Part 6

One specimen of _Nyctimene_ from Malaita Island is smaller than _Nyctimene major_, which is known from Shortland, Alu, Florida, New Georgia, Guadalcanal, Choiseul, and Malapa (see Fig. 15) and is larger than either of the two subspecies of _Nyctimene albiventer_ known from Bougainville, Fauro, Kolombangara, Guadalcanal, 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 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.

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. Bats of this monotypic genus occur on Bougainville, Choiseul, Santa Ysabel, and Guadalcanal (see Fig. 4). These four islands probably were contiguous during the maximum lowering of sea level in the Pleistocene (see Durham, 1963:362-363). Bats of the genus _Pteralopex_ are the only kind in the Solomons having a distribution that can be correlated with former land connections between islands.

The distributions of 16 species of megachiropterans known from the Solomons are summarized in Table 5 and in Figure 16. The larger islands (in terms of surface area and elevation) in general have the highest number of species (Guadalcanal 10, Choiseul 9, and Bougainville 8). But Fauro, one of the smallest islands for which data are available, has six species of megachiropterans whereas San Cristobal and Malaita, two of the larger islands, have only three and four species, respectively. Possibly this difference signals the need for additional collecting.

Bougainville and Choiseul, about 60 miles apart, have seven species of megachiropterans in common (Table 5). Fauro, 25 miles southeast of Bougainville and 35 miles west of Choiseul, shares five species with each of these islands (Fig. 16). _Pteralopex atrata_ and _Pteropus rayneri_ occur on Choiseul and on Bougainville, but not on Fauro. Individuals of these species are the largest fruit bats in the Solomons, and their absence on Fauro suggests, therefore, that this small island is ecologically unsuitable, at least in some months, for the support of populations of bats that require relatively large amounts of food. The small size of the island is consistent with this hypothesis, but several other islands as small as Fauro do support populations of the large kinds of _Pteropus_, at least in some months.

TABLE 5. A Summary of Distribution of All Species of Megachiropteran Bats Known from the Solomons. Only Islands Well Known Faunistically Are Listed.

Column headings:

A: Bougainville I: Vella Lavella B: Choiseul J: Kolombangara C: Santa Ysabel K: Russell D: Ndai L: Guadalcanal E: Malaita M: San Cristobal F: Florida N: Ugi G: Fauro O: Rennell H: Shortland P: Ontong Java

===================+==+==+==+==+==+==+==+==+==+==+==+==+==+==+==+== SPECIES | A| B| C| D| E| F| G| H| I| J| K| L| M| N| O| P -------------------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-- R. amplexicaudatus | X| X| X| | X| | X| | | X| | X| | | | P. atrata | X| X| X| | | | | | | | | X| | | | Pt. hypomelanus | | | | | | | | | | | X| | | | | Pt. admiralitatum | | | | X| | | | X| X| | X| X| | | | Pt. tonganus | | | | | | | | | | | | | | | X| Pt. howensis | | | | | | | | | | | | | | | | X Pt. rayneri | X| X| X| | X| | | | X| X| | X| X| X| X| Pt. woodfordi | | | | | | | X| | | X| X| X| | | | Pt. mahaganus | X| | X| | | | | | | | | | | | | D. inermis | X| X| X| | X| X| X| X| X| | | X| X| X| X| M. lagochilus | X| X| | | | X| X| | | X| | X| X| | | M. woodfordi | X| X| | | | | X| X| | | X| X| | | | M. aurantius | | X| | | | X| | | | | | | | | | N. albiventer | X| X| X| | | | X| | | X| | X| | | | N. major | | X| | | | X| | X| | | | X| | | | N. malaitensis | | | | | X| | | | | | | | | | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-- Totals | 8| 9| 6| 1| 4| 4| 6| 4| 3| 5| 4|10| 3| 2| 3| 1 -------------------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--

