- freely available
Diversity 2013, 5(1), 139-148; doi:10.3390/d5010139
Published: 21 March 2013
Abstract: The Wallacean island of Timor is of particular biological interest due to its relatively large size and transitional location between the Indo-Malayan and Australasian biogeographic realms. However, the origins and levels of endemism of its invertebrate fauna are poorly known. A recent study of Timorese ants revealed a diverse fauna with predominantly Indo-Malayan affinities, but species-level taxonomy was considered to be too poorly understood for an analysis of levels of endemism. The highly diverse Old World tropical genus Polyrhachis represents a notable exception, and here we analyse levels of endemism in the Polyrhachis fauna of Timor and surrounding islands. We supplement the species listed in the previous study with additional collections to record a total of 35 species of Polyrhachis from Timor and surrounding islands. Only 14 (40%) of the 35 species could be named (P. constricta, P. costulata, P. gab, P. sokolova, P. hera, P. illaudata, P. rixosa, P. acantha chrysophanes, P. saevissima, P. bicolor, P. cryptoceroides, P. dives, P. longipes and P. olybria), and the large majority of the remaining species have not previously been collected. These are very likely to be endemic to Timor and surrounding islands, and point to remarkably high levels (>50%) of endemism in the regional ant fauna.
The Wallacean islands of the eastern Indonesian region are of exceptional biological interest because they are transitional between the strongly contrasting Indo-Malayan and Australasian biogeographic realms [1,2,3]. Most of these islands are oceanic and have never been connected to either the Indo-Malayan (Sunda) or Australasian (Sahul) continental plates . Their biotas therefore have very mixed origins [4,5,6,7], and their isolation has resulted in high levels of endemism [8,9,10].
Timor (31,459 km2) is the second largest Wallacean island, lying 860 km east of Wallace’s Line and 470 km north of north-western Australia. It was formed about four million years ago by the collision of the northwardly advancing Australasian plate with the Banda Volcanic Arc. Although it has never been in contact with either continental Australia or South-East Asia, during the last Ice Age distances to Australia were reduced to as little as 75 km and to South East Asia to even less via a range of stepping-stone Wallacean islands such as Atauro, Wetar and Alor, which currently lie from 30 km to the north . Despite its size and location, Timor has attracted relatively little interest from biogeographers, and the origins and levels of endemism of its fauna have been poorly documented. This is especially the case for invertebrates.
A recent study of Timorese ants  revealed a diverse fauna with predominantly Indo-Malayan affinities, but species-level taxonomy was considered to be too poorly understood for an analysis of levels of endemism. However, the highly diverse Old World tropical genus Polyrhachis Fr. Smith represents a notable exception. One of us (RJK) has more than 30 years of experience undertaking taxonomic revisions of the genus from throughout the Indo-Malayan and Australian regions [13,14,15,16,17,18,19], is familiar with the available types of all described species, and has extensive holdings of undescribed species. Polyrhachis represents a particularly informative focal taxon for biogeographical analysis of the Timorese ant fauna because it includes numerous subgenera of both Indo-Malayan and Australian origin, and is extremely diverse ecologically, with different taxa nesting in the ground, within tree cavities, and inside woven leaves [20,21,22].
Here we analyse the Polyrhachis fauna of Timor and surrounding Lesser Sunder islands, describing its biogeographical affinities and, in particular, assessing apparent levels of endemism.
Our analysis is based primarily on the species of Polyrhachis recorded by  from Timor itself, Atauro and Wetar from the Timor group of islands to the north, and Alor, Lembata and Pantar from the Flores group of islands to the west. This was supplemented by subsequent collections from four other islands in the Timor group (Kisar, Romang, Sermata and Babar), from Flores, and from Tanimbar to the east (Figure 1, Table 1).
