Marmosa (Marmosa) macrotarsus (Wagner, 1842)

Voss, Robert S., Fleck, David W. & Jansa, Sharon A., 2019, Mammalian Diversity And Matses Ethnomammalogy In Amazonian Peru Part 3: Marsupials (Didelphimorphia), Bulletin of the American Museum of Natural History 2019 (432), pp. 1-89 : 25-27

Marmosa (Marmosa) macrotarsus

(Wagner, 1842)

VOUCHER MATERIAL (TOTAL = 20): Nuevo San Juan (268214, 272816, 272870, 273062, 273063, 273140, 273178, 273188, 276726; MUSM 11028, 11029, 13283, 15293–15297, 23798), Orosa (AMNH 73855, 73856).

OTHER INTERFLUVIAL RECORDS: Jenaro Herrera (as Marmosa murina ; Fleck and Harder, 1999), San Pedro (as M. murina ; Valqui, 1999).

IDENTIFICATION: The species currently recognized as Marmosa macrotarsus and M. waterhousei (Tomes, 1860) , both of which occur in eastern Peru, were long treated as subspecies or synonyms of M. murina ( Linnaeus, 1758) , but Rossi (2005) summarized evidence that these

three taxa are phenotypically distinct, and Gutiérrez et al. (2010) subsequently recovered them as reciprocally monophyletic mtDNA clades with average sequence divergence values of about 9% in all pairwise comparisons. According to Rossi’s (2005) still incompletely published revision, the species belonging to this complex are allopatric. Whereas Marmosa murina occurs in eastern Amazonia and the Atlantic Forest, M. waterhousei is in northwestern Amazonia, and M. macrotarsus is in southwestern Amazonia. In eastern Peru, M. waterhousei is said to occur north of the Amazon-Marañón (in Amazonas and northern Loreto departments), whereas M. macrotarsus is distributed south of the river (e.g., in Cuzco, Huánuco, Junín, Madre de Dios, Pasco, Ucayali, and southern Loreto). 5

To assess the diagnostic morphological traits attributed to Marmosa macrotarsus and M. waterhousei , we examined Peruvian specimens of the nominotypical subgenus from both sides of the Amazon. According to Rossi (2005) and Díaz (2015), M. macrotarsus can be distinguished from M. waterhousei by the absence of a gular gland (said to be present in M. waterhousei ) and by the form of the base of the upper canine (said to be less curved than in M. waterhousei ), but neither character seems to be taxonomically useful. None of the Peruvian specimens we examined from south of the Amazon (nominally M. macrotarsus ) showed any trace of a gular gland, but of the seven adult males we examined from north of the Amazon (nominally M. waterhousei ), only three showed any sign of glandular activity on the chest or throat. We observed considerable variability in canine curvature in specimens from both sides of the Amazon, and we were unable to consistently distinguish north-bank

5 According to Díaz (2014: 125), two Orosa specimens (“AMNH 73855, 73853”) identified by Rossi (2005) as Marmosa macrotarsus were subsequently reidentified by Gutiérrez et al. (2010) as M. waterhouesi , but this statement is erroneous on two counts: (1) Rossi (2005) did not examine AMNH 73853 (a specimen of Marmosops noctivagus ; see below), and (2) no Orosa material was examined or reidentified by Gutiérrez et al. (2010).

TABLE 6

from south-bank material by this criterion. Instead, the only trenchant difference we observed between Peruvian specimens of Marmosa (Marmosa) from opposite banks of the Amazon is size: specimens from the north side of the river are substantially larger, on average, than specimens from the south bank (table 6), and although our samples are inadequate to show the full range of intraspecific morphometric variation that might be expected, the lack of overlap in same-sex comparisons for several dimensions (e.g., HBL, LT, CBL, LIB, PL, PB, and MTR for males) seems noteworthy. Altogether, the morphometric evidence for genetically distinct populations on opposite banks of the upper Amazon seems reasonably compelling ( Rossi, 2005), although additional phenotypic criteria for species recognition would be very welcome.

ETHNOBIOLOGY: The Matses do not distinguish this species from other pouchless, longtailed, black-masked species of small opossums (all known as chekampi; see the account for Marmosa , above) and therefore have no particular beliefs about it.

MATSES NATURAL HISTORY: The Matses have no definite knowledge of this species.

REMARKS: Of the 13 specimens from Nuevo San Juan for which we have habitat information, 12 were trapped, shot, or captured by hand in secondary vegetation; only one specimen is known to have been taken in primary forest. Three additional specimens trapped by children in unrecorded circumstances at Nuevo San Juan were probably also taken in secondary growth (children seldom enter primary forest except in the company of adults). Most specimens were trapped, shot, or caught by hand at night, but two were taken in the daytime by men weeding gardens or clearing trash piles, who presumably disturbed sleeping individuals in their daytime refugia. Most specimens were taken at or near ground level (on the ground or on fallen logs), but one was caught by hand at a height of 2 m above the ground in a small tree, and another was shot from a tree at an unrecorded height above the ground.

OTHER SPECIMENS EXAMINED (TOTAL = 8): Peru — Huánuco, Pozuzo (FMNH 24754, 24755); Pasco, Nevati (AMNH 254508); San Martín, Moyobamba (FMNH 19352, 19357); Ucayali, Balta (MVZ 136368–136370).

SPECIMENS OF MARMOSA WATERHOUSEI EXAMINED (TOTAL = 14): Peru — Amazonas, Huampami on Río Cenepa (MVZ 154754, 154761), Kayamas on Río Cenepa (MVZ 153286), La Poza on Río Santiago (MVZ 157632), 12 mi SSW Nazareth (MVZ 139955); Loreto, 25 km S Iquitos (LACM 96112; TTU 98654, 98716, 98717, 98934, 100922, 101153), 61.5 km S Iquitos (TTU 124790, 124796).