N. B. Chilton

Detection by allozyme electrophoresis of cryptic species of Hypodontus macropi (Nematoda: Strongyloidea) from macropodid marsupials

Allozyme electrophoresis of 98 Hypodontus macropi from eight different species of hosts using 24 enzymes revealed a complex of at least six sibling species, with 15-50% fixed genetic differences between taxa. Except for the taxon parasitizing Macropus rufus/M. robustus, pairs of parasite taxa were, in each case, sympatric at each locality examined, thus supporting the conclusion that they represent valid species. The existence of a series of host-specific nematode taxa explains many of the inconsistencies noted previously in the host distribution of H. macropi. Comparison of parasite allozyme phenograms with host phylogeny suggests that four of the speciation events could be attributable to cospeciation and two to host switching. A clear case of host switching between M. rufus/M. robustus and M. fuliginosus was found.

Sibling species within Macropostrongyloides baylisi (Nematoda: Strongyloidea) from macropodid marsupials

Macropostrongyloides baylisi from four different species or subspecies of host were analysed electrophoretically at 27 enzyme loci. The results revealed the existence of two species, one in Macropus giganteus and the other in M. robustus robustus, M.r. erubescens and M.r. parryi, that had fixed genetic differences at 33% of loci. Populations of nematodes from two subspecies of M. robustus, M.r. robustus from Queensland and M.r. erubescens from South Australia, had fixed genetic differences at two (7.4%) of 27 loci and were considered to belong to the same species. No fixed genetic differences were detected between nematodes from M. parryi and M.r. robustus. A discriminant function analysis of morphological data assigned 96% of specimens to groups defined on the basis of the host species or subspecies from which they were obtained. This separation of Ma. baylisi into host-specific groups did not, however, totally correlate with the electrophoretic data. The species of M. baylisi in M. giganteus was genetically more distinct from the sibling species in M. robustus/M. parryi than to a related but morphologically dissimilar nematode, Ma. yamagutii from M. fuliginosus. This suggests an evolutionary parallel between host and parasite at the genetic level which is not reflected by morphological differences.

Electrophoretic comparison of Rugopharynx longibursaris Kung and R. omega Beveridge (Nematoda: Strongyloidea), with the description of R. sigma n. sp. from pademelons, Thylogale spp. (Marsupialia: Macropodidae)

An electrophoretic comparison of the nematodes Rugopharynx longibursaris and R. omega, both from Macropus rufogriseus in south-eastern Australia, revealed fixed genetic differences at 4.5% of the 23 enzyme loci examined. The electrophoretic data do not therefore reject the null hypothesis that the two taxa are conspecific. R. longibursaris was found in Tasmania and in the western mainland population of M. rufogriseus, while R. omega occurred only in the eastern mainland population. Implications for the taxonomic status of the western host population are considered. Specimens formerly assigned to R. omega, from Thylogale stigmatica from Queensland, were found to differ at 45.0% of enzyme loci from specimens from M. rufogriseus. Morphological examination revealed differences in the shape of the buccal capsule, the position of the deirid, the morphology of the spicule tip and the presence of a gubernaculum. A new species, R. sigma, is erected for specimens from T. stigmatica, T. thetis and T. calabyi.

The occurrence of species flocks in the nematode genus Cloacina (Strongyloidea : Cloacininae), parasitic in the stomachs of kangaroos and wallabies

