988 resultados para Reproductive Strategy
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Natural regeneration is an ecological key-process that makes plant persistence possible and, consequently, it constitutes an essential element of sustainable forest management. In this respect, natural regeneration in even-aged stands of Pinus pinea L. located in the Spanish Northern Plateau has not always been successfully achieved despite over a century of pine nut-based management. As a result, natural regeneration has recently become a major concern for forest managers when we are living a moment of rationalization of investment in silviculture. The present dissertation is addressed to provide answers to forest managers on this topic through the development of an integral regeneration multistage model for P. pinea stands in the region. From this model, recommendations for natural regeneration-based silviculture can be derived under present and future climate scenarios. Also, the model structure makes it possible to detect the likely bottlenecks affecting the process. The integral model consists of five submodels corresponding to each of the subprocesses linking the stages involved in natural regeneration (seed production, seed dispersal, seed germination, seed predation and seedling survival). The outputs of the submodels represent the transitional probabilities between these stages as a function of climatic and stand variables, which in turn are representative of the ecological factors driving regeneration. At subprocess level, the findings of this dissertation should be interpreted as follows. The scheduling of the shelterwood system currently conducted over low density stands leads to situations of dispersal limitation since the initial stages of the regeneration period. Concerning predation, predator activity appears to be only limited by the occurrence of severe summer droughts and masting events, the summer resulting in a favourable period for seed survival. Out of this time interval, predators were found to almost totally deplete seed crops. Given that P. pinea dissemination occurs in summer (i.e. the safe period against predation), the likelihood of a seed to not be destroyed is conditional to germination occurrence prior to the intensification of predator activity. However, the optimal conditions for germination seldom take place, restraining emergence to few days during the fall. Thus, the window to reach the seedling stage is narrow. In addition, the seedling survival submodel predicts extremely high seedling mortality rates and therefore only some individuals from large cohorts will be able to persist. These facts, along with the strong climate-mediated masting habit exhibited by P. pinea, reveal that viii the overall probability of establishment is low. Given this background, current management –low final stand densities resulting from intense thinning and strict felling schedules– conditions the occurrence of enough favourable events to achieve natural regeneration during the current rotation time. Stochastic simulation and optimisation computed through the integral model confirm this circumstance, suggesting that more flexible and progressive regeneration fellings should be conducted. From an ecological standpoint, these results inform a reproductive strategy leading to uneven-aged stand structures, in full accordance with the medium shade-tolerant behaviour of the species. As a final remark, stochastic simulations performed under a climate-change scenario show that regeneration in the species will not be strongly hampered in the future. This resilient behaviour highlights the fundamental ecological role played by P. pinea in demanding areas where other tree species fail to persist.
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Tese de doutoramento, Biologia (Biologia Marinha e Aquacultura), Universidade de Lisboa, Faculdade de Ciências, 2016
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Girls who grow up in households with an unrelated adult male reach menarche earlier than peers, a finding hypothesized to be an evolutionary strategy for families under stress. The authors tested the alternative hypothesis that nonrandom selection into stepfathering due to shared environmental and/or genetic predispositions creates a spurious relation between stepfathering and early menarche. Using the unique controls for genetic and shared environmental experiences offered by the children-of-twins design, the authors found that cousins discordant for stepfathering did not differ in age of menarche. Moreover, controlling for mother's age of menarche eliminated differences in menarcheal age associated with stepfathering in unrelated girls. These findings strongly suggest selection, and not causation, accounts for the relationship between stepfathering and early menarche.
