Displaying publications 1 - 20 of 168 in total

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  1. King M, King D
    Aust. J. Biol. Sci., 1975 Feb;28(1):89-108.
    PMID: 1164258
    The karyotypes have been determined of 16 of the 32 species of the genus Varanus, including animals from Africa, Israel, Malaya and Australia. A constant chromosome number of 2n = 40 was observed. The karyotype is divided into eight pairs of large chromosomes and 12 paris of microchromosomes. A series of chromosomal rearrangements have become established in both size groups of the karyotype and are restricted to centromers shifts, probably caused by pericentric inversion. Species could be placed in one of six distinct karyotype groups which are differentiated by these rearrangements and whose grouping does not always correspond with the current taxonomy. An unusual sex chromosome system of the ZZ/ZW type was present in a number of the species examined. The evolutionary significance of these chromosomal rearrangements, their origin and their mode of establishment are discussed and related to the current taxonomic groupings. The most likely phylogenetic model based on chromosome morphology, fossil evidence and the current distribution of the genus Varanus is presented.
    Matched MeSH terms: Biological Evolution*
  2. Durette-Desset MC, Chabaud AG
    Ann Parasitol Hum Comp, 1975 5 1;50(3):303-37.
    PMID: 1211768
    1. a) List of Nematodes collected by Professor Aellen in european Microchiroptera. Additionnal morphological data to the study of Molinostrongylus alatus, M. panousei, M. skrjabini. Description of M. aelleni n. sp. b) Description of M. richardae n. sp., M. benexae n. sp. et M. bauchoti n. sp., parasites of malagasian Molossidae. c) Description of M. colleyi n. sp. and M. owyangi n. sp., parasites of Malaysian Vespertilioninae, and of Allintoschius dunni n. sp., discovered in Myotis mystacinus from Malaysia and Pipistrellus nanus from Africa. 2. Taking into account the characteristics of the synlophe, the 17 species of the genus Molinostrongylus may be divided into five groups, each one being reasonably well characteristic of the genus of their Chiropteran host. 3. The composition of the Trichostrongyloidea fauna of Chiroptera and its relationship with Trichostrongyloidea from other Mammals (Tupaiidae, Pholidotes, Primates, Sciuridés) are analysed. Six groups are separated and divided into two well defined lines: 1) genus Strongylacantha, and 2) 12 genera stemming more or less directly from the Molineinae, 4. The three conical outgrowths at the tip of the female tail which differenciate presently the Anoplostrogylinae from the Molineinae appear to be an unreliable characteristic. The two subfamilies form a complex group which will be better understood if the evolution of the synlophe and that of the caudal bursa of the males are taken into account.
    Matched MeSH terms: Biological Evolution
  3. Durette-Desset MC, Chabaud AG
    Ann Parasitol Hum Comp, 1975 Mar-Apr;50(2):173-85.
    PMID: 1163943
    Matched MeSH terms: Biological Evolution
  4. Yosida TH, Sagai T
    Chromosoma, 1975;50(3):283-300.
    PMID: 1149576
    All subspecies of black rats (Rattus rattus) used in the present study are characterized by having large and clear C-bands at the centromeric region. The appearance of the bands, however, is different in the subspecies. Chromosome pair No. 1 in Asian type black rats (2n=42), which are characterized by an acrocentric and subtelocentric polymorphism, showed C-band polymorphism. In Phillipine rats (R. rattus mindanensis) the pair was subtelocentric with C-bands, but in Malayan black rats (R. rattus diardii) it was usually acrocentric with C-bands. In Hong-Kong (R. rattus flavipectus) and Japanese black rats (R. rattus tanezumi) it was polymorphic with respect to the presence of acrocentrics with C-bands or subtelocentrics without C-bands. The other chromosomes pairs showed clear C-bands, but in Hong-Kong black rats the pairs No. 2 and 5 were polymorphic with and without C-bands. In Japanese black rats, 6 chromosome pairs (No. 3, 4, 7, 9, 11 and 13) were polymorphic in regard to presence and absence of C-bands, but the other 5 chromosome pairs (No. 2, 5, 6, 8 and 10) showed always absence of C-bands. Only pair No. 12 usually showed C-bands. C-bands in small metacentric pairs (No. 14 to 20) in Asian type black rats generally large in size, but those in the Oceanian (2n=38) and Ceylon type black rats (2n=40) were small. In the hybrids between Asian and Oceanian type rats, heteromorphic C-bands, one large and the other small, were observed. Based on the consideration of karyotype evolution in the black rats, the C-band is suggested to have a tendency toward the diminution as far as the related species are concerned.
