The phylogeny of Neospora caninum

Morphological studies by electron microscopy on the protozoan Neospora caninum have shown that this organism possesses a subcellular structure typical of parasites classified in the family Sarcocystidae, subclass Coccidiasina of the phylum Apicomplexa. Using a strategy based on DNA sequence analysis of products derived by asymmetric PCR to determine the nucleotide sequences, we have tested the validity of this classification by comparing the small subunit ribosomal RNA (18S rRNA) gene sequences of N. caninum with those of other parasitic protozoa classified in the phylum Apicomplexa. The results of this analysis confirm the placing of N. caninum in the family Sarcocystidae and place it as a sister group to Toxoplasma gondii in the phylum Apicomplexa.

Evolution in New-Guinean Muridae (Rodentia) Assessed by Microcomplement Fixation of Albumin

The interrelationships of 19 genera and 28 species of New Guinean rodents representing 80% of the currently recognised New Guinean genera, were studied using microcomplement fixation of albumin to measure immunological distances among genera. The phylogenetic distinctiveness of Rattus and the closely related Stenomys from all other genera was confirmed. The remaining genera fall into three groups: (i) Lorentzimys; (ii) Anisomys, Coccymys, Chiruromys, Hyomys, Macruromys, Mallomys and Pogonomys; and (iii) Crossomys, Hydromys, Leptomys, Mayermys, Melomys, Neohydromys, Parahydromys, Pseudohydromys and Uromys. Solomys, from the Solomon islands, and Leggadina, Mesembriomys and Xeromys, from Australia, were shown to belong to this latter group. Groups (i) and (ii) are essentially endemic to New Guinea, while the third shares genera and species with Australia.

Evolution in Some South-East Asian Murinae (Rodentia), as Assessed by Microcomplement Fixation of Albumin, and Their Relationship to Australian Murines

The interrelationships of 16 genera and 49 species of predominantly South-east Asian murine rodents were studied by means of microcomplement fixation of albumin to measure immunological distances among taxa. The results are viewed as a hypothesis of the phylogenetic relationship of these taxa that can be tested by other data sets. Three main groupings are suggested: (1) Maxomys; (2) Leopoldomys, Niviventer and Tokudaia; and (3) Bandicota, Berylmys, Bullimus, Bunomys, Komodomys, Nesokia, Papagomys, Paruromys, Rattus, Stenomys, Sundamys and Taeromys. Within this latter group, Bunomys chrsogasta, Komodomys and Rattus timorensis group together, as do Bullimus, Rattus and Stenomys, and Bandicota with Nesokia. The Australian murines, represented by Mesembriomys, may be part of this South-east Asian radiation but, if so, arose early in its history. Biogeographically, the results support South-east Asia as being a centre of murine evolution with secondary foci in Sulawesi, New Guinea and Australia. There is some evidence to suggest that a relatively recent land bridge between Sulawesi, Flores and Timor may have existed.

Contributions to the phylogeny of Platyhelminthes based on partial sequencing of 18S ribosomal DNA

Partial sequencing of the 18S ribosomal DNA gene of one nemertean and 13 free-living and parasitic Platyhelminthes (556 nucleotides), and of one nemertean and 20 Platyhelminthes (556 nucleotides) was used to test several hypotheses concerning the phylogenetic relationships of Platyhelminthes. The following conclusions were reached: the Neodermata is monophyletic; Trematoda (Aspidogastrea and Digenea) is monophyletic, although a sister group relationship of the Aspidogastrea and all other Neodermata cannot be definitely ruled out; the Cestoda comprising the Eucestoda, Amphilinidea and Gyrocotylidea is monophyletic; it is unresolved whether the Monogenea is paraphyletic; neither Gyrocotylidea and Monopisthocotylea nor Gyrocotylidea and Monogenea as a whole are sister groups; Anoplodiscus is a monopisthocotylean monogenean; none of Proseriata, Pterastericolidae/Umagillidae, Kalyptorhynchia, Rhabdocoela as a whole, Dalyelliida or the Temnocephalidae is the sister group of the Neodermata; there is some evidence that a larger taxon consisting of Proseriata, Tricladida and Rhabdocoela may be the sister group of the Neodermata but definitive evidence for a sister group relationship between the Neodermata and any turbellarian taxon is lacking; Rhabdocoela and Lecithoepitheliata are not closely related; it is unresolved whether the Rhabdocoela is monophyletic; Umagillidae, Pterastericolidae and Temnocephalidae belong to one monophylum; the Temnocephalidae are very close to the dalyelliids; Tricladida and Rhabdocoela are sister groups, the exact position of the Catenulida and Nemertini in relation to the Platyhelminthes has not been resolved, although Catenulida and Lecithoepitheliata may belong to one clade.

