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  • 1
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    AIRCRAFT IN AUSTRALIAN AGRICULTURE (1957)
    Canberra : Periodicals Archive Online (PAO)
    Quarterly review of the rural economy. 10:1 (1957:Jan.) 1 
    Details
    ISSN: 0156-7446
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:6017-1957-010-01-000001
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  • 2
    Electronic Resource
    Electronic Resource
    Karyotype variation in dermestid beetles (1967)
    Springer
    Chromosoma 20 (1967), S. 371-385 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The system of nucleolar controlled sex-chromosome segregation which characterises Xyp species of hide beetles is also present in the one species (haemorrhoidalis) with an XY system. This, coupled with the fact that the karyotype in the XY species is asymmetrical, whereas species with smaller y-chromosomes show greater symmetry, suggests that “erosion” of the y may have involved translocation of the material of the y onto the autosomes rather than simple loss. Finally, supernumerary y chromosomes present in laboratory cultures of two species (maculatus and frischii) demonstrate the efficiency of the sex nucleolus as a mechanism for securing segregation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394261
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  • 3
    Electronic Resource
    Electronic Resource
    The supernumerary segment system of Stethophyma (1970)
    Springer
    Chromosoma 30 (1970), S. 326-343 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Three species of the genus Stethophyma carry supernumerary heterochromatic segments. The European species, S. grossa, has segments located close to the centromere on the S11 chromosome pair, while the North American species, S. lineatum and S. gracile, have both interstitial and terminal segments on the S10 and S11 chromosomes. The latter species show a high degree of segment variation between individuals and the interstitial segments also show variation in size. The presence of segments on the S10 and S11 chromosomes, whether homozygous or heterozygous, modifies the pattern of chiasma distribution in these chromosomes when compared with that found in the basic homozygotes. When interstitial, they also lead to a high frequency of ring bivalents. Two points suggest that interstitially located supernumerary segments may prove to be more common than has previously been accepted. Firstly, combined equational and reductional segregation in unequal bivalents is only otherwise explicable in terms of chiasma formation in a short arm. Secondly the rod chromosomes of many Acridids may well be telocentric as in the case under study. It is proposed that these segments have arisen through a process of duplication with no evidence of interchromosomal movement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00321065
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  • 4
    Electronic Resource
    Electronic Resource
    The chromosomal component of reproductive isolation in the grasshopper Caledia captiva (1982)
    Springer
    Chromosoma 86 (1982), S. 509-531 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A comparison of chiasma distribution patterns between two chromosomal taxa, Moreton and Torresian, and their F1 hybrids demonstrates highly significant differences between all chromosomes analysed. In chromosomes 1, 2, 4, 5, 6 and 8 these differences can be directly attributed to pericentric heterozygosity in the F1 hybrid. In chromosomes 7 and 8 where there is no pericentric heterozygosity these differences may be due to heterozygosity for interstitial and terminal bands of hetero-chromatin or possibly undetected paracentric rearrangements. The F1 hybrids also have a significantly lower mean cell chiasma frequency. The Moreton and Torresian taxa differ significantly in chiasma distribution pattern in chromosomes 1, 2, 4, 5, 6 and 8 and both Moreton populations analysed have a significantly lower mean cell chiasma frequency than the Torresian population. In addition the two Moreton populations, (MMX) and (MAX), differ significantly in the chiasma distribution pattern in chromosomes 1 and 2 and the chromosomally more polymorphic population (MMX) has a significantly lower mean cell chiasma frequency. There is some evidence that the differences in both chiasma distribution and frequency between these two populations may be due to genetic differences in addition to the effects caused by chromosomal polymorphism. It has been shown that in general there is a substantial reduction in recombination in the intersitial regions of most chromosomes in the Moreton and particularly the Torresian taxon because of a proximal-distal localisation of chiasmata. In the F1 hybrid, however, nearly all recombination events are located within these interstitial regions. This provides support for the hypothesis that the frequent placement of chiasmata in regions of normally low recombination may disrupt the internal coadapted genetic environment of both chromosomal forms resulting in non-functional recombinant progeny in the next generation. The recombination data in this study also provide a basis for an empirical test of this hypothesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330124
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  • 5
    Electronic Resource
    Electronic Resource
    Genetic and environmental components of chiasma control (1971)
    Springer
