ASReml-based estimation of early genetic parameters in hybrid mutton sheep populations.

The aim of this study was to analyze the effects of non-genetic factors on the estimation of genetic parameters of early growth traits in hybrid mutton sheep using ASReml software, in order to provide theoretical basis for screening the optimal hybriding combinations and accelerating the breeding process of new breeds of specialized housed-feeding mutton sheep. We selected the wellgrown hybrid Southhu (Southdown × Hu sheep) and Dorhu (Dorset × Hu sheep) sheep as the research objects, constructed weight correction formulae for SH and DH sheep at 60 and 180 days; and used ASReml software to investigate the effects of non-genetic factors on the estimation of genetic parameters of early growth traits in hybrid sheep. The results showed that the birth month and birth type were found significant for all traits (p < 0.001); the heritability of maternal effects ranged from 0.0709 to 0.1859. It was found that both SH and DH sheep emerged the potential for rapid early growth and development, early growth traits are significantly affected by maternal genetic effects, thereby the maternal effect should be taken into consideration for the purpose of improving accuracy in parameter estimations and therefore increasing the success of breeding programs.

Integrated morphometric and molecular approaches to screen hybrid from wild Labeo rohita and Labeo catla parent populations.

BACKGROUND: Interspecific hybrids of rohu (Labeo rohita) and catla (Labeo catla) are common, especially in India due to constrained breeding. These hybrids must segregate from their wild parents as part of conservational strategies. This study intended to screen the hybrids from wild rohu and catla parents using both morphometric and molecular approaches. METHODS & RESULTS: The carp samples were collected from Jharkhand and West Bengal, India. The correlation and regression analysis of morphometric features are considered superficial but could be protracted statistically by clustering analysis and further consolidated by nucleotide variations of one mitochondrial and one nuclear gene to differentiate hybrids from their parents. Out of 21 morphometric features, 6 were used for clustering analysis that exhibited discrete separation among rohu, catla, and their hybrids when the data points were plotted in a low-dimensional 2-D plane using the first 2 principal components. Out of 40 selected single nucleotide polymorphism (SNP) positions of the COX1 gene, hybrid showed 100% similarity with catla. Concerning SNP similarity of the 18S rRNA nuclear gene, the hybrid showed 100% similarity with rohu but not with catla; exhibiting its probable parental inheritance. CONCLUSIONS: Along with morphometric analysis, the SNP comparison study together points towards strong evidence of interspecific hybridization between rohu and catla, as these hybrids share both morphological and molecular differences with either parent. However, this study will help screen the hybrids from their wild parents, as a strategy for conservational management.

Phenotypic variation seems not to be associated with the genetic profile in Zygopetalum (Orchidaceae): a case study of a high-elevation rocky complex.

BACKGROUND: Hybridization associated with polyploidy studies is rare in the tropics. The genus Zygopetalum (Orchidaceae) was investigated here as a case study of Neotropical plants. In the rocky highlands of the Ibitipoca State Park (ISP), southeast Brazil, individuals with intermediate colors and forms between the species Z. maculatum and Z. triste were commonly identified. METHODS AND RESULTS: Chromosomal analysis and DNA quantity showed a uniform population. Regardless of the aspects related to the color and shape of floral structures, all individuals showed 2n = 96 chromosomes and an average of 14.05 pg of DNA. Irregularities in meiosis associated with chromosome number and C value suggest the occurrence of polyploidy. The genetic distance estimated using ISSR molecular markers revealed the existence of genetic variability not related to morphological clusters. Morphometric measurements of the flower pieces revealed that Z. maculatum shows higher variation than Z. triste although lacking a defined circumscription. CONCLUSION: The observed variation can be explained by the polyploid and phenotypic plasticity resulting from the interaction of the genotypes with the heterogeneous environments observed in this habitat.

The complex polyploid genome architecture of sugarcane.

Sugarcane, the world's most harvested crop by tonnage, has shaped global history, trade and geopolitics, and is currently responsible for 80% of sugar production worldwide1. While traditional sugarcane breeding methods have effectively generated cultivars adapted to new environments and pathogens, sugar yield improvements have recently plateaued2. The cessation of yield gains may be due to limited genetic diversity within breeding populations, long breeding cycles and the complexity of its genome, the latter preventing breeders from taking advantage of the recent explosion of whole-genome sequencing that has benefited many other crops. Thus, modern sugarcane hybrids are the last remaining major crop without a reference-quality genome. Here we take a major step towards advancing sugarcane biotechnology by generating a polyploid reference genome for R570, a typical modern cultivar derived from interspecific hybridization between the domesticated species (Saccharum officinarum) and the wild species (Saccharum spontaneum). In contrast to the existing single haplotype ('monoploid') representation of R570, our 8.7 billion base assembly contains a complete representation of unique DNA sequences across the approximately 12 chromosome copies in this polyploid genome. Using this highly contiguous genome assembly, we filled a previously unsized gap within an R570 physical genetic map to describe the likely causal genes underlying the single-copy Bru1 brown rust resistance locus. This polyploid genome assembly with fine-grain descriptions of genome architecture and molecular targets for biotechnology will help accelerate molecular and transgenic breeding and adaptation of sugarcane to future environmental conditions.

