914 resultados para alternative reproductive strategies
Resumo:
During the last years tropical forest has been a target of intense study especially due to its recent big scale destruction. Although a lot still needs to be explored, we start realizing how negative can the impact of our actions be for the ecosystem. Subsequently, the living community have been developing strategies to overcome this problem avoiding bottlenecks or even extinctions. Cooperative breeding (CB) has been recently pointed out as one of those strategies. CB is a breeding system where more than two individuals raise one brood. In most of the cases, extra individuals are offspring that delay their dispersal and independent breeding what allows them to help their parents raising their siblings in the subsequent breeding season. Such behavior is believed to be due, per example, to the lack of mates or breeding territories (ecological constraints hypothesis), a consequence of habitat fragmentation and/or disturbance. From this point, CB is easily promoted by a higher reproductive success of group vs pairs or single individuals. Accordingly, during this thesis I explore the early post-fledging survival of a cooperative breeding passerine, namely the impact of individual/habitat quality in its survival probability during the dependence period of the chicks. Our study species is the Cabanis’s greenbul (Phyllastrephus cabanisi), a medium-sized, brownish passerine, classified within the Pycnonotidae family. It is found over part of Central Africa in countries such as Angola, Democratic Republic of the Congo, Mozambique and Kenya, inhabiting primary and secondary forests, as well as woodland of various types up to 2700m of altitude. Previous studies have concluded that PC is a facultative cooperative breeder. This study was conducted in Taita Hills (TH) at the Eastern Arc Mountains (EAM), a chain of mountains running from Southeast Kenya to the South of Tanzania. TH comprises an area of 430 ha and has been suffering intense deforestation reflecting 98% forest reduction over the last 200 years. Nowadays its forest is divided in fragments and our study was based in 5of those fragments. We access the post-fledging survival through radio-telemetry. The juvenile survey was done through the breeding females in which transmitters were placed with a leg-loop technique. Ptilochronology is consider to be the study of feather growth bars and has been used to study the nutritional state of a bird. This technique considers that the feather growth rate is positively proportional to the individual capability of ingesting food and to the food availability. This technique is therefore used to infer for individual/habitat quality. Survival was lowest during the first 5 days post-fledging representing 53.3%. During the next 15 days, risk of predation decreased with only 14.3% more deceased individuals. This represents a total of only 33% survived individuals in the end of the 50 days. Our results showed yet a significant positive relationship between flock size and post-fledging survival as well as between ptilochronology values and post-fledgling survival. In practice, these imply that on this population, as bigger the flock, as greater the post fledging survival and that good habitat quality or good BF quality, will lead to a higher juvenile survival rate. We believe that CB is therefore an adaptive behaviour to the lack of mates/breeding territory originated from the mass forest destruction and disturbance. Such results confirms the critical importance of habitat quality in the post-fledging survival and, for the first time, demonstrates how flock size influences the living probability of the juveniles and therefore how it impacts the (local) population dynamics of this species. In my opinion, future research should be focus in disentangle individual and habitat quality from each other and verify which relationship exist between them. Such study will allow us to understand which factor has a stronger influence in the post-fledging survival and therefore redirect our studies in that direction. In order to confirm the negative impact of human disturbance and forest fragmentation, it would be of major relevance to compare the reproductive strategies and reproductive success of populations living in intact forests and disturbed patches.