The occurrence of species flocks within the nematode genus Cloacina was examined using the criteria of host specificity, co-occurrence and monophyly. Species of Cloacina generally exhibited a high degree of host specificity, with most species occurring either in a single host species or in two closely related host species. The frequency distribution of numbers of component species of Cloacina per host species indicated that most host species harboured 2–4 species of nematodes, with an approximately exponential decline in the number of species of parasites to a maximum of 20 species of nematode per host species. Host species harbouring eight or more species of Cloacina were found within a single recent macropodid clade, but there was no correlation between evolutionary age of the host and the number of parasite species harboured. Sampling effort was significantly correlated with the number of nematode species found and, in partial regression analysis, subsumed the effects of host body size and geographic range, which were found to be significant correlates with the number of nematode species present in preliminary analyses. Analysis of co-occurrences of nematode species indicated significant variation between host species, with some hosts (e.g. Macropus agilis) most commonly harbouring a single species of Cloacina, while closely related host species (e.g. M. dorsalis) most commonly harboured numerous species. Parsimony analysis of species of Cloacina based on morphological data suggested that while small series of related nematode species could be identified within a single host species, the species flock in each host species is polyphyletic in origin. Species flocks contributed significantly to community richness in some host species.

A morphological and electrophoretic study of Rugopharynx zeta (Johnston & Mawson, 1939) (Nematoda: Strongyloidea), with the description of a new species, R. mawsonae , from the black-striped wallaby Macropus dorsalis (Marsupialia: Macropodidae)

Rugopharynx zeta (Johnston & Mawson) (Nematoda: Strongyloidea) is redescribed from the rock wallabies Petrogale penicillata penicillata, P. p. herberti, P. inornata and P. assimilis from Queensland and New South Wales, Australia. Specimens formerly assigned to this nematode taxon from the wallabies Macropus dorsalis and M. parma are treated as a new species, R. mawsonae. R. mawsonae n. sp. differs from R. zeta in the shape of the dorsal ray, length of spicules, morphology of spicule tip, length of female tail and position of deirid. The morphological differences are supported by electrophoretic data. R. zeta and R. mawsonae n. sp. had fixed genetic differences at 45.0% of the 21 enzyme loci examined, while each differed at 38.1% and 45.0% of loci respectively from the morphologically distinct R. delta (Johnston & Mawson). The known host and geographical distributions of R. zeta and R. mawsonae n. sp. are reviewed.

Electrophoretic and morphological analysis of Paramacropostrongylus typicus (Nematoda: Strongyloidea), with the description of a new species, Paramacropostrongylus iugalis, from the eastern grey kangaroo Macropus giganteus

An allozyme study of four populations of Paramacropostrongylus typicus from Macropus fuliginosus and M. giganteus detected the presence of a distinct species, Paramacropostrongylus iugalis n. sp., which is described from the stomach of the eastern grey kangaroo Macropus giganteus. The description is based on samples possessing fixed allelic differences at 10 of 37 enzyme loci examined, minor morphological differences from its congener P. typicus in M. fuliginosus, and presumed limitation to a single host species, M. giganteus. Its differentiation from P. typicus is more clearly demonstrated by biochemical characters than by morphological ones. The two parasite species probably co-speciated with their hosts.

Genetic evidence for a complex of species within Rugopharynx australis (Mönnig, 1926) (Nematoda: Stronglyloidea) from macropodid marsupials

An electrophoretic analysis using 17 enzyme loci was carried out on specimens of the gastric nematode of macropodid marsupials, Rugopharynx australis (Mönnig, 1926), collected from Macropus eugenii (Desmarest), M. fuliginosus (Desmarest), M. giganteus Shaw, M. robustus Gould, M. rufogriseus (Desmarest), M. rufus (Desmarest), Thylogale billardierii (Desmarest) and Wallabia bicolor (Desmarest) from south-eastern Australia. The extent of fixed genetic differences between nematodes from different host species ranged from 0–53%. The two distinct morphological forms of the parasite found in M. rufogriseus differed at 50% of loci. Specimens present in M. fuliginosus and M. giganteus were indistinguishable genetically, as were nematodes from M. rufus and M. robustus. Of the two morphologically distinct congeners included in the analysis as controls, Rugopharynx epsilon (Johnston & Mawson, 1939) was genetically distinct (46–69% fixed genetic differences) from all specimens of the R. australis complex while R. rufogrisea Magzoub, 1964 was closely related to one of the two species occuring in M. rufogriseus. It was concluded that R. australis is a species complex, with a genetically distinct species present in M. eugenii, M. fuliginosus/M. giganteus, M. robustus/M. rufus, W. bicolor and T. billardierii, and two species in M. rufogriseus.