All species were identified by RJK, and the distribution of each species was assessed on the basis of published records combined with RJK’s knowledge of specimens from publicly available collections. Voucher collections of species are deposited in the Queensland Museum and at CSIRO’s Tropical Ecosystems Research Centre in Darwin.
|Table 1. Summary of supplementary sampling of Polyrhachis species, in addition to that described in .|
|Island||Survey dates||Survey effort (h)||Habitats sampled (elevation)|
|Flores||June/July 2011||6||Montane forest, secondary forest (625–1,625m)|
|Lembata||November 2011||8||Evergreen swamp forest (0–20 m)|
|Wetar||September–October 2010||30||Evergreen forest, Eucalyptus woodland (0–100 m)|
|Kisar||October 2010||20||Eucalyptus woodland, mangrove (0–150 m)|
|Romang||October 2010||30||Evergreen forest, Eucalyptus woodland (0–600 m)|
|Sermata||November 2010||20||Evergreen forest, mangrove (0–200 m)|
|Babar||August 2011||30||Evergreen forest, Eucalyptus woodland (0–600 m)|
|Tanimbar||August 2011||6||Evergreen forest (0–150 m)|
3. Results and Discussion
Our analysis considered a total of 35 species of Polyrhachis from nine subgenera, with the richest subgenera being Myrmhopla Forel (13 species), Chariomyrma Forel (6), Myrma Billberg (6) and Hedomyrma Forel (4) (Table 2; revised identifications of the species recorded by  are provided in Appendix 1). Only 14 (40%) of the 35 species could be named, and they include species occurring primarily in Australia and New Guinea (e.g., P. constricta, P. gab, and P. sokolova), species restricted to the eastern Indonesian region (e.g., P. acantha chrysophanes, P. hera), widely distributed Indo-Malayan species (e.g., P. rixosa, P. saevissima), and species occurring in both Indo-Malaya and Australia (e.g., P. bicolor, P. dives) (Table 3).
|Table 2. Species of Polyrhachis recorded from Timor and surrounding islands in this study.|
|FLORES GROUP||TIMOR GROUP|
|Polyrhachis sp. nr. insularis Emery||*||*|
|Polyrhachis cf. arcuata acutinota Forel||*||*|
|Polyrhachis cf. contemta Mayr||*|
|Polyrhachis costulata Emery||*||*|
|P. constricta Emery|
|P. gab Forel||*||*||*||*||*|
|P. sokolova Forel||*|
|Polyrhachis cf. gibba Emery||*||*||*|
|Polyrhachis cf. rastellata (Latreille)||*|
|Polyrhachis cf. penelope Forel||*||*|
|Polyrhachis hera Forel||*|
|Polyrhachis cf. machaon Santschi||*|
|Polyrhachis sp. A (cf. cupreata Emery)||*||*||*|
|Polyrhachis sp. B (cf. cupreata Emery)||*|
|Polyrhachis illaudata Walker||*||*|
|Polyrhachis cf. murina Emery||*|
|P. rixosa Fr. Smith||*||*|
|Polyrhachis cf. rixosa Fr. Smith||*||*|
|Polyrhachis cf. villipes Fr. Smith||*||*|
|Polyrhachis cf. zopyra Fr. Smith||*||*||*||*||*||*||*|
|Polyrhachis acantha chrysophanes Emery||*||*|
|Polyrhachis cf. acantha chrysophanes Emery||*|
|P. bicolor Fr. Smith||*|
|Polyrhachis cf. bicolor Fr. Smith||*|
|P. cryptoceroides Emery||*|
|P. dives Fr. Smith||*||*||*||*||*||*|
|P. longipes Fr. Smith||*||*||*||*||*|
|Polyrhachis cf. moesta Emery||*||*|
|Polyhrachis cf. mucronata Fr. Smith||*||*||*|
|Polyrhachis cf. saevissima Fr. Smith||*|
|Polyrhachis saevissima Fr. Smith||*|
|Polyrhachis cf. tibialis Fr. Smith||*||*||*||*||*||*|