Evolution of Trypanosoma cruzi: clarifying hybridisations, mitochondrial introgressions and phylogenetic relationships between major lineages

Several different models of Trypanosoma cruzi evolution have been proposed. These models suggest that scarce events of genetic exchange occurred during the evolutionary history of this parasite. In addition, the debate has focused on the existence of one or two hybridisation events during the evolution of T. cruzi lineages. Here, we reviewed the literature and analysed available sequence data to clarify the phylogenetic relationships among these different lineages. We observed that TcI, TcIII and TcIV form a monophyletic group and that TcIII and TcIV are not, as previously suggested, TcI-TcII hybrids. Particularly, TcI and TcIII are sister groups that diverged around the same time that a widely distributed TcIV split into two clades (TcIVS and TcIVN). In addition, we collected evidence that TcIII received TcIVS kDNA by introgression on several occasions. Different demographic hypotheses (surfing and asymmetrical introgression) may explain the origin and expansion of the TcIII group. Considering these hypotheses, genetic exchange should have been relatively frequent between TcIII and TcIVS in the geographic area in which their distributions overlapped. In addition, our results support the hypothesis that two independent hybridisation events gave rise to TcV and TcVI. Consequently, TcIVS kDNA was first transferred to TcIII and later to TcV and TcVI in TcII/TcIII hybridisation events.

Cisgenesis and Intragenesis: New tools For Improving Crops

Genetically Modified Organisms (GMO) could be the answer for many relevant problems affecting crops. However, improving crops through GMO is also often associated with safety concerns, environmental risks and health issues due to the presence of foreign DNA. These limitations have prompted the development of alternative technologies. Recently, cisgenesis and intragenesis have been developed as new tools aimed to modify crops. While cisgenesis involves genetic modification using a complete copy of natural genes with their regulatory elements that belong exclusively to sexually compatible plants, intragenesis refers to the transference of new combinations of genes and regulatory sequences belonging to that particular species. So far, application of cisgenesis and intragenesis as alternatives to conventional transgenesis are limited to a few species, mainly due to the lack of knowledge of the regulatory sequences required. The grape is one of the most cultivated crops worldwide and is the most economically relevant crop in Chile. Its genomic sequence has been completed, making available new sources of information to improve grape traits by genetic manipulation. This review is focused on the current alternatives to transgenesis in plants, including new approaches to develop marker-free crops, their application to economically relevant crops and future perspectives in the area. Also, the identification of grapevine promoters with a wide range of expression profiles is shown. The expression pattern of these genes was analyzed in different tissues and developmental stages, as well as under several stresses and stimuli, giving a broad range of expression patterns, including genes expressed exclusively during ripening, in response to sugars, senescence and biotic stress, among others. Genes with strong and constitutive expression were also identified. Functional analysis using reporter genes has been conducted in order to confirm the promoter's transcription activity, opening new possibilities for developing cisgenic/intragenic grapevines.

Biomphalaria tenagophila guaibensis (MOLLUSCA: PLANORBIDAE): avaliação da suscetibilidade a Schistosoma mansoni de status de subespécie

O registro da única subespécie do gênero Biomphalaria no Brasil, Biomphalaria tenagophila guaibensis, foi realizado no sul do país por Paraense (1984). A subespécie foi assim classificada devido a similaridades morfológicas com Biomphalaria tenagophila, especialmente pela presença de uma bolsa vaginal. Esta característica é a principal diferença que distingue esta subespécie de Biomphalaria occidentalis, espécie com a qual apresenta, também, grandes semelhanças. Informações sobre esta subespécie são escassas, inexistem dados de cruzamento de B. t. guaibensis com B. tenagophila e com B. occidentalis e há apenas um experimento demonstrando que esta subespécie não infectou-se quando exposta a cinco miracídios/molusco da cepa SJ de Schistosoma mansoni. Estas lacunas geram dúvidas quanto à classificação taxonômica da subespécie, uma vez que estudos de relação filogenética demonstram uma afinidade maior de B. t. guaibensis e B. occidentalis do que com B. tenagophila

