Salticidae (Arachnida, Araneae) of Islands Off Australia
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1999. The Journal of Arachnology 27:229±235 SALTICIDAE (ARACHNIDA, ARANEAE) OF ISLANDS OFF AUSTRALIA Barbara Patoleta and Marek ZÇ abka: Zaklad Zoologii WSRP, 08±110 Siedlce, Poland ABSTRACT. Thirty nine species of Salticidae from 33 Australian islands are analyzed with respect to their total distribution, dispersal possibilities and relations with the continental fauna. The possibility of the Torres Strait islands as a dispersal route for salticids is discussed. The studies of island faunas have been the ocean level ¯uctuations over the last 50,000 subject of zoogeographical and evolutionary years, at least some islands have been sub- research for over 150 years and have resulted merged or formed land bridges with the con- in hundreds of papers, with the syntheses by tinent (e.g., Torres Strait islands). All these Carlquist (1965, 1974) and MacArthur & Wil- circumstances and the human occupation son (1967) being the best known. make it rather unlikely for the majority of Modern zoogeographical analyses, based islands to have developed their own endemic on island spider faunas, began some 60 years salticid faunas. ago (Berland 1934) and have continued ever When one of us (MZ) began research on since by, e.g., Forster (1975), Lehtinen (1980, the Australian and New Guinean Salticidae 1996), Baert et al. (1989), ZÇ abka (1988, 1990, over ten years ago, close relationships be- 1991, 1993), Baert & Jocque (1993), Gillespie tween the faunas of these two regions were (1993), Gillespie et al. (1994), ProÂszynÂski expected. Consequently, it was hypothesized (1992, 1996) and Berry et al. (1996, 1997), that the Cape York Peninsula and Torres Strait but only a few papers were based on veri®ed islands were the natural passage for dispersal/ and suf®cient taxonomic data. expansion. In fact, the parts of this area cov- The present contribution is mostly based on ered with savannah and Eucalyptus forests do material collected by one of us (MZ) while form such a passage zone within these habi- visiting Queensland Museum (Brisbane), Aus- tats, but mostly in one directionÐfrom Aus- tralian Museum (Sydney), Western Australian tralia to South Papua, and no further north be- Museum (Perth) and Australian National In- cause of rainforest barrier. During glacial sect Collection (Canberra). The main purposes cooling, aridization and rainforest regression, of this paper are (1). To analyze the species habitats were further enhanced in favor of the composition in respect to their origin, total Australian fauna. Thus, for northern (Oriental distribution and dispersal abilities; (2). To es- and New Guinean) rainforest dwellers, the timate the expansiveness of Australian conti- Cape York Peninsula and Torres Strait islands nental faunas towards studied islands; (3). To should be treated as ®lters rather than a dis- evaluate the role of Torres Strait islands in persal route. faunistic exchange between Australia and New Guinea. THE SALTICIDS Continental faunaÐthe source.ÐAbout THE AREA 340 salticid species have been reported from The islands are of coral, volcanic or con- Australia so far (Davies & ZÇ abka 1989; ZÇ ab- tinental origin and are (with few exceptions) ka 1990, 1991, unpubl. data). Of them 286 located along the NE coast of Australia (Fig. belong to 63 veri®ed genera, others are clas- 1). Their surfaces are rather ¯at, either barren si®ed as incertae sedis. Approximately 60% or vegetated, mostly by Eucalyptus, wattles, of species are endemic and these increase in palms and ferns. Few have developed rain- number towards southern and central-western forest or mangrove communities. Due to Australia. The long-term isolation of the con- 229 230 THE JOURNAL OF ARACHNOLOGY platys, Ligurinus, Mopsus, Mopsolodes, Si- maetha, Tauala). Four species of this group (Ergane cognata, E. insulana, Simaetha atyp- ica and Tauala minutus) are known exclu- sively from the islands. However, their en- demic island status seems doubtful due to the young age of the inhabited islands. Group 2: At least 11 species are of wide distribution, ranging from west Africa through Sri Lanka to western Paci®c islands (in one case even to Hawaii) and belong to genera of alien (outside Australian) originÐusually SE Asian and New Guinean. Cytaea plumbeiv- entris, reported from 12 islands, was the most common here. This species can be found in gardens and parks of NE Queensland and as such has probably been dispersed by man. Figure 1: Map showing the geographical location of the analyzed islands along the coast of Australia Cosmophasis thalassina has a similar biology (for detailed information see Table 1). and distribution, though it is less common (three islands). Group 3: Four island species have cosmo- tinent and uniqueness of the Australian biota politan/pantropical distribution, and all live in made the speciation so successful. Further- human habitations and are spread by man. more, inhabiting various Eucalyptus com- Dispersal.