|Polyrhachis cf. thrinax Roger||*|
|Polyrhachis olybria Forel||*|
|Table 3. Previously known distributions of named species from Timor and surrounding islands.|
|P. (Chariomyrma) constricta||Australia, New Guinea|
|P. (Chariomyrma) gab||Australia|
|P. (Chariomyrma) sokolova||Australia, New Guinea, Aru, New Caledonia|
|P. (Chariomyrma) costulata||New Guinea|
|Polyrhachis (Hedomyrma) hera||Seram, Halmahera|
|Polyrhachis (Hedomyrma) illaudata||Sri Lanka, India, Thailand, Malaysia, Borneo, Sumatra, Java, Bali, Sumbawa, Philippines|
|P. (Myrma) rixosa||Sulawesi, Borneo|
|P. (Myrmhopla) acantha chrysophanes||Tanimbar, Flores|
|P. (Myrmhopla) bicolor||Throughout IndoMalaya, New Guinea, Australia|
|P. (Myrmhopla) cryptoceroides||Thailand, Malaysia, Borneo, Sulawesi, Java, Philippines|
|P. (Myrmhopla) dives||Throughout IndoMalaya, New Guinea, Australia|
|P. (Myrmhopla) longipes||Aru, New Guinea|
|P. (Myrmhopla) saevissima||Sulawesi, Sumatra, Seram|
|P. (Polyrhachis) olybria||Thailand, Malaysia, Borneo, Sumatra, Philippines|
Twenty three (66%) of the 35 species belong to subgenera of Indo-Malayan origin (Cyrtomyrma, Myrma, Myrmhopla, Myrmothrinax, Polyrhachis), with 12 (34%) belonging to subgenera of Australian origin (Campomyrma, Chariomyrma, Hagiomyrma, Hedomyrma). These figures are similar to the overall ant fauna of Timor and surrounding islands, with 76% of total species considered to be of Indo-Malayan origin .
A small number of the 21 species that we were unable to name belong to unresolved complexes and so their taxonomic and distributional status remains unclear. However, most are clearly distinct from any previously collected species, and are very likely to be endemic to Timor and surrounding islands. The majority of these new species were recorded from Timor itself, but others are known only from surrounding islands. For example, P. cf. thrinax is known only from Wetar, P. cf. rastellata is known only from Romang, and P. (Hedomyrma) sp. B (cf. cupreata) is known only from Tanimbar. Several of the new species (P. cf. murina, P. cf. villipes and P. cf. moesta) are known only from the Flores group of islands. One of the described species, P. acantha chrysophanes, also appears to be endemic to the region; it was previously known only from Tanimbar and Flores, but we recorded it on Timor itself. We recorded P. hera from Tanimbar and it was previously known only from Seram and Halmahera , further north in the Banda Sea.
Apparent levels of endemism might even be higher because we have been conservative with our species identifications. For example, the species we have identified as P. rixosa has sparser and shorter hairs, and the petiole is narrower, than in the typical Sulawesian specimens. Detailed analyses of a range of vertebrate groups in the Timor region have shown that taxa previously considered to represent widespread and variable species are actually multiple, locally endemic species [24,25,26,27,28]. For example, the ‘subspecies’ of the Rainbow Lorikeet (Trichoglossus haematodus) occurring on Timor, Wetar, Romang, Flores, Sumbawa and Sumba are now recognised as three distinct species .
