL); interorbital constriction (IOC); greatest zygomatic breadth (ZB); breadth of braincase (BB); length of nasals (NL); width of nasals (NW); length of frontals (FL); length of the upper diastema (DL); length of incisive foramina (LIF); breadth of incisive foramina (BIF); length of upper toothrow (TRL); palatal length (PL); breadth of palate at the level of the upper third molar (BPM3); breadth across the paraoccipital processes (BPP); and length of tympanic bullae (TBL). The definition of these measurements follows Contreras and Contreras (1984) and Ubilla and Rinderknecht (2014), with modifications (see Fig. 2). Fig. 2. Skull of Microcavia indicating the measurements used in this study. Refer to the text for measurement acronyms. page 3 of 18Zoological Studies 56: 29 (2017) © 2017 Academia Sinica, Taiwan Geographic variation Geographic samples (Fig. 1) were established according to the specimens available; a few samples were represented by a single locality but many others were obtained by pooling specimens from nearby localities (e.g., Musser 1968). This action was needed to obtain larger sample sizes amenable for statistical analyses. We used geographic proximity, absence of major geographical barriers among localities, and lack of obvious discrepancy in size and shape among specimens (see examples of this approach in Brennand et al. 2013; Chiquito et al. 2014; Libardi and Percequillo 2016) to construct the samples. The following groups were constituted: buen, southern Buenos Aires Province (N = 1); cata, Catamarca Province (N = 9); chub, Chubut Province (N = 19); cord, western Córdoba Province (N = 4); lapa, La Pampa Province (N = 1); lari, La Rioja Province (N = 40); menc, central Mendoza Province (N = 1); menh, northwestern highland Mendoza Province (N = 1); menl, northern lowland Mendoza Province (N = 20); mens, southern Mendoza Province (N = 2); neuq, Neuquén Province (N = 8); rion, Río Negro Province (N = 5); saes, Santiago del Estero Province (N = 8); salt: southwestern Salta Province (N = 5); salu, northern San Luis Province (N = 3); scru, Santa Cruz Province (N = 5); sjun, northeastern San Juan Province (N = 4); sjus, southern San Juan Province (N = 11); and tucu, Tucumán Province (N = 2). Anatomical terminology for cranial and dental features follows Cherem and Ferigolo (2012), with modifications. Analyses of qualitative characters of the skull and dentition were conducted using Thomas (1921), Kraglievich (1930) and Cabrera (1953) as data sources. Statistical analyses Patterns of geographic variation were assessed through descriptive statistics (i.e., mean, minimum and maximum values, standard deviation) and multivariate analyses, including principal component and discriminant function analyses (PCA and DFA, respectively). PCA was performed on a subsample of 144 adults (age classes 3-5; following Bezerra 2008), using log10transformed data to normalize the contribution of each measurement to the total variance. Principal components (PCs) were extracted from the variance-covariance matrix (Strauss 2010). Discriminant function analyses (DFA) were employed to assess the variable contributing to differentiate between samples (Strauss 2010). Finally, we also calculated the squared Mahalanobis (D2) distances among geographical samples with more than 5 individuals, depicting them in a dendrogram based on the unweighted pair-group method by using arithmetic averages (UPGMA; Sneath and Sokal 1973). All statistical analyses were carried out with InfoStat software (Di Rienzo et al. 2008). RESULTS Qualitative morphological variation Studied specimens have a relatively broad, bowed and short skull, that has its highest part over the posterior zygomatic root; rounded orbits; large incisive foramina, nearly triangular in outline, and large bullae (Figs. 3 and 4). Samples are also remarkably uniform in external appearance; no differences are noted in the distribution of vibrissae, or any gross aspect of the ears or feet, including the number of plantar pads. Most specimens exhibit a brownish to olive or grayish Fig. 3. Dorsal (A-C) and ventral (D-F) views of the skull of three species of Microcavia: M. australis (A, D; MACN-Ma 14.543), M. maenas (B, E; MACN-Ma 34.116) and Microcavia n. sp. (C, F; MACN-Ma 17333). Scale bars = 5 mm. (A) (D) (B) (E) (C) (F) page 4 of 18Zoological Studies 56: 29 (2017) © 2017 Academia Sinica, Taiwan dorsal coloration, with a more or less marked agouti effect; underparts are grayish to yellowish, usually with a patch of dark gray hairs on the neck. However, as detailed below, specimens vary in overall