Strong selection against hybrids at a hybrid zone in the Ensatina ring species complex and its evolutionary implications

The analysis of interactions between lineages at varying levels of genetic divergence can provide insights into the process of speciation through the accumulation of incompatible mutations. Ring species, and especially the Ensatina eschscholtzii system exemplify this approach. The plethodontid salamanders E. eschscholtzii xanthoptica and E. eschscholtzii platensis hybridize in the central Sierran foothills of California. We compared the genetic structure across two transects (southern and northern Calaveras Co.), one of which was resampled over 20 years, and examined diagnostic molecular markers (eight allozyme loci and mitochondrial DNA) and a diagnostic quantitative trait (color pattern). Key results across all studies were: (1) cline centers for all markers were coincident and the zones were narrow, with width estimates of 730 m to 2000 m; (2) cline centers at the northern Calaveras transect were coincident between 1981 and 2001, demonstrating repeatability over five generations; (3) there were very few if any putative F1s, but a relatively high number of backcrossed individuals in the central portion of transects: and (4) we found substantial linkage disequilibrium in all three studies and strong heterozygote deficit both in northern Calaveras, in 2001, and southern Calaveras. Both linkage disequilibrium and heterozygote deficit showed maximum values near the center of the zones. Using estimates of cline width and dispersal, we infer strong selection against hybrids. This is sufficient to promote accumulation of differences at loci that are neutral or under divergent selection, but would still allow for introgression of adaptive alleles. The evidence for strong but incomplete isolation across this centrally located contact is consistent with theory suggesting a gradual increase in postzygotic incompatibility between allopatric populations subject to divergent selection and reinforces the value of Ensatina as a system for the study of divergence and speciation at multiple stages. © 2005 The Society for the Study of Evolution. All rights reserved.

Genetic polymorphism, molecular characterization and relatedness of Macrobrachium species (Palaemonidae) based on RAPD-PCR.

The prawn genus Macrobrachium belongs to the family Palaemonidae. Its species are widely distributed in lakes, reservoirs, floodplains, and rivers in tropical and subtropical regions of South America. Globally, the genus Macrobrachium includes nearly 210 known species, many of which have economic and ecological importance. We analyzed three species of this genus (M. jelskii, M. amazonicum and M. brasiliense) using RAPD-PCR to assess their genetic variability, genetic structure and the phylogenetic relationship between them and to look for molecular markers that enable separation of M. jelskii and M. amazonicum, which are closely related syntopic species. Ten different random decamer primers were used for DNA amplification, yielding 182 fragments. Three of these fragments were monomorphic and exclusive to M. amazonicum or M. jelskii and can be used as specific molecular markers to identify and separate these two species. Similarity indices and a phylogenetic tree showed that M. amazonicum and M. jelskii are closest to each other, while M. brasiliense was the most differentiated species among them; this may be attributed to the different habitat conditions to which these species have been submitted. This information will be useful for further studies on these important crustacean species.

Influence of δβ-thalassemia or regulatory elements in individuals with increased fetal Hb levels in the São Paulo northwest population

Fetal hemoglobin (Hb F), formed by two alpha globin chains (α) and two gamma chains (γ) (α2 γ2), has reduced expression in adults, ranging from 0 to 1% of total hemoglobin. Increased levels of Hb F are due to mutations in the β-globin family, which cause hereditary persistence of fetal hemoglobin (HPFH) and delta-beta thalassemia (δβ-thalassemia).The control of the production takes place by the regulatory region and regions outside the β-globin family, among them 2q16, 6q23, 8q, and Xp22.2.The aims of this study were to determine the presence and frequency of two mutations for δβ-thalassemia, the XmnI polymorphism and β-globin haplotypes in healthy individuals with increased Hb F in the State of São Paulo. We analyzed 60 samples of peripheral blood of healthy adults, without complaints of anemia. The samples were separated into two groups according to Hb F level: group I - 34 samples with Hb F ranging from 2 to 15% and group II - 26 samples with Hb F over 15%. In relation to the polymorphisms examined, we found three heterozygous individuals (5%) for Spanish δβ-thalassemia, belonging to group I, whose Hb F levels were within the normal range.The Sicilian δβ-thalassemia mutation was not found, indicating the need to study other polymorphisms related to the increase of Hb F in adult life.The frequency of XmnI polymorphism was 33.3% and the mean Hb F levels were 15.48 ± 11.69%.The frequency observed in our study for this polymorphic site is higher than that found in the literature for healthy subjects.This polymorphism was more prevalent in individuals with Hb F levels below 15%. For four samples positive for this polymorphism, the Hb F levels were explained by the presence of HPFH and Spanish δβ-thalassemia mutations, so that the presence of the XmnI polymorphic site was not a determinant in the overexpression of γ-globin genes. Regarding β-globin haplotypes, 18 alleles and 27 distinct genotypic patterns were found.The pattern Atp1/Atp2 was the mostfrequent genotype (13.72%).Of the 18 alleles, 13 showed atypical patterns.The results show that the haplotype V was the most frequent (27.45%), followed by atypical Atp2 (13.72%) and Atp1 (11.76%), and that there was a higher correlation with the presence of HPFH and XmnI polymorphism.The high frequency of haplotype V in our samples and high frequency of atypical haplotypes may reflect a high rate of miscegenation in this population, suggesting an ethnic characteristic for the Brazilian population, requiring the evaluation of population genetic markers to corroborate this hypothesis. © FUNPEC-RP.

