www.publish.csiro.au/journals/ajz Australian Journal of Zoology, 2008, 56, 85–94
Helminth assemblages of Uromys spp. (Muridae:Hydromyinae)from Australia, Papua New Guinea and Papua Indonesia andcomparison with assemblages in Melomys spp.
L. R. SmalesA,B and D. M. SprattC,D
AFaculty of Sciences, Engineering and Health, Central Queensland University, Rockhampton, Qld 4702, Australia.
BParasitology Section, South Australian Museum, North Terrace, Adelaide, SA 5000, Australia.CCSIRO Sustainable Ecosystems, GPO Box 284, Canberra, ACT 2601, Australia.DCorresponding author. Email: [email protected]
Abstract. This study documents the helminth assemblages of Uromys caudimaculatus (Krefft, 1867) from Papua New Guinea and Australia as well as listing helminths found in U. anak Thomas, 1907 from Papua Indonesia and Papua New Guinea, and U. hadrourus (Winter, 1984) from Queensland Australia. In total, 36 species of helminth, comprising one acanthocephalan, three cestodes (excluding unidentifiable fragments) and 32 nematodes (including two not identified to genus) from 65 hosts were found. The Trichostrongylina nematodes were the dominant group of helminths, the most prevalent species being Odilia uromyos (Mawson, 1961), found in each of the species of Uromys across all regions, and O. melomyos (Mawson, 1961), occurring in U. caudimaculatus from Papua New Guinea and Australia. The helminth species assemblage from U. caudimaculatus, 14 species of helminth from 11 hosts from Papua New Guinea and 23 species of helminth from 51 hosts from Australia, had high species richness but was relatively equitable overall (1/SI = 0.92). The differences found between the helminth assemblages of U. caudimaculatus from Papua New Guinea and Australia suggest that U. caudimaculatus may have travelled to Australia from New Guinea with a small pool of helminth species that was subsequently added to by host switching from sympatric rodent hosts. Alternatively, U. caudimaculatus may have lost many of the helminths that travelled with it following arrival in Australia.
Introduction
The genus Uromys Peters, 1867 (Muridae:Hydromyinae) forms The helminth fauna of the genus is poorly known. Seven part of a heterogeneous assemblage of 14 genera comprising the species of nematodes (Mawson 1961; Sprent 1973; Hugot and tribe Uromyini (Flannery 1995). This taxon is derived from the Quentin 1985; Spratt and Haycock 1988; Singleton et al. earliest invasion of rodents into the island of New Guinea, prob- 1991) and one cestode (Beveridge 1985) have been recorded ably in the late Miocene or early Pliocene (15–10 million years from U. caudimaculatus from Australia but there are no ago) (Flannery 1995). Three of the nine species in the genus are records from U. hadrourus. There are no records of helminths found in the Australasian region: U. anak Thomas, 1907 lives in from either of the two species (U. caudimaculatus or U. anak)the montane forests of New Guinea, above 1000 m; U. caudi- found in New Guinea and there have been no systematicmaculatus (Krefft, 1867) in lowland and mid-montane New studies of their helminth communities in either region. While Guinea as well as along the north-eastern coast of Queensland; helminth assemblages have been studied in several murine and U. hadrourus (Winter, 1984) in the upland rain forests and rodents of the genus Rattus, the only uromyine rodents in tablelands of North Queensland (Moore 1995; Winter and
which helminth assemblages have been studied are species of Moore 1995). The remaining six species of Uromys are found
Melomys.off mainland New Guinea in the Schouten Island group, the
This study was undertaken (1) to document the helminth Bismarck Archipelago and the Solomon Islands (Groves and fauna of U. caudimaculatus, U. anak and U. hadrourus, (2) toFlannery 1994). compare the helminth assemblages of U. caudimaculatus fromUromys are all large Rattus-like species with relatively New Guinea and Australia, (3) to compare the helminth assem-simple molars and a generalised body form (Flannery 1995). blage of the Australian population of U. caudimaculatus withThey appear to be primarily herbivorous. U. anak is reported as the helminth assemblages of populations of Melomys burtoni including nuts and fruits in its diet (Flannery 1995), while
U. caudimaculatus has more generalised food habits, taking (Ramsay, 1887) and M. cervinipes (Gould, 1852) and (4) to beetles, crabs, small amphibians and reptiles, and birds eggs as compare the helminth assemblage of the Papua New Guinea well as fruits, nuts, fungi and bark (Moore 1995). Little is population of U. caudimaculatus with the assemblage of known about U. hadrourus, but nuts, fruits and beetles are M. lutillus (Thomas, 1913), the only other uromyine genus for known to be part of the diet (Winter and Moore 1995). which helminth data are available.