No intuito de ampliar os conhecimentos sobre esta subespécie, esta dissertação teve como objetivos 1) investigar possível cruzamento com as duas espécies crípticas, utilizando o caráter de albinismo e a técnica molecular de PCR-RFLP; 2) verificar a sua suscetibilidade a S. mansoni, com três diferentes cepas AL, SJ, e LE e 50 e 100 miracídios/molusco e 3) verificar a suscetibilidade dos moluscos F1 e F2 de possíveis cruzamentos. No cruzamento B. t. guaibensis X B. tenagophila albino, quatro albinos (27%) geraram F1 pigmentada, e o perfil molecular obtido foi de B. t. guaibensis, enquanto B. t. guaibensis x B. occidentalis não apresentaram evidências de cruzamento. Nos experimentos de exposição a S. mansoni, os moluscos B. t. guaibensis e os moluscos pigmentados F1 e F2 de B. tenagophila albino resultantes do cruzamento com B. t. guaibensis não se infectaram. Esses dados têm importância epidemiológica, uma vez que, afasta a possibilidade de focos da esquistossomose em regiões onde somente essa subespécie está presente. E ainda, foi demonstrado que o posicionamento de B. t. guaibensis como subespécie é válido, uma vez que houve cruzamento comprovado entre a B. t. guaibensis e a espécie B. tenagophila, e que, há isolamento reprodutivo entre B. t. guaibensis e B. occidentalis

Biomphalaria tenagophila guaibensis (MOLLUSCA: PLANORBIDAE): avaliação da suscetibilidade a Schistosoma mansoni de status de subespécie / Biomphalaria tenagophila guaibensis (MOLLUSCA: Planorbidae): evaluation of susceptibility to Schistosoma mansoni subspecies status

O registro da única subespécie do gênero Biomphalaria no Brasil, Biomphalaria tenagophila guaibensis, foi realizado no sul do país por Paraense (1984). A subespécie foi assim classificada devido a similaridades morfológicas com Biomphalaria tenagophila, especialmente pela presença de uma bolsa vaginal. Esta característica é a principal diferença que distingue esta subespécie de Biomphalaria occidentalis, espécie com a qual apresenta, também, grandes semelhanças. Informações sobre esta subespécie são escassas, inexistem dados de cruzamento de B. t. guaibensis com B. tenagophila e com B. occidentalis e há apenas um experimento demonstrando que esta subespécie não infectou-se quando exposta a cinco miracídios/molusco da cepa SJ de Schistosoma mansoni. Estas lacunas geram dúvidas quanto à classificação taxonômica da subespécie, uma vez que estudos de relação filogenética demonstram uma afinidade maior de B. t. guaibensis e B. occidentalis do que com B. tenagophila. No intuito de ampliar os conhecimentos sobre esta subespécie, esta dissertação teve como objetivos 1) investigar possível cruzamento com as duas espécies crípticas, utilizando o caráter de albinismo e a técnica molecular de PCR-RFLP; 2) verificar a sua suscetibilidade a S. mansoni, com três diferentes cepas AL, SJ, e LE e 50 e 100 miracídios/molusco e 3) verificar a suscetibilidade dos moluscos F1 e F2 de possíveis cruzamentos. No cruzamento B. t. guaibensis X B. tenagophila albino, quatro albinos (27%) geraram F1 pigmentada, e o perfil molecular obtido foi de B. t. guaibensis, enquanto B. t. guaibensis x B. occidentalis não apresentaram evidências de cruzamento. Nos experimentos de exposição a S. mansoni, os moluscos B. t. guaibensis e os moluscos pigmentados F1 e F2 de B. tenagophila albino resultantes do cruzamento com B. t. guaibensis não se infectaram. Esses dados têm importância epidemiológica, uma vez que, afasta a possibilidade de focos da esquistossomose em regiões onde somente essa subespécie está presente. E ainda, foi demonstrado que o posicionamento de B. t. guaibensis como subespécie é válido, uma vez que houve cruzamento comprovado entre a B. t. guaibensis e a espécie B. tenagophila, e que, há isolamento reprodutivo entre B. t. guaibensis e B. occidentalis.