Sistema de reprodução, parentesco e tamanho efetivo em sementes de polinização livre de populações fragmentadas de Copaifera langsdorffii Desf. por análise de locos microssatélites

Anthropogenic changes in the reproductive population density can affect the mating system and result in an increase in selfing and correlated matings. This study investigated the mating system in small fragmented populations of the insect pollinated tropical tree species Copaifera langsdorffii, using microsatellite loci and the mixed and correlated mating models. Open-pollinated seeds were collected from 15 seed-trees located in a small forest fragment (4.8 ha), denominated Bosque and from 14 other seed-trees located in other small forest fragments of the north-western region of São Paulo State. No significant differences were observed between the seed-trees from Bosque (tm=0.933±0.028) and other fragments (tm=0.971±0.032), although these estimates were significantly different from 1.0, suggesting that selfing was occurring. Differences between multilocus and unilocus outcrossing rate were significantly high in both seed-trees of Bosque (tm -ts=0.478±0.05) and other forest fragments (tm -ts=0.475±0.018), suggesting a spatial genetic structure in those stands. The results also showed high rates of correlated mating in the samples, indicating that a good part of the offspring were full-sibs. As a consequence of selfing, mating among relatives and correlated matings, the coancestry within families was equally high in the seed-trees of Bosque ((Θ=0.237) and in the seed-trees of the other forest fragments (Θ=0.241) and the effective population size was lower than expected in panmitic populations (Ne<4). The results were discussed, focusing on the sample size of seed-trees to collect seeds for genetic conservation and enviromental reforestation.

Development of microsatellite markers for the Neotropical endemic Brazilian Guanabara frog, Euparkerella brasiliensis, through 454 shotgun pyrosequencing

The new-generation 454 GS-FLX Titanium pyrosequencing was used to isolate microsatellite markers for the Brazilian Guanabara frog, Euparkerella brasiliensis, an Atlantic forest endemic species. Three multiplex polymerase chain reaction sets were optimized for genotyping of 11 polymorphic (di- and tetranucleotide) microsatellite markers. Genetic diversity was assessed in 21 individuals from a population (Reserva Ecológica de Guapiaçu, REGUA) locatedin the central region of the Rio de Janeiro State, in Brazil. The mean number of alleles per locus ranged from 3 to 12. Observed and expected heterozygosities ranged from 0.095 to 0.905 and from 0.094 to 0.904, respectively. After using the Bonferroni correction for multiple tests, there was no evidence of linkage disequilibrium between pairs of loci but deviations for Hardy-Weinberg equilibrium were found in 4 loci. We found no evidence for allele dropouts or stuttering, but we detected the presence of null alleles at loci Eb10 and Eb36. These markers will be useful for analyses of fine-scale population structure and determination of relative effects of habitat loss and fragmentation on population genetic variability within species. © FUNPEC-RP.

Variabilidade populacional de Plutella xylostella (L., 1758) (Lepidoptera: Plutellidae) e suscetibilidade a Bacillus thuringiensis Berliner

Pós-graduação em Agronomia (Entomologia Agrícola) - FCAV

Estudos de variabilidade genética em populações de Chrysoperla externa Hagen, 1861 (Neuroptera: Chrysopidae) do estado de São Paulo, Brasil

Pós-graduação em Agronomia (Entomologia Agrícola) - FCAV

Estudo do padrão de distribuição genético-haplotípico de Chrysoperla externa (Neuroptera: Chrysopidae) em áreas de citros no estado de São Paulo

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Desenvolvimento de metodologia high-throughput para estudo populacional do mosquito Aedes aegypti e comparação de dados de genes mitocondriais

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Caracterização molecular da estrutura genética de populações e espécies camarões palemonídeos Macrobrachium do gênero Macrobrachium

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fluxo de pólen e sementes em população isolada de Copaifera langsdorfii Desf. (LEGUMINOSAE - CAESALPINIOIDEAE) em um fragmento florestal localizado em área urbana

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Diversidade genética em populações de Myracrodruon urundeuva Fr. All., sob diferentes tipos de perturbação antrópica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comportamento de populações de Myracrodruon urundeuva Fr. All. procedentes de áreas com perturbação antrópica

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Análise da variabilidade e estruturação genética do tubarão azul, Prionace glauca (Chondrichthyes, Carcharhinidae) no Oceano Atlântico Sul Ocidental utilizando marcador molecular do DNA mitocondrial

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação da diversidade genética de populações de Pacu (Piaractus mesopotamicus Holmberg, 1887) do Pantanal Matogrossense com o uso de marcadores moleculares do tipo microssatélites

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)