    Matched MeSH terms: Biological Evolution
  5. Peters W
    Philos Trans R Soc Lond B Biol Sci, 1976 Sep 28;275(941):439-82.
    PMID: 10589
    The primary objective of this project was to study the life cycle and ecology of Plasmodium pitheci, a malaria parasite of the orang-utan. The field work was based on the orang-utan rehabilitation centre in the Sepilok Forest Reserve of eastern Sabah. Two visits were made to Sepilok, the first in February and March, 1972, and the second (by W.P.) in January 1974. On the first visit two species of "surrogate host" were taken to Sabah, i.e. chimpanzees and Aotus monkeys for experimental work. The arboreal habitat of the orang-utan in the dipterocarp forests of eastern Sabah is described. In the Sepilok Forest Reserve dwell gibbons and leaf-monkeys, in addition to a small population of semi-domesticated and wild, free-ranging orang-utans of various ages. Although numerous species of anopheline mosquitoes have been collected in eastern Sabah, longitudinal studies are not available. Anopheles balabacensis was caught both attracted to orang-utans and to man at Sepilok. This species which is the main vector of human malaria in the north of Borneo, is suspected also of transmitting orang-utan malaria in this part of Sabah. Repeated blood examinations have been made on a number of orang-utans in the centre since 1966 and a high prevalence of infection was recorded with Plasmodium pitheci. In 1966 10 out of 19 animals had demonstrable parasitaemia. Detailed case histories are presented to show the course of parasitaemia in several orang-utans. Infections of P. pitheci were found to run a very chronic course. During the 1972 expedition a second, previously undescribed malaria parasite of the orang-utan was discovered, and was named P. silvaticum. The new parasite was successfully transmitted both by blood inoculation and, later, by sporozoite inoculation, into splenectomized chimpanzees. Although both species of malaria parasite may cause transitory signs of illness, orang-utans in general appear to be little discomforted by the infection. The animals do however suffer from other infectious diseases such as amoebic and balantidial dysentery, and melioidosis is a serious natural hazard which may have accounted for several deaths of wild orang-utans. An unidentified, intraerythrocytic structure that appeared in the blood of one chimpanzee, which had been inoculated with blood from an orang-utan, may have contributed to its death. Detailed descriptions and illustrations of P. pitheci and P. silvaticum are given. All stages of the life cycle of P. silvaticum are known (the tissue stages having been described in the liver of a "surrogate host", the chimpanzee) but only the blood and sporogonic stages of P. pitheci have been seen. This species was not infective to a chimpanzee, although there is an earlier report of a transient infection in this host by other workers. In the blood both parasites showed a tertian periodicity. From the appearance of the tissue schizonts on the seventh day it was estimated that the complete pre-erythrocytic cycle of P. silvaticum in the chimpanzee would occupy 8 days. P...
    Matched MeSH terms: Biological Evolution
  6. Fleagle JG
    Folia Primatol., 1976;26(4):245-69.
    PMID: 1010498
    Wild, adult siamang were observed for over 800 h in lowland dipterocarp forest in the Krau Game Reserve, Pahang, West Malaysia. Siamang use four patterns of locomotion: brachiation, climbing, bipedalism and leaping. The pattern of locomotion used by the siamang varies with the size of arboreal supports and with major behavioral activity. Travel is primarily by brachiation along large boughs. Locomotion during feeding is primarily climbing among small branches. In feeding, siamang use suspensory postures among small supports and seated postures on large supports. Comparison of siamang locomotion and posture with that of other apes suggest that quadramanous climbing during feeding is the basic hominoid locomotor adaptation.