    Chromosoma 34 (1971), S. 281-301 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Variation in chiasma frequency within and between individuals has been investigated in Schistocerca gregaria and Stethophyma grossum. By taking sequential samples of the same testis in S. gregaria it has been demonstrated that there is considerable variation in chiasma frequency between times, within individuals, and that this variation is not evenly distributed between individuals of the same population. The response and recovery patterns after exposure to successive temperature treatments also indicate a differential sensitivity of individuals within the experimental population. — An analysis of interfollicular variation in chiasma frequency has revealed significant differences between follicles within individuals both in S. gregaria and a Spanish population of S. grossum. A comparable analysis on individuals of S. grossum carrying supernumerary segments shows that the presence of such segments increases the amount of variation between follicles within individuals and also between individuals within the population. — The distribution of cell chiasma frequencies in S. gregaria is normal whereas in Stethophyma cell frequencies approximate to a Poisson distribution. The structurally different supernumerary segments, present in Austrian and Spanish populations of S. grossum, both increase mean chiasma frequency and they modify the between cell variance in different ways — the former interchromosomally and the latter intrachromosomally. — The differences in chiasma frequency between follicles and between times within individuals and the differential reaction to heat shock reflect differences in the pattern of genotype-environment interaction. Similarly it can be argued that the presence of polymorphisms involving supernumerary material may play an equivalent role by increasing the between cell or between bivalent variance within individuals, a unique form of genotype-environment interaction at the endophenotypic level. — Such variation in genotype sensitivity to environmental modification has important adaptive value especially in organisms which are subject to recurrent, often random, changes in their environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00286154
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  • 6
    Electronic Resource
    Electronic Resource
    The supernumerary segment system of Stethophyma (1971)
    Springer
    Chromosoma 34 (1971), S. 19-39 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Three species of the genus Stethophyma have been cytologically examined and all three show variation both for supernumerary heterochromatic segments and for the distribution of standard heterochromatin among the autosomes. The European species, S. grossum, for example, shows considerable interpopulation variation for standard heterochromatin while two of the populations, from Spain and Austria, show supernumerary segment polymorphism. The segments are located interstitially on the S11 chromosome but occupy different positions in the different populations. — In all species, the presence of the extra heterochromatic segments increases the mean chiasma frequency. Moreover, the influence of the segments upon mean chiasma frequency is different in different populations and in different species. In the Spanish population, the increase is both intra- and interchromosomal whereas in Austria the influence of the segment is completely interchromosomal. — In the American species, S. gracile and S. lineatum, where supernumerary heterochromatic segments are carried on both S10 and S11 chromosomes, the effect on chiasma frequency shows a dosage relationship, an increase in the number of segments per individual being correlated with an increase in mean chiasma frequency. It is suggested that the interstitial segments found in all species have originated by direct duplication of chromosome material. By contrast the terminal segments in S. lineatum and S. gracile may be derived by translocation from a B-chromosome since such a chromosome has been found in one individual of the former species. — The variation in segment structure and the distribution of standard heterochromatin, among the European species of S. grossum suggests that these systems have evolved independently in different populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00285514
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  • 7
    Electronic Resource
    Electronic Resource
    Genetic and environmental components of chiasma control (1974)
    Springer
    Chromosoma 46 (1974), S. 365-374 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Two selected lines of Schistocerca gregaria with mean chiasma frequencies of 17.68 and 21.66 were crossed in all possible combinations up to the F2 generation. A genetic analysis of both generation means and within family variances reveals that the control of chiasma frequency in these lines is governed by a large additive genetic component (d) and a small dominance component (h) directed towards high frequency types. 40% of the total variance can be explained in terms of environmentally induced variation. It is argued that such significant and readily induced changes in the chiasma pattern, associated with a mean cellular difference of 4 chiasmata, can be expected to lead to an alteration in the linkage relationships within the genomes of each line. Unfortunately the intensity of the effect upon linked non-allelic associations can only be assumed since, at the present time, there is no evidence to correlate chiasma frequency variation in the parent with ensuing exophenotypic variation among the progeny.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331627
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  • 8
    Electronic Resource
    Electronic Resource
    Population cytogenetics of the genus Caledia (Orthoptera: Acridinae) (1977)
    Springer
