The 5S ribosomal DNA (rDNA) sequences are subject of dynamic evolution at chromosomal and molecul... more The 5S ribosomal DNA (rDNA) sequences are subject of dynamic evolution at chromosomal and molecular levels, evolving through concerted and/or birth-and-death fashion. Among grasshoppers, the chromosomal location for this sequence was established for some species, but little molecular information was obtained to infer evolutionary patterns. Here, we integrated data from chromosomal and nucleotide sequence analysis for 5S rDNA in two Abracris species aiming to identify evolutionary dynamics. For both species, two arrays were identified, a larger sequence (named type-I) that consisted of the entire 5S rDNA gene plus NTS (non-transcribed spacer) and a smaller (named type-II) with truncated 5S rDNA gene plus short NTS that was considered a pseudogene. For type-I sequences, the gene corresponding region contained the internal control region and poly-T motif and the NTS presented partial transposable elements. Between the species, nucleotide differences for type-I were noticed, while type-...
South American melanopline grasshoppers display a disproportionate number of derived karyotypes, ... more South American melanopline grasshoppers display a disproportionate number of derived karyotypes, including many cases of neo-sex chromosome systems. This is especially true of the genus Dichroplus and its Maculipennis species group. We analyzed the karyotype and neo-sex chromosomes in mitosis and meiosis of Dichroplus maculipennis and D. vittigerum from Argentina using conventional and fluorescent cytogenetic protocols in order to elucidate the behavior and origin of these neo-XY systems in relation to the current phylogeny of this group. Our results showed that D. maculipennis (2n = 22♂/22♀; neoXY/neoXX) and D. vittigerum, whose karyotype is described here for the first time (2n = 18♂/18♀; neoXY/neoXX), show highly evolved neo-XY systems, although with significant differences between them. Furthermore, both species differ for two autosomal fixed Robertsonian fusions present in D. vittigerum. Analysis of karyotypic character state optimization strongly suggests the independent origin and evolution of neo-sex systems within this species group.
Estudiamos la variación geográfica de tres caracteres morfométricos en relación al tamaño corpora... more Estudiamos la variación geográfica de tres caracteres morfométricos en relación al tamaño corporal, en dos saltamontes sudamericanos (Acrididae), Dichroplus vittatus Bruner y D. pratensis Bruner, p...
Page 1. _Journal of Orthoptera Research 2008,17(2): 149-156 Geographic and climatic factors relat... more Page 1. _Journal of Orthoptera Research 2008,17(2): 149-156 Geographic and climatic factors related to a body-size dine in Dichroplus pratensis Bruner, 1900 (Acrididae, Melanoplinae) * _Accepted March 29, 2008 Claudio J. Bidau and Dardo A. Marti ...
ABSTRACT The history of the study of orthopteran chromosomes is coincident with the formulation o... more ABSTRACT The history of the study of orthopteran chromosomes is coincident with the formulation of the chromosome theory of heredity and the rediscovery of Mendel's laws, thus with the birth of cytogenetics. We review the early contributions of grasshopper chromosomes to the chromosome theory, the understanding of sex chromosomes, the phenomena of mitosis, meiosis, linkage, crossing over and recombination, the problems of chiasma localization and terminalization, reproduction and parthenogenesis, the nature and behavior of B chromosomes and supernumerary segments, and the role of chromosomal rearrangements in microevolution and speciation. We also discuss the influence of early works on later research, and emphasize the fundamental contributions of Michael J. D.White to modern cytogenetics and evolutionary biology in general.
We studied the geographic variation of three morphometric characters in relation to body size in ... more We studied the geographic variation of three morphometric characters in relation to body size in two South American grasshoppers (Acrididae), Dichroplus vittatus Bruner and D. pratensis Bruner to test Allen's rule in these ectotherms. Since both species follow the converse to Bergmann's rule owing to latitudinal and/or altitudinal variation in time available for growth and reproduction, geographic variation in body size proportions of protruding parts may obey to differential allometric growth in different geographic areas. Alternatively, it could reflect true Allenian variation related to thermoregulation. Body proportions were studied by correlation/regression analyses with geographic and climatic variables. In D. pratensis, body proportions increased with latitude and decreased with altitude. These results probably obey to the effects of water balance and seasonality on final body size, and on the allometric growth of the three studied characters not being related to thermoregulation. In D. vittatus, a generally non-significant trend towards the decrease of the mean proportions of all three characters with increasing latitude was observed. Nevertheless, also in this species, it is probable that the environmental gradient responds to seasonality factors (although not to water balance) that affect the length of growing season and, in consequence, body size and its allometric relationships. We conclude that the regularities in the geographic distribution of body proportions of D. pratensis and D. vittatus do not follow Allen's rule in the sense of thermoregulation, and result from variables that determine growing season length and the allometric growth of different body parts.