Genetic variation in the mitochondrial cytochrome c oxidase subunit 1 within Progamotaenia festiva (Cestoda: Anoplocephalidae) from macropodid marsupials.

Genetic variation was examined in the anoplocephalid cestode Progamotaenia festiva, from Australian marsupials, in order to test the hypothesis that P. festiva, is a complex of sibling species and to assess the extent of host switching reported previously based on multilocus enzyme electrophoresis (MEE). Polymerase chain reaction (PCR)-based single-strand conformational polymorphism (SSCP) was used for the analysis of sequence variation in the cytochrome c oxidase subunit 1 (cox1) gene among 179 specimens of P. festiva (identified based on morphology and predilection site in the host) from 13 different host species, followed by selective DNA sequencing. Fifty-three distinct sequence types (haplotypes) representing all specimens were defined. Phylogenetic analyses of these sequence data (utilizing maximum parsimony and neighbour-joining methods) revealed 12 distinct clades. Other heterologous species, P. ewersi and P. macropodis, were used as outgroups and the remaining bile-duct inhabiting species, P. diaphana and P. effigia, were included in the analysis for comparative purposes. The latter 2 species were nested within the clades representing P. festiva. Most clades of P. festiva identified were restricted to a single host species; one clade primarily in Macropus robustus was also found in the related host species M. antilopinus in an area of host sympatry; another clade occurring primarily in M. robustus occurred also in additional kangaroo species, M. rufus and M. dorsalis. High levels of genetic divergence, the existence of distinct clades and their occurrence in sympatry provide support for the hypothesis that P. festiva represents a complex of numerous species, most of which, but not all, are host specific. Three distinct clades of cestodes were found within a single host, M. robustus, but there was no evidence of within-host speciation.

Morphological comparison of the adult and larval stages of the Australian ticks Ixodes holocyclus Neumann, 1899 and I. cornuatus Roberts, 1960 (Acari: Ixodoidea)

Abstract Morphological methods of distinguishing the adult and larval stages of the ticks Ixodes cornuatus and I. holocyclus were examined, using specimens whose identity had been determined using multilocus enzyme electrophoresis. Individual morphological characters identified most, but not all specimens. The only character which unequivocally distinguished males of the two species was the shape of the epimeral plate. Statistical analyses of metric characters revealed significant differences between the two species and among populations of I. holocyclus. However, no single metric character permitted unequivocal identification of all specimens. Discriminant function analyses were employed, resulting in the differentiation of all specimens of both males and females of the two species. In the larval stages, the numbers of marginal dorsal setae and supplementary setae, as well as the lengths of posterior marginal dorsal setae, allowed identification of the two species. The results highlight the advantages of utilising morphological methods in conjunction with genetic techniques to provide markers for accurate identification and characterisation in instances in which taxonomic confusion exists.

Systematic status of Aponomma tachyglossi Roberts (Acari: Ixodidae) from echidnas, Tachyglossus aculeatus, from Queensland, Australia

Abstract Evidence is presented based on morphological, electrophoretic and behavioural data, and on geographical distribution, that Aponomma tachyglossi Roberts is an independent species parasitic primarily on echidnas. Females of A. tachyglossi are distinguishable from the closely related species A. hydrosauri (Denny), parasitic on reptiles, in the shape of the porose areas, and males by the extent of the punctate areas between the scutum and the festoons. Nymphs and larvae of the two species could not be distinguished. In electrophoretic studies, A. tachyglossi was found to differ from A. hydrosauri at 16% of the 18 loci examined. Larvae of A. tachyglossi failed to attach and engorge on lizards, the usual host of A. hydrosauri. Futhermore, A. tachyglossi was found to have a limited geographical range in coastal areas of central Queensland. These data support the hypothesis that A. tachyglossi is a distinct species.