86 Australian Journal of Zoology L. R. Smales and D. M. Spratt
Materials and methods Data presented are based on examination of all material and records from the Australian Museum, Sydney (AM), the Queensland Museum, Brisbane (QM), the South Australian Museum, Adelaide (SAM), The Natural History Museum, London (BNHM), and the National Wildlife Collection, Canberra (CSIRO). Material was dissected from the digestive tracts of host bodies that had been stored in 70% ethanol at theAM and the Bernice Bishop Museum, Honolulu (BBM). Additional specimens dissected from U. caudimaculatus collected during small mammal surveys in Queensland were also examined. This represents a total of 65 hosts collected between 1956 and 1994.
The following list is of hosts from 26 localities in Papua, Indonesia, Papua New Guinea and Queensland, with the number of hosts collected at each locality shown in parentheses. Latitude and longitude are given for those localities where they are recorded in the Museum register or can reasonably be esti-mated from the locality data.
Uromys caudimaculatus. Papua New Guinea: Port Moresby, Central Province (9°31′S, 149°12′E) (2); Kokogadi Village, Fergusson Island, Milne Bay Province (9°30′S, 150°34′E) (1); Wilbeite Village, West Sepik District, Sanduan Province (3°25′S, 142°7′E) (1); Doido Village, Mt Karimui, Chimbu Province (6°33′S, 144° 50′E) (2); north-east slopes Mt Karimui, Chimbu Province (6°32′S, 144°48′E) (1); 5 km north-north-west Wanuma, Madang Province (4°53′S, 145°18′E) (2); 14 km north Wanuma, Madang Province (4°51′S, 145°19′E) (1); Situm Village, Bupu River, 19 km north-east Lae, Morobe Province (6°22′S, 147°05′E) (1). Queensland, Australia: Cairns (16°55′S, 145°46′E) (1); Atherton (17°16′S, 145°28′E) (4); Kurrimine Beach (17°46′S, 146°06′E) (1); Palmerston Highway (3); Palmerston (17°32′S, 145°46′E) (3); Innisfail (17°32′S, 146°01′E) (10); Etty Bay Road (17°34′S, 146°04′E) (3); East McIlwraith Range (13°45′S, 143°20′E) (2); Mt Spec (18°37′S, 146°11′E) (3); Paluma (19°00′S, 146°11′E) (5); Danbulla State Forest (17°10′S, 145°36′E) (3); Mt Windsor Tableland (16°13′S, 145°02′E) (1); El Arish (17°48′S, 146°00′E) (1); Dinner Creek (17°26′S, 146°E) (2); Mt Molloy (16°41′S, 145°20′E) (2); no locality given (7).
Uromys anak. Papua New Guinea: Tifalmin, West Sepik District, Western Province (5°7′S, 141°25′E) (1). Papua Indo-nesia: Tembagapura, Jayawijaya Mts (4°19′S, 137°03′E) (1).
Nematodes from five experimental infections are registered in the QM but not included in this dataset. All other helminth specimens registered in museums, as well as all specimens dis-sected from host bodies held in museum collections, were examined after clearing in lactophenol (nematodes) or staining in celestine blue, dehydrating in ethanol, clearing in methyl sali-cylate and mounting in Canada balsam (cestodes). All helminths were identified to species where possible. Following identifica-tion, all specimens were returned to their home institutions. Voucher specimens are listed in Appendices 1–3. The classifi-cation used for the Trichostrongylina is that of Durette-Desset and Chabaud (1993).
