991 resultados para plant populations


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The impact of a power plant cooling system in the Bahía Blanca estuary (Argentina) on the survival of target zooplanktonic organisms (copepods and crustacean larvae) and on overall mesozooplankton abundance was evaluated over time. Mortality rates were calculated for juveniles and adults of four key species in the estuary: Acartia tonsa Dana, 1849 and Eurytemora americana Williams, 1906 (native and invading copepods), and larvae of the crab Chasmagnathus granulata Dana, 1851 and the invading cirriped Balanus glandula Darwin, 1854. Mean total mortality values were up to four times higher at the water discharge site than at intake, though for all four species, significant differences were only registered in post-capture mortality. The findings show no evidence of greater larval sensitivity. As expected, the sharpest decrease in overall mesozooplankton abundance was found in areas close to heated water discharge.

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Morphometric variability among shrimp populations of the genus Palaemonetes Heller, 1869 from seven lakes (Huanayo and Urcococha, in Peru; Amanã, Mamirauá, Camaleão, Cristalino e Iruçanga, in Brasil) in the Amazon Basin, presumably belonging to Palaemonetes carteri Gordon, 1935 and Palaemonetes ivonicus Holthuis, 1950, were studied. The morphometric studies were carried out from the ratios obtained from the morphometric characters. Multivariated analysis (Principal Components Analysis-PCA, Discriminant Function Analysis and Cluster Analysis) were applied over the ratios. Intra- and interpopulation variations of the rostrum teeth, and the number of spines in the male appendix, were analyzed through descriptive statistics and bivariate analysis (Spearman Rank Correlation test). Results indicated a wide plasticity and overlapping in the studied ratios between populations. The Principal Components Analysis was not able to separate different populations, revealing a large intrapopulation plasticity and strong interpopulation similarity in the studied ratios. Although the Discriminant Functions Analysis was not able to fully discriminate populations, they could be allocated in three subgroups: 1) Cristalino and Iruçanga; 2) Huanayo, Urcococha and Camaleão and 3) Mamirauá and Amanã. The first two groups were morphometrically separated from each other, whereas the third one presented a strong overlap with the former two. The Cluster Analysis confirmed the first two subgroups separation, and indicated that the first and third groups were closely related. Rostrum teeth and number of spines in the appendix masculina showed a large intrapopulation variation and a strong overlapping among the studied populations, regardless of the species.

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Three isolated populations of the cricket Endecous itatibensis Rehn, 1918 had been analyzed to test the hypothesis of divergence in the calling song estridulation and to discuss its implications in the speciation process. The song registers were obtained from specimens in Corumbataí, Piraciacaba and Itatiba cities, state of São Paulo, Brazil. In the three analyzed populations, calling songs are composed by pairs of notes. Specimens from Corumbataí emit composed phrases with 3 to 18 pairs of notes, while those of Piracicaba and Itatiba have 1 to 3 pairs of notes. Inter- and intrapopulational variability in the frequencies of acoustic signals were detected. While recording the calling songs, other stridulations were registered, possibly from species of Orthoptera or Hemiptera. When the tapes were analyzed in the laboratory, it was verified that there was no overlap among the species' calling songs, in such a way that each species had their particular band of frequencies, avoiding interespecific acoustic competition.

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Ethological isolation of individuals from three allopatric Grammostola populations of Uruguay, G. iheringi (Keyserling, 1891), G. mollicoma (Auserer, 1875) northern population and G. mollicoma southern population, was tested under laboratory conditions. Grammostola iheringi behaved as a reproductive isolated species, whereas the two populations of G. mollicoma did not show ethological isolation between them. However, ecological isolating reproductive mechanisms could be acting on G. mollicoma populations. Artificial burrows seem to be important for reproductive isolation in these species.