Phylogenetic relationships of the thylacine (Mammalia: Thylacinidae) among dasyuroid marsupials: evidence from cytochrome b DNA sequences

DNA sequences from the mitochondrial cytochrome b gene were obtained from a museum specimen of the presumed extinct thylacine (Thylacinus cynocephalus) and were compared with homologous sequences from 13 representatives of the Australian marsupial family Dasyuridae. The relationship of the thylacine to dasyurids has been suggested by previous anatomical and molecular studies, but its position within the dasyuroid radiation has not been addressed with genetic data. Phylogenetic analysis of the sequences reported here suggests that the thylacine is a sister group to Dasyuridae and lends support to the hypothesis that Thylacinus represents an ancient Australian marsupial lineage. Relationships with Dasyuridae support the results of other recent molecular studies, particularly in showing the affinities of endemic New Guinean subfamilies with larger Australian clades.

The Evolution of Species of the Varanidae - Microcomplement Fixation Analysis of Serum Albumins

Phylogenetic relationships among 30 of the 40 species in the Varanidae were examined in the light of molecular information on albumin evolution derived from microcomplement fixation. A phylogeny based on these results is compared with proposed phylogenies based on data obtained using other techniques. Three separate radiations of Varanus are found in Australia, The movement of varanids to Australia from south-east Asia is thought to have occurred approximately 15-20 million years ago.

Ribosomal DNA sequence comparison of Babesia and Theileria

Previous studies on the taxonomy of Babesia spp. (phylum Apicomplexa) using morphological and life cycle characteristics have resulted in their classification into 3 subgenera, with the genus Theileria being most closely related to them. Using a strategy based on the direct sequence analysis of products derived by asymmetric PCR to determine the nucleotide sequences, we have tested the validity of this classification by sequencing the small subunit ribosomal RNA genes amplified from 2 Babesia species, namely Babesia bovis and Babesia rodhaini, and comparing these with previously published sequences of Theileria annulata and Babesia bigemina using Plasmodium falciparum as an outgroup. The results of this phylogenetic analysis support the recognition of at least 2 genera in Babesia--one to include B. bigemina and B. bovis, the other to include B. rodhaini.

Phylogenetic relationships of Sarcocystis species from sheep, goats, cattle and mice based on ribosomal RNA sequences

Partial sequences of the small subunit ribosomal RNA of four species of Sarcocystis were obtained by reverse transcription of total cellular RNA. The semi-conserved regions of these four species were aligned with homologous sequences of two other Sarcocystis species and a range of other eukaryotes including Toxoplasma, Eimeria and Cryptosporidium. Parsimony analysis of the aligned sequences showed that Sarcocystis and Toxoplasma had a more recent common ancestor with Eimeria than with Cryptosporidium. The six Sarcocystis spp. did not cluster together in this analysis; two monophyletic groups were observed, one formed by the two Sarcocystis spp. with felids as definitive hosts, and another by the four Sarcocystis spp. with canids as definitive hosts. These two clades were segregated by Toxoplasma. An analysis of nucleotide divergence suggests that the difference between the two groups of Sarcocystis spp. is similar to that between invertebrates and vertebrates. The results obtained here question the validity of a separation of the genus Sarcocystis from Toxoplasma and refute classifications that place these two genera into two different subfamilies of the Sarcocystidae.