In vitro rescue of interspecific embryos from Elaeis guineensis x E. oleifera (Arecaceae)

The African oil palm (Elaeis guineensis) is the most effective oil producer in tons per hectare. Nevertheless, its increasing cultivation in Latin America is harmed by the “lethal yellowing”. Genetic resistance to this anomaly can be found in the germplasm of American oil palm or caiaué (E. oleifera), a native species from the Amazon rainforest. However, the procedures adopted to induce seeds of E. guineensis to germination frequently result mild for interespecific hybrids. Embryo in vitro cultivation can be a viable option. This work was aimed initially to test liquid MS medium supplemented with different glucose or sucrose concentrations for the in vitro cultivation of zygotic embryos from E. guineensis x E. oleifera controlled pollinations. Additionally we investigated different compost mixtures to acclimatize the regenerated hybrid plantlets. Concentrations of 10, 20 and 30g/L of both sugars were tested on flasks containing five mature zygotic embryos, with 15 repetitions per treatment in a total of 450 explants. The number of embryos displaying shoots and radicles at least 2mm in length per experimental unit was evaluated during phase one of in vitro cultivation. Plantlets displaying shoots and radicles were transferred to phase two of in vitro cultivation and subsequently to acclimatization, under 70% shading with manual water supply. The experiments of acclimatization were conducted with 130 plantlets randomly distributed in pure horticultural compost, 3:1 or 1:1 compost:sand mixtures and each plantlet was defined as an experimental unit. Data were submitted to ANOVA, t test and analyzes of correlation (p≤0.05). Highest emergence rates were 97% for shoots and 73% for radicles, observed in MS medium supplemented with 20g/L (110mM) of glucose. This sugar in concentrations of 20 or 30g/L provided balanced shoot/root development, and this was considered one of the reasons for the higher frequency of plantlet establishment. The survival percentage was 55% after the first 43 days of acclimatization and by the fourth month, 66 plants developed simultaneously longer shoot and root systems in pure horticultural compost. in conclusion, radicle development was an impairment to plantlet establishment and was overcame under media with glucose above 110mM. Acclimatization could benefit from an extended period of in vitro development. Rev. Biol. Trop. 59 (3): 1081-1088. Epub 2011 September 01.

Elaeis guineensis es el productor de aceite más eficaz en toneladas por hectárea, su cultivo, cada vez mayor en América Latina, se ha visto perjudicado por el “amarilleamiento letal”. La resistencia genética a esta anomalía se puede encontrar en el germoplasma de la palma aceitera americana o caiaué (E. oleifera), una especie nativa de la selva amazónica. Sin embargo, los procedimientos adoptados para inducir la germinación de las semillas de E. guineensis frecuentemente produce resultados modestos para híbridos interespecíficos. El cultivo de embriones in vitro puede ser una opción viable. En este trabajo se probó el medio líquido MS complementado con diferentes concentraciones de glucosa o sacarosa en el cultivo in vitro de embriones cigóticos de E. guineensis x E. oleifera originados de polinización controlada. Además se investigaron diferentes mezclas de compost para aclimatar los híbridos regenerados. Las concentraciones de 10, 20 y 30 g/L de ambos azúcares se probaron en frascos que contenían cinco embriones cigóticos maduros, con 15 repeticiones por tratamiento y un total de 450 explantes. El número de embriones que muestran brotes y radículas de al menos 2mm de longitud por unidad experimental se evaluó durante la primera fase de cultivo in vitro. Las plántulas que mostraron brotes y radículas fueron trasladadas a la segunda fase de cultivo in vitro y, posteriormente, se aclimataron, por debajo de 70% de sombra con el suministro manual de agua. Los experimentos de aclimatación se llevaron a cabo con 130 plántulas distribuidas al azar en el compost hortícola puro, compost 3:1 o 1:1: mezclas de arena y cada plántula se definió como una unidad experimental. Los datos fueron sometidos a un análisis de varianza, prueba t y análisis de correlación (p≤0.05). Las tasas más altas de emergencia fueron 97% y 73% para brotes y radículas respectivamente, en el medio MS complementado con 20g/L (110mM) de glucosa. Este azúcar en concentraciones de 20 o 30g/L permitió un desarrollo balanceado de brotes/desarrollo de raíces, que fue considerado como una de las razones de la alta frecuencia de establecimiento de las plántulas. El porcentaje de supervivencia fue de un 55% después de los primeros 43 días de aclimatación y por el cuarto mes, 66 plantas desarrollaron simultáneamente hojas largas y un sistema radical en el compost hortícola puro. En conclusión, el desarrollo radicular fue un impedimento para el establecimiento de plántulas y se superó en el medio con glucosa por encima de 110mM. La aclimatación podría beneficiarse con un largo período de desarrollo in vitro.

