Monodelphis brevicaudata, (ERXLEBEN, 1777)

Pavan, Silvia Eliza, Rossi, Rogerio Vieira & Schneider, Horacio, 2012, Species diversity in the Monodelphis brevicaudata complex (Didelphimorphia: Didelphidae) inferred from molecular and morphological data, with the description of a new species, Zoological Journal of the Linnean Society 165 (1), pp. 190-223 : 199-201

MONODELPHIS BREVICAUDATA ( ERXLEBEN, 1777)

Type information: Holotype BM 67.4.12.540, an adult female preserved in fluid with an extracted skull. The original type locality ‘In Americae australis silvis’ was restricted to Suriname by Matschie (1916), and corrected to Kartabo, Guyana, 6 ° 23′N, 58 ° 41′W ( Gardner, 2008) by Voss et al. (2001).

Synonyms: [ Didelphis ] brevicaudata Erxleben, 1777 ; Didelphys brachyuros Schreber, 1777 ; Sorex (Surinamensis) Zimmermann, 1780 ; [ Didelphis ]. Sebae Gray, 1827 ; [ Didelphys ] Hunteri Waterhouse, 1841 ; Peramys brevicaudatus orinoci Thomas, 1899 ; Peramys brevicaudatus dorsalis Allen, 1904 .

Morphological diagnosis: Same as for the M. brevicaudata complex with the following additions: HBL averages 142 mm in adult females and 157 mm in adult males (Supporting Information Table S2). Dorsal pelage with slightly or nongrizzled brownish or greyish stripe at mid-dorsum, differing from the reddish sides, but with little or no contrast between them ( Fig. 4 ). Some specimens show indistinct middorsal stripe, and some lack it completely, with both mid-dorsal and lateral fur reddish or reddish brown; head pelage reddish laterally, with narrow mid-dorsal stripe (when distinguishable) varying from whitish grey or yellowish to orange, confined by a band of red hairs above each eye; underparts cream-grey, sharply differentiated from the reddish sides ( Fig. 4 ); throat and chin distinctly reddish; mammae at the inguinal/ abdominal region, one central and eight distributed circumferentially around it (L-1920); tail covered dorsally by body fur up to about one quarter of the caudal length; ventrally, the body fur is limited to the tail’s connection with the body; CBL averages 35.9 mm in adult females and 39.4 mm in adult males (Supporting Information Table S2); interorbital region relatively narrow ( Fig. 5 ); zygomatic arches slightly convergent anteriorly; maxillopalatine foramina relatively short ( Fig. 5 ); UMS averages 7.8 mm in adult females and 7.9 mm in adult males (Supporting Information Table S2).

Geographical distribution: Restricted to northern Guyana, Venezuela south of the Orinoco river (in the states of Bolívar and Amazonas), and north-western Brazil (north of the Negro river and west of the Branco river, in the states of Amazonas and Roraima) ( Fig. 6 ). No other species of the M. brevicaudata complex were found in sympatry with M. brevicaudata (sensu stricto).

Geographical variation: As mentioned above, the middorsal stripe can be present, absent, or indistinct. As a result, the dorsal pelage may exhibit (1) distinct bicoloured pattern, with mid-dorsal fur brownish or greyish, and reddish laterals (as generally occurs in specimens from Brazil, e.g. MN 69058 , 69367 , CGB 80, 90; south of Venezuela, e.g. USNM 385010 , 388355 , 406907 , 406910 ; and east of Venezuela, e.g. AMNH 16125 , L-1920, USNM 443781 , 448511 ); (2) indistinctly bicoloured pattern, with the mid-dorsal fur darker than laterals, but not forming a delimited stripe [specimens from east of Venezuela, e.g. USNM 385004 , 385005 ( Fig. 4 ); and north-western Guyana, e.g. USNM 568009 ]; and (3) unicoloured pattern, with the upperparts homogeneous, from reddish to reddish brown (specimens from north of Guyana, e.g. AMNH 48133 , ROM 98909). At the crown, the mid-dorsal stripe is commonly distinct, but quite variable in colour and intensity. The size of the specimens is also variable, generally smaller in the northern part of the distribution, and larger in southern Venezuela and Brazil .