Phylogeny of the Australian Rodents (Muridae) - a Molecular Approach Using Microcomplement Fixation of Albumin

Microcomplement fixation was used to assess albumin evolution in the history of the rodents of Australia. The results confirmed a monophyletic grouping consisting of the genera Pseudomys, Mastacomys and Notomys, and showed that the genus Pseudomys is paraphyletic. The genera Conilurus, Leporillus and Mesembriomys also formed a monophyletic group. A significant finding was that Leggadina was distantly related to all Pseudomys species, and indeed may be the earliest offshoot of all Australian rodents other than Rattus. Albumin evolution in the Australian rodents has occurred in a manner far from clock-like. Mastacomys Thomas, 1882 is synonymised with Pseudomys Gray, 1832.

Rates of Albumin Evolution in Parrots (Aves, Psittaciformes)

A number of lines of evidence suggest that the rate of molecular evolution in birds is slower than in other vertebrates. This hypothesis was tested by measuring the extent of amino-acid sequence divergence in albumin among species of parrots by means of microcomplement fixation. This group was chosen because its modern distribution is strongly suggestive of a Gondwanan origin. The results show that the intercontinental albumin distances are well below those expected for a Gondwanan group. These data are in accord with the hypothesis that birds have a slower rate of molecular evolution, although other explanations are possible.

Evolutionary Relationships of the Australasian Mud-Nesters (Grallinidae, Corcoracidae) - Immunological Evidence

The phylogenetic relationships of the genera of Australasian mud-nesters (Corcorax, Struthidea and Grallina) were examined by microcomplement fixation, and the results compared with morphological and DNA-DNA hybridisation data. There was general corroboration among all data sets such that (1) Corcorax and Struthidea were well-diverged members of a single lineage related to corvoids, and (2) Grallina comprised two species (Australian G. cyanoleuca and New Guinean G. bruijni) closely allied to Myiagra among the monarch flycatchers (Monarchidae). The immunological data also indicated that Corcorax and Struthidea were closer to Corvus (Corvinae) than to some other members of that subfamily identified by DNA-DNA hybridisation. There was further corroboration of evidence from DNA-DNA hybridisation for an endemic radiation among Australo-Papuan passerine families.

Conflicting phylogenetic hypotheses for the parasitic platyhelminths tested by partial sequencing of 18S ribosomal RNA

Partial sequencing of the 18S ribosomal RNA in nine parasitic and one free-living species of platyhelminth was used to test hypotheses on the phylogenetic relationships among the major groups. The eucestodes, amphilinideans, gyrocotylideans and monopisthocotylideans appeared as a monophyletic assemblage in a cladistic analysis of the data, with a very close association between the gyrocotylideans and monopisthocotylideans. The polyopisthocotylidean monogeneans were paraphyletic to the monopisthocotylideans. The digeneans appeared to be a sister group to the monogeneans and eucestodes, while the temnocephalidean was closely related to the free-living polyclad.

A Phylogenetic Comparison of 18s-Ribosomal Rna Sequences of Lungfish With Those of Other Chordates

A rapid RNA-sequencing technique was used to partially sequence the 18S ribosomal RNA of species representing seven taxa: Holocephali, Cladistia, Chondrostei, Holostei, Dipnoi, Anura and Caudata. Phylogenetic analysis of the nucleotide sequences strongly suggests that both the Holocephali and Cladistia, and the Anura and Caudata, are each monophyletic groups. There is a weaker suggestion that the Chondrostei and Holostei are monophyletic. The Dipnoi did not group with any one of these more than with any other.

Evolution of the Small Subunit Ribosomal-Rna in Higher Vertebrates

The potential value of rapid sequencing of the srRNA molecule for phylogenetic reconstruction of the higher vertebrates was investigated. The study involved partial sequencing of 19 taxa that, along with 6 sequences from the literature, covered all of the major groups of higher vertebrates. The results show that sequencing of the srRNA molecule is not suitable at this taxonomic level because: (i) there is insufficient nucleotide sequence variation; (ii) expansion segments, although common, have a high probability of convergence for both their position and their sequence; and (iii) the phylogenetic branching of the higher vertebrates has been mainly 'bush-like' rather than 'tree-like'.