saturation of pigments as well as some differences in qualitative and quantitative cranial traits (see Supplementary 2). Three main morphotypes within the current concept of Microcavia australis were recognized on the base of discrete and constant differences in the zygomatic arch, palate, and mesopterygoid fossa (Figs. 5 and 6), as well as in size and shape of the skull (see the section below). Most of these characters, such as the presence of a paraorbitary process, the form of the anterior border of the mesopterygoid fossa, and the size and shape of the sphenopalatine vacuities, do not vary within morphotypes and as such their variation is geographically structured. These differences are evident in most of the specimens, even when more than half of the studied crania have the post palatal portion broken. Morphotype 1 includes buen, chub, lapa, menh, mens, neuq, rion and scru samples, which have bowed to strongly bowed parietals; inferior process of the jugal extended to the level of the posterior border of the glenoid fossa (Fig. 5A); suture between palatines occupied by a triangular to more or less heart-shaped palatal crista; rounded to acute posterior palatal edges, large sphenopalatine vacuities and relatively narrow presphenoids (Figs. 5B and 6). Externally, this morphotype includes specimens with brownish to olive dorsal coloration, in a well-marked agouti pattern, and grayish to yellowish venter. Representatives of populations currently assigned to the subspecies M. a. australis, including topotypes of nigriana and australis, exhibit this morphotype. In turn, morphotype 2 is represented by specimens from cata, cord, lari, menc, menl, sjun, sjus, salt, salu, and tucu, which have a more flattened dorsal profile of the skull; inferior process of the jugal posteriorly extended beyond the border of the glenoid fossa (Fig. 7); long and narrow to long and slightly rhomboidal palatal crista along the suture between palatine bones; usually angled to rounded posterior palatal edges, sometimes with a distinctive nasal spine; proportionally smaller sphenopalatine vacuities, and broad presphenoids (Figs. 5-6). The dorsal coloration of this morphotype is more yellowish to grayish, with less evident agouti pattern. Specimens currently referred to maenas and salinia, including the holotypes of joannia, maenas, and salinia exhibit the diagnostic attributes of morphotype 2. Finally, morphotype 3 is only present in the sample referred as saes, which has an unique combination of character states, including a relatively flattened dorsal profile to the skull; inferior process of the jugal posteriorly extended beyond Fig. 4. Lateral views of the skull and right dentaries in labial views of three species of Microcavia: M. australis (A; MACN-Ma 14.543), M. maenas (B; MACN-Ma 34.116) and Microcavia n. sp. (C; MACN-Ma 17331). Scale bars = 5 mm. (A) (B) (C) page 5 of 18Zoological Studies 56: 29 (2017) © 2017 Academia Sinica, Taiwan Fig. 5. Selected anatomical traits of three species of Microcavia (A, MACN-Ma 16379; B, MACN-Ma 34.81; C, MACN-Ma 17331; D, MACN-Ma 16379; E, MACN-Ma 36.72; F, MACN-Ma 17333; G, MACN-Ma 28.51; H, MACN-Ma 36.84; I, MACN-Ma 17331), depicting the relative position of inferior process of the jugal (marked by the arrow) relative to the glenoid cavity (a-c) and size and shape of the palatal cristae (d-i). A, D, G = M. australis; B, E, H = M. maenas; C, F, I = M. n. sp. Abbreviations: gc = glenoid cavity; jf = jugal fossa; mpp = medial process of the palate; pc = palatal crista; sq = squamosal. Photographs are not in scale to facilitate comparisons among proportions. (A) (D) (G) (B) (E) (H) (C) (F) (I) page 6 of 18Zoological Studies 56: 29 (2017) © 2017 Academia Sinica, Taiwan the border of the glenoid fossa (Fig. 5C); suture between palatines occupied by a heart-shaped palatal crista that surpasses the posterior border of the palate, which has a nearly trapezoidal outline; small sphenopalatine vacuities and relatively broad presphenoids (Figs. 5 and 6). An additional unique feature of these specimens is the presence of a small but conspicuous paraorbital process on the zygomatic arch formed exclusively by the jugal (Fig. 7). Pelage coloration of morphotype 3 is yellowish brown, with grayish underparts; some individuals have conspicuous patches of pure white hairs at the throat, the inner side of the fore and hindfeet, and in the inguinal region. No name is available for this morphotype. Quantitative morphological variation PCA revealed that all variables were positively correlated with the 1st principal component (PC1 57%), indicating