Part 18

Diagnosis.--Size average for genus but larger than closest relative, Nyctimene albiventer; wing membranes brown with scattered yellow spots (dried specimen); uropatagium, ears, and feet brown; dorsal surface of tibia set with hair, ventral surface bare; dorsal surface of uropatagium sparsely set with hair, ventral surface having few, scattered hairs; dorsal surface of trailing edge of wing membrane sparsely set with hairs, ventral surface bare; proximal third of upper- and under-surface of forearm set with hair; pelage of back luxuriant and soft (about 10 long); hair on crown and nape shorter than on back (4 to 8); well-defined black dorsal stripe from shoulders to rump (about 2 wide); basal half of most hairs on dorsum Deep Mouse Gray, distal half Light Buff, tips Ochraceous-Tawny; some hairs on back entirely Light Buff; hairs of crown Light Ochraceous Buff tipped with Ochraceous-Tawny; hair on throat and along sides of abdomen Light Ochraceous Buff; hairs of ventral midline Smoke Gray; braincase narrow; zygomatic breadth relatively narrow; well-developed lambdoidal crest in female; rostrum short, wide; upper canines slanted posteriorly; upper incisors large; foramen ovale large (see Fig. 14).

Comparisons.--From Nyctimene major scitulus, the largest kind of Nyctimene in the Solomons, malaitensis differs as follows: smaller in all dimensions (forearm 65 as opposed to 73.5); greatest length of skull 32.4 as opposed to 37.0; length of maxillary tooth-row 10.5 as opposed to 13.0; length of mandibular tooth-row 11.8 as opposed to 14.2.

From nine adults of Nyctimene albiventer bougainville from Bougainville, Kolombangara, and Guadalcanal, malaitensis differs as follows: larger in all dimensions: forearm 65 as opposed to 57.9; greatest length of skull 32.4 as opposed to 29.7; zygomatic breadth 20.4 as opposed to 19.2; and length of maxillary tooth-row 10.5 as opposed to 9.5; length of mandibular tooth-row 11.8 as opposed to 11.1.

From five adults of Nyctimene albiventer minor, from Choiseul and Santa Ysabel, malaitensis differs in the same ways it differs from N. a. bougainville, but the contrast is even greater when malaitensis and minor are compared.

From Nyctimene sanctacrucis, known only from the Santa Cruz Islands, malaitensis differs in being smaller in all dimensions: forearm 65 as opposed to 75; greatest length of skull 32.4 as opposed to 34.5; and length of maxillary tooth-row 10.5 as opposed to 12.9.

Measurements of the holotype.--Length of head and body, 118; tail vertebrae, 23.0; hind foot, 16.0; ear, 14.0; length of forearm, 65.0; 2nd metacarpal, 33.2; 3rd metacarpal, 46.4; 4th metacarpal, 44.3; 5th metacarpal, 46.0; greatest length of skull, 32.4; condylobasal length, 30.6; palatal length, 13.0; breadth of braincase, 12.5; zygomatic breadth, 20.4; interorbital breadth, 5.5; breadth across first upper molars, 9.5; length of maxillary tooth-row, 10.5; length of mandibular tooth-row, 11.8.

Remarks.--In size, Nyctimene malaitensis is intermediate between N. albiventer and N. major. Because the type of malaitensis is brown and not pale gray, as are females of major, N. malaitensis most likely is more closely related to N. albiventer, in which the females are brown. The teeth of the holotype and only known specimen of malaitensis are too worn to be useful in determining the relationships between these species.

When more specimens are available, N. malaitensis may prove to be a subspecies of N. albiventer. At present, malaitensis is accorded specific rank in order not to obscure the apparent relationships of N. albiventer bougainville and N. a. minor. Additionally, N. malaitensis is given specific rank because (1) it is larger (especially in external dimensions) than the largest subspecies of N. albiventer (compare above measurements with those in Table 3), and (2) malaitensis does not form a cline with either of the two subspecies of N. albiventer.

Specimen examined (one female).--Malaita in July, 24103 (holotype).

=Nyctimene major=

This large species of tube-nosed bat has at least four subspecies, one of which (N. major scitulus) is endemic to the Solomons. The species occurs throughout eastern New Guinea and on many of the islands adjacent to the eastern coast of New Guinea, including the Trobriand Islands, the Bismarck Archipelago, and the Solomons (see Laurie and Hill, 1954:47). The geographic distribution of the species generally is the same as that of N. albiventer.

In Nyctimene major, as in N. albiventer, most males are grayish-brown, whereas most females are pale gray.