Timor and surrounding islands support a remarkably diverse and notable Polyrhachis fauna. We recorded nine of the 13 recognised subgenera, with three of the other four subgenera (Aulacomyrma Emery, Myrmatopa Forel and Hirtomyrma Kohout) known from other islands of eastern Indonesia (e.g., Aru, Misool, Ambon, Seram; R. Kohout, unpublished data), and therefore very possibly also occurring on Timor and/or surrounding islands. Only one subgenus, Hemioptica Roger, which extends from Sri Lanka and India to Malaysia, Borneo and Sumatra, is unlikely to occur in the region. Our analysis reveals that the Polyrhachis fauna of Timor and surrounding islands has an extremely high level of endemism, with up to two-thirds of the species not known to occur elsewhere. Such a level of endemism is far higher than in vascular plants (about 10%; ) and birds (about 20%; ). Most of the native land mammal fauna of Timor was probably endemic , but the status of Timor’s herpetofauna remains poorly known . We can think of no reason to suspect that levels of endemism are any higher in Polyrhachis than is typical for ants from the region, which suggests that more than half of all ant species occurring in Timor and surrounding islands are endemic. It also seems likely that many other invertebrate taxa show comparable levels of endemism.
We thank Mark Schellekens for his assistance with field collecting, and Ben Hoffmann for his comments on the draft manuscript.
|Appendix 1. Revised identifications of Polyrhachis species recorded in Trainor and Andersen (2010).|
|Identification in Trainor and Andersen (2010)||Revised identification|
|Polyrhachis (Campomyrma) sp. A||Polyrhachis cf. insularis Emery|
|Polyrhachis (Chariomyrma) sp. F (arcuata gp.)||Polyrhachis cf. arcuata acutinota Forel|
|Polyrhachis (Cyrtomyrma) sp. P||Polyrhachis cf. gibba Emery|
|Polyrhachis (Hedomyrma) sp. O (euterpe gp.)||Polyrhachis cf. machaon Santschi|
|Polyrhachis (Myrma) mayri||P. illaudata Walker|
|Polyrhachis (Myrma) sp. nr. villipes||Polyrhachis cf. villipes Fr. Smith|
|Polyrhachis (Myrmhopla) acantha||Polyrhachis acantha chrysophanes Emery|
|Polyrhachis (Myrmhopla) argentea||Polyrhachis cf. tibialis Fr. Smith|
|Polyrhachis sp. nr. bicolor||Polyrhachis cf. bicolor Fr. Smith|
|Polyrhachis (Myrmhopla) bicolor||P. bicolor Fr. Smith|
|Polyrhachis (Myrmhopla) concolor||P. longipes Fr. Smith|
|Polyrhachis (Myrmhopla) cryptoceroides||P. cryptoceroides Emery|
|Polyrhachis (Myrmhopla) dives||P. dives Fr. Smith|
|Polyrhachis gab||P. gab Forel|
|Polyrhachis sp.nr. inconspicua||Polyrhachis cf. insularis Emery|
|Polyrhachis mucronata||Polyhrachis cf. mucronata Fr. Smith|
|Polyrhachis sp. nr. mucronata||Polyrhachis (mucronata-group) sp.|
|Polyrhachis sp. B (bellicosa gp.)||P. olybria Forel|
|Polyrhachis sp. J (cupreata gp.)||Polyrhachis (Hedomyrma) sp. A (cf. cupreata Emery)|
|Polyrhachis sp. K (zopyra gp.)||Polyrhachis cf. murina Emery|
|Polyrhachis sp. L (tibialis gp.)||Polyrhachis cf. moesta Emery|
|Polyrhachis sp. L (zopyra gp.)||Polyrhachis cf. zopyra Fr. Smith|
|Polyrhachis sp. nr. obtusa||Polyrhachis costulata Emery|
|Polyrhachis rixosa||P. rixosa Fr. Smith|
- Wallace, A.R. The Malay Archipelago; Tynron Press: Stenhouse, Scotland, 1869.
- Van Oosterzee, P. Where Worlds Collide: The Wallace Line; Cornell University Press: Ithaca, NY, USA, 1997.
- Lohman, D.J.; de Bruyn, M.; Page, T.; von Rintelen, K.; Hall, R.; Ng, P.K.L.; Shih, H.-T.; Carvalho, G.R.; von Rintelen, T. Biogeography of the Indo-Australian Archipelago. Ann. Rev. Ecol. Evol. Syst. 2011, 42, 205–226, doi:10.1146/annurev-ecolsys-102710-145001.