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Boccardia proboscidea is a recently introduced polychaete in South Africa where it is a notorious pest of commercially reared abalone. Populations were originally restricted to abalone farms but a recent exodus into the wild at some localities has raised conservation concerns due to the species’ invasive status in other parts of the world. Here, we assessed the dispersal potential of B. proboscidea by using a population genetic and oceanographic modeling approach. Since the worm is in its incipient stages of a potential invasion, we used the closely related Polydora hoplura as a proxy due its similar reproductive strategy and its status as a pest of commercially reared oysters in the country. Populations of P. hoplura were sampled from seven different localities and a section of the mtDNA gene, Cyt b and the intron ATPSa was amplified. A high resolution model of the coastal waters around southern Africa was constructed using the Regional Ocean Modeling System. Larvae were represented by passive drifters that were deployed at specific points along the coast and dispersal was quantified after a 12-month integration period. Our results showed discordance between the genetic and modeling data. There was low genetic structure (Φ = 0.04 for both markers) and no geographic patterning of mtDNA and nDNA haplotypes. However, the dispersal model found limited connectivity around Cape Point—a major phylogeographic barrier on the southern African coast. This discordance was attributed to anthropogenic movement of larvae and adult worms due to vectors such as aquaculture and shipping. As such, we hypothesized that cryptic dispersal could be overestimating genetic connectivity. Though wild populations of B. proboscidea could become isolated due to the Cape Point barrier, anthropogenic movement may play the critical role in facilitating the dispersal and spread of this species on the southern African coast.
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Boccardia proboscidea is a recently introduced polychaete in South Africa where it is a notorious pest of commercially reared abalone. Populations were originally restricted to abalone farms but a recent exodus into the wild at some localities has raised conservation concerns due to the species’ invasive status in other parts of the world. Here, we assessed the dispersal potential of B. proboscidea by using a population genetic and oceanographic modeling approach. Since the worm is in its incipient stages of a potential invasion, we used the closely related Polydora hoplura as a proxy due its similar reproductive strategy and its status as a pest of commercially reared oysters in the country. Populations of P. hoplura were sampled from seven different localities and a section of the mtDNA gene, Cyt b and the intron ATPSa was amplified. A high resolution model of the coastal waters around southern Africa was constructed using the Regional Ocean Modeling System. Larvae were represented by passive drifters that were deployed at specific points along the coast and dispersal was quantified after a 12-month integration period. Our results showed discordance between the genetic and modeling data. There was low genetic structure (Φ = 0.04 for both markers) and no geographic patterning of mtDNA and nDNA haplotypes. However, the dispersal model found limited connectivity around Cape Point—a major phylogeographic barrier on the southern African coast. This discordance was attributed to anthropogenic movement of larvae and adult worms due to vectors such as aquaculture and shipping. As such, we hypothesized that cryptic dispersal could be overestimating genetic connectivity. Though wild populations of B. proboscidea could become isolated due to the Cape Point barrier, anthropogenic movement may play the critical role in facilitating the dispersal and spread of this species on the southern African coast.
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Recently shown in some termites, Asexual Queen Succession (AQS) is a reproductive strategy in which the primary queen is replaced by numerous parthenogenetically-produced neotenic queens that mate with the primary king. In contrast, the workforce and alate dispersers are produced sexually. If the primary king is replaced by a sexually-produced neotenic son, the matings between neotenic male and females beget asymmetries in the reproductive value of alates, promoting a female-biased alate sex-ratio. Cavitermes tuberosus (Termitidae: Termitinae) is a soil-feeding tropical species, which shows parthenogenetically-produced neotenics and an AQS syndrome. Our work aims to characterize the reproductive strategies in this species by determining (i) the developmental scheme, (ii) the genetic origin of sexuals, (iii) the level of genetic structure (analysis of 65 nests distributed in 14 sites) and (iv) the alate sex-ratio.Our results show that (i) neotenic females develop from the third or fourth nymphal instar; (ii) the majority of neotenic females (82%) are parthenogenetically-produced while only 2% of female alates are so; (iii) nests are differentiated within sites, indicating that the foundation of new nests mainly occurs by nuptial flights; (iv) numerical sex-ratio of alate-destined sexuals is balanced (SRN=0.509, IC95%=0.497-0.522) while investment sex-ratio is slightly female-biased (SRE=0.529, IC95%=0.517-0.542). Altogether, our results demonstrate AQS and its implications in C. tuberosus, and reveal particularities compared to other species in which AQS has been demonstrated: neotenic-headed nests are less frequent than primary-headed ones and neotenic females never become physogastric. AQS is found in various ecological contexts and seems phylogenetically more widespread than previously thought. This strategy shows some evolutionary advantages but these seem to differ depending on species.