    Matched MeSH terms: Biological Evolution*
  7. Teoh SB
    Theor Appl Genet, 1982 Mar;61(1):91-5.
    PMID: 24271380 DOI: 10.1007/BF00261517
    Four out of 10 diploid orchid species showed "complement fractionation" a complex cytological phenomenon, hitherto reported only in polyploid plants. The manifestation of this phenomenon during meiosis is the formation of chromosome subgroups resulting eventually in cells with more than the usual four sporads; five or six being the optimum number in the investigated orchid species. No implications whatsoever can be deduced as to the genetic or genomic constitution of the end products. The presence of the phenomenon in these orchid species could perhaps indicate a polyploid ancestry or concealed hybridity. The operation of "complement fractionation", however, could be interpreted as an alternative evolutionary pathway opposed to polyploidy.
    Matched MeSH terms: Biological Evolution
  8. Lanciotti RS, Lewis JG, Gubler DJ, Trent DW
    J Gen Virol, 1994 Jan;75 ( Pt 1):65-75.
    PMID: 8113741
    The nucleic acid sequences of the pre-membrane/membrane and envelope protein genes of 23 geographically and temporally distinct dengue (DEN)-3 viruses were determined. This was accomplished by reverse transcriptase-PCR amplification of the structural genes followed by automated DNA sequence analysis. Comparison of nucleic acid sequences revealed that similarity among the viruses was greater than 90%. The similarity among deduced amino acids was between 95% and 100%, and in many cases identical amino acid substitutions occurred among viruses from similar geographical regions. Alignment of nucleic acid sequences followed by parsimony analysis allowed the generation of phylogenetic trees, demonstrating that geographically independent evolution of DEN-3 viruses had occurred. The DEN-3 viruses were separated into four genetically distinct subtypes. Subtype I consists of viruses from Indonesia, Malaysia, the Philippines and the South Pacific islands; subtype II consists of viruses from Thailand; subtype III consists of viruses from Sri Lanka, India, Africa and Samoa; subtype IV consists of viruses from Puerto Rico and the 1965 Tahiti virus. Phylogenetic analysis has also contributed to our understanding of the molecular epidemiology and worldwide distribution of DEN-3 viruses.
    Matched MeSH terms: Biological Evolution
  9. Zin K, Morita K, Igarashi A
    Microbiol. Immunol., 1995;39(8):581-90.
    PMID: 7494497
    We determined the 240-nucleotide sequences of the E/NS1 gene junction of four dengue-2 viruses by the primer extension dideoxy chain termination method. These viruses were isolated from dengue patients with different clinical severities in Nakhon Phanom, Northeastern Thailand in 1993. The results were compared with the 52 published dengue-2 sequences of the same gene region. Sequence divergence of four new isolates varied from 4.17% to 5.42% compared with dengue-2 prototype New Guinea C strain whereas it varied from 5.42% to 6.67% and from 6.67% to 7.09% when compared with Jamaica 1409 strain and PR159/S1 strain, respectively. All nucleotide substitutions were found at the 3rd position of the codons which were silent mutations. All 56 isolates studied were classified into five genotypic groups by constructing the dendrogram. The results indicated that four new isolates from Northeastern Thailand belong to genotype II of dengue virus serotype 2, and were most closely related to prototype New Guinea C strain. We also observed the variation in nucleotide and amino acid sequences among clusters of isolates (Thailand-1980, Malaysia-1989 and Thailand-1993) which were obtained from the dengue patients with different clinical severities. The significance of these genetic differences have been discussed in terms of the possible correlation between genetic variability and virulence.
    Matched MeSH terms: Biological Evolution
  10. Cabauatan PQ, Melcher U, Ishikawa K, Omura T, Hibino H, Koganezawa H, et al.
    J Gen Virol, 1999 Aug;80 ( Pt 8):2229-37.