- Holloway, J.D.; Jardine, N. Two approaches to zoogeography: A study based on the distributions of butterflies, birds and bats in the Indo-Australian area. Proc. Lin. Soc. Lond. 1968, 179, 153–188, doi:10.1111/j.1095-8312.1968.tb00975.x.
- How, R.A.; Kitchener, D.J. Biogeography of Indonesian snakes. J. Biogeogr. 1997, 24, 725–735.
- Clode, D.; O’Brien, R. Why Wallace Drew the Line: A Reanalysis of Wallace’s Bird Collections in the Malay Archipelago and the Origins of Biogeography. In Faunal and Floral Migrations and Evolution in SE Asia–Australasia; Metcalfe, I., Smith, J.M.B., Morwood, M., Davidson, I., Eds.; AA Balkema Publishers: Tokyo, Japan, 2001; pp. 313–321.
- Inger, R.F.; Voris, H.K. The biogeographical relations of the frogs and snakes of Sundaland. J. Biogeogr. 2001, 28, 863–891, doi:10.1046/j.1365-2699.2001.00580.x.
- How, R.A.; Schmitt, L.H.; Suyanto, A. Geographical variation in the morphology of four snake species from the Lesser Sunda Islands, eastern Indonesia. Biol. J. Lin. Soc. 1996, 59, 439–456.
- Jønsson, K.A.; Irestedt, M.; Fuchs, J.; Ericson, P.G.P.; Christidis, L.; Bowie, R.C.K.; Norman, J.A.; Pasquet, E.; Fjeldså, J. Explosive avian radiations and multi-directional dispersal across Wallacea: Evidence from the Campephagidae and other crown Corvida (Aves). Mol. Phylogenetics Evol. 2008, 47, 221–236, doi:10.1016/j.ympev.2008.01.017.
- Outlaw, D.C.; Voelker, G. Pliocene climatic change in insular southeast Asia as an engine of diversification in Ficedula flycatchers. J. Biogeogr. 2008, 35, 739–752, doi:10.1111/j.1365-2699.2007.01821.x.
- Voris, H.K. Maps of Pleistocene sea levels in Southeast Asia: Shorelines, river systems and time durations. J. Biogeogr. 2000, 27, 1153–1167, doi:10.1046/j.1365-2699.2000.00489.x.
- Trainor, C.R.; Andersen, A.N. The ant fauna of Timor and neighbouring islands: Potential bridges between the disjunct faunas of South East Asia and Australia. Aust. J. Zool. 2010, 58, 133–144, doi:10.1071/ZO09113.
- Kohout, R.J. Three new Polyrhachis sexspinosa-group species from the Philippines (Hymenoptera: Formicidae: Formicinae). Mem. Qld. Mus. 1987, 25, 169–176.
- Kohout, R.J. Nomenclatural changes and new Australian records in the ant genus Polyrhachis Fr. Smith (Hymenoptera: Formicidae: Formicinae). Mem. Qld. Mus. 1987, 25, 429–438.
- Kohout, R.J. A review of the Polyrhachis viehmeyeri species-group (Hymenoptera: Formicidae: Formicinae). Mem. Qld. Mus. 1990, 28, 499–508.
- Kohout, R.J. Review of Polyrhachis (Cyrtomyrma) Forel (Hymenoptera: Formicidae: Formicinae) of Australia, Borneo, New Guinea and the Solomon Islands with descriptions of new species. Mem. Qld. Mus. 2006, 52, 87–146.
- Kohout, R.J. A review of the Polyrhachis ants of Sulawesi with keys and descriptions of new species (Hymenoptera: Formicidae: Formicinae). Mem. Qld. Mus. 2008, 52, 255–317.
- Kohout, R.J. A review of the Australian Polyrhachis ants of the subgenera Myrmhopla Forel and Hirtomyrma subgen. nov. (Hymenoptera: Formicidae: Formicinae). Mem. Qld. Mus. 2010, 55, 167–204.