Page 1. INTRODUCTION The widespread existence of chromosomal polymor-phisms and polytypisms in na... more Page 1. INTRODUCTION The widespread existence of chromosomal polymor-phisms and polytypisms in natural populations of animal and plant species, is interpreted by several authors as a means of controlling genetic recombination ...
We tested the centromeric drive theory of karyotypic evolution in the grasshopper Dichroplus prat... more We tested the centromeric drive theory of karyotypic evolution in the grasshopper Dichroplus pratensis, which is simultaneously polymorphic for eight Robertsonian fusions and two classes of B chromosomes. A logistic regression analysis performed on 53 natural populations from Argentina revealed that B chromosomes are more probably found in populations with a higher proportion of acrocentric chromosomes, as the theory predicts. Furthermore, frequencies of B-carrying individuals are significantly negatively correlated with the mean frequency of different Robertsonian fusions per individual. No significant correlations between presence/absence or frequency of Bs, and latitude or altitude of the sampled populations, were found. We thus provide the first intraspecific evidence supporting the centromeric drive theory in relation to the establishment of B chromosomes in natural populations.
The South American acridid grasshopper Dichroplus pratensis (Melanoplinae) is polymorphic and pol... more The South American acridid grasshopper Dichroplus pratensis (Melanoplinae) is polymorphic and polytypic for a system of Robertsonian fusions across most of its distribution range. Several chromosomal races and hybrid zones have been identified. Since the fusions exert profound inter- and intrachromosomal effects on recombination, it has been proposed that these fusion systems could preserve sets of adaptive gene combinations in central (ecologically optimal) populations, and that marginal populations would show lower levels of chromosomal polymorphism and thus, increased recombination potential to cope with the harsher conditions of marginal habitats. In this paper, we describe a series of central and marginal populations which display typical features of each type and also, identify for the first time completely standard telocentric marginal populations at the southernmost and northernmost limits of the species distribution and show, as expected, the highest recombination indices. However, this modification of chiasma patterns, is only true of the male sex since females of both standard and Robertsonian populations show low chiasma frequencies. The hypothesis that higher levels of recombination would be adaptive in marginal populations is reinforced by the fact that the latter also show unusually high frequencies of B chromosomes some of which increase mean cell chiasma frequency.
Geographic body size variation was analysed in males and females of 19 populations of the South A... more Geographic body size variation was analysed in males and females of 19 populations of the South American grasshopper Dichroplus vittatus Bruner spanning 20 degrees of latitude and 2700 m of altitude. Using mean and maximum body length of each sex and factors obtained from principal components analyses of six morphometric linear characters it was shown that D. vittatus followed the converse to Bergmann's rule latitudinally but not altitudinally where no significant trends were observed. For males, variability of body size increased with latitude but not with altitude. Both types of trends were significantly correlated with mean annual temperature and minimum annual temperature (positive correlations), and two estimators of seasonality, the coefficients of variation of mean annual temperature (negative) and mean annual precipitation (positive). Some allometric relationships also showed geographic variation. It is suggested that the observed decrease in size with latitude together with the increase in morphological variability is a consequence of a number of factors: the shortening of the growing season southwards; the increasing seasonality and climatic unpredictability; and the fact that the species exhibits protandry which contributes to smaller and more variable size in males and smaller but more constant body size in females.
Annals of the Entomological Society of America, 2007
ABSTRACT We studied geographical body size variation in 23 populations and sexual size dimorphism... more ABSTRACT We studied geographical body size variation in 23 populations and sexual size dimorphism in 19 populations of the grasshopper Dichroplus pratensis Bruner in Argentina, spanning 22° of latitude and between sea level and >2,474-m altitude. Six characters were measured in 609 individuals (334 males and 275 females): total body, femur 3, tibia 3, tegmina and pronotum lengths, and pronotum height. Significant negative correlations between all six characters and latitude occurred. Correlations with altitude were weaker, although individuals at higher altitudes tended to be smaller, except at high latitudes. Extreme latitudes and altitudes correspond to the geographical and ecological margins of the species distribution and share comparable strenuous environmental conditions. Thus, this species follows the converse to Bergmann's rule, that is, individuals tend to be smaller as the environment becomes cooler (when latitude or altitude are used as a proxy for temperature). When the six morphological characters where analyzed in both sexes with respect to mean January and July temperatures at each locality, positive (although not significant) correlations were obtained in all cases. Sexual dimorphism occurred throughout the geographic range involving not only differences in body size but also in body proportions, which can be explained through differential allometric growth and shorter developmental time in males (the species exhibits protandry). The latter can also explain the inversion of Rensch's rule that occurs in D. pratensis: sexual size dimorphism decreases as general body size increases.