    PMID: 10466823
    The DNA of three biological variants, G1, Ic and G2, which originated from the same greenhouse isolate of rice tungro bacilliform virus (RTBV) at the International Rice Research Institute (IRRI), was cloned and sequenced. Comparison of the sequences revealed small differences in genome sizes. The variants were between 95 and 99% identical at the nucleotide and amino acid levels. Alignment of the three genome sequences with those of three published RTBV sequences (Phi-1, Phi-2 and Phi-3) revealed numerous nucleotide substitutions and some insertions and deletions. The published RTBV sequences originated from the same greenhouse isolate at IRRI 20, 11 and 9 years ago. All open reading frames (ORFs) and known functional domains were conserved across the six variants. The cysteine-rich region of ORF3 showed the greatest variation. When the six DNA sequences from IRRI were compared with that of an isolate from Malaysia (Serdang), similar changes were observed in the cysteine-rich region in addition to other nucleotide substitutions and deletions across the genome. The aligned nucleotide sequences of the IRRI variants and Serdang were used to analyse phylogenetic relationships by the bootstrapped parsimony, distance and maximum-likelihood methods. The isolates clustered in three groups: Serdang alone; Ic and G1; and Phi-1, Phi-2, Phi-3 and G2. The distribution of phylogenetically informative residues in the IRRI sequences shared with the Serdang sequence and the differing tree topologies for segments of the genome suggested that recombination, as well as substitutions and insertions or deletions, has played a role in the evolution of RTBV variants. The significance and implications of these evolutionary forces are discussed in comparison with badnaviruses and caulimoviruses.
    Matched MeSH terms: Biological Evolution
  11. Yu H, Wang W, Fang S, Zhang YP, Lin FJ, Geng ZC
    Mol Phylogenet Evol, 1999 Dec;13(3):556-65.
    PMID: 10620413
    The sequences of the mitochondrial ND4 gene (1339 bp) and the ND4L gene (290 bp) were determined for all the 14 extant taxa of the Drosophila nasuta subgroup. The average A + T content of ND4 genes is 76.5% and that of ND4L genes is 83.5%. A total of 114 variable sites were scored. The ND4 gene sequence divergence ranged from 0 to 5.4% within the subgroup. The substitution rate of the ND4 gene is about 1.25% per million years. The base substitution of the genes is strongly transition biased. Neighbor-joining and parsimony were used to construct a phylogeny based on the resultant sequence data set. According to these trees, five distinct mtDNA clades can be identified. D. niveifrons represents the most diverged lineage. D. sulfurigaster bilimbata and D. kepulauana form two independent lineages. The other two clades are the kohkoa complex and the albomicans complex. The kohkoa complex consists of D. sulfurigaster sulfurigaster, D. pulaua, D. kohkoa, and Taxon-F. The albomicans complex can be divided into two groups: D. nasuta, D. sulfurigaster neonasuta, D. sulfurigaster albostrigata, and D. albomicans from Chiangmai form one group; and D. pallidifrons, Taxon-I, Taxon-J, and D. albomicans from China form the other group. High genetic differentiation was found among D. albomicans populations. Based on our phylogenetic results, we hypothesize that D. niveifrons diverged first from the D. nasuta subgroup in Papua New Guinea about 3.5 Mya. The ancestral population spread to the north and when it reached Borneo, it diversified sequentially into the kohkoa complex, D. s. bilimbata, and D. kepulauana. About 1 Mya, another radiation occurred when the ancestral populations reached the Indo-China Peninsula, forming the albomicans complex. Discrepancy between morphological groupings and phylogenetic results suggests that the male morphological traits may not be orthologous.
    Matched MeSH terms: Biological Evolution*
  12. Wang E, Ni H, Xu R, Barrett AD, Watowich SJ, Gubler DJ, et al.
    J Virol, 2000 Apr;74(7):3227-34.
    PMID: 10708439
    Endemic/epidemic dengue viruses (DEN) that are transmitted among humans by the mosquito vectors Aedes aegypti and Aedes albopictus are hypothesized to have evolved from sylvatic DEN strains that are transmitted among nonhuman primates in West Africa and Malaysia by other Aedes mosquitoes. We tested this hypothesis with phylogenetic studies using envelope protein gene sequences of both endemic/epidemic and sylvatic strains. The basal position of sylvatic lineages of DEN-1, -2, and -4 suggested that the endemic/epidemic lineages of these three DEN serotypes evolved independently from sylvatic progenitors. Time estimates for evolution of the endemic/epidemic forms ranged from 100 to 1,500 years ago, and the evolution of endemic/epidemic forms represents relatively recent events in the history of DEN evolution. Analysis of envelope protein amino acid changes predicted to have accompanied endemic/epidemic emergence suggested a role for domain III in adaptation to new mosquito and/or human hosts.