- Kohout, R.J. A review of the Australian Polyrhachis ants of the subgenera Myrma Billberg, Myrmatopa Forel, Myrmothrinax Forel and Polyrhachis Fr. Smith (Hymenoptera: Formicidae: Formicinae). Mem. Qld. Mus. Nat. 2012, 56, 25–59.
- Dorow, W.H.O. Revision of the ant genus Polyrhachis Smith, 1857 (Hymenoptera: Formicidae: Formicinae) on subgenus level with keys, checklist of species and bibliography. Cour. Forsch.–Inst. Senckenberg 1995, 185, 1–113.
- Robson, S.K.A.; Kohout, R.J. Evolution of nest-weaving behaviour in arboreal nesting ants of the genus Polyrhachis Fr. Smith (Hymenoptera: Formicidae). Aust. J. Ent. 2005, 44, 164–169, doi:10.1111/j.1440-6055.2005.00462.x.
- Robson, S.K.A.; Kohout, R.J. A review of the nesting habits and socioecology of the ant genus Polyrhachis Fr. Smith. Asian Myrmecol. 2007, 1, 81–99.
- Kohout, R.J. Revision of the subgenus Hedomyrma Forel of the genus Polyrhachis Fr. Smith (Hymenoptera: Formicidae: Formicinae). 2013. unpublished work.
- Churchill, S. Australian Bats, 2nd ed.; Allen and Unwin: Crows Nest, Australia, 2008.
- Gjershaug, J.O.; Kvaløy, K.; Røv, N.; Prawiradilaga, D.M.; Suparman, U.; Rahman, Z. The taxonomic status of the Flores Hawk Eagle Spizaetus floris. Forktail 2004, 20, 55–62.
- Pianka, E.R.; King, D.; King, R.A. Varanoid Lizards of the World; Indiana University Press: Bloomington, IN, USA, 2004.
- Sangster, G.; Rozendaal, F.G. Systematic notes on Asian birds. 41. Territorial songs and species-level taxonomy of nightjars of the Caprimulgus macrurus complex, with the description of a new species. Zool. Verh. Leiden 2004, 350, 7–45.
- Trainor, C.R.; Verbelen, P.; Johnstone, R.E.J. The avifauna of Alor and Pantar, Lesser Sundas, Indonesia. Forktail 2012, 28, 77–92.
- Schodde, R.; Mason, I.J. Aves (Columbidae to Coraciidae). In Zoological Catalogue of Australia, Volume 37.2: Aves (Columbidae to Coraciidae); Houston, W.W.K., Wells, A., Eds.; Australian Government Publishing Service: Canberra, Australia, 1997.
- Roos, M.C.; Kessler, P.J.A.; Gradstein, R.S.; Baas, P. Species diversity and endemism of five major Malesian islands: Diversity-area relationships. J. Biogeogr. 2004, 31, 1893–1908, doi:10.1111/j.1365-2699.2004.01154.x.
- Stattersfield, A.J.; Crosby, M.J.; Long, A.J.; Wege, D.C. Endemic Bird Areas of the World: Priorities for Biodiversity Conservation; BirdLife International: Cambridge, UK, 1998.
- Aplin, K.; Helgen, K.M. Quaternary murid rodents of Timor Part I: New material of Coryphomys buehleri Schaub, 1937, and description of a second species of the Genus. Bull. Am. Mus. Nat. Hist. 2010, 341, 1–80, doi:10.1206/692.1.
- Kaiser, H.; Carvalho, V.L.; Ceballos, J.; Freed, P.; Heacox, S.; Lester, B.; Richards, S.J.; Trainor, C.R.; Sanchez, C.; O’Shea, M. The herpetofauna of Timor-Leste: A first report. ZooKeys 2011, 109, 19–86, doi:10.3897/zookeys.109.1439.
© 2013 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).