For U. caudimaculatus the diversity of helminth communi-ties was calculated using Simpson’s Index (Simpson 1949) as
employed by Holmes and Podesta (1968) and expressed as the reciprocal, 1/SI (Leong and Holmes 1981). Data showing preva-lence of infection, as defined by Bush et al. (1997), were used to characterise community structure according to the core and satellite species concept as interpreted by Bush and Holmes (1986) and Stock and Holmes (1987). The overall similarities of the helminth communities of U. caudimaculatus and U. anak were calculated using Sorensen’s Index. The host samples for U. anak and U. hadrourus were too small to allow any other meaningful comparisons or analyses.
Results In all, 36 species of helminths plus unidentified cestode frag-ments were found in 65 specimens of Uromys (comprising two U. anak, one U. hadrourus and 62 U. caudimaculatus). The helminth assemblage comprised one acanthocephalan, three cestodes and 32 nematodes (including two not identified to genus), 14 of which were members of the suborder Trichostrongylina. No trematodes were found. The helminths, their geographical distributions and prevalences, are given for U. caudimaculatus in Table 1 and U. anak in Table 2. The single specimen of U. hadrourus harboured four helminth species: some unidentified cestode fragments, Ophidascaris robertsi larvae, Odilia uromyos and Capillaria s.l.
The larval acanthocephalan, Porrorchis hydromuris, a new host record, was found only in U. caudimaculatus and only from Papua New Guinea.
Of the three cestode species found, two occurred only in U. caudimaculatus from Australia; one of these, Raillietina celebensis, is a new host record. The third, Hymenolepis dimin-uta, a cosmopolitan cestode, was not found in Australian hosts.
Three nematode species, the ascaridid Ophidascaris robertsi, the onchocercid Cercopithifilaria johnstoni and the capillariid Calodium hepaticum, reported previously from U. caudimaculatus from Australia, were not found in hosts from New Guinea. An additional three species, the heligmonel-lids Odilia mackerrasae, O. melomyos and O. uromyos, also known previously from Australian hosts, were found in U. caudimaculatus from Papua New Guinea. The remaining 26 nematode species were all new host records. Of these, the sub-order Trichostrongylina was represented by members of the families Trichostrongylidae (Peramelistrongylus sp.), Heli-gmonellidae (Macrostrongylus ingens, Nippostrongylus sembeli, Odilia carinatae, O. implexa) and Molineidae (Pithecostrongylus anak). These Trichostrongylina, in addition to the oxyurid Syphacia longaecauda, the rictulariid Rictularia sp., the seuratid Seuratum sp. and the spirurid Protospirura kaindiensis occurred only in hosts from New Guinea, while the capillariids Capillaria s.l. and the subulurid Subulura ander-soni were found in hosts from Papua New Guinea and Australia. Seventeen nematode species, including Odilia brachybursa, O. emanuelae and O. mawsonae, were found only in Australian hosts.
Uromys anak harboured nine species of helminths. Four species of Odilia, N. sembeli and S. andersoni were a subset of those found in U. caudimaculatus from Papua New Guinea. The remaining three species (Sabanema macrovulva, Pitheco-strongylus anak and Syphacia longaecauda) were found only in U. anak.
Helminth assemblages of Uromys spp. Australian Journal of Zoology 87
Table 1. Helminth parasites of 62 Uromys caudimaculatus (Krefft, 1867), 11 from Papua New Guinea (PNG) and 51 from Australia
Taxon Total prevalence Site in host Prevalence, Prevalence, (%) PNG Australia
The dominant nematode group, the Trichostrongylina, occurred in all three species of Uromys, the Heligmonellidae taxon Odilia, represented by eight species, being the dominant taxon. O. melomyos and O. uromyos, each with a prevalence of 64% in U. caudimaculatus from Papua New Guinea and O. melomyos, with a prevalence of 47%, in Australian hosts, were the most common species. One other animal from Papua New Guinea was infected with heligmonellid larvae that could not be fully identified.
The Papua New Guinea population of 11 U. caudimaculatus had a helminth assemblage of 14 species (one acanthocephalan, one cestode, 12 nematodes) while the Australian population of 51 hosts harboured 23 species (2 cestodes, 21 nematodes). Of these, only three species, O. mackerrasae, O. melomyos, O. uromyos, and one genus, Capillaria s.l., were common to populations in both Papua New Guinea and Australia.