Immunological Evolution of Albumin in the Estrildine Finches (Aves, Passeriformes) Is Far From Clock-Like

On the basis of microcomplement fixation studies, the finch Taeniopygia guttata has an albumin whose immunological properties are very different from those of other finches. Outgroup analysis, microcomplement fixation of transferrin, and electrophoretic behaviour of finch albumin, together with phylogenetic considerations based upon chromosomes and allozymes, revealed that the difference is due to rapid change in the immunological properties of T. guttata albumin rather than to a distant relationship of T. guttata to other finches. Indeed, the immunological properties of the albumin of T. guttata has undergone about 15 times as much change as would be expected for an albumin clock. The results highlight the caution that should be exercised when applying the molecular clock ad hoc to immunological data.

Small subunit ribosomal RNA evolution in the genus Acanthamoeba

Reverse transcription of small subunit ribosomal RNA (srRNA) was used to determine the partial nucleotide sequences of the srRNA of seven isolates of Acanthamoeba. These seven sequences and the sequence of the corresponding region in an A. castellanii previously totally sequenced were compared in order to investigate evolution of the srRNA gene in Acanthamoeba. The results of the comparisons were consistent with the hypotheses that the genus is monophyletic, that the Pussard and Pons grouping system is valid, that the Acanthamoeba expansion segments in the srRNA gene evolve at a much faster rate than the rest of the gene, and that the extent of nucleotide sequence divergence in the genus Acanthamoeba is roughly similar to that differentiating vertebrates and invertebrates.

Phylogenetic relationships of Cryptosporidium determined by ribosomal RNA sequence comparison

Reverse transcription of total cellular RNA was used to obtain a partial sequence of the small subunit ribosomal RNA of Cryptosporidium, a protist currently placed in the phylum Apicomplexa. The semi-conserved regions were aligned with homologous sequences in a range of other eukaryotes, and the evolutionary relationships of Cryptosporidium were determined by two different methods of phylogenetic analysis. The prokaryotes Escherichia coli and Halobacterium cuti were included as outgroups. The results do not show an especially close relationship of Cryptosporidium to other members of the phylum Apicomplexa.

Immunological Relationships and Generic Revision of the Australian Lizards Assigned to the Genus Leiolopisma (Scincidae, Lygosominae)

The phylogenetic relationships of the Australian scincid lizards currently assigned to the genus Leiolopisma have been examined by quantitative micro-complement fixation (MC'F) comparisons of serum albumin. The results of these comparisons do not support the monophyly implicit in these species' current congeneric status, but suggest instead that the Australian species of Leiolopisma belong to several distinct phyletic lineages within the Eugongylus group. These findings are supported by several sets of non-biochemical characters, including features of scalation, osteology and karyotype. None of the Australian species shares a close relationship with the type-species of Leiolopisrna (L. telfairii), and so a new taxonomic arrangement is proposed which distributes them among the following genera: Bartleia, gen. nov. (jigurru); Bassiana, gen. nov. (duperreyi, platynotum and trilineata); Cautula, gen. nov. (zia); Niveoscincus, gen. nov. (coventryi, greeni, metallicus, microlepidotus, ocellatus, orocryptus, palfreymani and pretiosus); and Pseudemoia Fuhn, 1967 (baudini, entrecasteauxii Group 1; entrecasteauxii Group 2, rawlinsoni and spenceri). Preliminary comparisons suggest that other Leiolopisma species, from New Caledonia, Lord Howe I. and New Zealand, belong to phyletic lineages which are distinct from any of the Australian 'Leiolopisma' and from the type-species.

Albumin Immunological Relationships of Australian Marsupials. 2. The Pseudocheiridae

Microcomplement fixation of albumin was used to examine the phylogenetic relationships among the ringtail possums, family Pseudocheiridae. Phylogenetic analysis of the data supports the hypothesis of at least three distinct clades within the family: one containing Petauroides and Hemibelideus; a second consisting of Pseudocheirus herbertensis, Ps. forbesi, Ps. mayeri, and Ps. canescens; and a third containing Ps. archeri, Ps. corinnae, Ps. cupreus and Ps. dahli. The data have not resolved the phylogenetic position of Ps. peregrinus, which may either form a separate clade or lie close to the Ps. archeri clade.