=Nyctimene major scitulus= Andersen

1910. Nyctimene scitulus Andersen, Ann. Mag. Nat. Hist., ser. 8, 6:623, December 1, type from Shortland; 1912, Andersen, Catalogue of the Chiroptera ... British Museum, 1:711, from Shortland, New Georgia, Florida, Guadalcanal; 1931, Troughton, Proc. Linnean Soc. New South Wales, 56:206, July 15; 1931, Sanborn, Publ. Field Mus. Nat. Hist., 18:22, February 12, from Choiseul and Malapa; 1942, Tate, Bull. Amer. Mus. Nat. Hist., 80:342, December 31.

1954. Nyctimene major scitulus, Laurie and Hill, List of land mammals of New Guinea, Celebes and adjacent islands, p. 47, June 30.

1862. Harpyia pallasi, Gerrard, Catalogue of the bones ... British Museum, p. 58.

1870. Harpyia cephalotes, Gray, Catalogue of monkeys, lemurs and fruit-eating bats in the British Museum, p. 121.

1878. Harpyia major, Dobson, Catalogue of the Chiroptera ... British Museum, p. 90; 1879, Trouessart, Rev. Mag. Zool., 3:207; 1887, Thomas, Proc. Zool. Soc. London, p. 323; 1888, Thomas, Proc. Zool. Soc. London, p. 476; 1897, Trouessart, Catalogus Mammalium ..., 1:87.

1899. Cephalotes major, Trouessart, Catalogus Mammalium ..., 2:1277.

1899. Gelasinus major, Matschie, Die Megachiroptera ... naturkunde, p. 84; 1904, Trouessart, Catalogus Mammalium ..., Suppl., p. 64.

Specimens examined (four males and one female; dried skins with skulls inside).--Florida in October, 24397, 24413, 24418, 24419.

Measurements.--External measurements of four males and one female are, respectively, as follows: Length of head and body, 134, 128, 134, 134, 136; tail vertebrae, 28, 23, 27, 26, 21; hind foot, 20, 16, 19, 16, 21; ear, 17, 17, 17, 17, 18; length of forearm, 73.8, 68.0, 74.0, 73.6, 78.0.

Remarks.--Nyctimene major scitulus has been recorded only from the western chain of islands in the Solomons (see Fig. 15). Specimens examined by me agree well in external dimensions and color with specimens described by Andersen (1912:712) and Troughton (1931:206-207).

ZOOGEOGRAPHY AND SPECIATION

De Beaufort (1951:113) considered bats of "less zoogeographical importance" than other mammals because the ocean is not an "absolute barrier to their dispersal." Volant animals are ecologically terrestrial and therefore are more nearly earthbound than De Beaufort's remarks would suggest (see Miller, 1966:10). Indeed, many kinds of volant animals are endemic to the Solomons. Birds, for example, are well adapted for flight but pose some of the most complex zoogeographic problems in the area of New Guinea and the Solomon Islands (Mayr, 1940:198; 1942:81-83; Koopman, 1957). Rapid speciation can take place in any situation where there is a high degree of isolation (Wright, 1931; Lack, 1947). In fact, isolation is a most important factor in speciation of insular populations (Baker, 1951:55). The one genus, nine species, and 19 subspecies of megachiropterans that are endemic to the Solomons (Table 4) obviously indicate that bats, although volant, can be restricted to one or more islands long enough for new taxa to evolve.

TABLE 4. A Summary of the Kinds of Megachiropteran Bats in the Solomon Islands and Their Affinities with Faunas of Adjacent Islands.

===========+========+==========+===========+============+=============== | | | Common | Common to | Common to | | Endemic | only to | Solomons, | Solomons, | Totals | to | Solomons | Bismarcks, | New Hebrides, | | Solomons | and | and | and | | | Bismarcks | New Guinea | New Caledonia -----------+--------+----------+-----------+------------+--------------- Genera | 7 | 1 | 0 | 6 | 0 Species | 16 | 9 | 1 | 6 | 1 Subspecies | 20 | 19 | 0 | 0 | 1 -----------+--------+----------+-----------+------------+---------------

The megachiropteran bats of the Solomons have their affinities with the fauna of New Guinea (Table 4); the Solomons and New Guinea have six genera and six species in common. Because the two areas never have been connected (via the Bismarck Archipelago) by dry land, bats probably have reached the Solomons by flying from island to island (see Durham, 1963:357, 359, 361, 363). Deignan (1963:266) has dismissed voluntary or involuntary flight as possible explanations for distributions of bats and birds on islands of the Pacific.