Morphological Analysis of House Mice, Mus Musculus (Rodentia, Muridae) in Southern and Eastern Indonesia and Western Australia

Mammal Study 30: 53–63 (2005) © the Mammalogical Society of Japan

Morphological analysis of house mice, Mus musculus (Rodentia, Muridae) in Southern and Eastern Indonesia and Western Australia

Ibnu Maryanto1,*, Darrel J. Kitchener2 and Siti N. Prijono1

1 Museum Zoologicum Bogoriense, Balitbang Zoologi, Puslitbang Biologi-LIPI. Jl. Raya Jakarta-Bogor KM 46, Cibinong, Bogor, Indonesia 2 Western Australian Museum, Francis Street, Perth, West Australia

Abstract. Univariate and multivariate statistical analysis of 14 skull, dentary and dental characters and five external characters recorded from 78 specimens of Mus musculus indicated the occurrence of two distinct forms in southern and eastern Indonesia. The two forms were distinct from Mus musculus domesticus in Western Australia. The more widespread form was attributed to M. m. castaneus which occurred on Bali, Lombok, Flores, Lembata, Alor, Kai, Banda, Neira, Timor and Roti islands. The other form all of which are new record for the reason from Kisar and Tanimbar Islands (which represent new distributional records for Mus musculus), differed consistently from M. m. castaneus. Descriminant Function Analysis (DFA) using a reduced set of five skull, dental and external characters correctly allocated 98% of individuals to their appropriate form; bulla length, C1M3 length and M1 length were important discriminants between the two forms. Unlike local populations of Western Australian M. m. domesticus, which morphologically differed significantly, the island populations of the widespread M. m., castaneus did not appear to differ significantly.

Key words: house mice, Indonesia, morphological, Mus musculus, W-Australia.

Between 1987–1993 the authors and colleagues were Mus musculus. bactrianus Blyth, 1846 (Southeast Asia) made numerous expeditions to the islands of Jawa, Mus musculus castaneus Waterhouse, 1843 — Type Madura, Bali and those in the Inner and Outer Banda locality Philippines (Southeast Asia) Arcs, Indonesia. During these expeditions, mice com- Mus musculus domesticus Rutty, 1772 — Type local- mensal with people was collected. These were attributed ity Dublin, Ireland (Europe west and south of the dis- to Mus musculus Linnaeus. These house mice showed tribution of M. m. musculus, including British Isles; considerable morphological variation among the island introduced into North and South America, Australia, populations. Additionally a single Mus caroli Bonhote, New Zealand, South Africa and elsewhere) 1902 was collected from Bali (previously only reported We take this taxonomy as our starting and this paper in the study region from Java-Madura and Flores (see reports on a study of morphological variation in Mus Marshall 1977). musculus in Indonesia and briefly compares their The taxonomy of the subspecies of M. musculus has morphology with that of Western Australia populations, been un settled for long time. Studies by Marshall considered to be Mus musculus domesticus (Singleton (1986) and Moriwaki et al. (1986, 1990) have clarified and Redhead 1990). The principal objective of the study the situation to a certain extent and these now appears to was to identify and describe the Indonesia forms and also be agreement among workers that three taxa can be the region and to define their distribution, because there recognized in South-east Asia and Australia on both are still not found information of the mention grouping morphological and biochemical characters. These are: in Indonesia.

*To whom correspondence should be addressed. E-mail: [email protected]; [email protected] 54 Mammal Study 30 (2005)

Fig. 1. Locality of musculus used in this study, M. m. castaneus, ■; M. m. subsp. indet, ●; M. m domesticus, ○.