Genetic molecular analysis of Coffea arabica (Rubiaceae) hybrids using SRAP markers

In Coffea arabica (arabica coffee), the phenotypic as well as genetic variability has been found low because of the narrow genetic basis and self fertile nature of the species. Because of high similarity in phenotypic appearance among the majority of arabica collections, selection of parental lines for inter-varietals hybridization and identification of resultant hybrids at an early stage of plant growth is difficult. DNA markers are known to be reliable in identifying closely related cultivars and hybrids. Sequence Related Amplified Polymorphism (SRAP) is a new molecular marker technology developed based on PCR. In this paper, sixty arabica-hybrid progenies belonging to six crosses were analyzed using 31 highly polymorphic SRAP markers. The analysis revealed seven types of SRAP marker profiles which are useful in discriminating the parents and hybrids. The number of bands amplified per primer pair ranges from 6.13 to 8.58 with average number of seven bands. Among six hybrid combinations, percentage of bands shared between hybrids and their parents ranged from 66.29% to 85.71% with polymorphic bands varied from 27.64% to 60.0%. Percentage of hybrid specific fragments obtained in various hybrid combinations ranged from 0.71% to 10.86% and ascribed to the consequence of meiotic recombination. Based on the similarity index calculation, it was observed that F1 hybrids share maximum number of bands with the female parent compared to male parent. The results obtained in the present study revealed the effectiveness of SRAP technique in cultivar identification and hybrid analysis in this coffee species. Rev. Biol. Trop. 59 (2): 607-617. Epub 2011 June 01.

En Coffea arabica (café arabica), el fenotipo y la variabilidad genética son bajos debido a la estrecha base genética y la autofecundación de la especie. Por su alta similitud fenotípica entre la mayoría de las colecciones de arábica, la selección de líneas parentales para hibridación entre variedades, y la identificación de los híbridos resultantes en una fase inicial de crecimiento, es difícil. Para la identificación de variedades estrechamente relacionadas y sus híbridos, los marcadores de ADN son confiables, pero los polimorfismos de amplificación de secuencias relacionadas (SRAP, por sus siglas en inglés) constituyen una nueva tecnología de marcadores moleculares basada en PCR. En este trabajo, sesenta progenies arábica híbridas, pertenecientes a seis cruces, fueron analizadas utilizando 31 marcadores altamente polimórficos. El análisis reveló siete tipos de perfiles de marcadores que son útiles en la discriminación de los progenitores y los híbridos. El número de bandas amplificadas por pares de cebadores estuvo entre 6.13 a 8.58 con un promedio de siete bandas. Entre las seis combinaciones de híbridos, el porcentaje de bandas compartidas entre híbridos y sus progenitores estuvo entre 66.29% y 85.71% con bandas polimórficas que variaron entre 27.64% y 60.0%. El porcentaje de fragmentos híbridos específicos obtenidos en diversas combinaciones híbridas varió entre 0.71% y 10.86% lo que se atribuye a la recombinación meiótica. Con base en el cálculo del índice de similitud, se observó que los híbridos F1 compartieron un número máximo de bandas con el progenitor femenino que con el masculino. Los resultados obtenidos en este estudio muestran la eficacia de la técnica de SRAP en la identificación de cultivos e híbridos de esta especie de café.

Alterações genômicas na endometriose / Genomic alterations in endometriosis

A endometriose (EDT) é uma doença ginecológica crônica e heterogênea considerada um importante problema de saúde pública. As metodologias de Hibridação Genômica Comparativa de Alta resolução (HR-CGH) e CGH array (aCGH) são ferramentas importantes para a triagem de alterações genômicas em diferentes lesões endometrióides. No presente estudo, as análises de HR-CGH foram realizadas em 20 amostras de EDT fixadas em formalina e em blocos de parafina, de diferentes sítios e tipos histológicos, obtidas de oito pacientes submetidas à laparoscopia (Grupo I). Os componentes estromais e epiteliais foram isolados por microdissecção a laser. As amostras de endométrio tópico de três pacientes apresentaram perfis genômicos normais. Nos tecidos ectópicos, foi observada uma média de 68 regiões alteradas por caso. Análises comparativas entre os componentes estromais e epiteliais demonstraram alta freqüência de alterações genômicas comuns. As perdas foram mais prevalentes e envolveram principalmente os cromossomos 3p, 5q, 7p, 9p, 11q, 16q, 18q e 19q. A comparação entre os perfis de alteração de lesões de diferentes localizações derivadas da mesma paciente revelou a predominância de regiões comuns envolvidas em perdas e ganhos. Baseado nestes resultados foi realizada a análise de expressão protéica de sete marcadores de células-tronco pela metodologia de imunohistoquímica. A maioria das amostras apresentou expressão positiva dos marcadores CD9, CD34, c-Kit e Oct-4 em células isoladas do epitélio glandular e/ou células estromais...