The diversity of helminths occurring in U. caudimaculatus, as measured by the reciprocal of Simpson’s Index, was 0.64 for
Fig. 1. Relationship between number of helminth species found in 62 Uromys caudimaculatus and the prevalence at which these parasites occurred.
L. R. Smales and D. M. Spratt
Papua New Guinea hosts, 1.76 for Australian hosts and 0.92 for the total helminth assemblage from U. caudimaculatus.
No species reached a prevalence >49% and the prevalence of most species was <10% (Table 1). Prevalence class distributions are given in Fig. 1. Sorensen’s Indices (Table 3) indicate that the helminth assemblages of U. caudimaculatus from Queensland, U. caudimaculatus from Papua New Guinea and U. anak from Papua, Indonesia and Papua New Guinea were dissimilar.
Discussion This study is a compilation of information available on the helminths of the hydromyine rodent genus Uromys. The analysis of the helminth assemblage of U. caudimaculatus must be treated with some caution. Although dissection records of hosts are available through museum archives, not all helminths found may have been registered in museum collections. Conversely, the lack of helminths in some hosts may not have been recorded. Furthermore, those hosts kept in spirit in museum collections were dissected only for helminths of the digestive tract. Consequently, estimates of species normally occurring in sites other than the digestive tract may be understated and estimates of prevalence may be overstated.
The total of 36 helminth species recorded from 62 Uromys caudimaculatus from both Papua New Guinea and Australia is similar to the species richness of 33 helminths found in 125 Melomys cervinipes in Queensland (Smales et al. 2004), one of only three uromyine rodents in which helminth communities have been studied previously. However, helminth species rich-ness was lower in the Queensland population of U. caudimacu-latus (23 species) than in M. cervinipes (Smales et al. 2004). By contrast, U. caudimaculatus in Queensland and overall has a richer helminth assemblage than that in the eastern Australian population of Melomys burtoni (with 19 helminth species from 67 hosts) (Smales 2005). Similarly, with 14 helminth species from 11 hosts the Papua New Guinea population of U. caudi-maculatus had a richer species assemblage than Melomys lutil-lus with 5 helminth species from 20 hosts (Smales 2005).
The larval acanthocephalan Porrorchis hydromuris, reported from Uromys caudimaculatus from Papua New Guinea, has pre-viously been recorded from Hydromys chrysogaster Geoffroy, 1804 in both Australia and New Guinea and Parahydromys asper (Thomas, 1906), also in Papua New Guinea (Smales 1997, 2006a, 2006b). Neither acanthocephalans nor trematodes were a large component of the helminth assemblages of Uromys spp. (one species) or Melomys spp. (one species) (Smales et al. 2004). The largely herbivorous diet of the two host groups may preclude the establishment of substantial populations of helminth species that use molluscs (trematodes) or arthropods (acanthocephalans) in their life cycles.
In contrast, the three cestode species found in Uromys caudi-maculatus form a larger component of the helminth assemblage than was the case in Melomys spp. (Smales et al. 2004; Smales 2005). The cosmopolitan Hymenolepis diminuta was not found in U. caudimaculatus from Australia although it has been reported from Rattus spp. and H. chrysogaster from Australian localities (Smales 1997). Raillietina celebensis, although not found in New Guinea in this study, has been reported previously from M. lutillus and M. burtoni from Papua New Guinea and Australia (Smales et al. 2004; Smales 2005). Bertiella baylisi,
Helminth assemblages of Uromys spp. Australian Journal of Zoology 89
Table 3. Overall similarities of the helminth assemblages of Uromys species from three geographical regions as expressed by Sorensen’s Index
U. caudimaculatus U. caudimaculatus U. anak Queensland Papua New Papua Indonesia
Guinea and Papua New Guinea
U. caudimaculatus 100 Queensland
U. caudimaculatus 10.8 100 Papua New Guinea
U. anak 9.7 21.7 100 Papua Indonesia and Papua New Guinea
reported from U. caudimaculatus in Australia, was not found in Papua New Guinea.
Strongyloides sp. was found only in Australian hosts. These small, slender nematodes live deeply embedded in the lining of the intestinal mucosa and are difficult to detect during dissec-tion. Consequently, they may have been present but not found in the dissections of the hosts from Papua Indonesia and Papua New Guinea.