    Matched MeSH terms: Biological Evolution*
  13. Kingston T, Lara MC, Jones G, Akbar Z, Kunz TH, Schneider CJ
    Proc Biol Sci, 2001 Jul 7;268(1474):1381-6.
    PMID: 11429138
    We present evidence that a relatively widespread and common bat from South East Asia comprises two morphologically cryptic but acoustically divergent species. A population of the bicoloured leaf-nosed bat (Hipposideros bicolor) from Peninsular Malaysia exhibits a bimodal distribution of echolocation call frequencies, with peaks in the frequency of maximum energy at ca. 131 and 142 kHz. The two phonic types are genetically distinct, with a cytochrome b sequence divergence of just under 7%. We consider the mechanisms by which acoustic divergence in these species might arise. Differences in call frequency are not likely to effect resource partitioning by detectable prey size or functional range. However, ecological segregation may be achieved by differences in microhabitat use; the 131kHz H. bicolor is characterized by significantly longer forearms, lower wing loading, a lower aspect ratio and a more rounded wingtip, features that are associated with greater manoeuvrability in flight that may enable it to forage in more cluttered environments relative to the 142 kHz phonic type. We suggest that acoustic divergence in these species is a consequence of social selection for a clear communication channel, which is mediated by the close link between the acoustic signal and receptor systems imposed by the highly specialized nature of the hipposiderid and rhinolophid echolocation system.
    Matched MeSH terms: Biological Evolution
  14. Campbell P, Schneider CJ, Adnan AM, Zubaid A, Kunz TH
    Mol Phylogenet Evol, 2004 Dec;33(3):764-81.
    PMID: 15522802
    Taxonomic relationships within the Old World fruit bat genus, Cynopterus, have been equivocal for the better part of a century. While nomenclature has been revised multiple times on the basis of phenotypic characters, evolutionary relationships among taxa representing the entire geographic range of the genus have not been determined. We used mitochondrial DNA sequence data to infer phylogenetic relationships among the three most broadly distributed members of the genus: C. brachyotis, C. horsfieldi, and C. sphinx, and to assess whether C. brachyotis represents a single widespread species, or a complex of distinct lineages. Results clearly indicate that C. brachyotis is a complex of lineages. C. sphinx and C. horsfieldi haplotypes formed monophyletic groups nested within the C. brachyotis species complex. We identified six divergent mitochondrial lineages that are currently referred to C. brachyotis. Lineages from India, Myanmar, Sulawesi, and the Philippines are geographically well-defined, while in Malaysia two lineages, designated Sunda and Forest, are broadly sympatric and may be ecologically distinct. Demographic analyses of the Sunda and Forest lineages suggest strikingly different population histories, including a recent and rapid range expansion in the Sunda lineage, possibly associated with changes in sea levels during the Pleistocene. The resolution of the taxonomic issues raised in this study awaits combined analysis of morphometric characters and molecular data. However, since both the Indian and Malaysian Forest C. brachyotis lineages are apparently ecologically restricted to increasingly fragmented forest habitat, we suggest that reevaluation of the conservation status of populations in these regions should be an immediate goal.
    Matched MeSH terms: Biological Evolution
  15. Teo J, Abbass HA
    Evol Comput, 2004;12(3):355-94.
