Novltates PUBLISHED by the AMERICAN MUSEUM of NATURAL HISTORY CENTRAL PARK WEST at 79TH STREET, NEW YORK, N.Y
Total Page:16
File Type:pdf, Size:1020Kb
AMERICANt MUSEUM Novltates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2989, 18 pp., 10 illustrations, 1 table October 25, 1990 Sulawesi Rodents: Species Traits and Chromosomes of Haeromys minahassae and Echiothrix leucura (Muridae: Murinae) GUY G. MUSSER' ABSTRACT Results from analyses of chromosomal spreads pairs, two telocentric pairs, and three small met- ofa male tree mouse, Haeromys minahassae, and acentric pairs; a small submetacentric X chro- a male shrew rat, Echiothrix leucura, are described mosome; and small telocentric Y. Although the and illustrated. A 2N of 48, FN of 54, autosomes karyotypes constitute additional sets of data to consisting of 21 pairs oftelocentric chromosomes that provided by morphology of skins, skulls, and and two pairs ofsmall metacentrics, and sex chro- teeth (also briefly described here), the information mosomes made up of a large submetacentric X they provide on the phylogenetic relationships of and smaller submetacentric Y characterize the either species is ambiguous. Rather than indicat- karyotype of H. minahassae. The chromosomal ing closest relatives, these chromosomes may con- set of E. leucura encompasses a 2N of 40; FN of tribute more to polarizing karyotypic characters 75; an autosomal component of 14 submetacentric in certain groups of Indo-Australian murids. INTRODUCTION The small tree mouse, Haeromys mina- countered by collectors -a reflection of the hassae (fig. 1), and large shrew rat, Echiothrix arboreal life style and spotty distribution of leucura (fig. 3), are among the more than 40 the granivorous tree mouse, and the special- species of murid rodents which occur on Su- ized and secretive habits of the vermivorous lawesi and nowhere else. Both species are rep- shrew rat. resented by samples collected only in the Phylogenetic relationships of each species northern and central parts ofthe island, have have yet to be determined. Haeromys mi- been found only in tropical lowland ever- nahassae is related to other species of Hae- green rain forest, and are infrequently en- romys which are found on the Sundaic is- I Archbold Curator, Department of Mammalogy, American Museum of Natural History. Copyright © American Museum of Natural History 1990 ISSN 0003-0082 / Price $2.60 2 AMERICAN MUSEUM NOVITATES NO. 2989 lands of Palawan and Borneo. The genus is Karyotypes were prepared and stained in characterized by retention ofmany primitive the field from chromosomes ofbone marrow, morphological traits and a few derived fea- and processed by employing colchicine, hy- tures. Some of these specializations are also potonic citrate, and flame-drying, procedures shared by species of Chiropodomys, arboreal that were described by Patton (1967). mice indigenous to Indochina and islands on I use four terms to describe the shape of the Sunda Shelf (Musser, 1979; Musser and each chromosome relative to position of the Newcomb, 1983), but this link is weak and centromere: metacentric (the chromosome is whether or not it reflects close relationship biarmed, one arm being about the same length has to be tested with additional data. In what as the other); submetacentric (one arm is has been documented ofits morphology based shorter than the other, about a third of its on museum study skins, crania and mandi- length); subtelocentric (one arm is very short bles, and dentitions, E. leucura retains some relative to the long arm on the other side of primitive characters but most of its diagnos- the centromere); and telocentric (the centro- tic traits are derived. Its closest relative is mere is at the tip of the chromosome or near unknown, and the species seems as isolated enough that any portion on the other side of within a phylogenetic framework as it is in the centromere is so short as to be indistin- its geographic distribution (Misonne, 1969; guishable or nearly so). Musser, 1969). I will try to clarify these muddled views in a systematic revision of Haeromys (Musser, ACKNOWLEDGMENTS in prep.) and a morphological analysis of the Curators at the institutions cited above al- specialized traits peculiar to Echiothrix lowed me access to collections under their (Musser and Sawitzke, in prep.). Here I pre- care and loaned me specimens; I appreciate sent results from analyses of a different data their generous help. set-chromosomal number and morpholo- I am grateful to Charles J. Cole and Carol gy-and discuss its significance for inferring Townsend who taught me the techniques re- phylogenetic relationships between these two quired to obtain and preserve chromosome Sulawesian endemics and other elements of spreads, procedures I could use in isolated the murine fauna native to the Indo-Austra- forest camps. When I returned with my boxes lian region. First, I will introduce the rodents ofslides, Jay allowed full