The nematode fauna was, however, dominated by the Trichostrongylina (14 species), including 10 species of the family Heligmonellidae. Odilia uromyos was found in each of the three host species and from the three geographical regions although O. melomyos was the most prevalent species (48%). Odilia mackerrasae, O. emanuelae and O. melomyos have been identified from M. burtoni in Australia as well as from Mayermys ellermani Laurie and Hill, 1954 and Parahydromys asper, both uromyine genera from New Guinea (Smales 2006a, 2006b).
The Trichostrongylina assemblage occurring in each of the host populations was distinctive however. The Australian popu-lation of U. caudimaculatus harboured only the heligmonellids O. melomys, O. uromyos, O. mackerrasae, O. brachybursa, O. mawsonae and Nippostrongylus magnus. All of these species have been found in other Australian rodent hosts (Smales 1997). The New Guinea population of U. caudimaculatus was infected by three endemic heligmonellids (O. carinatae, O. implexa and N. sembeli) as well as three species (O. mackerrasae, O. melomyos and O. uromyos) that occur in both Papua New Guinea and Australia and the trichostrongylid Perameli-strongylus sp. Peramelistrongylus is a monospecific genus, described by Mawson (1960) from bandicoots (Peramelidae) in Australia, that has also been recorded as an occasional infection in Australian rodents, including Melomys spp. (Smales et al. 2004; Smales 2005) and H. chrysogaster (see Mawson 1961). There are, however, no records of the genus, either from bandi-coots or rodents, in New Guinea, so it cannot be assumed that the female Peramelistrongylus reported here was P. skedastos Mawson, 1960, although it was similar morphologically.
The presence of two additional species of Odilia in hosts from New Guinea provides further evidence that the genus is widely distributed across the bioregion and that the origins of the genus may lie either in New Guinea or Sulawesi, as sug-gested by Smales (2005, 2008), with foci of speciation also in Australia (Smales and Spratt 2004). At least five species,
namely O. mackerrasae, O. emanuelae, O. mawsonae, O. melomyos and O. uromyos, appear to have travelled with their rodent hosts between New Guinea and Australia, as noted in this study and by Smales (2006a, 2006b).
In addition, finding species of Macrostrongylus, Pitheco-strongylus and Sabanema in Uromys spp. is indicative of links between Malaysian and New Guinean fauna. These three genera were previously known only from Malaysian rats (Ow Yang et al. 1983; Smales 2007).
Durette-Desset et al. (1994) proposed that Nippostrongylus reached Australia by travelling with migrating Rattus species from Asia. The finding of N. sembeli, previously known from Sulawesi Indonesia (Hasegawa and Tarore 1995), in New Guinea supports the possibility of an Indonesian link while the finding of N. magnus only in Australian hosts does not support the migration of U. caudimaculatus across Torres Strait from Australia to New Guinea, as proposed by Smales and Spratt (2004) for Rattus leucopus (Gray, 1867).
The nematode lungworm Marsupostrongylus fragilis is a parasite of members of the dasyurid marsupial genus Antechinus Macleay, 1841 and uses snails and slugs as interme-diate hosts (Mackerras and Sandars 1953; Spratt 1979, 1984). The low prevalence of infection supports the suggestion made above that molluscs are not a major dietary item of Uromys spp. This is the first record of a species of Marsupostrongylus in a host other than a marsupial.
The oxyurid fragments found in the Australian population of U. caudimaculatus were poorly preserved and could not be iden-tified to genus. Syphacia darwini Hugot and Quentin, 1985 is, however, the only oxyurid recorded from Australian Melomys spp. (Smales et al. 2004; Smales 2005). No oxyurids were found in the Papua New Guinea population of U. caudimaculatus but Syphacia longaecauda, known only from Melomys spp. in New Guinea (Smales 2001a), was found in U. anak. This lends support to the hypothesis of Smales (2004) that endemic species of Syphacia were derived from syphaciine populations intro-duced into the region by invading rodents.