Santa Ysabel has six species of megachiropterans and 10 occur on Guadalcanal (Table 5). These two islands, separated by about 100 miles of water, share five species (_Rousettus amplexicaudatus_, _Pteralopex atrata_, _Pteropus rayneri_, _Dobsonia inermis_, and _Nyctimene albiventer_). The Nggela Group, in which Florida is the largest island and the only one from which bats have been collected, is 50 miles southeast of Santa Ysabel and 30 miles north of Guadalcanal (Fig. 16). Four species of megachiropterans are known from Florida (_Dobsonia inermis_, _Macroglossus lagochilus_, _Melonycteris aurantius_, and _Nyctimene major_). Three of these are known from Guadalcanal and one occurs on Santa Ysabel. This situation resembles the one involving Fauro, Bougainville, and Choiseul because none of the large bats (_Pteropus_ and _Pteralopex_) is known from Florida, even though two species of large bats that occur on Santa Ysabel to the northwest occur also on Guadalcanal to the south. Possibly Florida and the smaller islands that comprise the Nggela Group are ecologically unsuitable for large bats, or perhaps these small islands can support only limited numbers of individuals during part of a year.

Some of the small islands in the Solomons have populations of large fruit bats. For example, _Pteropus admiralitatum_ and _P. hypomelanus_ have been reported from the small islands in the Russell Group (Table 5). Possibly these species do not live concurrently in the Russells; specimens of the two were obtained in different years. Two small megachiropterans, _P. woodfordi_ and _Melonycteris woodfordi_, also inhabit the Russells. Shortland, a small island about 15 miles south of Bougainville, supports one large bat, _P. admiralitatum_, as well as smaller megachiropterans.

Kolombangara and Vella Lavella are about the same size and are separated by about 15 miles of water. _Rousettus amplexicaudatus_, _Pteropus rayneri_, _P. woodfordi_, _Macroglossus lagochilus_, and _Nyctimene albiventer_ have been collected on Kolombangara but only _P. admiralitatum_, _P. rayneri_, and _Dobsonia inermis_ have been found on Vella Lavella. The difference in the known megachiropteran faunas is more striking when one compares each island with adjacent islands. Two species on Vella Lavella occur also on Choiseul, which is about 35 miles northeastward, and two species occur also on Shortland, which is 120 miles northwestward (Fig. 16). Four of the five megachiropterans on Kolombangara also have been found on Choiseul, about 50 miles northward (Table 5). _Pteropus rayneri_ is the only megachiropteran known from both Kolombangara and Vella Lavella, even though the islands are separated by only a few miles of water. Inadequate data possibly account for the differences in the megachiropteran fauna, but I suspect that some other factors are involved. Although Vella Lavella and Kolombangara do have one species (_P. rayneri_) in common, a different subspecies occurs on each island--_rubianus_ on Kolombangara and _lavellanus_ on Vella Lavella (Fig. 17 and Table 6). This indicates that some factor or factors are operating to keep megachiropterans from moving frequently or easily from one island to the other.

Each of several subspecies of species in the genus _Pteropus_ are known from one or two small islands separated by only a few miles from other islands on which different subspecies occur (see Fig. 6). Judging from this kind of distribution, these bats do not move frequently from island to island. Possibly this is because they cannot easily cross water barriers, or are not inclined to do so because food is abundantly available throughout the year on their home island. Because "flying foxes" frequently are seen in flight over water several hundred yards from shore, the first factor probably is unimportant--at least where short distances are involved. It seems most likely that when abundant food is available these bats have no reason to move even moderate distances.

Distributions of subspecies of polytypic species are summarized in Table 6 and Figure 17. Generally, more subspecies are known from the larger islands than from the smaller islands (Guadalcanal with 5, Bougainville, Choiseul, and Santa Ysabel with 4, Fauro with 2.) The distributions of some subspecies can be used to judge the differential effectiveness of water gaps between islands. The distribution of _Pteropus rayneri lavellanus_ and _P. rayneri rubianus_ is an example.