Remarks: Monodelphis brevicaudata was originally described as [ Didelphis ] brevicaudata Erxleben 1777 . In the same year, Schreber (1777) described Didelphis brachyuros . Both descriptions were based on the description and illustration of Muris sylvestris Americani faemina from Seba (1734). Thomas (1888) gave priority to Erxleben’s name, considering D. brachyuros to be a junior synonym. The specimen from Seba ( BM 67.4.12.540) exhibits pelage ‘distinctly bicolored, reddish dorsally and abruptly paler ventrally’, as quoted by Voss et al. (2001) who analysed the type specimen’s skin and confirmed the association of Erxleben’s and Schreber’s names to it. Synonymizing S. surinamensis Zimmermann, 1780 and D. sebae Gray, 1827 with M. brevicaudata is justified because the former two names were also created based on Seba’s specimen/illustration, being objective synonymies of M. brevicaudata . The descriptions of D. hunteri Waterhouse, 1841 and P. b. dorsalis Allen, 1904 were based on specimens that fit our definition of M. brevicaudata , and are therefore junior synonymies of the latter. The type of P. b. orinoci Thomas, 1899 does not exactly fit our morphological definition of M. brevicaudata , because it has mid-dorsal stripe more grizzled (broader at head), flanks paler, and smaller size than any specimen recognized by us as M. brevicaudata . However, because we do not understand all morphological variation within M. brevicaudata yet, and there is considerable variation with regard to the mid-dorsal stripe and size in this species (see Geographical variation section above), we consider M. orinoci as a junior synonym of M. brevicaudata .

Didelphis brevicaudata Erxleben, 1777 is the oldest available name for specimens of the north-western clade ( Fig. 3 ). The restriction of the name M. brevicaudata herein proposed is supported by the morphological similarity between the specimen ROM 98909 (placed in our north-western clade) and the type specimen of M. brevicaudata (BM 67.4.12.540), both exhibiting homogeneously reddish dorsal fur without a mid-dorsal stripe (‘bicolored pattern’ of Voss et al., 2001). Additionally, our genetic samples from Venezuela and northern Guyana, which include localities close to the type locality of M. brevicaudata (Kartabo, northern Guyana), grouped together and formed a monophyletic lineage in the molecular analyses ( Fig. 2 ) with considerable genetic divergence from any other lineage (Supporting Information Table S1). It is important to note that this clade includes both bicoloured (ROM 98909) and tricoloured specimens (L-1917, L-1920, USNM 568009), showing that the colour of the dorsal pelage is a variable feature of this species (see Geographical variation section above).

Figures

Figure 2. Phylogenetic relationships of species of the Monodelphis brevicaudata complex represented by the Bayesian tree resulting from the analysis of the combined matrices of 471 base pairs of the mitochondrial cytochrome b gene and 402 base pairs of the mitochondrial 16S rDNA gene. Numbers above branches represent parsimony followed by maximum-likelihood bootstrap; numbers below branches correspond to Bayesian posterior probabilities (‘-’ means a value lower than 50%). Asterisks refer to specimens/localities not examined morphologically.

Figure 3. Collecting localities of specimens included in molecular analyses, and corresponding clade structure found in the molecular phylogeny, with taxon names associated with them (tree to the right).

Figure 4. Dorsal (left) and ventral (right) views of the skins of adult specimens of (top to bottom): Monodelphis glirina (USNM 521429), Monodelphis palliolata (USNM 406904), Monodelphis brevicaudata (USNM 385005), Monodelphis arlindoi sp. nov. (UFMG 3190, paratype), Monodelphis touan (IEPA 1154). Scale bar = 50 mm.

Figure 5. Dorsal (top) and ventral (bottom) views of the skulls of old adult specimens of: A, Monodelphis glirina (USNM 521431, female); B, Monodelphis palliolata (USNM 371285, female); C, Monodelphis brevicaudata (USNM 385005, female); D, Monodelphis arlindoi sp. nov. (MPEG 38052, holotype, male); E, Monodelphis touan (ISEM V-1563, male). Scale bar = 10 mm.

Figure 6. Distribution of species of the Monodelphis brevicaudata complex recognized in this study. Species boundaries (shades) are based on our data and Pine & Handley (2008). Points indicate collecting localities of specimens examined by us (except for species B, not analysed). Monodelphis palliolata also occurs in Colombia, but distribution in that country cannot be correctly drawn because of the absence of known precise localities (Pine & Handley, 2008).