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991.
Vítor Carvalho‐Rocha Benedito Cortês Lopes Selvino Neckel‐Oliveira 《Austral ecology》2018,43(2):150-158
Studies with disparate taxa suggest that generalist populations are composed of relatively specialist individuals that use a narrow part of a population's resource pool. Models based on optimum diet theory (ODT) can be used to predict different patterns of variation in resource use among individuals. In this work, we investigated the diet and measured the degree of individual specialization of three anuran species, Hypsiboas leptolineatus, Pseudis cardosoi and Scinax granulatus, from the Atlantic Forest of southern Brazil. The study is based on gut content obtained using a stomach‐flushing technique. Additionally, we tested for a correlation between the individuals’ diet and morphological variation. Furthermore, we applied methods based on network theory to investigate patterns of resource use among individuals of each species. All three study species showed generalized diets and significant values of individual specialization. However, we did not find any correlation between diet and morphology, indicating that diet variation is not a consequence of morphological trade‐offs. The individual‐resource networks of H. leptolineatus and S. granulatus showed a nested pattern. This result indicates the presence of individuals with more diverse diets than others, and the diets of the more specialist individuals are a predictable subset of the diets of the more generalist ones. The individual‐resource network of P. cardosoi did not show a distinct pattern, diverging from what was predicted by optimal diet theory‐based models. Although nested or modular patterns are commonly found in individual‐resource networks, our results indicate that they are not ubiquitous and that random patterns can also be found. 相似文献
992.
Testing Wallace's intuition: water type,reproductive isolation and divergence in an Amazonian fish 下载免费PDF全文
Tiago H. S. Pires Elio A. Borghezan Valeria N. Machado Daniel L. Powell Cristhiana P. Röpke Claudio Oliveira Jansen Zuanon Izeni P. Farias 《Journal of evolutionary biology》2018,31(6):882-892
Alfred Russel Wallace proposed classifying Amazon rivers based on their colour and clarity: white, black and clear water. Wallace also proposed that black waters could mediate diversification and yield distinct fish species. Here, we bring evidence of speciation mediated by water type in the sailfin tetra (Crenuchus spilurus), a fish whose range encompasses rivers of very distinct hydrochemical conditions. Distribution of the two main lineages concords with Wallace's water types: one restricted to the acidic and nutrient‐poor waters of the Negro River (herein Rio Negro lineage) and a second widespread throughout the remaining of the species’ distribution (herein Amazonas lineage). These lineages occur over a very broad geographical range, suggesting that despite occurring in regions separated by thousands of kilometres, individuals of the distinct lineages fail to occupy each other's habitats, hundreds of metres apart and not separated by physical barrier. Reproductive isolation was assessed in isolated pairs exposed to black‐water conditions. All pairs with at least one individual of the lineage not native to black waters showed significantly lower spawning success, suggesting that the water type affected the fitness and contributed to reproductive isolation. Our results endorse Wallace's intuition and highlight the importance of ecological factors in shaping diversity of the Amazon fish fauna. 相似文献
993.
994.
Carvalho Helena Sunkel Claudio Salema Roberto Cullimore Julie V. 《Plant molecular biology》1997,35(5):623-632
We have cloned and sequenced the cDNAs corresponding to the two cytosolic glutamine synthetase (GS) polypeptides (a and b) of Medicago truncatula. Using these two cDNAs we have prepared a construct encoding the N-terminal domain of b and the C-terminal domain of a in order to produce a domain-swapped polypeptide which should assemble to give an enzyme containing chimeric active sites. Both the native and the domain-swapped enzymes were expressed in Escherichia coli where they were catalytically and physiologically active as they were able to rescue a glnA deletion mutant. The expressed polypeptides were of the correct size and the isoenzymes behaved similarly to their native homologues on ion-exchange chromatography. We have found slight differences in the kinetic properties of the purified enzymes and in the modulation of their activities by several putative cellular effectors. In vitro dissociation of the purified a and b homo-octamers, followed by reassociation, showed that the subunits are able to self-assemble, perhaps randomly, to form heteromeric isoenzymes. Moreover, heteromeric isoenzymes occur in the plant as revealed by studies on the GS isoenzymes of nodules, roots, stems and stipules. 相似文献
995.
Javier Francisco-Ortega Daniel J. Crawford Arnoldo Santos-Guerra Jose A. Carvalho 《Plant Systematics and Evolution》1996,202(3-4):137-152
The genusArgyranthemum (Asteraceae: Anthemideae) comprises 38 taxa and is restricted to the archipelagos of the Canaries, Selvagens, Madeira, and Desertas in the Macaronesian biogeographic region. An electrophoretic study, including 17 enzyme loci and at least one population of each of the described taxa, was carried out. High identity (low distance) values between taxa (mean of 0.893) were obtained despite the old age of the islands, their close proximity to the African continent, and the fact thatArgyranthemum is the most species-rich and variable genus in Macaronesia. These results suggest that the genus is monophyletic and that it has evolved very rapidly in these islands. There is little correspondence between taxonomy and neighbor-joining analysis based on Roger's genetic distances, but in several instances populations from the same islands cluster together despite being from different species or even different sections. It is suggested that repeated genetic bottlenecks associated with the founding of new populations during radiation of the genus resulted in lineage sorting of ancestral allozyme polymorphisms. Because every population has a high average identity with all other populations, lineage sorting could result in populations of different taxa being slightly more similar than populations of the same taxon. Gene flow between different species on the same island could account for some populations clustering by island of origin rather than taxonomic disposition. Average allozyme diversity within populations (0.098) is 50% higher than the mean total diversity for species endemic to oceanic islands. 相似文献
996.