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O estudo teve como objetivo descrever a biologia reprodutiva e a dieta de populações de Thamnodynastes hypoconia em ambientes úmidos subtemperados do extremo sul brasileiro. Para avaliação da reprodução foram feitas análises macroscópicas das gônadas. Para avaliação da ecologia alimentar foram empregadas análises de conteúdo estomacal e de isótopos estáveis (δ13C e δ15N). Os machos apresentaram maior comprimento rostro-cloacal que as fêmeas e atingiram a maturidade sexual com menor tamanho corporal. O ciclo reprodutivo das fêmeas foi sazonal, com vitelogênese secundária ocorrendo entre o inverno e a primavera. Os machos apresentaram ciclo contínuo. Aparentemente a cópula ocorre entre o final da primavera e o início do verão, quando foram detectados embriões nas fêmeas e a parturição ocorreu no verão. Não houve relação entre o tamanho da ninhada e o tamanho da fêmea, e a frequência reprodutiva de 40% foi considerada relativamente baixa. Todavia, por ser uma espécie dominante em banhados subtemperados do extremo sul do Brasil sua estratégia reprodutiva parece ser eficiente. Dessa forma, o ciclo contínuo dos machos, bem como a viviparidade possam potencializar o deslocamento do pico reprodutivo da população de modo a ajustar-se de acordo com os picos de temperatura do ambiente. A análise de conteúdo estomacal mostrou uma dieta predominantemente anurófaga, exceto por um único lagarto. Hylidae foi a família mais representativa, com predomínio de Hypsiboas pulchellus, seguida de Leptodactylidae, onde Leptodactylus latrans teve maior importância. As análises de isótopos estáveis corroboraram a importância dessas espécies na alimentação da serpente. Apesar de ser uma serpente terrestre, T. hypoconia apresentou assinatura isotópica mais próxima das fontes primárias oriundas do ambiente aquático, o que indica a importância das áreas alagáveis para a subsistência de organismos terrestres de habitats adjacentes.
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Coastal lagoons are semi-isolated ecosystems exposed to wide fluctuations of environmental conditions and showing habitat fragmentation. These features may play an important role in separating species into different populations, even at small spatial scales. In this study, we evaluate the concordance between mitochondrial (previous published data) and nuclear data analyzing the genetic variability of Pomatoschistus marmoratus in five localities, inside and outside the Mar Menor coastal lagoon (SE Spain) using eight microsatellites. High genetic diversity and similar levels of allele richness were observed across all loci and localities, although significant genic and genotypic differentiation was found between populations inside and outside the lagoon. In contrast to the FST values obtained from previous mitochondrial DNA analyses (control region), the microsatellite data exhibited significant differentiation among samples inside the Mar Menor and between lagoonal and marine samples. This pattern was corroborated using Cavalli-Sforza genetic distances. The habitat fragmentation inside the coastal lagoon and among lagoon and marine localities could be acting as a barrier to gene flow and contributing to the observed genetic structure. Our results from generalized additive models point a significant link between extreme lagoonal environmental conditions (mainly maximum salinity) and P. marmoratus genetic composition. Thereby, these environmental features could be also acting on genetic structure of coastal lagoon populations of P. marmoratus favoring their genetic divergence. The mating strategy of P. marmoratus could be also influencing our results obtained from mitochondrial and nuclear DNA. Therefore, a special consideration must be done in the selection of the DNA markers depending on the reproductive strategy of the species.
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Sexual reproduction is the main reproductive strategy of the overwhelming majority of eukaryotes. This suggests that the last eukaryotic common ancestor was able to reproduce sexually. Sexual reproduction reflects the ability to perform meiosis, and ultimately generating gametes, which are cells that carry recombined half sets of the parental genome and are able to fertilize. These functions have been allocated to a highly specialized cell lineage: the germline. Given its significant evolutionary conservation, it is to be expected that the germline programme shares common molecular bases across extremely divergent eukaryotic species. In the present review, we aim to identify the unifying principles of male germline establishment and development by comparing two very disparate kingdoms: plants and animals. We argue that male meiosis defines two temporally regulated gene expression programmes: the first is required for meiotic commitment, and the second is required for the acquisition of fertilizing ability. Small RNA pathways are a further key communality, ultimately ensuring the epigenetic stability of the information conveyed by the male germline.