1 3 Materials and methods excluding cochlea process; I M , length from upper alve- oli anterior margin to last upper molar alveoli posterior A total of 78 adult specimens of Mus musculus was margin; M1M3, upper molar row cusp lengths; M1L, first examined (see Specimens Examined) from the following upper molar cusp length; M1B, first upper molar cusp Indonesian islands: Jawa (1), Bali (1), Lombok (1), breadth; ANCON, distance between tips of dentary Flores (6), Lembata (4), Alor (12), Kisar (3), Tanimbar Is angular and coronoid process; SVL, snout tip to anus (10), Kai Besar (1), Banda Neira (4), Ambon (2), Timor length; TVL, tail tip to anus length; EAR, ear length, (6), Roti (3), and from Western Australian localities: basal notch to distal tip; TIB, tibia length; PES, pes Marchagee (11) Bungalbin (7), Yowie (2), Woodstock length, excluding claw. Homestead (2), Hamelin Homestead (2). The locality of Pelage descriptions follow the color terminology of these specimens is listed in Figure 1. All specimens are Ridgway (1912). currently lodged in the Western Australian Museum. Adult condition was difficult to diagnose. This was Fourteen measurements of skull, dentary and dental because animals frequently had a basicranial region with characters and five of external characters (all in mm) incompletely fused but the animal was clearly adult in were recorded from adult specimens. The claw, dental that it had bred, or had scrotal testes with enlarged epi- and dentary characters were measured to 0.01 mm and didymis or had considerably worn teeth. In judging adult the externals to 0.1 mm. Terminology used in the condition the following criteria were adopted. Some descriptions of the skull and dentary follow Musser and degree of fusion of sutures had progressed between the Heaney (1992). The measurements recorded were: CBL, basioccipital/basisphenoid and basisphenoid/presphe- condylobasal length; RB, rostrum breadth; IOB, least noid sutures; the basisphenoid median ridge was elevated interorbital breadth; ZW, zygomatic width; IFL, incisive and thin; the crest in the region of contact between the foramen breadth; DL, dentary length, from condyle to I, posterior arms of the post-tympanic hook and both the alveoli anterior edge; PL, palatal edge; BL, bulla length lateral point of the occipital and periotic capsule was Maryanto et al., Morphological analysis of Mus musculus 55 apparent; some tooth wear apparent; and evidence of Table 1. Multiple regressions on sex and island or locality of Mus reproductive activity. Several animals with excessive musculus for skull, dentary, dental and external characters. tooth wear indicative of very old age were also excluded. MAIN EFFECTS The effect of sex and island on all skull dentary and Character Sex Island/Locality Interanction dental characters was examined by two way anova for CBL 0.921 0.508 0.86 those islands/localities with both male and female speci- RB 0.179 5.346*** 0.53 mens present (Indonesia. Flores, Lembata, Alor, Tanim- IOB 0.434 1.901 0.97 bar, Banda, Timor, Roti; Western Australia. Marchagee, ZW 4.162 1.612 0.68 Bungalbin, Yowie). A similar analysis was run for the IFL 0.393 1.439 0.41 external characters but with only 10 islands/localities IFB 0.255 5.709*** 0.94 (there were no external characters for the Western Aus- DL 0.358 1.071 1.36 tralia localities). Examination of the residuals from the PL 0.42 0.404 0.38 two way anova analysis gave no indication of hetero- BL 0.03 12.385*** 0.53 IlM3 0.304 1.183 0.98 scedasticity. Because of the number of associations M1M1 0 1.837 0.41 being tested the level of significance was set at P < 0.01. 1 M L 0.557 0.561 0.83 Significance levels were as follows **0.01 > P > 0.001; M1B 0.028 3.114 0.53 ***P < 0.001. ANCON 0.952 0.702 0.44 Stepwise Canonical Variate (Discriminant Function) SVL 0.041 2.964 0.89 analysis (DFA) were run separately for skull, dentary TVL 0.435 2.544 0.41 and dental characters and external characters, using all EAR 0.005 1.81 0.41 characters measured and for males and females com- TIB 0.335 1.854 0.56 bined after first examining for sexual dimorphism. PES 0.002 0.427 0.54 A reduced set of five skull, dentary and dental charac- F values are presented for the main effects (there were no significant ters was used in all the presented DFA because in all interactions). For explanation of character codes see Materials and instances they provide similar DF plots to those, which methods section. Significance levels are *, 0.05 > P > 0.01; **, 0.01 > P > 0.001; ***P > 0.001. utilized the full set of 14 characters. This reduced set of characters was selected in all these analysis because the sample size of the smallest group selected was always Bulla length was the character most significantly influ- less than the total number of characters measured. This enced by island or locality (F1, 24 = 12.385; P < 0.001). reduced set of characters was selected because they No character had a significant interaction between sex provided values that minimized Wilk’s lambda. and island/locality.

Results Multivariate analyses Males and females were combined in the following Univariate statistics analyses because none of the characters were signifi- Mean, standard deviation, minimum and maximum cantly influenced by sex and there were no significant values and sample size for The Jawan, Kisar and West- interactions between sex and locality/island. ern Australian group are presented in Table 3 for all All islands/localities characters examined. (a) Skull, dentary and dental characters A DFA was run using all 14 characters based on all Two way anova islands and each of the Western Australian localities as The two way anova was run for all skulls, dentary the a. priori groups. Three broad groups of islands/local- dental and external characters for islands/locality group. ities were recognizable from that analysis; these groups Sex were still apparent when a reduced set of five characters No characters were significantly influenced by sex was selected. These groups were as follows (Table 1). (i) The Jawan Group comprises Java I., Bali I., Lembata Island/locality I., Flores I., Lembata I., Alor I., Kai Is, Ambon I., Only island or locality significantly influenced three Timor I. and Roti I. of the 19 characters. These were RB, IFB, BL (Table 1). (ii) Kisar Group comprises Kisar I., Selaru I. and 56 Mammal Study 30 (2005)