The 5S ribosomal DNA (rDNA) sequences are subject of dynamic evolution at chromosomal and molecul... more The 5S ribosomal DNA (rDNA) sequences are subject of dynamic evolution at chromosomal and molecular levels, evolving through concerted and/or birth-and-death fashion. Among grasshoppers, the chromosomal location for this sequence was established for some species, but little molecular information was obtained to infer evolutionary patterns. Here, we integrated data from chromosomal and nucleotide sequence analysis for 5S rDNA in two Abracris species aiming to identify evolutionary dynamics. For both species, two arrays were identified, a larger sequence (named type-I) that consisted of the entire 5S rDNA gene plus NTS (non-transcribed spacer) and a smaller (named type-II) with truncated 5S rDNA gene plus short NTS that was considered a pseudogene. For type-I sequences, the gene corresponding region contained the internal control region and poly-T motif and the NTS presented partial transposable elements. Between the species, nucleotide differences for type-I were noticed, while type-...
South American melanopline grasshoppers display a disproportionate number of derived karyotypes, ... more South American melanopline grasshoppers display a disproportionate number of derived karyotypes, including many cases of neo-sex chromosome systems. This is especially true of the genus Dichroplus and its Maculipennis species group. We analyzed the karyotype and neo-sex chromosomes in mitosis and meiosis of Dichroplus maculipennis and D. vittigerum from Argentina using conventional and fluorescent cytogenetic protocols in order to elucidate the behavior and origin of these neo-XY systems in relation to the current phylogeny of this group. Our results showed that D. maculipennis (2n = 22♂/22♀; neoXY/neoXX) and D. vittigerum, whose karyotype is described here for the first time (2n = 18♂/18♀; neoXY/neoXX), show highly evolved neo-XY systems, although with significant differences between them. Furthermore, both species differ for two autosomal fixed Robertsonian fusions present in D. vittigerum. Analysis of karyotypic character state optimization strongly suggests the independent origin and evolution of neo-sex systems within this species group.
Estudiamos la variación geográfica de tres caracteres morfométricos en relación al tamaño corpora... more Estudiamos la variación geográfica de tres caracteres morfométricos en relación al tamaño corporal, en dos saltamontes sudamericanos (Acrididae), Dichroplus vittatus Bruner y D. pratensis Bruner, p...
Page 1. _Journal of Orthoptera Research 2008,17(2): 149-156 Geographic and climatic factors relat... more Page 1. _Journal of Orthoptera Research 2008,17(2): 149-156 Geographic and climatic factors related to a body-size dine in Dichroplus pratensis Bruner, 1900 (Acrididae, Melanoplinae) * _Accepted March 29, 2008 Claudio J. Bidau and Dardo A. Marti ...
ABSTRACT The history of the study of orthopteran chromosomes is coincident with the formulation o... more ABSTRACT The history of the study of orthopteran chromosomes is coincident with the formulation of the chromosome theory of heredity and the rediscovery of Mendel's laws, thus with the birth of cytogenetics. We review the early contributions of grasshopper chromosomes to the chromosome theory, the understanding of sex chromosomes, the phenomena of mitosis, meiosis, linkage, crossing over and recombination, the problems of chiasma localization and terminalization, reproduction and parthenogenesis, the nature and behavior of B chromosomes and supernumerary segments, and the role of chromosomal rearrangements in microevolution and speciation. We also discuss the influence of early works on later research, and emphasize the fundamental contributions of Michael J. D.White to modern cytogenetics and evolutionary biology in general.
We studied the geographic variation of three morphometric characters in relation to body size in ... more We studied the geographic variation of three morphometric characters in relation to body size in two South American grasshoppers (Acrididae), Dichroplus vittatus Bruner and D. pratensis Bruner to test Allen's rule in these ectotherms. Since both species follow the converse to Bergmann's rule owing to latitudinal and/or altitudinal variation in time available for growth and reproduction, geographic variation in body size proportions of protruding parts may obey to differential allometric growth in different geographic areas. Alternatively, it could reflect true Allenian variation related to thermoregulation. Body proportions were studied by correlation/regression analyses with geographic and climatic variables. In D. pratensis, body proportions increased with latitude and decreased with altitude. These results probably obey to the effects of water balance and seasonality on final body size, and on the allometric growth of the three studied characters not being related to thermoregulation. In D. vittatus, a generally non-significant trend towards the decrease of the mean proportions of all three characters with increasing latitude was observed. Nevertheless, also in this species, it is probable that the environmental gradient responds to seasonality factors (although not to water balance) that affect the length of growing season and, in consequence, body size and its allometric relationships. We conclude that the regularities in the geographic distribution of body proportions of D. pratensis and D. vittatus do not follow Allen's rule in the sense of thermoregulation, and result from variables that determine growing season length and the allometric growth of different body parts.