ÐFor the analyzed case two dis- munities, remote desert and semi-desert areas persal methods, aerodispersal and antropod- and/or microhabitats (e.g., under bark, in leaf ispersal, should be considered. Rafting, litter), particular species have biological and though theoretically possible, is not discussed structural limitations to expansion. The sec- because of lack of published or other data re- ond largest group of continental salticids, but garding Salticidae. smaller than expected especially in compar- Aerodispersal: Salticidae occupy various ison with other spider families (Araneidae, habitats, each providing different aerodisper- Theridiidae, see Main 1981), is formed of sal possibilities. Leaf-litter or bark dwellers, tropical immigrants from the Oriental Region for instance, are poorer candidates for bal- and New Guinea. They spread to north and looning than those living in open areas, tree north-eastern coastal rainforest remnants, and canopies or human habitats. Salticidae con- decrease in number to the south. Finally, the stitute only 1.5±7% of all spiders in aero- third group is made up of cosmopolitan/pan- plankton (Horner 1975; Salmon & Horner tropical species, distributed by human activ- 1977; Greenstone et al. 1987). It is widely ity. known that juveniles are more effective bal- Island fauna.ÐDuring the last ten years looners than adults; and in our research they substantial progress has been made in studies constituted 50.7% of all specimens which of the Paci®c island Salticidae (ZÇ abka 1988; seems to support the aerodispersal hypothe- ProÂszynÂski 1992, 1996; Berry et al. 1996, sis. Some indirect data from the analyzed 1997). In our research, we analyzed 39 spe- area were provided by ZÇ abka (1991) from cies, though no island had more than eight tree canopies of NE Queensland. Amongst 70 species. Being aware of the limitations, we specimens found there, the most common distinguish three groups of species (Tables 2, were representatives of Tara, Simaethula, 3). Opisthoncus, Prostheclina. Except for the Group 1: The largest (24 species) is made latter, those genera have also been recorded up of Australian endemics. Although some of in our study. Tara and Simaethula have not them have also spread to south Papua (savan- been considered as identi®ed to the genus nah, Eucalyptus forests) they seem to be of (not species) level only. Helpis minitabunda Australian origin and belong to Australian en- (found in tree canopies) is spread from Aus- demic genera (Abracadabrella, Astia, Holo- tralia and New Guinea to adjacent archipel- PATOLETA & ZÇ ABKAÐSALTICIDS OF AUSTRALIAN ISLANDS 231 Table 1.ÐNumber of species recorded on individual islands. Number Geographical location of species Island SE 8 Fitzroy 168569, 1468009 Queensland 8 Masthead 238329, 1518439 Queensland 7 Horn 108379, 1428179 Torres Strait 5 Heron 238269, 1518559 Queensland 4 Barrow 208469, 1158249 Western Australia 4 Lizard 148409, 1458289 Queensland 4 Motmot 3 Cairncross West 118159, 1428559 Torres Strait 3 Hannibal East 118369, 1428569 Torres Strait 2 Campbell 98349, 1438299 Torres Strait 2 Darnley 98359, 1438469 Torres Strait 2 Fraser 258229, 1538079 Queensland 2 Friday 108369, 1428109 Torres Strait 2 Murray 98569, 1448049 Torres Strait 2 North West 238189, 1518429 Queensland 2 Pellew 158319, 1368539 Northern Territory 2 Pethebridge 148449, 1458059 Queensland 2 Stephens 98319, 1438329 Torres Strait 2 Thursday 108359, 1428139 Torres Strait 2 Tryon 238159, 1518469 Queensland 2 Yam 98539, 1438459 Torres Strait 1 Binstead 138139, 1438339 Queensland 1 Gannett Cay 218599, 1528289 Queensland 1 Little Fitzroy 168559, 1468019 Queensland 1 Low 228039, 1508069 Queensland 1 Moreton 278119, 1538249 Queensland 1 Percy 218429, 1508209 Queensland 1 Rocky 158369, 1458219 Queensland 1 Saibai 98239, 1428409 Queensland 1 Tana 1 Wharton Reef 148089, 1448009 Queensland 1 Wilson 238189, 1518559 Queensland 1 Yorke 98449, 1438259 Torres Strait agos and to New Zealand, and has also been inappropriate. Even some large continental found in our research. genera are missing on the islands or are rep- Anthropodispersal: This way of dispersal is resented by single species only (Table 4). This typical for species occupying human habita- supports the idea (quite obvious for resident tions, and their distribution is world-wide. Australian arachnologists) that the enormous- Four such species (Hasarius adansoni, Me- ly diverse Australian spider/salticid fauna is nemerus bivittatus, Plexippus paykulli, P. pe- largely the result of habitat variability and ¯o- tersi) are found on the islands. It is likely that ristic