Table 2. Canonical Variate Function coefficients from DFA between three locality groups (Jawan, and Western Australian — see text for explanation of groups). a) Character Function 1 Function 2 BL 0.8885 (8.8597) –0.0038 (–0.0375) RB –1.0139 (–4.7727) 0.7872 (3.7056) IlM3 –0.2123 (–0.5331) –2.3625 (–5.9332) PL –0.4800 (–1.0256) 1.1048 (2.3604) CBL 1.0730 (1–5394) 0.6919 (0.9927) Constant –28.9263 0.0593 Variation explained 78.6 21.4 b) Character Function 1 Function 2 SVL 0.2991 (0.0540) 1.0959 (0.1980) TVL 0.6842 (0.0877) –0.0416 (–0.0053) EAR –1.1067 (–1.4007) 0.2221 (0.2812) TEB 0.1668 (0.1785) –0.9240 (–0.9888) Constant 4.2878 2.2484 Variation explained 89.5 10.5 Standardized values, followed by (in brackets) unstandardized values for (a) a reduced set of five skull and dental characters, and (b) all five external characters. For explanation of character codes see Materials and methods section.

Yamdena I. (iii)Western Australian Group comprises Marchagee, Bungalbin, Yowie, Woodstock Homestead and Hamelin Homestead. A DFA run on a reduced set of five characters (see Table 2a), selected from the above analysis, based on these above three broad groups, extracted two very significant Functions (
2 = 163.7; df = 10; P < .00001 and
2 = 52.4; df = 4; P ? .00001). Function 1 explained 78.6% of the variance and Function 2, 21.4%. A total of

95.7% of individuals were classified to their correct Fig. 2. Plot of Functions 1 and 2 from Canonical Variate Analysis group. Misclassifications were in the Jawan Group with on three island/locality groups (Jawan, Kisar and Western Australian) one of the 35 individuals classified to the Western Aus- based on (a) a reduced set of five skull and dental characters, and (b) tralian Group and two individuals to the Kisar Group. all five external characters. Island codes are as follows: a, Alor; b, Bali; d, Banda Neira; f, Flores; h, Bungalbin; i Kai; j. Jawa; k, Kisar; 1, The Western Australian Group separated from both Lembata; m, Marchagee; n, Ambon; o, Roti; s, Selaru (Tanimbar); t, the Kisar and Jawan Groups on Function 1 (Fig. 2a). The Timor; w, Woodstock H. S - Hamelin H.S.; x, Yamdena (Tanimbar); characters loading heavily (>0.5) on Function 1 were y, Yowie; z, Lombok. RB, CBL, and BL (Table 2a). The Kisar and Jawan Groups were partially separated on Function 2 (Fig. 2a). based on all islands/localities and using the three above The characters loading heavily (>0.5) on Function 2 broad island/locality groups (the Jawan, Kisar and West- were I1M3; PL and RB. ern Australian). This DFA extracted two significant (b) External characters Functions (
2 = 55.51; df = 8; P < .00001 and
2 = 8.20; The DFA was run using all five external characters df = 3; P < 0.042). Function 1 explained 89.5% of the Maryanto et al., Morphological analysis of Mus musculus 57 variance and Function 2, 10.5%. incisive foramen breadth, snout to vent length, and M1M3 A total of 69.5% of individuals were classified to their length, for the islands groupings of Alor, Flores, Banda, correct group. However, most misclassifications were Lembata and Timor (Roti was excluded because its spec- between the Kisar and Jawan Groups. 89.5% of the imens were missing a number of external measurements) members of the Western Australian Group (one was extracted two significant functions (
2 = 27.02; df = 12; misclassified to the Kisar Group and one to the Jawan P = 0.008 and
2 = 13.03; df = 6; P = 0.043) which Group). explained a total of 92.7% of the variance. However, The plots of Functions 1 and 2 (Fig. 2b) indicated that these island groups overlap considerably in discriminant the Western Australian Group largely separated, I from function space, such that only 40% of individuals were the other two groups on Function 1. The characters classified to their correct island (Fig. 3). loading heavily (>0.5) on Function 1 were EAR, and The Jawan and Kisar Groups SVL (Table 2b). A DFA using a reduced set of five skull dental and The Jawan Group external characters (listed in Table 4) and based on the The sample size of the island populations in the Jawan two groups of Jawa and Kisar, extracted a significant Group was small. Only Alor, Flores Banda, Lembata, Function (
2 = 47.05; df = 5; P < 0.00001) (Fig. 4). A Roti and Timor had a sample size of three or more indi- total of 97.6% of all individuals were classified to their viduals. There is no evidence from these rather small correct group. The only misclassification was a Jawan sample sizes of morphological variation between island Group individual that was classified to the Kisar Group. populations within the Jawan Group. MANOVA to The characters loading heavily (>0.5) were I1M3 length, examine for significant differences of the skull, dentary, bulla length and M1 length. dental (omitting nasal length and zygomatic width which The Western Australian Group were absent from a number of individuals) and sepa- Within the Western Australian Group only the popula- rately for external characters between these above island tions of Marchagee and Bungalbin had individuals with populations, revealed that none of these characters varied both skull and external measurements complete and were significantly between these islands (Wilk’s lambda = large enough to compare morphologically (samples N = 0.010; df = 70; P = 0.548 and Wilk’s lambda = 0.520; 10 and N = 7 respectively). A one-way ANOVA to com- df = 25; P = 0.520 for skull etc. and external characters, pare the morphology of these two populations indicated respectively). that several characters differed significantly between Further, a DFA of a reduced set of three characters, these populations. These were IOB (F1, 15 = 5.439, P = 0.034); SVL (F1, 15 = 5.110, P = 0.039) and PES (F1, 15 = 4.731, P = 0.046). A DFA between these two popula- tions using a reduced set of three characters (IOB, SVL and DL) extracted a highly significant Function (
2 = 25.72; df = 3, P < .00001) with all individuals classified