Page 1. INTRODUCTION The widespread existence of chromosomal polymor-phisms and polytypisms in na... more Page 1. INTRODUCTION The widespread existence of chromosomal polymor-phisms and polytypisms in natural populations of animal and plant species, is interpreted by several authors as a means of controlling genetic recombination ...
We tested the centromeric drive theory of karyotypic evolution in the grasshopper Dichroplus prat... more We tested the centromeric drive theory of karyotypic evolution in the grasshopper Dichroplus pratensis, which is simultaneously polymorphic for eight Robertsonian fusions and two classes of B chromosomes. A logistic regression analysis performed on 53 natural populations from Argentina revealed that B chromosomes are more probably found in populations with a higher proportion of acrocentric chromosomes, as the theory predicts. Furthermore, frequencies of B-carrying individuals are significantly negatively correlated with the mean frequency of different Robertsonian fusions per individual. No significant correlations between presence/absence or frequency of Bs, and latitude or altitude of the sampled populations, were found. We thus provide the first intraspecific evidence supporting the centromeric drive theory in relation to the establishment of B chromosomes in natural populations.
The South American acridid grasshopper Dichroplus pratensis (Melanoplinae) is polymorphic and pol... more The South American acridid grasshopper Dichroplus pratensis (Melanoplinae) is polymorphic and polytypic for a system of Robertsonian fusions across most of its distribution range. Several chromosomal races and hybrid zones have been identified. Since the fusions exert profound inter- and intrachromosomal effects on recombination, it has been proposed that these fusion systems could preserve sets of adaptive gene combinations in central (ecologically optimal) populations, and that marginal populations would show lower levels of chromosomal polymorphism and thus, increased recombination potential to cope with the harsher conditions of marginal habitats. In this paper, we describe a series of central and marginal populations which display typical features of each type and also, identify for the first time completely standard telocentric marginal populations at the southernmost and northernmost limits of the species distribution and show, as expected, the highest recombination indices. However, this modification of chiasma patterns, is only true of the male sex since females of both standard and Robertsonian populations show low chiasma frequencies. The hypothesis that higher levels of recombination would be adaptive in marginal populations is reinforced by the fact that the latter also show unusually high frequencies of B chromosomes some of which increase mean cell chiasma frequency.
Geographic body size variation was analysed in males and females of 19 populations of the South A... more Geographic body size variation was analysed in males and females of 19 populations of the South American grasshopper Dichroplus vittatus Bruner spanning 20 degrees of latitude and 2700 m of altitude. Using mean and maximum body length of each sex and factors obtained from principal components analyses of six morphometric linear characters it was shown that D. vittatus followed the converse to Bergmann's rule latitudinally but not altitudinally where no significant trends were observed. For males, variability of body size increased with latitude but not with altitude. Both types of trends were significantly correlated with mean annual temperature and minimum annual temperature (positive correlations), and two estimators of seasonality, the coefficients of variation of mean annual temperature (negative) and mean annual precipitation (positive). Some allometric relationships also showed geographic variation. It is suggested that the observed decrease in size with latitude together with the increase in morphological variability is a consequence of a number of factors: the shortening of the growing season southwards; the increasing seasonality and climatic unpredictability; and the fact that the species exhibits protandry which contributes to smaller and more variable size in males and smaller but more constant body size in females.
Annals of the Entomological Society of America, 2007
ABSTRACT We studied geographical body size variation in 23 populations and sexual size dimorphism... more ABSTRACT We studied geographical body size variation in 23 populations and sexual size dimorphism in 19 populations of the grasshopper Dichroplus pratensis Bruner in Argentina, spanning 22° of latitude and between sea level and >2,474-m altitude. Six characters were measured in 609 individuals (334 males and 275 females): total body, femur 3, tibia 3, tegmina and pronotum lengths, and pronotum height. Significant negative correlations between all six characters and latitude occurred. Correlations with altitude were weaker, although individuals at higher altitudes tended to be smaller, except at high latitudes. Extreme latitudes and altitudes correspond to the geographical and ecological margins of the species distribution and share comparable strenuous environmental conditions. Thus, this species follows the converse to Bergmann's rule, that is, individuals tend to be smaller as the environment becomes cooler (when latitude or altitude are used as a proxy for temperature). When the six morphological characters where analyzed in both sexes with respect to mean January and July temperatures at each locality, positive (although not significant) correlations were obtained in all cases. Sexual dimorphism occurred throughout the geographic range involving not only differences in body size but also in body proportions, which can be explained through differential allometric growth and shorter developmental time in males (the species exhibits protandry). The latter can also explain the inversion of Rensch's rule that occurs in D. pratensis: sexual size dimorphism decreases as general body size increases.
Uploads
Papers by Dardo Marti