Larvae of Ophidascaris robertsi were found only in Australian hosts in this study although they have been recorded from Rattus leucopus from New Guinea (Smales and Spratt 2004). The finding of the spirurid Protospirura kaindiensis in hosts in Papua New Guinea supports the suggestions of Smales (2001b) and Smales and Spratt (2004) that P. kaindiensis is endemic to New Guinea while the cosmopolitan spirocercid,
90 Australian Journal of Zoology L. R. Smales and D. M. Spratt
Mastophorus muris, which fills the same ecological niche, arrived in Australia with recent introductions of cosmopolitan Rattus spp. and is found in occasional infections of endemic rodent hosts. The other spirocercid found in this study, Physocephalus sexalatus, has been reported from pigs in Australia (Mackerras 1958) and most likely represents an occa-sional infection of U. caudimaculatus.
The rictulariid, Rictularia sp., found in a Papua New Guinea host, had cuticular spination, morphology of the anterior end and morphometrics, including egg size, congruent with the description of Rictularia pearsoni but only female specimens were available for study. Rictularia pearsoni was described by Mawson (1971a) from Rattus fuscipes (Waterhouse, 1839) from Pearson Island, South Australia. Female specimens of a Rictularia sp. also with characters consistent with R. pearsoni were found subsequently in Melomys cf. burtoni from the Kimberly Region of Western Australia (Smales 2005). This sug-gests that R. pearsoni may be a widespread but rare nematode. Three other species of Rictularia have been described from Australian rodents (Smales 1997), thus the specific identity of our specimens could not be confirmed.
Species of Subulura have been identified from M. cervi-nipes, H. chrysogaster, R. fuscipes and R. leucopus (Mawson 1971b; Smales 2006a; Smales et al. 2004; Smales and Spratt 2004). There is now sufficient material available to allow revi-sion of the genus in the Australasian region, thus resolving some of the anomalies of its distribution, as also noted by Smales and Spratt (2004).
Metathelazia caballeroi found in the bronchi of a single Australian U. caudimaculatus (see Spratt 2007) was originally described by Quentin and Krishnasamy (1977) from the lungs of the primate Tupaia glis (Diard, 1820), from Lalong Kepong and Kuala Terengganu and a specimen from the duodenum of the same host species from Ulu Gombak, Selangor, Malaysia. The other representative of this genus, Metathelazia naghiensis, was originally described from the lungs of the marsupial long-nosed bandicoot, Perameles nasuta Geoffroy, 1804 by Spratt (1980) and is now known from peramelid and dasyurid hosts from northern, eastern and southern Australia (Spratt 2007).
The filarioid nematode Cercopithifilaria johnstoni, with skin-inhabiting microfilariae, occurs in murids, monotremes and dasyurid, peramelid, petaurid and phalangerid marsupials, and utilises ixodid ticks as intermediate host and vector (Spratt and Varughese 1975; Spratt and Haycock 1988). The additional filarioid, Monanema australe, occurred in blood vessels of the liver of three animals from the Mt Windsor Tablelands (Spratt 2008). Known species of Monanema occur in rodents, also have skin-inhabiting microfilariae and use ixodid ticks as intermedi-ate host and vector (Petit et al. 1988).
Of the capillariids, Calodium hepaticum may have been present in the livers of hosts in New Guinea but would not have been detected during dissection because of the nature of the material. Capillaria s.l. species have been reported from the intestine of Melomys spp. from Australia and are found consis-tently, but at low prevalences, in endemic rodents in Papua New Guinea and Australia, although often only single degenerate females are found, as was the case with the specimen from New Guinea. The available material was inadequate for identification to species level. Similarly, the trichurid Trichuris muris has been
found in Australian melomys (Smales et al. 2004; Smales 2005). The Trichuris specimens found in an Australian host may be the cosmopolitan T. muris but their loss has precluded confirmation of this identification.
The helminth assemblage of U. caudimaculatus with high species richness (36 species including one lot of unidentified oxyurids and one of heterakids) was relatively equitable, as indi-cated by the diversity indices I/SI = 0.64 for the least diverse Papua New Guinea population of hosts, and I/SI = 1.76 for Queensland hosts, with an overall diversity of 0.92. These values are similar to those for four populations of M. cervinipes (I/SI = 1.53, 1.66, 1.82, 2.39) (Smales et al. 2004), one popu-lation of R. leucopus (I/SI = 1.75) (Smales and Spratt 2004) and one population of Rattus sordidus (Gould, 1858) (I/SI = 3.8) (Smales 1992) but lower than those for two populations of H. chrysogaster from Queensland (I/SI = 12.17, 13.59) (Smales and Cribb 1997).