that it summarizes mainly latent size variation (see Tables 1 and 2). The plot of individual scores labeled by geographic provenance shows marked overlap of individuals from different samples in relation to the PC1 (Fig. 8A; Table 1). However, when only centroids are considered, two main groups can be recognized, one encompassing buen, chub, lapa, menh, mens, neuq, rion, saes and scru, and a second including cata, cord, lari, menc, menl, sjun, sjus, salu, and tucu. The distribution along the 2nd principal Fig. 6. Selected anatomical traits of three species of Microcavia (A, MACN-Ma 14543; B, MACN-Ma 36.72; C, MACN-Ma 17331; D, MACN-Ma 25.51; E, MACN-Ma 36.84; F MACN-Ma 17333), depicting the contour of the posterior border of the palate and size of sphenopalatine vacuities (epv). Abbreviations: fo = foramen oval; pc = palatal crista; ps = presphenoid; pt = pterygoid. Photographs are not in scale to facilitate comparisons among proportions. (A) (D) (B) (E) (C) (F) page 7 of 18Zoological Studies 56: 29 (2017) © 2017 Academia Sinica, Taiwan component (PC2 7%, Fig. 8A) does not reveal any clear pattern, with broad overlap among pooled samples. Table 2. The DFA revealed three major morphometric clusters dispersed along the 1st and 2nd discriminant axes (Fig. 8B; Table 1), which summarize 64% of the variance. The 1st group is composed of samples from buen, chub, lapa, menh, mens, neuq, rion and scru (= morphotype 1), including most of the populations allocated to M. a. australis. The 2nd cluster comprises the samples cata, cord, lari, menc, menl, sjun, sjus, salu, and tucu (= morphotype 2), compassing those populations referred in the literature as M. a. maenas and some of those now identified as M. a. salinia. This cluster includes topotypes of joannia, maenas and salinia. Finally, the 3rd cluster is formed by specimens from saes (= morphotype 3), which departs from the other two clusters in both discriminant functions. The classification matrix determined by the discriminant function is presented in the Supplementary 3. The holotypes of joannia, maenas, nigriana, and salinia (see Table 3) were measured by R. Ojeda, so we opted to exclude these specimens from the multivariate analyses. However, a posteriori classification of the holotypes of joannia and salinia nested their scores within the cluster of specimen scores represented by the morphotype 2 in the canonical variate plots, while the holotype of nigriana grouped with those samples referred to morphotype 1 (results not shown). The UPGMA supports the geographic clustering into three main groups; one composed by samples referred to morphotype 1 from chub, menh, neuq, rion and scru; another corresponds to morphotype 2 comprised of samples from cata, lari, menl, and sjus. The sample from saes, the sole representative of morphotype 3, remained as a divergent unit, eventually joined to morphotype 1 group (Fig. 9). Based on the results of qualitative and quantitative analyses of cranial traits, we conducted a between-group PCA and an additional DFA pooling the samples into three main morphotypes (labeled here as australis [= morphotype 1], maenas [= morphotype 2], and n. sp. [= morphotype 3]). Results of these analyses are shown in figures 8C and 8D (tables not shown), which strongly support the recognition of three morphological entities among populations referred to M. australis. Craniodental measurements, including mean, standard deviation (SD), and range, are summarized in table 2; external measurements are provided in the Supplementary 4. Abbreviations: M1/m1, first upper/lower molar; M2/m2, second upper/lower molar; M3/m3, third upper/lower molar; PM4/pm4, fourth upper/lower premolar. Taxonomy The results of quantitative and qualitative morphological analyses support the existence of three different morphotypes within populations currently referred to Microcavia australis. Fig. 7. Lateral view of the zygomatic arch in three species of Microcavia: M. australis (A; MACN-Ma 14.543), M. maenas (B; MACN-Ma 34.116) and Microcavia n. sp. (C; MACN-Ma 17333). Abbreviation: pp = paraorbitary process. Photographs are not in scale to facilitate comparisons among proportions. (A) (B) (C) page 8 of 18Zoological Studies 56: 29 (2017) © 2017 Academia Sinica, Taiwan Qualitative cranial traits are remarkably constant within groups, distinguished them and implying that they independently evolved from each other. As such, the three morphotypes are here regarded as distinct lineages at the species level. We therefore propose that M. australis is in fact a species complex, including M. australis