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Pagurus exilis (Benedict, 1892) is an endemic South Atlantic hermit crab with a distribution ranging from Rio de Janeiro State, Brazil, to Buenos Aires Province, Argentina. The present study analyzed the reproduction of two populations at the extremes of this geographical distribution, and compared their reproductive period, fecundity, and changes in egg size and egg volume during the incubation period in order to assess the variability over this latitudinal range. Hermit crabs were collected monthly over a 2-year period. In total, 108 females were analyzed for Brazil (44 non-ovigerous and 64 ovigerous), and 141 for Argentina (87 non-ovigerous and 54 ovigerous). Reproduction in Brazil occurs year-round, with peaks in the fall and winter seasons; in Argentina reproduction occurs only in spring and summer. The Brazilian ovigerous females were significantly larger than the Argentina ones (Brazil: SL = 5.33 +/- 1.45 mm; Argentina: SL = 4.15 +/- 0.52 mm; P < 0.001). The fecundity was 1447 +/- 831 eggs (317 to 2885) in Brazil and 987 +/- 711 eggs (114 to 2665) in Argentina, with a trend towards higher fecundity in Brazil. Eggs in the Argentina population were larger than those in Brazil for all the three stages investigated, and no changes in egg volume were found during egg development for both populations. The reproductive traits of the two populations showed some important differences, which may reflect adaptations to local environmental conditions, demonstrating a high plasticity of reproductive features of the species in Brazilian and Argentine waters. The strategy adopted by the Argentina population involves a lower production of larger eggs compared to the population in Brazil; this lower production is associated with reproduction in cold-water regions.
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The genus Cyrtopodium comprises about 42 species distributed from southern Florida to northern Argentina. Cyrtopodium polyphyllum occurs on rocks or in sandy soils, in restinga vegetation along the Brazilian coast. It flowers during the wet season and its inflorescences produce a high number of resupinate yellow flowers. Cyrtopodium polyphyllum offers no rewards to its pollinators, but mimics the yellow, reward-producing flowers of nearby growing Stigmaphyllon arenicola (oil) and Crotalaria vitellina (nectar) individuals. Several species of bee visit flowers of C. polyphyllum, but only two species of Centris (Centris tarsata and Centris labrosa) act as pollinators. Visits to flowers of C. polyphyllum were scarce and, as a consequence, low-fruit set was recorded under natural conditions. Such low-fruit production contrasts with the number of fruits each plant bears after manual pollination, suggesting deficient pollen transfer among plants. C. polyphyllum is self-compatible and has a high-fruit set in both manual self- and cross-pollinated flowers. Furthermore, fruits (2%) are formed by self-pollination assisted by rain. This facultative self-pollination mechanism is an important strategy to provide reproductive assurance to C. polyphyllum as rainfall restricts the foraging activity of its pollinating bees. Fruits derived from treatments and under natural conditions had a similar high rate of potentially viable seed. Moreover, these seeds had a low polyembryony rate, which did not exceed 5%. C. polyphyllum acts by deceit involving optical signals and exploits other yellow-flowered species within its habitat by attracting their pollinators. The low capsule production under natural conditions was expected, but its reproductive success is assured through self-pollination by rain and high seed viability.
