Systematics of Megachiropteran Bats in the Solomon Islands Part 10

---------------+------------------+------------------+------------------- Length of head and body 107.0 (105 -109 ) 109.2 (105 -112 ) 110.0 (106 -117) Tail vertebrae 20.0 (19.3- 20.5) 21.0 ( 20 - 22 ) 19.2 ( 15.5- 23.0) Hind foot 14.2 (13.5- 15.0) 14.3 ( 13.0- 15.9) Ear 11.9 (11.0- 13.0) 12.8 ( 11.8- 14.5) Length of forearm 54.8 (54.0- 55.8) 57.1 (55.9- 59.0) 57.9 ( 55.8- 59.8) Greatest length of skull 28.2 (27.2- 28.9) 28.6 (28.3- 29.7) 29.7 ( 28.6- 30.1) Condylobasal length 26.7 (26.2- 27.5) 27.4 (26.6- 28.0) 28.0 ( 27.8- 28.9) Palatal length 11.2 (10.9- 11.9) 11.6 (11.3- 11.8) 11.7 ( 11.0- 12.5) Breadth of braincase 12.0 (11.5- 12.4) 12.0 (11.7- 12.2) 12.3 ( 12.1- 12.8) Zygomatic breadth 18.9 (18.4- 19.7) 18.6 (18.4- 19.2) 19.2 ( 18.7- 20.0) Interorbital breadth 5.0 ( 4.7- 5.6) 5.3 ( 5.0- 5.6) 5.1 ( 4.7- 5.5) Breadth across first upper molars 8.6 ( 8.4- 8.9) 8.9 ( 8.7- 9.1) 9.1 ( 8.8- 9.6) Maxillary tooth-row 8.9 ( 8.7- 9.3) 9.3 ( 9.1- 9.5) 9.5 ( 9.2- 9.8) Mandibular tooth-row 10.3 (10.0- 10.6) 10.5 (10.2- 11.1) 10.9 ( 10.7- 11.4) ---------------+------------------+------------------+-------------------

_Measurements._--Measurements of the two subspecies from the Solomons are given in Table 3. Some measurements of the type are as follows: Length of head and body, 108; tail vertebrae, 20.5; hind foot, 14.7; ear, 11.3; length of forearm, 55.1; 2nd metacarpal, 27.4; 3rd metacarpal, 39.0; 4th metacarpal, 37.5; 5th metacarpal, 39.1; greatest length of skull, 28.6; condylobasal length, 27.5; zygomatic breadth, 18.4; length of maxillary tooth-row, 9.0; length of mandibular tooth-row, 10.4.

_Remarks._--_Nyctimene albiventer minor_ closely resembles _N.

albiventer bougainville_, differing from the latter mostly in size.

Although adults of _minor_ average only slightly smaller than adults of _bougainville_ (see Table 3), there is only slight overlap (about 0.2 at most) in most minimum dimensions of external and cranial features of _bougainville_ and corresponding maximum dimensions of externals and crania of _minor_. The difference in size is clearly shown in Figs. 13 and 14.

Four specimens of _Nyctimene albiventer_ from Fauro herein are considered to be intergrades between _N. a. bougainville_ and _N. a.

minor_. As shown in Table 3, the specimens from Fauro average slightly larger than those of _minor_ from Choiseul and Santa Ysabel and slightly smaller than specimens of _bougainville_ from Kolombangara and Guadalca.n.a.l. I have a.s.signed the specimens from Fauro to _N. a. minor_ because they generally are closer to _minor_ in size (see Fig. 13).

_Specimens examined_ (five males and four females; seven in alcohol; seven crania extracted and cleaned).--Choiseul in February and March, 23636 (holotype), 23631, 23540, 23646; Santa Ysabel in February, 23539; Fauro in April, 23742, 23743, 23763, 23764.

One specimen of _Nyctimene_ from Malaita Island is smaller than _Nyctimene major_, which is known from Shortland, Alu, Florida, New Georgia, Guadalca.n.a.l, Choiseul, and Malapa (see Fig. 15) and is larger than either of the two subspecies of _Nyctimene albiventer_ known from Bougainville, Fauro, Kolombangara, Guadalca.n.a.l, Choiseul, and Santa Ysabel. This specimen represents a previously unknown species and may be named and described as follows:

=Nyctimene malaitensis=, new species

_Type._--Adult female, skin and skull, in good condition (originally stored in alcohol for about one year), no. BSIP 24103, Bernice P. Bishop Museum; from Malaita Island, British Solomon Islands Protectorate; obtained on 1 July 1964, by Peter Shanahan, original no. unknown.

_Distribution._--Known only from Malaita (see Fig. 16).

_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 spa.r.s.ely set with hair, ventral surface having few, scattered hairs; dorsal surface of trailing edge of wing membrane spa.r.s.ely 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).

[Ill.u.s.tration: FIG. 14. Dorsal and ventral views of skulls of (A) _Nyctimene albiventer minor_ [specimen 23631 [M]], (B) _N. a. bougainville_ [specimen 23381 [M]], and (C) _N. malaitensis_ [specimen 24103 [F]].]

_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 Guadalca.n.a.l, _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.

[Ill.u.s.tration: FIG. 15. Distribution of _Nyctimene malaitensis_ [BC]

and _N. major scitulus_ [RW]. For names of islands see Fig. 2.]

_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 relations.h.i.+ps 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 relations.h.i.+ps 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, Guadalca.n.a.l; 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.

The taxonomic level of endemism can be used as an indicator of antiquity (Dobzhansky, 1941; Koopman, 1958:429-430). The one megachiropteran genus (_Pteralopex_) endemic to the Solomons apparently is an ancient relic.