s.s., M. maenas and a third, unnamed species, which is described at the end of this section: Microcavia australis (I. Geoffroy and d’Orbigny, 1833) (Figs. 3-6) C[avia]. australis I. Geoffroy and d’Orbigny, 1833:1. Kerodon Kingii Bennett, 1836:190 [type locality “apud Portum Desire dictum, ad Patagoniæ littus orientale” (= Puerto Deseado, Santa Cruz, Argentina)]. Caviella australis nigriana Thomas, 1921:446 [type locality “Neuquen, R. Negro” (= Neuquén, Argentina). Fig. 8. Specimen scores of adult individuals (ages 3-5) of Microcavia (N = 144) for: A) Principal components 1 and 2; B) Canonical variates 1 and 2, extracted from discriminant function analyses of 18 geographic groups; C) Between morphogroup principal components 1 and 2; D) Canonical variates 1 and 2, extracted from three-group discriminant function analysis. For the acronyms of the geographical samples see Materials and Methods section. (A) (C) (B) (D) page 9 of 18Zoological Studies 56: 29 (2017) © 2017 Academia Sinica, Taiwan de Mamíferos Lillo, Tucumán), and Ulyses F. J. Pardiñas (Colección de Mamíferos del Centro Nacional Patagónico, Chubut). Carolina Madozzo Jaén helped us with the revision of specimens, sharing with us her anatomical knowledge on this group of rodents. Bruce Patterson and two anonymous reviewers made useful comments in a previous version of this manuscript. We acknowledge support from Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina. Authors’ contributions: PT, RAO, SOL and GD designed the study and wrote the manuscript. PT performed the statistical analyses. PT and RAO analyzed and measured the specimens. All authors participated in revising the manuscript. All authors read and approved the final manuscript. Competing interests: Authors declare that they have no conflict of interest. Availability of data and materials: Key datasets of the manuscript are presented as supplementary files. Consent for publication: Not applicable. Ethics approval consent to participate: Not applicable. REFERENCES Balakirev AE, Abramov AV, Rozhnov VV. 2017. The Phylogeography of red spiny rats Maxomys surifer (Rodentia, Muridae) in Indochina with Comments on Taxonomy and Description of New Subspecies. Zool Stud 56:6. doi:10.6620/ZS.2017.56-06. Bezerra A. 2008. Revisão taxonômica do gênero Galea Meyen, 1832 (Rodentia, Caviidae, Caviinae) Dissertation, Universidad de Brasilia, Brasília, Brazil. 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Dense sampling allows revisiting the southern geographic distribution and taxonomy of the cavies Galea and Microcavia (Rodentia). Mammalia 80:335-340. Vallejos M, Volante JN, Mosciaro, MJ, Vale LM, Bustamante ML, Paruelo JM. 2015. Transformation dynamics of the natural cover in the Dry Chaco ecoregion: A plot level geodatabase from 1976 to 2012. J Arid Envir 123:3-11. Wiens JJ, Serveido MR. 2000. Species delimitation in systematics: Inferring diagnostic differences between species. Proc Royal Soc Lond Ser B 267:631-636. Woodman N, Timm RM. 2016. A new species of small-eared shrew in the Cryptotis thomasi species group from Costa Rica (Mammalia: Eulipotyphla: Soricidae). Mamm Res 62:89-101. page 17 of 18Zoological Studies 56: 29 (2017) © 2017 Academia Sinica, Taiwan Supplementary 1 - Appendix. List of the specimens of Microcavia examined in this study and their collecting localities in Argentina. Localities are grouped by provinces and departments. Studied specimens are housed at the following mammal collections: BM, The Natural History Museum (London, UK); CEM, Colección Elio Massoia (acquired by the Fundación de Histora Natural Félix de Azara, Ciudad Autónoma de Buenos Aires, Argentina); CMI, Colección de Mamíferos del Instituto Argentino de Investigaciones de Zonas Áridas (Mendoza, Argentina); CML, Colección de Mamíferos de la Facultad de Ciencias Naturales e Istituto Miguel Lillo (San Miguel de Tucumán, Argentina); CNP, Colección de Mamíferos del Centro Nacional Patagónico (Puerto Madryn, Argentina); MACN, Colección Nacional de Mastozoología, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (Ciudad Autónoma de Buenos Aires, Argentina). (download) Supplementary 2 - Fig. 1sm. Dorsal and ventral views of the skins of M. australis (A, D; MACNMa 49.115), M. maenas (B, E; MACN-Ma 34.58) and Microcavia n. sp. (C, F; MACN-Ma 17331). (download) Supplementary 3 - Table 1s. Classification matrix determined by the discriminant function. See matherials and metods for abreviations. (download) Supplementary 4 - Table 2s. External measurements for individual specimens of Microcavia. (download) page 18 of 18Zoological Studies 56: 29 (2017)