Choiseul and Santa Ysabel are separated by about 50 miles of water (see Fig. 17) but have three subspecies in common (_Pteropus rayneri grandis_, _Dobsonia inermis minimus_, and _Nyctimene albiventer minor_.) Choiseul is about 50 miles from Kolombangara and about 35 miles from Vella Lavella, but shares no subspecies with these smaller islands although some species are shared (Tables 5 and 6). From these data one can conclude that exchange of genes between populations on Choiseul and populations on Santa Ysabel is frequent but for some reason exchange of genes between populations on Vella Lavella and Choiseul and Kolombangara and Choiseul is infrequent. A series of small islands (Rob Roy, Wagina, and the Arnavon Islands, not named on the maps) connect Choiseul and Santa Ysabel in stepping-stone fashion (see Fig. 17). Possibly these small islands enhance movement of megachiropterans between Choiseul and Santa Ysabel.

TABLE 6. A Summary of Distribution of Polytypic Species of Megachiropteran Bats in the Solomon Islands. Only Islands Well Known Faunistically Are Listed.

Column headings:

A: Bougainville I: Vella Lavella B: Choiseul J: Kolombangara C: Santa Ysabel K: Russell D: Ndai L: Guadalcanal E: Malaita M: San Cristobal F: Florida N: Ugi G: Fauro O: Rennell H: Shortland P: Ontong Java

===================+==+==+==+==+==+==+==+==+==+==+==+==+==+==+==+== SUBSPECIES | A| B| C| D| E| F| G| H| I| J| K| L| M| N| O| P -------------------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-- P. atrata atrata | X| X| | | | | | | | | | | | | | P. atrata anceps | | | X| | | | | | | | | X| | | | Pt. a. solomonis | | | | | | | | | X| | X| X| | | | Pt. a. colonus | | | | | | | | X| | | | | | | | Pt. a. grandis | | | | X| | | | | | | | | | | | Pt. r. rayneri | | | | | X| | | | | | | X| | | | Pt. r. grandis | X| X| X| | | | | | | | | | | | | Pt. r. rubianus | | | | | | | | | | X| | | | | | Pt. r. lavellanus | | | | | | | | | X| | | | | | | Pt. r. monoensis | | | | | | | | | | | | | | | | X Pt. r. cognatus | | | | | | | | | | | | | X| X| | Pt. r. rennelli | | | | | | | | | | | | | | | X| D. i. inermis | X| | | | X| X| X| X| X| | | X| X| X| X| D. i. minimus | | X| X| | | | | | | | | | | | | N. a. bougainville | X| | | | | | | | | X| | X| | | | N. a. minor | | X| X| | | | X| | | | | | | | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-- Totals | 4| 4| 4| 1| 2| 1| 2| 2| 3| 2| 1| 5| 2| 2| 2| 1 -------------------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--

Florida, of the Nggela Group, is approximately halfway between Santa Ysabel and Guadalcanal. _Pteralopex atrata anceps_ occurs on Santa Ysabel and on Guadalcanal but is unknown from Florida. Fauro lies between Bougainville and Choiseul. _Pteralopex atrata atrata_ and _Pteropus rayneri grandis_ occur on Choiseul and on Bougainville but are unknown from Fauro. As suggested earlier, small islands like Fauro and Florida possibly cannot support large fruit bats, although they probably would utilize these small islands when in transit between larger islands.

Fauro apparently is important to the distribution of the two subspecies of _Dobsonia inermis_ and _Nyctimene albiventer_ in the Solomons (see Figs. 9 and 13). In both species, one subspecies is found in the eastern chain of islands and one subspecies is found in the western chain. Specimens of _Dobsonia inermis_ from Fauro and Bougainville can be identified as the subspecies _inermis_ whereas those from Choiseul are assignable to the subspecies _minimus_. _Nyctimene albiventer bougainville_ occurs on Bougainville but specimens of _N. albiventer_ from Fauro and Choiseul can be identified as the subspecies _minor_. Although interchange of genes occurs between populations on Bougainville and Fauro in the case of _D. inermis_, the population of _N. albiventer_ on Fauro is at least partially isolated from the population on Bougainville.