Micronycteris (Schizonycteris) minuta (Gervais, 1856)

Velazco, Paúl M., Voss, Robert S., Fleck, David W. & Simmons, Nancy B., 2021, Mammalian Diversity And Matses Ethnomammalogy In Amazonian Peru Part 4: Bats, Bulletin of the American Museum of Natural History 2021 (451), pp. 1-201 : 61-64

Micronycteris (Schizonycteris) minuta

(Gervais, 1856)

VOUCHER MATERIAL (TOTAL = 5): Isla Muyuy (MUSM 21196), Nuevo San Juan (AMNH 273172, 273173; MUSM 15227, 15228); see table 30 for measurements.

TABLE 29

Roosting Groups of Micronycteris microtis Observed near Nuevo San Juan

UNVOUCHERED OBSERVATIONS: None.

IDENTIFICATION: Micronycteris minuta is widely distributed from Central America to northern Bolivia and eastern Brazil (Williams and Genoways, 2008; Reid, 2009; Siles and Baker, 2020), but there has been considerable controversy regarding the content of this species over the last two decades (Simmons and Voss, 1998; Lim and Engstrom, 2001a; Ochoa-G. and Sánchez, 2005; Siles and Baker, 2020). Micronycteris homezorum (originally named M. megalotis homezi ; Solari, 2008) was described by Pirlot (1967) based on three specimens from the state of Zulia, Venezuela; unfortunately, the type series was destroyed along with other Pirlot specimens sometime in the 1970s (Simmons and Voss, 1998). Simmons and Voss (1998) elevated M. homezorum from subspecies to full species based on a male specimen from French Guiana that exhibited the characteristic cutaneous fossa on the head described by Pirlot (1967). Lim and Engstrom (2001a) subsequently reported a high level of variability among specimens from Guyana in the diagnostic characteristics alleged to differentiate M. minuta from M. homezorum . After reviewing the morphology of a large series of Venezuelan specimens assignable to either M. minuta or M. homezorum , Ochoa-G. and Sánchez (2005) concluded that the cutaneous fossa is sexually dimorphic (well developed only in mature males) and is not taxonomically diagnostic; therefore, M. homezorum should be regarded as a junior synonym of M. minuta . Given that there are no other morphological traits that unambiguously distinguish these taxa, we follow their recommendation here.

Nevertheless, several subsequent molecular studies have suggested that Micronycteris minuta is a complex of at least three and perhaps as many as five species (Porter et al., 2007; Clare et al., 2011; Larsen et al., 2011; Siles et al., 2013). Most recently, Siles and Baker (2020) described

TABLE 30

External and Craniodental Measurements (mm) and Weights (g) of Micronycteris minuta

and M. hirsuta from the Yavarí-Ucayali Interfluve

two new species from this complex, Micronycteris tresamici (from Honduras and Costa Rica) and M. simmonsae (from eastern Ecuador). Those authors applied the name M. minuta to samples from Panama southward through northern South America, western Ecuador, Peru, Bolivia, and Brazil; however, they suggested that M. minuta (thus restricted) may still be a complex of more than one species. In the absence of denser geographic sampling of South American populations and molecular data from topotypic specimens of minuta (with type locality at Capella-Nova, Minas Gerais, Brazil), homezorum (with type locality fixed by neotype selection as Hato El Cedral, Apure, Venezuela; Ochoa-G. and Sánchez, 2005), and hypoleuca Allen, 1900 (with type locality Bonda, Magdalena, Colombia), it is not yet possible to determine whether additional genetic lineages in this complex are distinct taxa, nor to decide which names apply to them. For now, we follow Siles and Baker (2020) and treat these nominal taxa as conspecific.

As thus defined, Micronycteris minuta is distinguished from other congeners by the following characteristics: dark-brown dorsal fur and pale (gray or buff) ventral fur; a cutaneous fossa on the top of the head in mature males; calcar shorter than foot; zygomatic breadth greater than breadth of braincase, but less than mastoid breadth; sagittal crest absent or present only on the anteriormost third to two-thirds of the parietals; upper incisors bilobed; M1 narrower than M 2 in occlusal view; lower incisors bilobed; first lower premolar slightly larger and taller than third lower premolar; and second lower premolar reduced, shorter than first and third lower premolars (Ochoa-G. and Sánchez, 2005; Williams and Genoways, 2008; Siles and Baker, 2020). Descriptions and measurements of Micronycteris minuta were provided by Simmons and Voss (1998), Bernard (2001), Lim and Engstrom (2001a), Ochoa-G. and Sánchez (2005), Siles et al. (2013), and Siles and Baker (2020). 9 We follow Williams and Genoways (2008) and Siles and Baker (2020) in not recognizing subspecies of Micronycteris minuta due to the taxonomic uncertainties described above.

Fleck et al. (2002) correctly identified their material from Nuevo San Juan as Micronycteris minuta , but one individual from this series (AMNH 273172) was subsequently identified as M. cf. schmidtorum by Larsen et al. (2011), as M. schmidtorum by Siles et al. (2013) and, finally, as M. minuta again by Siles and Baker (2020). Our material from the Yavarí-Ucayali interfluve conforms to previous descriptions of M. minuta , with measurements that fall within the range of size variation previously documented for the species. However, a cytochrome b sequence from AMNH 273172 is 4.4% divergent from both a Bolivian clade of M. minuta and a second clade encompassing Brazilian and northern South American sequences (Siles and Baker, 2020). Therefore, it is possible that the population in the Yavarí-Ucayali interfluve may eventually be shown to represent a distinct taxon and require another name if M. minuta is further subdivided.

REMARKS: All our specimens of Micronycteris minuta from Nuevo San Juan were collected from a single roost, where about 17 individuals were clustered approximately 4 m above the ground inside a hollow standing tree in primary hillside forest ; of these, one adult male and three adult females were collected on 23 October 1999. No other bat species were observed in this roost.

Other members of the Micronycteris minuta complex are also known to roost in hollow standing trees (Goodwin and Greenhall, 1961; Handley, 1976; Rengifo et al., 2013).

9 But note that some authors measured specimens that are now treated as distinct species (i.e., M. tresamici and M. simmonsae ).