Fig. 3. Histogram of Function 1 from Canonical Variate Analysis Fig. 4. Histogram of Function 1 from Canonical Variate Analysis based on a reduced set of five skull, dental and external characters for based on a reduced set of three skull dentary and external characters the two island groups (Jawan /black color, and Kisar/white color). for the two Western Australian localities Marchagee (white color) and Island codes are as for Figure 2 caption. Bungalbin (black color) ■. 58 Mammal Study 30 (2005) correctly to their appropriate population (Fig. 5). TAXONOMY These data indicate the occurrence of morphological Mus musculus castaneus differences between populations of Western Australian Waterhouse, 1843 Mus musculus. Holotype The Jawan, Kisar and Western Australian Groups Apparently lost (Marshall 1977: 209) identified by the DFA represent three distinct forms of Type locality Mus. The taxonomy of these forms will be discussed Philippine islands below. Specimens examined See later section ‘Specimens Examined’ Diagnosis Mus musculus castaneus in southern and eastern Indo- nesia differs from Mus musculus subsp. indet. From Kisar and Tanimbar Islands by averaging slightly larger in some characters (Table 3). For example (in mm), condylobasal length 20.33 ± 0.75 Vs. 20.02 ± 0.70; rostrum breadth 3.93 ± 0.23 Vs. 3.86 ± 0.20; incisive foramen breadth 1.73 ± 0.13 Vs. 1.68 ± 0.11; bulla length 3.57 ± 0.10 Vs. 3.39 ± 0.09; and snout to vent length 67.1 ± 5.90 Vs. 63.6 ± 6.66, but averages smaller in some dental characters. For example, I1M3 length 9.95 ± 0.41 Vs. 10.28 ± 0.50 and M1M3 length 3.83 ± 0.26 Vs. 3.93 ± 0.23. I1M3 length shorter relative to condylobasal length (Fig. 6a) and bulla length generally longer relative to I1M1 length (Fig. 6b). It differs from Mus musculus domesticus from West- ern Australia by averaging larger in some characters (see Table 3). For example (mean ± SD, in mm), rostrum breadth 3.93 ± 0.23 Vs. 3.53 ± 0.17; incisive foramen length 5.08 ± 0.24 Vs. 4.83 ± 0.24; incisive foramen breadth 1.73 ± 0.13 Vs. 1.58 ± 0.06; palatal length 10.68 ± 0.54 Vs. 10.47 ± 0.40; I1M3 length 9.95 ± 0.41 Vs. 9.81 ± 0.35; M1M3 length 3.83 ± 0.26 Vs. 3.69 ± 0.16; snout to vent length 67.1 ± 5.9 Vs. 61.7 ± 6.6; tail to vent length 83.5 ± 8.1 Vs. 75.5 ± 6.4 but with bulla length averaging smaller 3.57 ± 0.10 Vs. 3.78 ± 0.11 and ear length averaging smaller 12.7 ± 0.7 Vs. 13.6 ± 0.9. Ros- trum broader relative to I1M3 length. Bulla shorter relative to rostrum breadth. Tail to vent length longer relative to ear length (Fig. 7), zygomatic plate inclined forward rather than vertical, as illustrated in Marshall (1981: Fig. 3.1 and 3.2). Description As described in Marshall (1977, 1981). Pelage of dorsal surface Sepia to Ochraceous-Tawny with base of furs Deep Neutral Gray. venter hair Brown to Ochra- ceous Buff with basal fur also Deep Neutral Gray. 1 3 Fig. 5. Plot of I M length versus (a) condylobasal length (CBL) Manus dorsal surface Warm Buff to Ochraceous Buff. and (b) bulla length (BL) for Mus musculus subsp. indet. from Kisar and Tanimbar and M. m. castaneus from the Jawan Group. Island Pes Light Brownish Olive. Tail Light Brownish Olive, codes as for Figure 2 caption (mm). not bicolored. Maryanto et al., Morphological analysis of Mus musculus 59