    Chromosoma 63 (1977), S. 181-204 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The acridine grasshopper, Caledia captiva exists as two chromosomal races in south-east Queensland. One of these, the “Moreton” race inhabits the coastal region to the east of the Great Dividing Range. All chromosomes of the complement (2n=11II+XO/XX) have been involved in centromeric rearrangement, which transforms the acro- and telocentric chromosomes into submeta- and metacentric elements. The second, or “Torresian” race is widely distributed through southern Papua, Arnhem Land, Cape York Peninsula and down the east coast of Australia as far south as Brisbane. This race, which is characterised by a completely acro- and telocentric chromosome complement, approaches the “Moreton” race in south-east Queensland where the two races are separated by less than 1 km, along a front of at least 150 km. Evidence is presented to show that chromosome introgression is occurring across the contact zone and this takes place in one direction only, namely the “Torresian” chromosomes are infiltrating into the “Moreton” race but not reciprocally. Furthermore, the introgression of chromosomes across the zone is limited to certain members of the Torresian complement and even then these successful chromosomes show highly variable degrees of penetrance into the “Moreton” race. It is proposed that a “tension zone” exists between these two races which is maintained by the interaction of (a) ecological tolerance differences on either side of the zone and (b) by partial competitive exclusion due to the interracial differences in phenology. This case of parapatric association with limited hybridisation is unique in its clarity due to the marked differences in the appearance of the chromosome complements of these races which permits direct assessment of the behaviour of most members of the genome in hybrids and their derivatives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292729
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  • 9
    Electronic Resource
    Electronic Resource
    A comparison of chromosomal and allozymal variation across a narrow hybrid zone in the grasshopper Caledia captiva (1979)
    Springer
    Chromosoma 75 (1979), S. 333-351 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A hybrid zone between the Moreton and Torresian taxa of the grasshopper Caledia captiva in S.E. Queensland has been characterised in terms of allozyme and chromosome variation within the same individuals. — On chromosomal criteria (pericentric rearrangements), the zone is asymmetrical with evidence of high levels of introgression of Torresian chromosomes into the Moreton taxon. This is apparent from the analysis of two independent transects across the hybrid zone. Major changes in chromosomal frequency occur over distances of less than 0.5 km. and the level of introgression differs between the two transects, with much higher levels in the northern Moreton populations, characterised by an acrocentric X-chromosome, when compared with the southern metacentric-X Moreton populations. Chromosome analysis of samples taken from the same transect over two years has revealed no major changes in the structure of the zone. Moreover, a Moreton population located only 0.5 km. from the null point was found to be stable over 6 generations with evidence for a new balanced genome having originated following the differential incorportation of Torresian chromosomes. — Contrary to the chromosomal situation, the same hybrid zone was found to be symmetrical with respect to allozyme variation with evidence of movement of diagnostic alleles in both directions across the zone. The alleles are independent and not tightly linked to any of the pericentric rearrangements. Thus these 5 alleles are acting as markers of the background genome and reveal the relatively free movement of genes which are located outside the pericentric rearrangements. — It is proposed that the hybrid zone in Caledia captiva is unstable and is moving slowly in a westerly direction into the Torresian territory. This is due to the ability of the Moreton taxon to incorporate more readily into its genome those Torresian chromosomes or chromosome segments which increase the fitness of the Moreton taxon. On chromosomal criteria, the Torresian taxon does not share the same capacity. — It is suggested that, so long as the two taxa retain their ability to hybridise with subsequent asymmetrical introgression, the zone will continue to move westwards and eventually lead to the selective incorporation of the Torresian genome into the Moreton taxon. This will result in a polymorphic situation with clinal variation in chromosomal frequencies. The structure of the zone is dependent upon a fine balance between genomic reorganisation in recombinant genotypes and the relative dispersal capacities of the two hybridising taxa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293476
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  • 10
    Electronic Resource
    Electronic Resource
    Environmental predictions and distributional limits of chromosomal taxa in the Australian grasshopperCaledia captiva (F.) (1988)
    Springer
    Oecologia 75 (1988), S. 483-493 
    Details
    ISSN: 1432-1939
    Keywords: Caledia captiva ; Climatic prediction ; Grasshopper ecology ; Ecological ordination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Correlations between environmental parameters and the distribution of four chromosomal taxa in the acridine grasshopperCaledia captiva (F.) have been analyzed. A bioclimate prediction system (BIOCLIM) was used as a model to determine their bioclimatic envelopes and to predict their probable geographic distributions, based on climatic similarities with actual distributions. New, and formerly unsuspected, distribution areas are predicted. Parapatric boundaries are defined that actually coincide with known limits. The general distribution of the four taxa is correlated with rainfall seasonality and a temperature gradient. Their distributional boundaries are mostly in accordance with extreme values in rainfall in an east-west direction and temperature in a north-south direction. A nonmetric multidimensional scaling analysis of one selected narrow parapatric boundary confirms the nature of the geographic correlation with several climatic extreme values. The climatic and vegetation analyses suggest that sharp parapatric distributions can be maintained by gradual environmental influences and that coincidence with abrupt ecotones is not necessary. At least one of the parapatric boundaries seems to be relatively recent in origin (2000–6000 years) and on the basis of the location of extreme climatic values as well as chromosomal and genetic markers it is expected to slowly move further south and east of its present location apparently following a climatically established boundary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00776409
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