Wim Van den Ende ré Van Laere Katrien Le Roy Rudy Vergauwen David Boogaerts Rita C. L. Figueiredo-Ribeiro Maria Angela Machado de Carvalho 《Physiologia plantarum》2005,125(4):419-429
Inulin-type fructans are stored in the tuberous roots of the Brazilian cerrado plant Viguiera discolor Baker (Asteraceae). In Cynara scolymus (artichoke) and Echinops ritro (globe thistle), the fructans have a considerably higher degree of polymerization (DP) than in Cichorium intybus (chicory) and Helianthus tuberosus (Jerusalem artichoke). It was shown before that the higher DP in some species can be attributed to the properties of their fructan: fructan 1-fructosyl transferases (1-FFTs; EC 2.4.1.100), enzymes responsible for chain elongation. Here, we describe the cloning of a high DP (hDP) 1-FFT cDNA from V. discolor and its heterologous expression in Pichia pastoris . Starting from 1-kestose and Neosugar P (a mixture of oligo-inulins from microbial origin) as substrates, the recombinant enzyme produces a typical hDP inulin profile in vitro, closely resembling the one observed in vivo. The enzyme shows no invertase activity and sucrose: sucrose 1-fructosyl transferase (1-SST; EC 2.4.1.99) activity in vitro. Pattern evolution during incubation suggests that inulins with DP ≥ 6 are much better substrates than sucrose or lower DP oligo-fructans. Because hDP inulin-type fructans show superior properties for specific food and non-food applications, the hDP 1-FFT gene from V. discolor has potential for the production of hDP inulin in vitro or in transgenic crops. 相似文献
997.
L M Bini L G Oliveira D C Souza P Carvalho M P Pinto 《Revista brasleira de biologia》2005,65(1):19-24
The relationship between the aquatic macrophyte cover in upper segments of tributaries and this cover in these tributaries but near the reservoir's main body was tested. Sixteen taxa belonging to 12 families of aquatic macrophytes were recorded in Cachoeira Dourada Reservoir. The most frequent species were Eichhornia azurea (frequency of occurrence=92%; n=37 sites) and E. crassipes (44%). Upper segments of the tributaries were the main areas colonized by these aquatic macrophytes. The positive relationship between the aquatic macrophyte cover between the upper and lower segments of tributaries indicates the importance of dispersion in the colonization of the arms and the reservoir's main body. 相似文献
998.
T I B Bruno E M Zanotti-Magalh?es L A Magalh?es J F Carvalho 《Revista brasleira de biologia》2005,65(1):43-49
The development of cercariae from Schistosoma mansoni strains BH and SJ in Biomphalaria glabrata and Biomphalaria tenagophila treated with saccharose was studied. The molluscs were maintained in dechlorinated tap water containing 0.01% saccharose. After one week of treatment with saccharose, B. glabrata and B. tenagophila were exposed to ten S. mansoni miracidia, from BH and SJ strains respectively. Control snails of both species were maintained in dechlorinated tap water without saccharose and exposed to the same number of miracidia. There was no significant difference between the infection rates of snails treated or not with saccharose. However, the two groups of B. glabrata had significantly greater infection rates than the corresponding B. tenagophila groups. Molluscs treated with saccharose had a lower survival rate, with the greatest mortality occurring immediately before and at the beginning of cercariae release. Treatment with saccharose did not result in the release of more cercariae, but larvae from molluscs so treated showed a greater capacity to penetrate mouse skin, which was attributed to the greater energy supply during larval development in the mollusc. 相似文献
999.
The integration of alien plants in mutualistic plant–hummingbird networks across the Americas: the importance of species traits and insularity 下载免费PDF全文
Pietro K. Maruyama Jeferson Vizentin‐Bugoni Jesper Sonne Ana M. Martín González Matthias Schleuning Andréa C. Araujo Andrea C. Baquero Juliana Cardona Paola Cardona Peter A. Cotton Glauco Kohler Carlos Lara Tiago Malucelli Oscar Humberto Marín‐Gómez Jeff Ollerton Ana M. Rui Allan Timmermann Isabela G. Varassin Thais B. Zanata Carsten Rahbek Marlies Sazima Bo Dalsgaard 《Diversity & distributions》2016,22(6):672-681