Collocalia esculenta lagonoleucos Schodde, Rheindt & Christidis

Rheindt, Frank E., Christidis, Les, Norman, Janette A., Eaton, James A., Sadanandan, Keren R. & Schodde, Richard, 2017, Speciation in Indo-Pacific swiftlets (Aves: Apodidae): integrating molecular and phenotypic data for a new provisional taxonomy of the Collocalia esculenta complex, Zootaxa 4250 (5), pp. 401-433 : 426-428

Collocalia esculenta lagonoleucos Schodde, Rheindt & Christidis , new subspecies

Holotype: ANWC 2993 , adult female, collected by R. Schodde and Yaga Kanz at Konone, south foot of Mt. Takuan massif, c. 760 m altitude, south Bougainville Island, 16 August 1964.

Diagnosis: Differs from geographically flanking C. e. tametamele (New Britain) in its usually all-dusky dorsal under-down, finer and more rounded grey freckling over the flanks, more extensive white sides to the rump, and larger size; from C. e. hypogrammica (Nissan Island) in its more vividly dark blue-glossed dorsum, with extensive white sides to the rump, and larger size; and from C. e. becki (central Solomon Islands) in its more extensively white sides to the rump, more extensively white belly and large size. Wing (100–)102–107(–109) mm (both sexes).

Distribution: Buka and Bougainville Islands, Solomon Islands. The population on adjacent Shortland Island may belong to this subspecies, although Salomonsen (1983) and Mayr & Diamond (2001: 383) have referred it to C. e. becki (see below).

Etymology: the epithet lagonoleucos is an arbitrarily formed word derived from the Greek noun λαγον, meaning “flanks”, and the Greek adjective λευκος, meaning “white”, in reference to the distinctive white sides to the rump of this subspecies. It is to be treated as a noun in apposition [Article 31.2.3 of the Code ( ICZN 1999)].

Uniformly dark-rumped populations in the Solomons (becki) are found from Choiseul and Vella Lavella in the northwest to Malaita and Guadalcanal in the southeast, but they are rather variable in the extent of dark ventral freckling ( Mayr 1931) and may comprise more than one taxon. On Makira and satellite islets, makirensis has been distinguished by a darker back, more extensively white belly and patchy white feather edging at the sides of the rump, all traits accentuated in the form desiderata on Rennell and Bellona in the extreme southeast of the Solomons. Apparently unique to makirensis, however, and previously unreported, is a finely dusky-feathered tarsus (n=9 of 9) and feathered hind toe (n= 7 of 9), which may reflect deep genetic divergence and speciation. C. e. desiderata has a naked tarsus and hind toe (n=10).

Differentiation in central Melanesia. New Caledonian-Loyalty Island populations are differentiated from those in Santa Cruz-Vanuatu in their much paler, freckled breasts and clearer tail spots, as described by Salomonsen (1983). Enclaves in the Banks Islands, northern Vanuatu (n=4), have rather clear white lore spots, approaching

those of C. esculenta , and may also prove to have differentiated.

Classification of the eastern esculenta group. In summary, we propose the following taxonomic arrangement

for the eastern esculenta group. C. esculenta itself may comprise several allospecies. We have already followed this

newly proposed treatment in a recent treatise on the birds of the Indonesian Archipelago ( Eaton et al. 2016)

C. sumbawae

• C. sumbawae sumbawae Stresemann, 1925 —Sumbawa; Flores (subspecies?) • C. sumbawae sumbae Schodde, Rheindt & Christidis , this work — Sumba

C. neglecta

• C. neglecta neglecta G.R. Gray, 1866 —Sawu, Roti, Semau, Timor

• C. neglecta perneglecta Mayr, 1944 a—Alor, Wetar, Kisar,?intergradient with nominate C. esculenta on Romang, Damar and Tanimbar

C. esculenta

• C. esculenta minuta Stresemann, 1925 —Tanahjampea, Kalao

• C. esculenta esculenta ( Linnaeus, 1758) —S & C Sulawesi, Banggai and Sula Archipelagos, S Moluccas (Buru, Seram, Ambon, and Seram Laut, Watubella, Kai Islands), Aru Islands (subspecies?) • C. esculenta manadensis Salomonsen, 1983 —N Sulawesi (Minahassa Peninsula), Sangihe and Talaud Archipelagos

• C. esculenta spilura G.R. Gray, 1866 —N Moluccas (Morotai, Halmahera and offshore islands, Bacan, Obi)

• C. esculenta amethystina Salomonsen, 1983 —Waigeo

• C. esculenta numforensis Salomonsen, 1983 —Numfor,? Biak Islands (Cenderawasih Bay, New Guinea) • C. esculenta nitens Ogilvie-Grant, 1914 — Western Papuan Islands, New Guinea, Yapen and Karkar Islands (includes C. e. erwini Collin & Hartert, 1927)

• C. esculenta misimae Salomonsen, 1983 —Trobriand and Woodlark Islands, Louisiade Archipelago, D’Entrecasteaux Archipelago (subspecies?)