Table 4. Canonical Variate Function coefficients from DFA based on a reduced set of five skin dental and external characters for the two Groups: Jawan and Kisar (see text for explanation of groups).

Character Function 1

from three broad BL 0.7644 (7.5036) I1M3 –1.3130 (–2.8401) RB 0.4821 (2.0738) M1L 0.5015 (4.2870)

Mus musculus EAR 0.4842 (0.7021) Constant –23.7131 SVL TVL EAR TIB PES Standardized values followed by (in brackets) unstandardized values. For explanation of character codes see Materials and methods section. , standart deviation; MIN, minimum and MAX, ANGCON SD B 1 racter codes) of adult LM ). Mean; 1 M 3 M 1 M explanation of cha 3 M M. m. domesticus 1 and methods section for Western Australian Group ( Western subsp indet.); and (iii) M. m. ntal and external characters (see Material 0.75 0.45 0.23 0.13 0.40.7 0.24 0.55 0.13 0.2 0.28 0.54 0.12 0.1 0.320.59 0.41 0.19 0.48 0.26 0.11 0.17 0.16 0.25 0.11 0.05 0.49 0.4 0.09 0.31 0.24 0.5 5.9 0.06 0.23 0.24 8.1 0.1 0.4 0.7 0.05 0.11 0.9 0.25 0.35 0.16 0.8 6.6 0.11 8.8 0.04 0.8 0.34 16.6 3.6 0.5 6.4 0.9 0.7 0.5 (s.s.)); (ii) Kisar Group ( 20221222222211011212 Mean 20.33SD 7.34MIN 3.93 18.81MAX 3.64 22.01 6.51N 10.8 8.71 4124414138404039373940404141363132331933 3.43Mean 4.42 5.08 20.02 3.37SD 3.99 7.32 1.73 9.98MIN 11.71 3.86 4.92 4.57 18.3MAX 5.7 10.68 3.72 20.98 1.55 6.53N 3.57 10.77 8.03 2.16 121012121112121212121212111110111112 4.48 3.43Mean 9.95 5.08 4.2 5.52 20.23 9.63 3.51SD 11.65 3.83 1.68 7.36 3.42 10.03 2.13MIN 3.77 4.98 4 3.53 10.82 9.06 4.65 19.07 10.56 1.02MAX 3.64 11.28 21.27 6.07 4.4 3.16 1.53 3.39N 10.79 5.94 8.05 5.35 10.28 1.88 2319242424242424242424242424221920202020 3.22 4.47 2.61 4.83 3.88 1.84 67.1 3.93 0.94 3.42 9.76 1.11 1.58 1.97 3.85 5.28 83.5 3.26 9.82 5.41 11.45 11.35 6.8 5.05 1.04 12.7 9.42 4.15 10.47 49.7 3.55 5.23 18.6 5.84 11.08 3.52 1.45 3.78 68.6 1.69 77 16.5 1.84 4.31 63.6 4.44 9.81 11.3 5.48 100 2.15 0.97 83.3 11.02 9.29 3.69 16.3 1.14 12.2 3.98 3.57 14 5.39 14.8 2 10.3 6.16 8.96 21.2 48.4 1.5 1.07 3.96 3.28 72.1 17.8 70.9 16.3 2.22 1.79 5.75 95.5 13.4 1.12 1.01 61.7 21.6 6.17 4.94 75.5 15.6 13.6 69.5 55.5 12 18.1 85.4 59.1 17.1 16.4 14.9 11.2 19.3 16.8 17.3 14.7 M. m. castaneus )