Endometriosis (EDT) is a chronic and heterogeneous gynecological disease increasingly recognized as an important women’s health issue. High Resolution Comparative Genomic Hybridization (HR-CGH) and array-CGH (aCGH) methods are potential tools for screening of genomic imbalances in distinct EDT lesions. In this study, HR-CGH was performed on 20 formalin-fixed paraffin-embedded EDT samples from different anatomical sites and histological types obtained from eight patients undergoing laparoscopy (Group 1). Stromal and epithelial components from each sample were laser microdissected. Eutopic endometrium from three patients was also analyzed and presented normal genomic pattern. In ectopic tissues, an average of 68 genomic imbalances was detected per sample. The comparison between stroma and epithelia showed the prevalence of common genomic alterations. DNA losses were more frequently detected and involved mainly 3p, 5q, 7p, 9p, 11q, 16q, 18q and 19q. Interestingly, the comparison among genomic profiles of distinct endometriotic lesions from particular patients also showed a high frequency of common losses and gains. Based on these findings, we also evaluated the expression of seven stemness-related markers by immunohistochemistry. Positive immunostaining for CD9, CD34, c-kit and Oct-4 markers was detected in isolated epithelial and/or stromal cells in majority of analyzed samples...

Aislamiento reproductivo asimétrico entre Lutzomyia pseudolongipalpis y Lutzomyia longipalpis (especie C2), vectores neotropicales de leishmaniasis visceral (Diptera: Pshychodidae)

Asymmetric reproductive isolation between Lutzomyia pseudolongipalpis and Lutzomyia longipalpis (species C2), Neotropical vectors of visceral leishmaniasis (Diptera: Pshychodidae). Lutzomyia pseudolongipalpis and Lutzomyia longipalpis (species C2, L. sp n.) are two endemic species of Phlebotominae sand fly vectors from Venezuela. The two insects are sympatric and monophyletic but have deeply diverging, morphological differences. They belong to the L. longipalpis complex. A study of their reproductive isolation is necessary to understand the process of speciation and maintenance of the two sister species as two discrete taxonomic and biological entities. Cross-mating tests were conducted (homo and hetero-specific) and monitored under two criteria: biological (presence of copulation and offspring) and genetic (using two isozymic markers diagnostic for the L. longipalpis complex; enzyme diagnosis AK and HK). Results indicate reproductive isolation, with an asymmetrical genetic exchange in a direction of hybridization between the two species under experimental conditions, and production of a low number of heterozygotes. These findings support the existence of negative selection on hybrids, and explain the absence of hybrids under natural conditions, in the sympatric locality. Rev. Biol. Trop. 57 (1-2): 23-31. Epub 2009 June 30.

Lutzomyia pseudolongipalpis y Lutzomyia longipalpis (especie C2, L. n. sp) son dos especies de flebotominos vectores endémicos de Venezuela, simpátricas, monofiléticas, con profundas divergencias, morfológicamente diferentes y pertenecientes al complejo de especies L. longipalpis. El estudio de su aislamiento reproductivo es clave para entender el proceso de especiación y el mantenimiento de estas dos especies hermanas como entidades taxonómicas y biológicas discretas. Por tal motivo, se realizaron ensayos de entrecruzamiento homo y heteroespecíficos, los cuales fueron monitoreados por dos criterios: biológico (presencia de cópula y progenie) y genético (utilizando dos marcadores isoenzimáticos diagnósticos para el complejo L. longipalpis, las enzimas AK y HK). Los resultados indican aislamiento reproductivo, con un intercambio genético asimétrico hacia la hibridización en condiciones experimentales, y producción de un bajo número de heterocigotos, lo que apoya la existencia de selección negativa sobre los híbridos y explica su ausencia en condiciones naturales en la localidad simpátrica.

Hypotheses to explain the origin of species in Amazonia / Hipóteses para explicar a origem das espécies na Amazônia