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The composition and the seasonality of the natural populations of Drosophila species in relation to the climatic variables temperature and rainfall were analyzed from September 1998 through October 1999 by monthly collections, in two woodlands in the Northwest of the State of São Paulo, Brazil. The diversity dominance component curves were inclined, reflecting low diversity and high dominance of few species. Among the 25 species recorded, Drosophila sturtevanti Duda, 1927 was the most frequent and abundant. On the opposite to data in literature, D. paranaensis Barros, 1950 abundance and frequency were greater than those from D. mercatorum Patterson & Wheeler, 1942. A positive correlation between abundance and rainfall was observed for D. nebulosa Sturtevant, 1916. These data are indicative of changes in the populations structure due to new adaptive strategies arised in response to environmental modifications.

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This study characterizes the calling song and ultramorphology of the stridulatory file of two geographically isolated populations of the tropical bush cricket Eneoptera surinamensis (De Geer, 1773) from city of Foz do Iguaçu, state of Paraná, and town of Rio Claro, state of São Paulo, Brazil, distant 1,000 Km from each other. The teeth are shell-shaped, the larger ones are distributed in the medium region of the file, decreasing gradually in size towards the edges. Specimens from Foz do Iguaçu have a file with 82 ± 9.8 teeth, length=1.89 mm ± 0.15 with 43.76 ± 5.94 teeth per mm (n=15). Specimens from Rio Claro present a file with 87 ± 9.81, length=1.96 ± 0.19 mm with 44.52 ± 4.61 teeth per mm (n=15). Statistical differences found between the two populations are not significant. The calling song is an uninterrupted trill that alternates two sets of notes distinct for its temporal features.

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Physalaemus henselii (Peters, 1872) is a little known leiuperid frog that has not been studied since the 1960’s. Herein, we redescribe its advertisement call, and assess the female sexual cycle and the reproductive period on the basis of the macroscopic analysis of the ovaries and field observations. The Ovarian Size Factor (OSF) was calculated. The study was made in Departamento de Rivera, northern Uruguay. The advertisement call consists of short (177 ± 21ms), multipulsed (20 ± 3 pulses/note) notes, with a note repetition rate of 1.57 ± 0.13 notes/s. Physalaemus henselii has a female sexual cycle with unimodal distribution of gravid females, which are present from February to September. The OSF and the ratio "females with mature oocytes / females without mature oocytes" reached the highest values from April to June. The number and size of oocytes were positively correlated with female size. The smallest female (SVL =18.94mm, weight =0.78g) with mature oocytes was found in July. The observed sexual cycle with a single annual reproductive period during the cold season (autumn and early winter), is an uncommon fact for anuran species in the region.

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To assess genetic structure and phenotypic diversity of Eupemphix nattereri Steindachner, 1863, morphometric and molecular analyses were carried out for nine populations from the State of Goiás. A total of 11 morphometric traits were evaluated and genetic information was estimated using RAPD markers. Genetic and phenotypic distances were determined as a function of geographical origin. Correlation among genetic, morphometric, micro, and macroenviromental were analyzed by the Mantel test. Genetic data indicated high levels of genetic diversity (Φst= 0.3) among the nine populations. Mantel tests did not reveal a significant positive correlation between genetic and geographical distances, indicating that locally geographical populations were not genetically similar, even in distances smaller than 50 km. Discriminant analysis on 11 morphometric measurements showed a high divergence among the nine populations. However, a marginally significant correlation (P=0.08) between genetic and morphometric distances was found. The observed correlation was not causal in terms of the relationship between phenotype and genotype, but indicated common spatial structures. Thus, our results suggest that isolation-by-distance processes may explain population divergence in Eupemphix nattereri.

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v. 6 (1903)

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v. 4

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Different populations of Pseudonannolene strinatii Mauriès, 1974 collected from three caves in Iporanga, state of São Paulo, were cytogenetically compared using techniques of conventional coloration, C-banding and silver nitrate impregnation. Specimens were morphologically similar and small cytogenetic differences were observed between the populations with relation to the distribution of constitutive heterochromatin.