Resumo:
Butterflies are insects known, in a variety of environments and for easy visual identification. The adult form may be frequently found in flowers looking for nectar. However, for many species of Heliconius (Lepidoptera, Nymphalidae) to visit the flower also represents the collecting of pollen, an important source of protein for adults. The protein obtained from the pollen allows the maintenance of physiological processes that increase the performance of the individual, promoting greater longevity and egg production. For males, proteins can also be part in your investment in reproductive success and fitness of offspring through a nutritional contribution that is transferred to the female in the act of mating as a nuptial present. It is known that this protein contains essential to the performance of the female oviposition, however the proportion of content and specific importance to the monogamous and polygamous species is not known yet. Whereas the species studied in this work have different patterns of mating in the strategy was to verify a significant difference in the quality of the spermatophore, and H. erato and H. melpomene, on the amount of protein present in this structure, indicating a difference in investment between the male reproductive strategies
Resumo:
This thesis is focused on improving the calibration accuracy of sub-millimeter astronomical observations. The wavelength range covered by observational radio astronomy has been extended to sub-millimeter and far infrared with the advancement of receiver technology in recent years. Sub-millimeter observations carried out with airborne and ground-based telescopes typically suffer from 10% to 90% attenuation of the astronomical source signals by the terrestrial atmosphere. The amount of attenuation can be derived from the measured brightness of the atmospheric emission. In order to do this, the knowledge of the atmospheric temperature and chemical composition, as well as the frequency-dependent optical depth at each place along the line of sight is required. The altitude-dependent air temperature and composition are estimated using a parametrized static atmospheric model, which is described in Chapter 2, because direct measurements are technically and financially infeasible. The frequency dependent optical depth of the atmosphere is computed with a radiative transfer model based on the theories of quantum mechanics and, in addition, some empirical formulae. The choice, application, and improvement of third party radiative transfer models are discussed in Chapter 3. The application of the calibration procedure, which is described in Chapter 4, to the astronomical data observed with the SubMillimeter Array Receiver for Two Frequencies (SMART), and the German REceiver for Astronomy at Terahertz Frequencies (GREAT), is presented in Chapters 5 and 6. The brightnesses of atmospheric emission were fitted consistently to the simultaneous multi-band observation data from GREAT at 1.2 ∼ 1.4 and 1.8 ∼ 1.9 THz with a single set of parameters of the static atmospheric model. On the other hand, the cause of the inconsistency between the model parameters fitted from the 490 and 810 GHz data of SMART is found to be the lack of calibration of the effective cold load temperature. Besides the correctness of atmospheric modeling, the stability of the receiver is also important to achieving optimal calibration accuracy. The stabilities of SMART and GREAT are analyzed with a special calibration procedure, namely the “load calibration". The effects of the drift and fluctuation of the receiver gain and noise temperature on calibration accuracy are discussed in Chapters 5 and 6. Alternative observing strategies are proposed to combat receiver instability. The methods and conclusions presented in this thesis are applicable to the atmospheric calibration of sub-millimeter astronomical observations up to at least 4.7 THz (the H channel frequency of GREAT) for observations carried out from ∼ 4 to 14 km altitude. The procedures for receiver gain calibration and stability test are applicable to other instruments using the same calibration approach as that for SMART and GREAT. The structure of the high performance, modular, and extensible calibration program used and further developed for this thesis work is presented in the Appendix C.
Resumo:
As a result of rapid urbanisation, population growth, changes in lifestyle, pollution and the impacts of climate change, water provision has become a critical challenge for planners and policy-makers. In the wake of increasingly difficult water provision and drought, the notion that freshwater is a finite and vulnerable resource is increasingly being realised. Many city administrations around the world are struggling to provide water security for their residents to maintain lifestyle and economic growth. This chapter reviews the global challenge of providing freshwater to sustain lifestyles and economic growth, and the contributing challenges of climate change, urbanisation, population growth and problems in rainfall distribution. The chapter proceeds to evaluate major alternatives to current water sources such as conservation, recycling and reclamation, and desalination. Integrated water resource management is briefly looked at to explore its role in complementing water provision. A comparative study on alternative resources is undertaken to evaluate their strengths, weaknesses, opportunities and constraints, and the results are discussed.
Resumo:
Whilst the compression ignition (CI) engine exhibits many design advantages relative to its spark ignition engine counterpart; such as: high thermal efficiency, fuel economy and low carbon monoxide and hydrocarbon emissions, the issue of Diesel Particulate Matter (DPM) emissions continues to be an unresolved problem for the CI engine. Primarily, this thesis investigates a range of DPM mitigation strategies such as alternative fuels, injection technologies and combustion strategies conducted with a view to determine their impact on the physico-chemical properties of DPM emissions, and consequently to shed light on their likely human health impacts. Regulated gaseous emissions, Nitric oxide (NO), Carbon monoxide (CO), and Hydrocarbons (HCs), were measured in all experimental campaigns, although the major focus in this research program was on particulate emissions...
Resumo:
As a result of rapid urbanisation, population growth, changes in lifestyle, pollution and the impacts of climate change, water provision has become a critical challenge for planners and policy-makers. In the wake of increasingly difficult water provision and drought, the notion that freshwater is a finite and vulnerable resource is increasingly being realised. Many city administrations around the world are struggling to provide water security for their residents to maintain lifestyle and economic growth. This chapter reviews the global challenge of providing freshwater to sustain lifestyles and economic growth, and the contributing challenges of climate change, urbanisation, population growth and problems in rainfall distribution. The chapter proceeds to evaluate major alternatives to current water sources such as conservation, recycling and reclamation, and desalination. Integrated water resource management is briefly looked at to explore its role in complementing water provision. A comparative study on alternative resources is undertaken to evaluate their strengths, weaknesses, opportunities and constraints, and the results are discussed.