access to equipment by presenting brief descriptions of their in- and supplies in his laboratory; he and Carol sular distributions, morphological character- tutored me in the craft of extracting the sig- istics, forest habitats, and habits. nificant data pressed between glass slide and cover slip. The chromosomal spreads were photographed by Cameron Newcomb. SPECIMENS AND METHODS The manuscript has been strengthened by Specimens cited here are in collections of the intelligent criticisms and contributions of the American Museum of Natural History, Audrone Biknevicius, Charles J. Cole, Law- New York (AMNH); the British Museum rence R. Heaney, and James L. Patton; I thank (Natural History), London (BM); the Muse- them for their time and effort. um Zoologicum Bogoriense, Bogor (MZB); My work in Sulawesi was financially sup- the Rijksmuseum van Natuurlijke Historie, ported by the Celebes Fund ofthe American Leiden (RMNH); and the National Museum Museum of Natural History and Archbold of Natural History of the Smithsonian Insti- Expeditions Inc. I lived in Indonesia under tution, Washington, D.C. (USNM). the auspices of the Lembaga Ilmu Pengeta- I measured external dimensions-total, tail, huan Indonesia and the Museum Zoologi- hind foot, and ear lengths-and took weights cum Bogoriense. The Director of the Muse- shortly after the animals were captured; length um at that time, Dr. Sampurno Kadarsan, ofhead and body was derived by subtracting was my amiable and gracious host as well as tail length from total length. Crania and mo- sponsor. lar rows were measured by me in the labo- This report is Number 120 in Results of ratory. the Archbold Expeditions. 1 990 MUSSER: SULAWESI RODENTS 3 250 and 500 ft in the Malakosa region of ANIMALS AND HABITATS central Sulawesi (see the map in Musser and Haeromys minahassae is the smallest na- Dagosto, 1987: 30). Two specimens from for- tive murid living on Sulawesi (fig. 1; table 1). est along the Sungai Sadaunta (1°22'S, Its short head and body-about as long and 119°59'E) at 3050 and 3300 ft (AMNH thick as my thumb -is clothed by a soft taw- 226817 and 226816) constitute the only oth- ny brown dorsal coat, a white or whitish gray er records from the central part ofthe island. ventral coat, and counterbalanced by a long Elsewhere in Sulawesi, H. minahassae has and brown whiplike tail. been collected in the northeastern arm, but The tree mouse has a gracile cranium (fig. nowhere else. One example, the holotype (BM 5) in which the rostrum is short and wide; 97.1.2.39), comes from Rurukan (1°21'N, the zygomatic plates are narrow, and the zy- 124°52'E); two others (RMNH 21159 and gomatic notches very shallow; the interorbit 21160) were taken near Tumaratus (1°09'N, is wide; the braincase is globular, its dorso- 124°48'E) at 700-800 m; and another (MZB lateral margins weakly defined by indistinct 4840) was obtained from 700-800 m near ridges; the zygomatic arches are slender and Tomohon (1°19'N, 124°49'E). delicate; the incisive foramina are short, as Haeromys minahassae is rarely encoun- is the wide bony palate; the sphenopalatine tered by biologists and infrequently collected, vacuities are small, set in a wide mesopter- possibly because of its arboreal habits and ygoid fossa; the pterygoid plates are wide; and patchy distribution within the forest. As in- the auditory bullae are small. The mandible dicated by specimens I have studied, the al- is stocky, and the ramus is nearly square in titudinal distribution of the tree mouse ex- side view; the coronoid is a low projection, tends from 250 to 3300 ft, a range contained as are the condylar and angular processes. within the elevational brackets of tropical Incisors are short and orange, the molars lowland evergreen rain forest on Sulawesi. In low-crowned and white. Coronal cusp pat- this type of forest along Kuala Navusu, rel- terns are simple. A cusp is retained on the ative humidity is about 100 percent and am- anterolabial corner of each second and third bient air temperatures are moderately high. upper molar, a prominent posterior cingulum For example, during 95 days in 1975, the forms the back ofeach first and second upper period when the mice were collected, the av- tooth, an anterocentral cusp connects large erage minimum air temperature was 73.6°F anterolingual and anterolabial cusps at the (range, 72-76°) and the average maximum front of each first lower molar, and labial temperature was 80.9°F (range, 74-87o). The cusplets are few (fig. 7). Three roots anchor canopy is 20-40 m high, with emergent trees each upper molar, two roots each lower tooth, reaching 50-70 m. The high diversity of spe- which is a primitive condition (Musser and cies includes not only the tall canopy-formers Newcomb, 1983). but understory trees, shrubs, palms, and Characteristics of the Sulawesian tree rat woody vines as well; Musser and Dagosto are generally representative ofthe genus Hae- (1987: 41-44) provided a fuller description.