• C. esculenta tametamele Stresemann, 1921 —Long, Witu and Tolokiwa Islands , New Britain ( Bismarck Archipelago)

• C. esculenta stresemanni Rothschild & Hartert, 1914 —Admiralty Islands (Bismarck Archipelago) • C. esculenta heinrothi Neumann, 1919 —New Hanover, Nusa, New Ireland, Djaul (Bismarck Archipelago) • C. esculenta spilogaster Salomonsen, 1983 —Tabar, Lihir, Tanga, Feni (Hibernian Islands) • C. esculenta hypogrammica Salomonsen, 1983 —Nissan (Hibernian Islands) • C. esculenta lagonoleucos Schodde, Rheindt , & Christidis, this work—Buka, Bougainville, Shortland (?subspecies) (NW Solomon Islands)

• C. esculenta becki Mayr, 1931 —all Solomon Islands between, but excluding, Bougainville and Makira • C. esculenta makirensis Mayr, 1931 — Makira Group (SE Solomon Islands) • C. esculenta desiderata Mayr, 1931 — Rennell and Bellona Islands (SE Solomon Islands)

C. uropygialis

• C. uropygialis uropygialis G.R. Gray, 1866 —Utupua, Vanikoro (Santa Cruz Islands), Vanuatu • C. uropygialis albidior Salomonsen, 1983 — New Caledonia, Loyalty Islands

English names for newly defined species taxa. We suggest the following English names for the species-level groups newly distinguished here: Collocalia affinis —Plume-toed Swiftlet (named for its distinctive feathered hallux setting it apart from C. linchi , with which it is sympatric); Collocalia natalis — Christmas Island Swiftlet (named for the island to which it is restricted); Collocalia isonota —Ridgetop Swiftlet (named for its preference for mountainous and hilly settings in areas where it co-occurs with sympatric C. marginata ); Collocalia sumbawae — Tenggara Swiftlet (named for its occurrence in comparatively large areas of Nusa Tenggara, literally “the southeastern archipelago”); Collocalia neglecta —Drab Swiftlet (named for its comparative lack of iridescence and general drabness); Collocalia uropygialis —Satin Swiftlet (named for its exceptionally glossy plumage suggestive of satin texture and hue). Other species of white-bellied swiftlets for which English names are already in common use are Collocalia linchi ( Linchi or Cave Swiftlet), C. dodgei (Kinabalu or Bornean Swiftlet), C. marginata (Grayrumped Swiftlet) and C. esculenta (Glossy Swiftlet) ( Sibley & Monroe 1990; Moyle et al. 2008; Gill & Donsker 2016).

Correlates of differentiation. Morphological differences among species and subspecies in the white-bellied swiftlet complex are slight and frequently cryptic, and similarities such as hallux feathering probably often convergent given that they occur in such widely disjunct forms as C. affinis , C. neglecta and C. esculenta makirensis . Morphological trends, such as north-south dulling and paling of plumage from the Moluccas to Timor and stepped whitening of the rump from the Solomon Islands to Vanuatu, should be treated with caution as indicators of gene flow until confirmed by molecular data.

Despite the great geographic range of the complex and its aerial capabilities, its individual taxa are not consistent over-sea colonisers. That is obvious from the separation of species through the Philippines and Lesser Sundas, and splitting of subspecies along the Wallacean-Papuasian arc. Neighbouring species in the Philippines may be separated by as little as 20–50 km-wide stretches of water, with so far only localized evidence of intergradation. In the Lesser Sundas, sea straits apparently separating C. sumbawae and C. neglecta on the inner Banda arc are barely 10 km wide. Subspecies between Sulawesi and the Solomons are commonly separated by water gaps about 80 km wide. Processes of allopatric localization appear to offer the simplest explanation for resultant patterns of differentiation: small founder populations, roost- and nest-site philopatry, competitive exclusion and periodic genetic bottlenecks during Pleistocene fluctuations have combined to generate divergence between local populations and genetic integrity within them.

Speciation in the complex is centred zoogeographically in the region between the Philippines, Greater Sundas and Wallacea, on either side of Wallace’s Line ( Wallace 1860; Mayr 1944b; van Oosterzee 1997, 2006). Five of the most deeply diverged species groups in the complex reach their eastern ( linchi , affinis , and isonota ) or western ( sumbawae , esculenta ) limits on or near Wallace’s Line. Although the Sunda shelf fringing southeast Asia has been a relatively stable land form since the early Mesozoic, the region to the north and east, from the Philippines through Wallacea to the west rim of the Australo-Papuan plate, has been perhaps the most tectonically volatile on earth through the Cenozoic. Rough and approximate dating of the divergence process in white-bellied swiftlets based on Weir & Schluter’s (2008) mitochondrial clock rate for avian mtDNA coding genes indicates that diversification in the complex commenced ~5–4 mya ( Figure 2 ), coinciding with major tectonic rearrangements in the region that have shaped the present-day geographic position of most regional landmasses ( Hall 2002, 2009), underlining the importance of earth-historic processes for biotic differentiation in the region.

Figures

FIGURE 2. Phylogenetic tree topology based on Bayesian analysis of cyt b sequence data. Taxon names and localities are given for each population. High branch support is given in Maximum Parsimony bootstrap, Maximum Likelihood bootstrap and Bayesian posterior probability (multiplied by 100 for ease of reference) in the same order with a cut-off of Ż 85 for bootstrap and Ż 99 for posterior probability.