The analysis of prevalence classes revealed only two species with a prevalence ≥40% and two species with prevalences between 10 and 30%. The remaining 32 species occurred at prevalences of ≤10%. Thus, the community structure is neither isolationist and species poor, nor interactive and species rich, as defined by Stock and Holmes (1987). The distribution of preva-lences could be characterised as bimodal with O. melomyos and O. uromyos secondary species (47–48% prevalence), as defined by Stock and Holmes (1987), and 34 satellite species (1–26% prevalence). Within the satellite species group are those that could be classed as rare species, species unique to Uromys, those that are similarly rare in other host species or species that are occasional infections in the satellite component of other host species.
This helminth community structure is similar to that described for M. cervinipes (see Smales et al. 2004), R. leuco-pus (see Smales and Spratt 2004) and R. sordidus (see Smales 1992). By contrast, the helminth community of R. fuscipes from Victoria, a temperate host population, had a diverse but equi-table community (I/SI = 0.5) structured as core (two species), secondary (seven species) and satellite (11 species) species (see Smales and Cribb 1997), congruent with an interactive commu-nity as described by Bush and Holmes (1986).
Although the dominant Trichostrongylina occurred in each of the three host populations there were considerable differences between helminth assemblages of U. caudimaculatus and U. anak, as indicated by Sorensen’s Index. Helminth assem-blages from U. caudimaculatus from Queensland and U. caudi-maculatus from Papua New Guinea were more dissimilar (10.8%) than those from U. caudimaculatus and U. anak from New Guinea. There was almost no similarity between hosts from localities in Queensland and hosts from Papua Indonesia and Papua New Guinea. These differences may be explained in part by the smaller samples of hosts from localities in the latter two countries. The differences may also reflect, however, a scenario where a limited pool of helminths travelled with U. caudimaculatus from New Guinea to Australia and the hel-minth fauna was subsequently enriched by host switching of helminths from sympatric rodent hosts that were already estab-lished in Australia. Alternatively, when a small population of a host species and its helminths disperses, i.e. is introduced into a new environment, many of the parasite species may be lost or
Helminth assemblages of Uromys spp. Australian Journal of Zoology 91
die out because the host population is too small to be able to sustain infection of new hosts by parasites with a direct life cycle or suitable intermediate hosts may not exist to maintain parasites with an indirect life history (see Torchin et al. 2003). Under such a scenario, U. caudimaculatus may have lost many of the members of its helminth community following arrival in Australia from Papua New Guinea.
The Uromyini, including Uromys, have had a long evolu-tionary history in New Guinea. The genera that are shared with Australia, namely Melomys, Uromys and Pogonomys, are thought to have travelled across a woodland and savannah land bridge during the Pleistocene (Flannery 1995). The period for speciation in Australian Uromys species, ~40000 years, seems relatively brief. Consequently, the rich parasite species diversity found in U. caudimaculatus may be the result of the host switch-ing scenario described above rather than of coevolution of host and parasite since arrival in Australia.
Acknowledgements Our thanks go to Peter Haycock, Les Moore and Ian Mason for collection of rats in Australia, to Carla Kisinami and Tim Flannery for access to host bodies from the Bishop Museum and the Australian Museum and to Ian Beveridge for assistance with the identification of the cestodes. We are grateful to two anonymous referees whose comments and suggestions contributed significantly to the final form of the manuscript.
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Manuscript received 30 January 2008, accepted 8 July 2008
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Appendix 1. Registration numbers for voucher specimens (examined for this study) obtained from Uromys caudimaculatus Specimens were obtained from the collections of the Natural History Museum, London (no letter prefix), the Bishop Museum, Honolulu, the AustralianMuseum, Sydney (W), the South Australian Museum, Adelaide (AHC) the Queensland Museum, Brisbane (G, GL) and the National Wildlife Collection,