The Chromosomes of 4 Genera of Possums From the Family Petauridae (Marsupialia, Diprotodonta)

The standard and C-banded (four species) karyotypes of six species of the family Petauridae (Gymnobelideus leadbeateri, Petaurus australis, P. breviceps, P. norfolcensis, Dactylopsila trivirgata and Dactylonax palpator) are described. The G-banded karyotype of P. norfolcensis is also described. Gymnobelideus and Petaurus have diploid chromosome number of 22. All three species of Petaurus have a similar karyotype, consisting of biarmed autosomes and very small sex chromosomes, which differs from Gymnobelideus by a minimum of one chromosomal rearrangement of each autosome. Dactylopsila and Dactylonax have similar karyotypes with diploid chromosome numbers of 18. The relationship of these two genera to Petaurus is still uncertain but all members of this family differ from Pseudocheiridae in the small size of the sex chromosomes.

A genetic approach to species criteria in the amoeba genus Naegleria using allozyme electrophoresis

The present study employs allozyme electrophoresis to characterize and inter-relate 61 isolates of Naegleria. Diploidy was confirmed, with heterozygotes observed at 29 of the 33 loci established and in all but two isolates. With a single exception, isolates clustered at two levels of similarity, either below 21% or above 52%. It is argued that such a major discontinuity provides a sound biological basis for a species concept in Naegleria. On this basis the present species-level taxonomy does not reflect the genetic diversity of the genus. The study recognized 18 genetic groups of species rank. The subspecies N. australiensis italica deserves specific rank; additional thermophilic species not closely related to N. fowleri and N. lovaniensis are recognized; and N. gruberi as currently conceived is a complex of 10 species, at least five of which are represented in the formal culture collections. Most species are genetically too different for relationships to be elucidated by allozyme electrophoresis, supporting the view that some of the times of divergence within the genus are extremely ancient.

Genetic characterization of three strains of Hymenolepis diminuta at 39 enzyme loci

The technique of allozyme electrophoresis was applied to three strains of Hymenolepis diminuta to distinguish between three hypotheses [(1) multiple species, (2) genetically distinct founder stocks and (3) response to differential selection among similar stocks] proposed to account for metabolic differences among strains. There was no evidence from the 39 enzyme loci established that the three strains represented more than one species. In the absence of knowledge of the population structure of H. diminuta in the wild, electrophoretic data herein could not distinguish between the latter hypotheses. Nevertheless, all three strains were distinguishable on electrophoretic profiles and allelic similarities between strains question the view of their proposed origins.

Genetic characterization of three species of Onchocerca at 23 enzyme loci

The technique of allozyme electrophoresis was applied to species of Onchocerca from cattle to increase the number of enzyme loci established and therefore provide a genetic basis for a rational species-level taxonomy. Twenty-three enzyme loci were established and provided unequivocal genetic evidence for the taxonomic validity of Onchocerca gibsoni, O. gutturosa and O. lienalis. Furthermore, the diagnostic enzyme markers detected form the basis for identification of life-cycle stages, individuals and species and population structure analyses.

srRNA evolution and phylogenetic relationships of the genus Naegleria (Protista: Rhizopoda)

A rapid RNA sequencing technique was used to partially sequence the small-subunit ribosomal RNA (srRNA) of four species of the amoeboid genus Naegleria. The extent of nucleotide sequence divergence between the two most divergent species was roughly similar to that found between mammals and frogs. However, the pattern of variation among the Naegleria species was quite different from that found for those species of tetrapods characterized to date. A phylogenetic analysis of the consensus Naegleria sequence showed that Naegleria was not monophyletic with either Acanthamoeba castellanii or Dictyostelium discoideum, two other amoebas for which sequences were available. It was shown that the semiconserved regions of the srRNA molecule evolve in a clocklike fashion and that the clock is time dependent rather than generation dependent.