Resumo:
This research is part of a major project with a stimulus that rose from the need to manage a large number of ageing bridges in low traffic volume roads (LTVR) in Australia. The project investigated, designed and consequently constructed, involved replacing an ageing super-structure of a 10m span bridge with a disused Flat-bed Rail Wagon (FRW). This research, therefore, is developed on the premises that the FRW can be adopted as the main structural system for the bridges in LTVR network. The main focus of this research is to present two alternate deck wearing systems (DWS) as part of the design of the FRW as road bridge deck conforming to AS5100 (2004). The bare FRW structural components were first examined for their adequacy (ultimate and serviceability) in resisting the critical loads specified in AS5100(2004). Two options of DWSs were evaluated and their effects on the FRW examined. The first option involved usage of timber DWS; the idea of this option was to use all the primary and secondary members of the FRW in load sharing and to provide additional members where weaknesses in the original members arose. The second option involved usage of reinforced concrete DWS with only the primary members of the FRW sharing the AS5100 (2004) loading. This option inherently minimised the risk associated with any uncertainty of the secondary members to their structural adequacy. This thesis reports the design phases of both options with conclusions of the selection of the ideal option for better structural performance, ease of construction and cost. The comparison carried out here focuses on the distribution of the traffic load by the FRW as a superstructure. Advantages and disadvantages highlighting cost comparisons and ease of constructability of the two systems are also included.
Resumo:
The area of intensively managed forests, in which required conditions for several liverwort species are seldom found, has expanded over the forest landscape during the last century. Liverworts are very sensitive to habitat changes, because they demand continuously moist microclimate. Consequently, about third of the forest liverworts have been classified as threatened or near threatened in Finland. The general objective of this thesis is to increase knowledge of the reproductive and dispersal strategies of the substrate-specific forest bryophytes. A further aim was to develop recommendations for conservation measures for species inhabiting unstable and stable habitats in forest landscape. Both population ecological and genetic methods have been applied in the research. Anastrophyllum hellerianum inhabits spatially and temporally limited substrate patches, decaying logs, which can be considered as unstable habitats. The results show that asexual reproduction by gemmae is the dominant mode of reproduction, whereas sexual reproduction is considerably infrequent. Unlike previously assumed, not only spores but also the asexual propagules may contribute to long-distance dispersal. The combination of occasional spore production and practically continuous, massive gemma production facilitates dispersal both on a local scale and over long distances, and it compensates for the great propagule losses that take place preceding successful establishment at suitable sites. However, establishment probability of spores may be restricted because of environmental and biological limitations linked to the low success of sexual reproduction. Long-lasting dry seasons are likely to result in a low success of sexual reproduction and decreased release rate of gemmae from the shoots, and consequent fluctuations in population sizes. In the long term, the substratum limitation is likely to restrict population sizes and cause local extinctions, especially in small-sized remnant populations. Contrastingly, larger forest fragments with more natural disturbance dynamics, to which the species is adapted, are pivotal to species survival. Trichocolea tomentella occupies stable spring and mesic habitats in woodland. The relatively small populations are increasingly fragmented with a high risk for extinction for extrinsic reasons. The results show that T. tomentella mainly invests in population persistence by effective clonal growth via forming independent ramets and in competitive ability, and considerably less in sexuality and dispersal potential. The populations possess relatively high levels of genetic diversity regardless of population size and of degree of isolation. Thus, the small-sized populations inhabiting stable habitats should not be neglected when establishing conservation strategies for the species and when considering the habitat protection of small spring sites. Restricted dispersal capacity, also on a relatively small spatial scale, is likely to prevent successful (re-)colonization in the potential habitat patches of recovering forest landscapes. By contrast, random short-range dispersal of detached vegetative fragments within populations at suitable habitat seems to be frequent. Thus, the restoration actions of spring and streamside habitats close to the populations of T. tomentella may contribute to population expansion. That, in turn, decreases the harmful effects of environmental stochasticity.