Measurements, in mm, for skull dentary, de 1 3

Location CBL NL RB IOB ZW IFL IFB DL PL BL I Fig. 6. Plot of rostrum breadth (RB) versus (a) I M length and (b) bulla length (BL) for Mus musculus subsp. indet. from Kisar and Tan- subsp. indet. imbar; M. m. castaneus from the Jawan Group. and M. m. domesticus

M. m. castaneus from Western Australia. Island codes as for Figure 2 caption (mm). Jawan Group ( Kisar/Tanimbar Group Group Kisar/Tanimbar M. m. Group Australian Western M. m. domesticus locality groups. Table 3. maximum and N, sample size. N, sample and maximum (i) Jawan Group ( 60 Mammal Study 30 (2005)

Distribution ± 0.11; ear length 12.2 ± 0.8 Vs. 13.6 ± 0.9. Rostrum Nepal; India (West Bengal, Calcutta, Maharashtra breadth larger relative to I1M3 length. Bulla length State, Bombay, Poona, Mysore State); Sri Lanka; smaller relative to rostrum breadth (tail to vent length China; Japan; Taiwan; Burma; Vietnam; Thailand; West longer relative to ear length, Fig. 7). Malaysia; Singapore; Indonesia (Sumatera, Java, North Description Sulawesi; Sumba; Sangir; Buru; Ambon; Komodo; The morphology of the skull and externals and pelage Philippines (Luzon, Mindanao) (Marshall 1977). Bali; color, apart from close detailed in the diagnosis, is simi- Lombok; Flores; Lembata; Alor; Kai Is; Banda Neira; lar to Mus musculus castaneus. Timor and Roti (this study). Distribution Kisar Island, Selaru and Yamdena (Tanimbar Is). Mus musculus subsp. indet. Remarks Specimens Examined The specimens from Kisar and Tanimbar are clearly See Specimens Examined section closest morphologically to Mus musculus castaneus but Diagnosis are distinct from that subspecies. From descriptions and Mus musculus subsp. indet. from Kisar and Tanimbar measurement of other Mus musculus that have an Asian Islands differs from Mus m. castaneus from eastern distribution and which are presented in Marshall (1977, Indonesia as detailed in the earlier diagnosis of the latter 1981, 1986). These specimens are also close to Mus. m. species. tytleri Blyth, 1859, but differ from that species in having Mus musculus subsp. indet. Differs from Mus muscu- a shorter pes length (mean ± STD) 16.3 ± 0.5 Vs. 17.4 ± lus domesticus from Western Australia by some larger 0.8, broader interorbital breadth 3.72 ± 0.12 Vs. 3.46 ± mean skull, dental and external measurements (Table 3). 0.11, and larger incisive foramen length 5.08 ± 0.19 Vs. For example, rostrum breadth 3.86 ± 0.20 Vs. 3.53 ± 4.70 ± 0.20 and bulla shorter 3.39 ± 0.09 Vs. 3.59 ± 0.14. 0.17; incisive foramen length 5.08 ± 0.19 Vs. 4.83 ± 0.24; I1M3 length 10.28 ± 0.50 Vs. 9.81 ± 0.35; M1M3 Mus musculus domesticus Rutty, 1772 length 3.93 ± 0.23 Vs. 3.69 ± 0.16, but averages small in Name attributed to Rutty (1772) where it was a nomen some others. For example, condylobasal length 20.02 ± nudem (Schwarz and Schwarz 1943). 0.70 Vs. 20.23 ± 0.59; bulla length 3.39 ± 0.09 Vs. 3.78 Discussion

