Maria Isabel Remis

Teeth and Bones as Sources of DNA for Genetic Diversity and Sex Identification of Commerson's Dolphins ( Cephalorhynchus commersonii ) from Tierra del Fuego, Argentina

Museum specimens are often the only source of genetic material for many species of cetaceans. Most of the protocols that have been developed to extract DNA from teeth and bone samples involve mechanical or chemical disintegration of the material. An alternative method to the mechanical reduction process is presented here for 212 Commerson’s dolphin (Cephalorhynchus commersonii) samples collected in Tierra del Fuego, Argentina, from 1974 to 2004. From the total samples, 82.5% (n = 175) allow for amplification to occur of a minimum length of 200 pb for the mtDNA control region, 66.5% (n = 141) of 400 bp, and 51% (n = 108) of 500 bp. A total of 11 haplotypes were defined from 10 polymorphic sites. From the initial number of samples, 64.6% could be sexed via molecular markers. This method is effective for processing large quantities of degraded samples over a short time period, analysing a representative number of mtDNA haplotypes, and allowing robust estimation of historical genetic diversity and trends over time.

Molecular and morphometric variation in chromosomally differentiated populations of the grasshopper Sinipta dalmani (Orthopthera: Acrididae).

Sinipta dalmani is an Argentine grasshopper whose chromosome polymorphisms have been widely studied through cytogenetic, morphometric, and fitness component analyses. The present work analysed molecular and morphometric variation in seven chromosomally differentiated populations from Entre Rios and Buenos Aires provinces to analyse population structure. Molecular studies were performed studying RAPD loci and morphometric analyses were carried out measuring five morphometric traits. Genetic variability was high in all studied populations and was characterized by a decrease in H as a function of latitude and temperature. Both conventional FST analysis and Bayesian approach for dominant marker showed that there were significant genetic differences among all populations, between provinces, and among populations within provinces. Entre Rios populations showed higher mean numbers of migrants per generation as well as low genetic differentiation and high gene flow with almost all populations whereas Buenos Aires populations may be considered as a result of a more recently colonization. There is considerable morphometric variation between populations and this variation correlates with latitude and temperature. Our results suggest that selection contributes to phenotypic differentiation among populations by moulding the differences in trait means whereas genetic drift is responsible for differences in the matrix of variance-covariance. The gene flow detected is insufficient to prevent phenotypic and chromosome divergences.

Mitochondrial DNA variation in the South American grasshopper Dichroplus elongatus (Orthoptera: Acrididae).

Abstract Dichroplus elongatus (Giglio-Tos) is a phytophagous grasshopper widely distributed in Argentina. In the current work, the genetic variation and phylogeography of this species was studied with mtDNA techniques. In total, 171 individuals from northwestern (Las Yungas province) and eastern (Espinal and Pampeana provinces) Argentina populations were analyzed using restriction fragment-length polymorphism. The number of substitutions per site between pairs of haplotypes ranged from 0.65 to 3.84%. The neighbor-joining phenogram yielded two main groups; one clusters together the haplotypes restricted to the east and the other the haplotypes restricted to the northwestern region. Phylogenetic consensus unrooted tree among mtDNA haplotypes allowed us to propose the ancestral haplotype, which occupies the central position of the network. The unweighted pair-group method with arithmetic average dendrogram from nucleotide divergence among populations showed that populations are roughly grouped according to their geographic distribution. There was a significant heterogeneity of the mtDNA distribution when populations from all three biogeographic provinces were compared. The distribution patterns of mtDNA variation observed in D. elongatus may be explained by isolation by distance when referring to the main biogeographic provinces. In Las Yungas and Pampeana provinces, ecological factors seem to have contributed to the genetic differentiation among populations.

Morphometric and Cytogenetic Studies in Mimosa diversipila (Mimosoideae, Leguminosae) and Their Taxonomic and Evolutionary Inferences

Abstract Here we describe the morphological variability, chromosome number, and chromosome size in Mimosa diversipila. This species comprises two varieties, which are distinguished by the indumentum. However, this character is insufficient for circumscription of these infraspecific taxa. Using multivariate techniques, we found that quantitative characters were useful for identification of the varieties, which also have a different geographic distribution. Cytogenetic studies revealed that these taxa form a polyploid complex and that the polyploidy may contribute to the morphological variability observed.