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Successful surgical treatment of deep bowel endometriosis depends on obtaining detailed information about the lesions, prior to the procedure. The objective of this study was to determine the capability of transvaginal ultrasonography with bowel preparation (TVUS-BP) to predict the presence of one or more rectosigmoid nodules and the deepest bowel layer affected by the disease. A prospective study of 194 patients with clinical and TVUS-BP suspected deep endometriosis submitted to videolaparoscopy. Image data were compared with surgical and histological results. With respect to bowel nodule detection and presence of at least two rectosigmoid lesions, TVUS-BP had a sensitivity of 97 and 81%, specificity 100 and 99%, positive predictive value (PPV) 100 and 93% and negative predictive value (NPV) 98 and 96%, respectively. Regarding diagnosis of infiltration of the submucosal/mucosal layer, TVUS-BP had a sensitivity of 83%, specificity 94%, PPV 77%, NPV 96%. These findings show that TVUS-BP is an adequate exam for evaluating the presence of one or more rectosigmoid nodules and the deepest layer affected in deep infiltrating bowel endometriosis, confirming the importance of this technique for defining the most appropriate surgical strategy to be implemented.
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The relationships between reproductive condition, level of reproductive investment and adrenocortical modulation to capture stress in marine turtles form the basis of this study. When subjected to either capture or ecological stressors, nesting marine turtles have demonstrated adrenocortical responses that are both small in magnitude, and slow in responsiveness. These observations were further investigated to determine whether this minimal stress response was a physiological strategy to maximize reproductive investment in adult green Chelonia mydas and hawksbill Eretmochelys imbricata turtles. Female green and hawksbill turtles exhibited a decrease in adrenocortical responsiveness with progressive reproductive condition. Breeding turtles exhibited most suppression of their adrenocortical response to capture compared to both non-breeding and pre-breeding female counterparts. Nesting green turtles maintained a suppressed adrenocortical response to capture throughout the nesting season despite decreased reproductive investment. In contrast, male green and hawksbill turtles were less able to modulate their corticosterone (B) response to acute capture stress. During breeding, male turtles possessed significantly greater adrenocortical responses to capture than females. These results could indicate that the large reproductive investment necessary for female marine turtle reproduction might underlie the marked decrease in adrenocortical responsiveness. This hormonal mechanism could function as one strategy by which female marine turtles maximize their current reproductive event, even though under certain situations this mechanism could entail costs to female survival.
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The proliferation of Aedes aegypti, a species of mosquito that is the vector of the dengue pathogen, is being augmented by the population's lack of care in allowing the formation of larval habitats. One form of controlling dengue is the distribution of information on the mosquito to improve awareness and to provide the means necessary for the elimination of its reproductive habitats. To evaluate a teaching method concerning the vector and dengue, students from the 5th and 6th years of primary education were compared before and after didactic intervention with a group of control students. The students who received intervention were more successful in identifying the stages of the cycle, biological and morphological characteristics of the adult insect and the importance of the mosquito in health issues. The didactic intervention was successful in developing knowledge leading to increased awareness of the importance of preventative measures that should be taken against the vector and the disease.
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A Socioecological Field Study.This monograph reports on a 26 month socioecological study of black spider monkeys (Ateles paniscus paniscus)in the Raleigh-vallen — Voltzberg Nature Reserve, Surinam. It recognizes the fundamental importance of food to the behavior and the regulation of population density fox this primate. It clarifies the complex temporal and spatial effects of tropical rain forest food sources on the behavior of a group of spider monkeys, concentrating on food category, food plant identity and phenology, and quantity, density and dispersion of the most important food sources. In addition, the present study describes habitat choice, optimal feeding strategy and sexual behavior of the spider monkey, and discusses implications of diet for social behavior. This study is also fundamental to conservation. Specialized in eating mature fruits, the spider monkey is a very important dispersal agent for many trees and lianes, particularly canopy species. However, the spider monkey is probably the most vulnerable monkey species in Surinam and it is disappearing rapidly throughout the remainder of its range. Unfortunately, it is large and noisy and can be easily tracked and hunted. It is largely restricted to undisturbed high forest, and consequently habitat destruction has more effect on it than on most other species. Together with its slow reproductive rate (a female gives birth only once every four or five years), this means that the species is poorly adapted to recover from exploitation. In order to implement proper measures for conservation, data on forest type preferences, diet and social behavior of the species, or on closely related species, in undisturbed areas, such as the one described in this monograph, are essential tools for assessing the potential of proposed protected areas.