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Garupá, Argentina

Martinez P.A.,Federal University of Rio Grande do Norte | Bidau C.J.,Parana y Los Claveles
Mammalian Biology | Year: 2016

Sexual size dimorphism (SSD) is affected by a large number of factors, mating system being one of the most relevant. Almost 70 species of subterranean rodents of the genus Ctenomys are considered highly polygynic, and polygyny jointly with absence of paternal care of the young, favours high SSD. In this respect, Rensch's rule predicts that SSD scales with body size so that when males are larger than females SSD tends to increase with body size. We studied SSD and Rensch's rule in 28 taxa of Ctenomys using a phylogenetic approach employing the method of phylogenetic reduced major axis (pRMA) to perform reduced major axis (RMA) model II regression in the form of log 10(male mass) on log. 10(female mass). The RMA regression slope (β) was statistically tested to accept or reject the null hypothesis that βpRMA = 1.0. A slope significantly >1.0 would signal concordance with Rensch's rule. Our results showed that despite a high degree of male-biased SSD as expected from polygynic species, Rensch's rule is not verified in this rodent group. The causes of the non-concordance with Rensch's rule as well as its taxonomic level of application are discussed in terms of current models of SSD. © 2014 Deutsche Gesellschaft für Säugetierkunde. Source

Bidau C.J.,Parana y Los Claveles | Marti D.A.,National University of Misiones | Marti D.A.,CONICET
European Journal of Entomology | Year: 2013

We discuss and criticise the contention of Colombo (2012) that the central-marginal model does not apply to three species of chromosomally polymorphic acridid grasshoppers, and that chromosomal clines in these species are a consequence of temperature gradients. We also discuss Colombo's interpretation of our own results on the South American melanopline grasshopper, Dichroplus pratensis Bruner. Source

Castillo E.R.,National University of Misiones | Marti D.A.,CONICET | Bidau C.J.,Parana y Los Claveles
Journal of Orthoptera Research | Year: 2010

We review historical and pioneering work as well as recently published papers about orthopteran sex chromosomes and neo-sex mechanisms, highlighting Michael White's significant contributions. Meiotic research in Orthoptera in the early twentieth century was central to confirming that sex determination had a chromosomal basis: the study of sex chromosomes produced fundamental support to the chromosome theory of heredity. We also explore recent theoretical models of sex-chromosome evolution and consider the possible causes of crossing over restriction in proto-sex chromosomes, as well as the progressive differentiation (erosion and degeneration) of the Y chromosome in neo-chromosome systems in different taxa. We discuss neo-XY and neo-X1X2Y chromosome systems of South American Melanoplinae (Acrididae) as potential experimental models to study steps in sex-chromosome evolution because these systems fall within a continuum of evolutionary stages, some of them recently established. We also provide an explanation for the disproportionate frequency of neo-sex systems and Robertsonian-derived karyotypes in Neotropical Melanoplinae, based on the centromeric drive theory, and propose that Neotropical melanoplines' high karyotypic diversity supports an ancient South American origin of the subfamily. We discuss the hypothesis that neo-sex chromosome systems produce favorable new linkage relationships between genes in the X and the involved autosome, some of which could be sex determination related, creating a new balance between sex chromosomes and autosomes. We also review Mesa's hypothesis that, based on the observed fact that no major taxon of orthopterans shows neo-sex chromosomal mechanisms in all their species, the acquisition of a neo-sex chromosome system could condemn species of grasshoppers to a short evolutionary career. Little is yet known about the role of neo-Y chromosomes in Orthoptera, thus mostly speculative explanations about neo-sex chromosome function can be made at present. New studies with modern molecular techniques are needed to understand chromosomal sex determination in Orthoptera, which could in turn help explain the role of new chromosomal sex systems in grasshopper species. Source

Bidau C.J.,Parana y Los Claveles | Marti D.A.,National University of Misiones
Journal of Orthoptera Research | Year: 2010

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. Source

Martinez P.A.,Federal University of Rio Grande do Norte | Martinez P.A.,Rey Juan Carlos University | Zurano J.P.,Federal University of Rio Grande do Norte | Zurano J.P.,Federal University of Paraiba | And 6 more authors.
Molecular Phylogenetics and Evolution | Year: 2015

Tropical reef fishes show contrasting patterns of karyotypic diversity. Some families have a high chromosomal conservatism while others show wide variation in karyotypic macrostructure. However, the influence of life-history traits on karyotypic diversity is largely unknown. Using phylogenetic comparative methods, we assessed the effects of larval and adult species traits on chromosomal diversity rates of 280 reef species in 24 families. We employed a novel approach to account for trait variation within families as well as phylogenetic uncertainties. We found a strong negative relationship between karyotypic diversity rates and body size and depth range. These results suggest that lineages with higher dispersal potential and gene flow possess lower karyotypic diversity. Taken together, these results provide evidence that biological traits might modulate the rate of karyotypic diversity in tropical reef fishes. © 2015 Elsevier Inc. Source

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