    PMID: 15355605
    In this paper, we investigate the use of a self-adaptive Pareto evolutionary multi-objective optimization (EMO) approach for evolving the controllers of virtual embodied organisms. The objective of this paper is to demonstrate the trade-off between quality of solutions and computational cost. We show empirically that evolving controllers using the proposed algorithm incurs significantly less computational cost when compared to a self-adaptive weighted sum EMO algorithm, a self-adaptive single-objective evolutionary algorithm (EA) and a hand-tuned Pareto EMO algorithm. The main contribution of the self-adaptive Pareto EMO approach is its ability to produce sufficiently good controllers with different locomotion capabilities in a single run, thereby reducing the evolutionary computational cost and allowing the designer to explore the space of good solutions simultaneously. Our results also show that self-adaptation was found to be highly beneficial in reducing redundancy when compared against the other algorithms. Moreover, it was also shown that genetic diversity was being maintained naturally by virtue of the system's inherent multi-objectivity.
    Matched MeSH terms: Biological Evolution*
  16. Fix AG
    Am J Hum Biol, 2004 Jul-Aug;16(4):387-94.
    PMID: 15214057
    Migration among local populations classically has been seen as the principal process retarding genetic microdifferentiation. However, as Sewall Wright pointed out long ago, migration may also act as a random differentiating force. In fact, when migrants comprise a biological kin group, migration may be considered a component of genetic drift. The causes of kin-structured migration (KSM) lie in the common, if not universal, tendency for kin to associate and cooperate. However, similar to genetic drift, KSM has its greatest effect in smaller populations and is most apparent in low-density fission-fusion societies such as the Yanomamo of South America and the Semai of Malaysia, and less salient in higher density, low-mobility populations such as those of the New Guinea Highlands. The evolutionary consequences of KSM begin with increased genetic variation among populations. Such intergroup variation provides a basis for group selection. The origin of larger-scale geographic differentiation can arise from kin-structured migrant groups colonizing new regions. Waves of colonizing kin-structured founder groups may produce gene frequency clines, mimicking demic diffusion and natural selection. Finally, because kin structuring reduces the effective size of a population, it may be speculated that the extremely small effective size inferred for ancestral populations of Homo sapiens may be an artifact of kin-structured demographically larger populations.
    Matched MeSH terms: Biological Evolution
  17. Forster P, Matsumura S
    Science, 2005 May 13;308(5724):965-6.
    PMID: 15890867
    Matched MeSH terms: Biological Evolution
  18. Schilthuizen M, Davison A
    Naturwissenschaften, 2005 Nov;92(11):504-15.
    PMID: 16217668
    The direction that a snail (Mollusca: Gastropoda) coils, whether dextral (right-handed) or sinistral (left-handed), originates in early development but is most easily observed in the shell form of the adult. Here, we review recent progress in understanding snail chirality from genetic, developmental and ecological perspectives. In the few species that have been characterized, chirality is determined by a single genetic locus with delayed inheritance, which means that the genotype is expressed in the mother's offspring. Although research lags behind the studies of asymmetry in the mouse and nematode, attempts to isolate the loci involved in snail chirality have begun, with the final aim of understanding how the axis of left-right asymmetry is established. In nature, most snail taxa (>90%) are dextral, but sinistrality is known from mutant individuals, populations within dextral species, entirely sinistral species, genera and even families. Ordinarily, it is expected that strong frequency-dependent selection should act against the establishment of new chiral types because the chiral minority have difficulty finding a suitable mating partner (their genitalia are on the 'wrong' side). Mixed populations should therefore not persist. Intriguingly, however, a very few land snail species, notably the subgenus Amphidromus sensu stricto, not only appear to mate randomly between different chiral types, but also have a stable, within-population chiral dimorphism, which suggests the involvement of a balancing factor. At the other end of the spectrum, in many species, different chiral types are unable to mate and so could be reproductively isolated from one another. However, while empirical data, models and simulations have indicated that chiral reversal must sometimes occur, it is rarely likely to lead to so-called 'single-gene' speciation. Nevertheless, chiral reversal could still be a contributing factor to speciation (or to divergence after speciation) when reproductive character displacement is involved. Understanding the establishment of chirality, the preponderance of dextral species and the rare instances of stable dimorphism is an important target for future research. Since the genetics of chirality have been studied in only a few pulmonate species, we also urge that more taxa, especially those from the sea, should be investigated.
    Matched MeSH terms: Biological Evolution*
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