The main hypotheses proposed to explain barrier formation separating populations and causing the differentiation of species in Amazonia during the course of geological history are based on different factors, as follow: (1) Changes in the distribution of land and sea or in the landscape due to tectonic movements or sea level fluctuations (Paleogeography hypothesis), (2) the barrier effect of Amazonian rivers (River hypothesis), (3) a combination of the barrier effect of broad rivers and vegetational changes in northern and southern Amazonia (River-refuge hypothesis), (4) the isolation of humid rainforest blocks near areas of surface relief in the periphery of Amazonia separated by dry forests, savannas and other intermediate vegetation types during dry climatic periods of the Tertiary and Quaternary (Refuge hypothesis), (5) changes in canopy-density due to climatic reversals (Canopy-density hypothesis) (6) the isolation and speciation of animal populations in small montane habitat pockets around Amazonia due to climatic fluctuations without major vegetational changes (Museum hypothesis), (7) competitive species interactions and local species isolations in peripheral regions of Amazonia due to invasion and counterinvasion during cold/warm periods of the Pleistocene (Disturbance-vicariance hypothesis) and (8) parapatric speciation across steep environmental gradients without separation of the respective populations (Gradient hypothesis). Several of these hypotheses probably are relevant to a different degree for the speciation processes in different faunal groups or during different geological periods. The basic paleogeography model refers mainly to faunal differentiation during the Tertiary and in combination with the Refuge hypothesis. Milankovitch‡ cycles leading to global main hypotheses proposed to explain barrier formation separating populations and causing the differentiation of species in Amazonia during the course of geological...

As principais hipóteses propostas para explicar as formações de barreiras separando populações e causando diferenciações de espécies na Amazônia são baseadas em diferentes fatores (a maioria históricos), como os seguintes: 1) Mudanças na distribuição da terra e mar ou na paisagem devido a movimentos tectônicos ou flutuações do nível do mar (hipótese Paleogeográfica); 2) o efeito de barreiras dos rios amazônicos (hipótese de Rios); 3) uma combinação de efeitos de barreiras de rios largos e mudanças vegetacionais no norte e sul da Amazônia (hipótese de Refúgio-rios), 4) o isolamento dos blocos de floresta úmida das áreas de relevo de superfície na periferia da Amazônia separadas por florestas secas, savanas e outros tipos de vegetação intermediária durante os períodos climáticos secos do Terciário e Quaternário (hipótese de Refúgios), 5) mudanças na densidade do dossel devido a mudanças climáticas (hipótese de Densidade do dossel), 6) o isolamento e especiação de populações animais em pequenas áreas montanhosas na Amazônia devido a flutuações climáticas sem maiores mudanças vegetacionais (hipótese de Museu), 7) interações competitivas entre espécies e isolamentos de espécies locais em regiões periféricas da Amazônia devido a invasão e contra-invasão durante períodos frios/quentes do Pleistoceno (hipótese Distúrbio-vicariante), e 8) especiação parapátrica através de acentuados gradientes ambientais sem separação das respectivas populações (hipótese de Gradiente). Muitas dessas hipóteses provavelmente são relevantes para diferentes graus de processos de especiação em diferentes grupos da fauna ou durante diferentes períodos geológicos. O modelo básico de paleogeografia refere-se principalmente a diferenciação faunística durante o terciário e em combinação com a hipótese de Refúgio. Os ciclos de Milankovitch que levam a mudanças climáticas-vegetacionais globais afetaram os biomas do mundo não apenas durante o Pleistoceno mas também durante...

Biological aspects of crosses between Triatoma maculata (Erichson, 1848) and Triatoma pseudomaculata Corrêa & Espínola, 1964 (Hemiptera: Reduviidae)

Due to morphological similarities between Triatoma maculata and T. pseudomaculata, which comprise the "maculate complex", both had been regarded as the same species until 1964. Considering that the studies on triatomine hybridization permit hypotheses formulation concerning origin and divergence of species, enabling a quantitative analysis of taxonomic relationships between species, the present investigation was aimed at broadening further understanding related to the capacity of hybrid production by determining the degree of reproductive isolation between T. maculata and T. pseudomaculata. Our results have demonstrated that T. maculata and T. pseudomaculata showed no differences regarding reproduction patterns and they are able to cross, generating infertile hybrids.

New evidence for nucleolar dominance in hybrids of Drosophila arizonae and Drosophila mulleri

Drosophila mulleri (MU) and D. arizonae (AR) are cryptic species of the mulleri complex, mulleri subgroup, repleta group. Earlier cytogenetic studies revealed that these species have different regulatory mechanisms of nucleolar organizing activity. In these species, nucleolar organizing regions are found in both the X chromosome and the microchromosome. In the salivary glands of hybrids between MU females and AR males, there is an interspecific dominance of the regulatory system of the D. arizonae nucleolar organizer involving, in males, amplification and activation of the nucleolar organizer from the microchromosome. The authors who reported these findings obtained hybrids only in that cross-direction. More recently, hybrids in the opposite direction, i.e., between MU males and AR females, have been obtained. The purpose of the present study was to evaluate, in these hybrids, the association of the nucleoli with the chromosomes inherited from parental species in order to cytogenetically confirm the dominance patterns previously described. Our results support the proposed dominance of the AR nucleolar organizer activity over that of MU, regardless of cross-direction.

