Oryzomys macconnelli Thomas, 1910

PATTON, JAMES L., DA SILVA, MARIA NAZARETH F. & MALCOLM, JAY R., 2000, Mammals Of The Rio Juruá And The Evolutionary And Ecological Diversification Of Amazonia, Bulletin of the American Museum of Natural History 2000 (244), pp. 1-306 : 159-160

Oryzomys macconnelli Thomas, 1910

TYPE LOCALITY: ‘‘River Supinaam, a tributary of the lower Essequibo, Demerara, British Guiana,’’ Supenaam River, District Demerara, Guyana, 06°59̍N, 58°31̍W (Musser et al., 1998: 178).

DESCRIPTION: See above, figures 95 and 96, and tables 38 and 40.

SELECTED MEASUREMENTS: See table 39.

MOLECULAR PHYLOGEOGRAPHY: The number of specimens is too few to permit any valid morphometric comparison between localities along the river. However, we do have at least 414 base pairs of cytochrome­b sequence from seven different individuals,

three from Condor (locality 6), two from Barro Vermelho (locality 12), and two from Vai­Quem­Quer (locality 15). Sequences from individuals taken from the same locality are identical, so all variation recorded is distributed among populations. Haplotypes from Condor and Barro Vermelho differ by 1.71%, but these two differ by an average of 4.11% relative to that from the mouth of the river, which in turn is nearly identical to haplotypes from the upper Rio Urucu to the east of the Rio Juruá (see map, fig. 98 and tree fig. 99). Considerable structure thus occurs over a relatively short distance for this species within the Rio Juruá basin, and further geographic sampling of this species in western Amazonia would be profitable.

DISTRIBUTION AND HABITAT: This species is widely distributed within Amazonia (Musser et al., 1998), but nowhere is it apparently common. Within the Rio Jurua´, we obtained specimens only at three localities: Condor (locality 6) in the Upper Central Region Barro Vermelho (locality 12) in the Lower Central Region, and Vai­Quem­Quer (locality 15) in the Mouth Region. In all cases, the species was only taken in undisturbed terra firme forest, where it was sympatric with both O. perenensis and O. yunganus . Indeed its presence seemed to be a good indicator of relatively pristine forest, which has been our experience with this species at other sites in Amazonia, including the Río Cenepa in the Departamento de Amazonas, Perú (Patton et al., 1982), Balta, on the Río Curanja Departamento de Ucayali, Perú (Gardner and Patton, 1976; Voss and Emmons, 1996), the upper Rio Urucu (M. N. F. da Silva, J. R Malcolm, and C. A. Peres, unpublished), and the Rio Jaú (M. N. F. da Silva and J. L. Patton, unpublished), both in central Estado do Amazonas, Brazil. At the reserves of the INPA/WWF/Smithsonian­sponsored Biological Dynamics of Forest Fragments Project north of Manaus (PDBFF), O. macconnelli was only one of two small mammal species negatively affected by forest fragmentation (Malcolm, 1991b; the other was Caluromys philander ). All specimens were taken in terrestrial traps.

REPRODUCTION: All individuals of both sexes collected were adults of toothwear age class 3 or older. Pregnant or lactating females were taken at a both Condor (locality 6) and Vai­Quem­Quer (locality 15), and hence in both dry and rainy seasons (September and May, respectively); embryo counts ranged from 2 to 4, with a mode of 3.

KARYOTYPE: 2n = 64, FN = 70. The karyotype from JUR 386 (Vai­Quem­Quer, locality 15) is figured in Musser et al. (1998: fig. 106). Additional preparations are available from five specimens from Condor (JLP 15548, 15549, 15563, MNFS 529, 530) and two others from Vai­Quem­Quer (JUR 355 and 393). The autosomal complement consists of 27 pairs of acrocentrics grading evenly from large to small and four pairs of small biarmed elements. The sex chromosomes include a large subtelocentric X and a small acrocentric Y.

SPECIMENS EXAMINED (n = 24): (6) 12m, 7f — JLP 15548–15549, 15563, 15572, 15600, 15619, 15645, 15648, 15662, 15670– 15671, 15685, MNFS 529–530, 536, 548– 550, 563; (12) 2m — JLP 15859, MNFS 747; (15) 1m, 2f — JUR 355, 386, 393.