Resumo:
Two regiospecific modifications have been developed in the synthesis of valeranone. The first one is based on the regiospecific protection of a diol and the second is based on the Wittig reaction of a hemiacetal.
Resumo:
This paper reviews the scientific data on the ecosystem services provided by shoreline habitats, the evidence for adverse impacts from bulkheading on those habitats and services, and describes alternative approaches to shoreline stabilization, which minimize adverse impacts to the shoreline ecosystem. Alternative shoreline stabilization structures that incorporate natural habitats, also known as living shorelines, have been popularized by environmental groups and state regulatory agencies in the mid-Atlantic. Recent data on living shoreline projects in North Carolina that include a stone sill demonstrate that the sills increase sedimentation rates, that after 3 years marshes behind the sills have slightly reduced biomass, and that the living shoreline projects exhibit similar rates of fishery utilization as nearby natural fringing marshes. Although the current emphasis on shoreline armoring in Puget Sound is on steeper, higher-energy shorelines, armoring of lower-energy shorelines may become an issue in the future with expansion of residential development and projected rates of sea level rise. The implementation of regulatory policy on estuarine shoreline stabilization in North Carolina and elsewhere is presented. The regulatory and public education issues experienced in North Carolina, which have made changes in estuarine shoreline stabilization policy difficult, may inform efforts to adopt a sustainable shoreline armoring strategy in Puget Sound. A necessary foundation for regulatory change in shoreline armoring policy, and public support for that change, is rigorous scientific assessment of the variety of services that natural shoreline habitats provide both to the ecosystem and to coastal communities, and evidence demonstrating that shoreline armoring can adversely impact the provision of those services.
Resumo:
Drug calculations are an essential skill for nurses. The clinical skill of performing a drug calculation has come under recent scrutiny,resulting in the development of essential skills clusters inwhich pre-registration nurses must be competent before qualifying (Nursing and Midwifery Council 2007). The focuson drug calculation skills places renewed emphasis on how these skills are taught in higher education institutions and how they are learned by students theoretically and in clinical practice.
Resumo:
Reproductive performance in the high-yielding dairy cow has severely decreased in the last 40 yr. The aim of this study was to compare the effectiveness of 4 nutritional strategies in improving the reproductive performance of high-yielding dairy cows. It was hypothesized that offering cows a high-starch ration in early lactation would enhance the onset of luteal activity, and that decreasing the severity of negative energy balance in the early postcalving period would improve reproductive parameters. Nutritional regimens aimed at improving fertility were applied to 96 Holstein-Friesian dairy animals. Upon calving, animals were allocated in a balanced manner to one of 4 dietary treatments. Primiparous animals were balanced according to live weight, body condition score and calving date. Multiparous animals were balanced according to parity, previous lactation milk yield, liveweight, body condition score and calving date. Treatment 1 was based on an industry best practice diet (control) to contain 170 g of crude protein/kg of dry matter. Treatment 2 was an individual cow feeding strategy, whereby the energy balance (EB) of individual animals was managed so as to achieve a predetermined target daily EB profile (+/- 10 MJ/d). Treatment 3 was a high-starch/high-fat combination treatment, whereby an insulinogenic (high-starch) diet was offered in early lactation to encourage cyclicity and followed by a lipogenic (low-starch, high-fat) diet to promote embryo development. Treatment 4 was a low-protein diet, containing 140 g of crude protein/kg of dry matter, supplemented with protected methionine at an inclusion level of 40 g per animal per day. The nutritional strategies implemented in this study had no statistically significant effects on cow fertility measures, which included the onset of luteal activity, conception rate, in-calf rate, and the incidence of atypical cycles. The individual cow feeding strategy improved EB in early lactation but had no benefit on conception rate to first insemination. However, conception rate to second insemination, 100-d pregnancy rate (from the commencement of breeding), and overall pregnancy rate tended to be higher in this group. The high-starch/high-fat treatment tended to decrease the proportion of delayed ovulations and increase the proportion of animals cycling by d 50 postcalving. Animals that failed to conceive to first insemination had a significantly longer luteal phase in the first cycle postpartum and a longer inter-ovulatory interval in the second cycle postpartum. With regards to estrous behavior, results indicate that as the size of the sexually active group increased, the intensity of estrus and the expression of mounting or attempting to mount another cow also increased. Furthermore, cows that became pregnant displayed more intense estrous behavior than cows that failed to become pregnant.