Population differentiation in the grasshopper Sinipta dalmani: body size varies in relation to karyotype and climatic conditions

Abstract Sinipta dalmani is an Argentine grasshopper whose chromosome polymorphisms have been widely studied through cytogenetic and fitness-component analyses. This paper reviews the available information on its body-size variations as they relate to differences between sexes, karyotype and mating success, and shows a preliminary analysis of a pattern of geographic variation. A significant body-size sexual dimorphism was evident, with females being significantly larger than males. Polymorphic populations for M4 pericentric inversion showed considerable variation in both adult male and adult female sizes, a variation in part related to this chromosomal rearrangement, which has a negative effect on body size. Simultaneous cytogenetic, morphometric and fitness analyses showed direct evidence of phenotypic directional selection within populations favoring larger males and smaller females. The patterns of body-size differentiation among populations in relation to geographic conditions suggest local adaptation. Our results in S. dalmani demonstrate significant variation in body size within polymorphic populations and among geographical populations, which may be explained under a selective scenario.

Morphometric Variation Affecting Sexual Size Dimorphism in Neopedies brunneri (Orthoptera: Acrididae)

ABSTRACT Neopedies brunneri (Giglio-Tos, 1894) is a grasshopper belonging to the family Acrididae. This group of insects usually has economic importance in Argentina because of their ability to experience outbreaks, but little is known about them. Insect populations usually differ at the phenotypic level, often according to geographical and environmental variables, which may be a good indicator of some other factors with adaptive significance (such as developmental rate, seasonal resource disposal, and growing seasonal length). The aim of this article is to report the first preliminary analysis of phenotypic variation in natural populations of N. brunneri from central Argentina to study the amount of intra- and interpopulation variation in morphometric traits and their probable association with geographic and climatic variables.Wefound the existence of morphometrical differences among populations and a pattern of geographical variation, with males and females from eastern populations being larger than the ones from the west. Sexual size dimorphism was also detected and found to be correlated to geographical and climactic variation. Moreover, geographic patterns of sexual size dimorphism were determined, helping to clarify differential susceptibility of both sexes to environmental conditions.

Supernumerary chromosome variants in Dichroplus elongatus (Acrididae): fluorescent banding and cline variation pattern

Abstract Dichroplus elongatus is a South American grasshopper that shows simultaneous polymorphisms for B chromosomes and several supernumerary segments located in chromosome pairs S10, S9, and M6 (SS10, SS9 and SS6 respectively), in natural populations from Argentina. Heterochromatin characterization with DAPI-CMA3 banding reveals that B chromosomes show an interstitial GC-rich band. The distal SS10 segment seems to also be GC-rich, whereas the proximal supernumerary segments (SS6 and SS9) show two different heterochromatin regions: one GC-rich region (CMA3+/DAPI-) and the other that has no specificity to AT or CG base pairs (CMA3/DAPI dull). The results obtained permit us to distinguish two types of constitutive heterochromatin in the supernumerary segments of D. elongatus. The variation in the frequency of these chromosome polymorphisms was analysed with respect to some climatic and geographic variables. There is considerable B chromosome variation between populations, and this variation correlates negatively with latitude and positively with altitude and mean annual temperature. The incidence of the proximal SS9 segment is positively correlated with altitude. The pattern of chromosome variation is discussed in relation to the populations ability to maintain supernumerary DNA in more climatically favorable geographic regions.

Microsatellite DNA analysis of population structure in Cornops aquaticum (Orthoptera: Acrididae), over a cline for three Robertsonian translocations

The grasshopper Cornops aquaticum occurs between Mexico (23°N) and Uruguay and Central Argentina (35°S). It was recently introduced as a pest control agent of the neotropical water-hyacinth Eichhornia crassipes in South Africa. The information about the amount and distribution of genetic variability of the native populations may optimise the results of biological control programmes. Here we analyse microsatellite variability at the south of C. aquaticum’s distribution, coinciding with a cline for three polymorphic Robertsonian translocations along the Paraná River in order to: (1) estimate the amount of intrapopulation variation and its correlation with geographic/climatic variables, (2) infer interpopulation genetic variation and assess connectivity between local populations and (3) compare chromosome, morphometric and molecular variation patterns to analyse the probable causes involved in the maintenance of intraspecific variation. Our sample of 170 individuals of C. aquaticum from seven Argentine populations between latitudes 27°S to 34°S showed 211 alleles across seven microsatellite loci. Genetic diversity was estimated through average number of alleles, allelic richness, expected heterozygosity and observed heterozygosity. The analysis of molecular variance showed significant genetic differentiation among populations. Pairwise comparisons of FST/RST and Bayesian population assignment method and the discriminant analysis of principal components revealed that the two southernmost populations are more differentiated. Genetic diversity is negatively correlated with Southern latitude and with Robertsonian translocation frequencies. Our results showed that the Paraná River’s middle course populations are genetically undifferentiated and more genetically diverse than the highly chromosomally polymorphic downstream ones. The chromosomal polymorphisms are associated with increased body size in the direction in which larger size is adaptive. This may be relevant for C. aquaticum’s role as a pest control agent, since chromosome variability would enhance the ability of the species for a successful settlement in its new habitats, especially in temperate regions of the world.