A problem endemic to examination of morphological differences between and among species of Mus is the dif- ficulty in aging specimens (Marshall 1977, Corbet 1990). Considerable care was taken in this study to exclude juvenile, subadult and very old animals from the analy- ses such that discrimination between the various Mus groups is considered to be little affected by age of indi- viduals. Evidence for this is obtained from the univariate plots of some skull and dental characters (Figs. 6a) and external characters (Fig. 7) which show that relationships between the characters which discriminate between the forms and among M. musculus domesticus, had different covariances. The Kisar and Tanimbar (Selaru and Yamdena Is) populations of M. musculus were morphologically close to M. m. castaneus. They were, however, distinct mor- phologically from the other widespread island popula- Fig. 7. Plot of tail to vent length versus ear length for Mus musculus tions of M. m. castaneus, which probably represent M. m. subsp. indet. from Kisar and Tanimbar Islands M. m. castaneus (s.s.) from the Jawan Group, and M. m. domesticus from Western Australia. castaneus (sensu stricto). The skull morphology of the Island codes as for Figure 2 caption. Kisar and Tanimbar M. musculus is about as divergent in Maryanto et al., Morphological analysis of Mus musculus 61 discriminant function space from M. m. castaneus as is vegetation and climate are not dramatically different to M. m. domesticus from M. m. castaneus. Further, unlike those on some of the other islands (Oldeman et al. 1980). the situation with M. m. domesticus in Western Australia, It would appear, then, most likely that the Kisar and which showed morphological divergence between local Tanimbar form of Mus musculus is taxonomically dis- populations, we were unable to demonstrate that M. m. tinct from M. m. castaneus (s.s.) elsewhere in Indonesia. castaneus varied morphologically between islands. This Morphological differentiation of several other wide- raises the question as to the nature of the morphological spread species in addition to Mus musculus has recently divergence of the Kisar and Tanimbar populations from been reported for the island of Wetar, which adjoins M. m. castaneus. Kisar, and from the Tanimbar group. A recent study by The extent of the morphological divergence and Kitchener et al. (1995) on morphological variation in the pelage coloration which occurred between local popula- bat Myotis adversus (Horsfield 1824) which is wide- tions of M. m. domesticus in Western Australia and other spread throughout Nusa Tenggara where it changes little M. musculus populations in Australia (Singleton and from Java to Alor. However, on Wetar Island M. Redhead 1990) has developed since the arrival of Euro- adversus differentiates into a distinct subspecies and pean people, whether with early Dutch vessels or more further east on Tanimbar Island it differentiates again to a recently following settlement of Western Australia. Evi- second subspecies. Another bat, Nyctimene keasti from dence for this is the occurrence of Mus musculus only in Maluku Tenggara, also differentiates into a morphologi- the uppermost layers of Western Australian palaeonto- cally distinct subspecies on Tanimbar Island (Kitchener logical sites that have a European association (A. et al. 1995b). Baynes, pers. comm.). In Australia M. musculus regularly A new species of mosaic-tailed rat, Melomys has also reaches plague proportions (Newsome 1969, Chapman recently been described by Kitchener and Maryanto 1981) providing opportunity for widespread gene flow (1995), from Yamdena Island (Tanimbar). Clearly popu- across local populations. This suggests that the morpho- lations of mammals on islands in the southwestern part logical divergence between local populations, such as of the Maluku Tenggara administrative province (see that of Marchagee and Bungalbin in Western Australia, Fig. 1) offer either opportunity for greater genetic drift be as a consequence of strong differential natural selec- and/or different selection pressures than occurs on adja- tion. Opportunity for such strong selection (and genetic cent islands. drift) may be heightened at the end of plagues when pop- ulations may pass through severe bottlenecks (Singleton Acknowledgments: We are grateful for the support of and Redhead, 1990). Mr A. Reeves, Director, Western Australian Museum, Given its Asian origin of some one million years and to Dr Soetikno, Director, Puslitbang Biologi, Mr ago (Moriwaki et al. 1990), island populations of M. m. Drs. M. Amir MSc, Director, Balitbang Zoologi Bogor, castaneus in southern and eastern Indonesia presumably Indonesia and the Directors of Sub Balai Konservasi in have been in situ for a much longer period of time than Nusa Tenggara Barat (Ir. P. Supriadi); Nusa Tenggara has M. m. domesticus in Western Australia. Despite this, Timur (Ir. J. Mochtar) and Maluku Tenggara (Ir. J. we were unable to demonstrate morphological variations Rustandi). between these island populations such as occurred A number of colleagues assisted in the field work, between local populations in Western Australia. This including the following: Bapak Boeadi; Maharada- indicates that comparable natural selection pressures tumkamsi; A. Suyanto (Balitbang Zoologi); R. A. How, were not operating between these island populations of K. Aplin and R. E. Johnstone (Western Australian M. m. castaneus or that colonization events between Museum), L. Schmitt (University of Western Australia), these islands were frequent to prevent their morphologi- Mr D. King (Agricultural Protection Board, Western cal divergence. Whatever is the situation, the Kisar and Australia), C. Watts (South Australian Museum). Prof Tanimbar Islands would not appear to offer a more diffi- Seigo Higashi (Graduate School of Enviromental Earth cult route for colonizing events that do the other islands Science, Hokkaido University. Sapporo-Japan) and JSPS considered; they were not, for example, more isolated by under Ronpaku program support this paper. Mr Peter current or past sea barriers than some of these other Easton (Curtin University of Technology) and Mr C. islands (Heaney 1991). Further, these two islands would Keast (Western Australian Museum) removed and cleaned not appear to offer unique selection pressures in that their the skull of Mus used in this study. All measurements 62 Mammal Study 30 (2005) were taken and recorded by Mr P. Easton. Mrs N. Indonesia, Australia, Papua New Guinea and Solomon Islands. Cooper, Western Australian Museum ran the computer Record of the Western Australian Museum 17: 191–212. Kitchener, D. J. and Maryanto, I. 1995. A new species of Melomys programmes. Mrs S. Dalton, Western Australian Muse- (Rodentia, Muridae) from Yamdena Island, Tanimbar Group, um, typed the manuscript. Particular thanks are extended Eastern Indonesia. Record of the Western Australian Museum to Rick How who shared the burden of trapping on 17: 43–50. Kitchener, D. J., Packer, W. C. and Suyanto, A. 1995. Systematic almost all of the twelve principal Indonesian expeditions. review of Nyctimene cephalotes and N. albiventer (Chiroptera: The fieldwork was supported by a number of grants Pteropodidae) in the Maluku and Sulawesi regions, Indonesia. including National Geographic Society Research Grants, Record of the Western Australian Museum 17: 125–142. Washington; Australian Research Council Canberra; Kuroda, N. 1934. Korean mammals preserved in the collection of Marguis Yamashina. Journal of Mammalogy 15: 229–239. and Australian Nature Conservation. Agency, Canberra. Marshall, J. 1977. A synopsis of the Asian species of Mus. 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Maryanto et al., Morphological analysis of Mus musculus 63