The synthesis of a new cassava-derived species, Manihot vieiri Nassar

A new species was synthesized artificially by chromosome doubling in a hybrid. The ensuing polyploid type exhibits an apomictic nature and maintains its morphological characteristics in the progeny. It showed a frequency of multiembryonic sacs of 29% in the ovules examined, whereas sacs were absent in the diploid type.

Evidence for a natural hybrid of peacock bass (Cichla monoculus vs Cichla temensis) based on esterase electrophoretic patterns

Esterase (Est) and esterase-D (Est-D) electrophoretic patterns identified by starch gel electrophoresis of skeletal muscle protein extracts of 184 specimens of three species of peacock bass, locally known as tucunares (Cichla monoculus, C. temensis and Cichla sp), plus four specimens of a supposed hybrid (C. monoculus vs C. temensis), collected from the Central Amazon, were examined to determine if they could aid in identifying a supposed hybrid between C. monoculus and C. temensis. Six zones of electrophoretic activity were found with these enzyme systems. The Est enzyme showed one zone of activity, formed by bands 1, 2 and 3, plus three zones of activity, presumably controlled by Est-1, 2 and 3 loci. The Est-D enzyme had two zones of activity, presumably controlled by Est-D1 and Est-D2 loci. Cichla monoculus and C. temensis shared band 2 and alleles Est-1(1), Est-2(1), Est-3(2), and Est-D1(1), and therefore these were useless for identifying hybrids between the two species. However, a probable hybrid pattern of bands 1, 2, and 3, presumably generated by a combination of pattern 12 from C. monoculus with pattern 23 from C. temensis, resulting from a possible cross between these two species, was detected. Although the Est-D2 locus cannot be considered an ideal diagnostic marker for identifying the supposed hybrid (C. monoculus vs C. temensis), as it is polymorphic, it proved to be useful for determining the origin of the hybrid, i.e., which parental species were involved in the hybridization process

Gene flow between cassava, Manihot esculenta Crantz, and wild relatives

Controlled and natural hybridization between cassava and wild relatives does occur. Barriers within the genus appear to be weak due to recent evolution of the group. All Manihot species examined cytogenetically have a chromosome number of 2n = 36. However, they behave meiotically as diploids. The weak interspecific barriers have led to an extremely heterozygous gene pool that may begin a sequence of hybridization followed by speciation. Introgression from cassava into a number of wild species (M. neusana, M. alutacea, M. reptans and M. anomala) has been detected by both morphological marker genes and molecular techniques. Winged fruit, setaceous bracteoles, and wide leaf sinus were dominant genes that came from cassava and appeared in the hybrids. The characteristic protein bands of cassava were recognized in the hybrid seed protein electrophoresis

Evaluation of the courtship and of the hybrid male sterility among Drosophila buzzatii cluster species (Diptera, Drosophilidae)

In the Drosophila repleta group the establishment of subgroups and complexes made on the basis of morphological and cytological evidences is supported by tests of reproductive isolation. Among species in the repleta group, the buzzatii cluster, due to its polymorphism and polytipism, is an excellent material for ecological and speciation studies. Some interspecific crosses involving Drosophila seriema, Drosophila sp. B, D. koepferae and D. buzzatii strains were completely sterile while others involving strains from these species produced F1 hybrids that did not yield F2. In the present work, data on courtship duration and copula occurrence obtained in the analysis of flies from parental sterile crosses and on spermatozoon mobility observed in F1 hybrids that did not yield F2 are presented. Copula did not occur during one hour of observation and the spermatozoon also did not show mobility at any of the analyzed stages (3, 7, 9 and 10 days old). There was a high variation in courtship average duration and in the percentage of males that courted the females. The reproductive isolation mechanisms indicated by these observations were pre and post-zygotic, as supported by the absence of copula and male sterility. Data obtained also showed the occurrence of different degrees of reproductive compatibility among the strains classified as the same species but from distinct geographic localities

Hunting for differentially expressed genes

Differentially expressed genes are usually identified by comparing steady-state mRNA concentrations. Several methods have been used for this purpose, including differential hybridization, cDNA subtraction, differential display and, more recently, DNA chips. Subtractive hybridization has significantly improved after the polymerase chain reaction was incorporated into the original method and many new protocols have been established. Recently, the availability of the well-known coding sequences for some organisms has greatly facilitated gene expression analysis using high-density microarrays. Here, we describe some of these modifications and discuss the benefits and drawbacks of the various methods corresponding to the main advances in this field