Apomys (Megapomys) minor, Heaney & Balete & Duya & Duya & Kyriazis & Rickart & Steppan & Rowsey, 2025

Heaney, Lawrence R., Balete, Danilo S., Duya, Mariano Roy M., Duya, Melizar V., Kyriazis, Christopher C., Rickart, Eric A., Steppan, Scott J. & Rowsey, Dakota M., 2025, Three new species of Philippine forest mice (Apomys, Muridae, Mammalia), members of a clade endemic to Mindoro Island, Zootaxa 5647 (1), pp. 1-26 : 21

Apomys (Megapomys) minor , new species lsid:zoobank.org:act: 937153CD-4A47-4E8D-BA0F-FC1A3DDAA702

Figs. 2D and 6B ; Tables 1 and 4

Holotype. Originally cataloged as FMNH 228798 ; to be transferred to PNM, where it has been assigned catalog number PNM 9667 .Adult male captured on 3 February 2015, field number D. S. Balete 10652. Fresh tissue removed from thigh and placed in 95% ethanol. The rest of the specimen was prepared as a full skeleton, stored in 95% ethanol, then cleaned using dermestid beetles and a weak ammonia solution. All parts in good condition.

Type Locality. Philippines: Mindoro Island: Occidental Mindoro Province: Rizal Municipality: Mt. Iglit-Baco National Park : 0.6 km S, 1.1 km W Mt. Wood peak, elevation 1280 m; 12.74101 o N, 121.19833 o E ( Fig. 1 ) .

Measurements. Tables 1 and 4.

Specimens examined (6). Magsaysay Municipality: 4.25 km S, 2.65 km W Mt. Alibug peak, elevation 300 m, 12.30259 o N, 121.2165 o E ( FMNH 235042 ); Rizal Municipality: Mt. Iglit-Baco National Park: 0.6 km S, 1.0 km W Mt. Wood peak, elevation 1280 m; 12.74101 o N, 121.19833 o E ( FMNH 228504 , 228504 , 228506 ; 228797, 228798) .

Etymology. An adjective from the Latin minor , meaning small, in recognition of the status of this species as the smallest in the subgenus Megapomys currently known.

Diagnosis and description. A member of the genus Apomys , with diagnostic features as listed above. The smallest member of the subgenus Megapomys (HB 122 mm, BOL 30.79 mm; Tables 1, 4). The dorsal fur of A. minor is medium-dark brown with barely evident ochraceous highlights; fur behind the ear dark, similar to adjacent fur; darkened “mask” on muzzle largely absent; ventral pelage pale brown, often with white blaze on lower abdomen that rarely extends to below jaw; ears dark brown; skin of fore and hind feet unpigmented, sometimes lightly pigmented ventrally; tail dark brown dorsally, nearly white ventrally ( Fig. 2D ). Skull of A. minor differs from A. crinitus in being smaller overall (e.g., BOL = 30.79 mm vs. 31.5 mm, HB = 122 mm vs. 128 mm), but relative to other members of the A. gracilirostris group, zygomatic breadth is narrow, nasals and diastema are short; nearly equal orbito-temporal length, upper molar toothrow length, and M1 breadth; and greater labial breadth at M3 ( Table 4). Compared to the series from Mt. Wood, our single specimen from Mt. Alibug is similar but has dorsal and ventral fur that is slightly paler and more ochraceous, with a slight but inconspicuous patch of less dark fur behind the ears.

Comparisons. See above.

Distribution. Currently known only from 1280 m elevation, 0.6 km S, 1.0 km W Mt. Wood peak in Mt. Iglit-Baco National Park, and from 300 m elevation at 4.25 km N, 2.65 km W Mt. Alibug peak, near the southern tip of Mindoro ( Fig. 1 ).

Ecology. We captured five A. minor along our transect of Mt. Wood (sampling area 6 in Fig. 1 ), which is one of many peaks within Mt. Iglit-Baco National Park. We also captured one at 300 m near the southern tip of Mindoro, near Mt. Alibug (sampling area 9 in Fig. 1 ). All individuals were captured at night on the ground in traps baited with either live earthworms or thin slices of coconut fried and coated with peanut butter. At Mt. Wood, we captured them only at our lowest sampling area, 1280 m, and not at 1480 m or 1520 m; number per 100 trap-nights at 1280 m was 0.64. Suncus murinus and Rattus tanezumi were the most common species of small mammals at this locality; both are non-native species. Also present in small numbers were the following native small mammals: Crocidura grayi , Anonymomys mindorensis , Apomys microdon , Apomys musculus , Chrotomys mindorensis , Rattus everetti gala , and Rattus mindorensis ; Apomys minor was the most common native species. Vegetation consisted of disturbed montane forest, with trees of the genera Agathis , Acer , Elaeocarpus , Ficus , Lithocarpus , Magnolia , and Syzygium the most common, reaching 12–20 m in height. Because the canopy was rather open, understory and ground-cover plants were abundant. Leaf litter and humus were each 1–5 mm thick.

On Mt. Alibug, we captured one specimen at 300 m in open-canopy secondary lowland forest over limestone heavily impacted by logging and charcoal-making. Molave ( Vitex parviflora ) trees that once dominated this karstic habitat were present but scarce due to heavy logging; small, young Sterculia and Ficus were the most common native tree species, but plantations of the non-native Gmelina predominated. At this elevation, we also captured the native species Crocidura grayi and Apomys microdon , but the non-native pest rat Rattus tanezumi was by far the most abundant small mammal. Our intensive sampling areas at lower elevations (15 m, 90 m, and 170 m) near Mt. Alibug captured no A. minor ; Rattus tanezumi was by far the most abundant species.

Two male A. minor weighing 55–64 g had scrotal testes measuring 6 x 3 to 7 x 4 mm. Two females weighing 52 and 58 g had pigmented mammae, and one weighing 50 g had tiny, unpigmented mammae.

Figures

FIGURE 1. A, Map of Mindoro Island showing topographic features and the locations of areas intensively surveyed by the authors. 1 = Mt. Calavite; 2 = Mt.Abra de Ilog; 3 = Mt. Halcon; 4 = Mt. Tallulah; 5 = Mt. Mangibok; 6 = Mt.Wood; 7 = Barangay Morente; 8 = Mt. Masulong; 9 = Sta. Teresa Hill and Mt.Alibug; 10 = Ilin Island. Apomys gracilirostris were captured in area 3; A. veluzi sp. nov. in area 2; A. crinitus sp. nov. in areas 4 and 5; and A. minor sp. nov. in areas 6 and 9. Members of the subgenus Megapomys were not detected in areas 1, 7, 8, and 10. B, Elevational ranges of the four species of Megapomys on Mindoro based on specimens reported here. For each species, black circles indicate elevations at which the given species was documented; open circles are elevations along the same transects where the relevant species was not documented; short horizontal lines indicate the maximum elevation along the given transect. For A. gracilirostris, open triangles indicate elevations at which Ruedas (1995) reported that species. Dark vertical lines connect localities along a single transect where the given species was documented.

FIGURE 2. Drawings of four species of Apomys (Megapomys) from Mindoro. A = A. gracilirostris (from study area 3 in Fig. 1), B = A. veluzi sp. nov. (from study area 2 in Fig. 1), C = A. crinitus sp. nov. (from study areas 4 and 5 in Fig. 1), D = A. minor sp. nov. (from study areas 6 and 9 in Fig. 1).

FIGURE 6. Photographs of the skulls of A Apomys crinitus sp. nov. (holotype, FMNH 222954) and B Apomys minor sp. nov. (holotype, FMNH 228798).