Appendix 1.

Specimens examined.

INDONESIA M. musculus castaneus Alor Island: Kalabahi (8°14'S, 124°32'E), WAM M (37608-9, 37614, 37633, 37653, 37660-1, 37669, 37684-5, 37697) (4 males, 8 females). Ambon Island: Ambon (3°41'S, 128°10'E), WAM M (42366-7) (2 females). Bali Island: Gianyar (8°33'S, 115°23'E), WAM M 38275 (female). Banda Neira Island: Banda Neira (4°31'S, 129°50'E), WAM M 42371 (male). Bangko Bata (4°31'S, 129°50'E), WAM M (42028-9, 42039) (3 females). Flores Island: Kelimutu Woloaru (8°42'S, 121°54'E), WAM M (32003, 32045, 32049, 32055-6, 32058) (2males, 4 females). Java Island: Jakarta, West Java (6°08'S, 106°45'E) WAM M 27865 (male). Kai Besar Island: Elat (5°39'S, 132°59'E) WAM M42878 (male). Lembata Island: Belang Watokobu (8°26'S, 123°22'E), WAM M (32151, 32163-4, 32170) (1 male, 3 females). Lombok Island: Batu Koq (8°19'S, 116°-26'E), WAM M33883 (female). Roti Island: Baa (10°44'S, 123°06'E, WAM M (35427, 35444) (2 females). Oeseli (10°51'S, 123°05'E), WAM M 35455 (male). Timor Island: Baumata (10°11'S, 123°43'E), WAM M 30206 (male). Boentuka, WAM M 27821 (male). Lando, WAM M (27819-20) (2 females). Lifuleo Oisina (9°18'S, 123°30'E), WAM M 38106 (male). Panite (9°50'S, 124°29'E) WAM M 34986 (female).

Mus musculus subsp. indet. Kisar Island: Wonreli (8°5'S, 127°12'E), WAM M (44489, 44491, 44733) (2 females 1 sex unknown). Yamdena: Lat Dalam (7°03'S, 131°07'E), WAM M 43654 (female). Selaru Island: Adaut (8°09'S, 131°08'E), WAM M (44210-1, 44285, 44289, 44292-3, 44295-6, 44307) (3 males, 6 females)

Mus musculus domesticus Western Australia: Bungalbin Hill Area (30°17'30''–30°18'30''S, 119°42'30''–119°44'E), WAM M (20287-90, 203133 20315, 20317) (5 males, 1 female, 1 sex unknown). Hamelin Station (26°26'S, 114°11'E), WAM M (28120, 28122) (male, female). Marchagee Town (Siding), (30°02'10''–30°03'05''S, 116°05'55''–116°05'55''E), WAM M (13824, 13826-34, 13836) (8 males, 3 females). Woodstock Area (21°36'35''–21°37'01''S, 118°57'13''–118°57'44''°E), WAM M (28080, 29248) (1 male, 1 female). Yowie Rockhole, -Kurnalpi (30°28'S, 122°24'E), WAM M (20391-2) (1 male, 1 female).