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111.
Simultaneous hermaphroditism with outcrossing, a previously unconfirmed sexual system in decapod crustaceans, is documented
in the shrimp Lysmata wurdemanni (Gibbes), using time-lapse video observations on mating in pairs of “female-phase” (FP) individuals. Copulations between
FPs resulted in successful spawning and development of embryos. However, female-phase hermaphrodites maintained in isolation
were unable to self-fertilize spawned eggs. All smaller individuals possessed characters typical of caridean males, including
male gonopores, appendices masculinae, ejaculatory ducts, and cincinnuli on the first pleopods. However, the gonad of these
male-phase (MP) individuals was an ovotestis with an undeveloped ovarian portion. FPs, which spawn eggs and incubate embryos,
also had male gonopores and an ovotestis terminating in ejaculatory ducts containing sperm. In FPs, male pleopod characters
were absent or reduced, and a female incubatory character, expanded pleopod flanges, showed a greater relative size. Smaller
size classes of the population were composed only of MPs while larger size classes consisted of both MPs and FPs. “Transitionals,”
individuals with MP characters but an ovotestis containing vitellogenic oocytes, were rare and overlapped completely in size
with FP and larger MP individuals. It is suggested that not all MPs transform into FP hermaphrodites. Social interactions
may mediate MP change into FP hermaphrodites in L. wurdemanni. The social system of L. wurdemanni and other Lysmata spp. may determine the exact form of the sexual system in these species.
Received: 26 October 1997 / Accepted: 21 April 1998 相似文献
112.
Three marine diatoms Lauderia annulata Cleve, Odontella sinensis (Greville) Grunow and Thalassiosira rotula Meunier were exposed to ultraviolet (UV) radiation of different wavebands under controlled laboratory conditions (0.035 vol%
CO2, 18 °C). Several changes in the patterns of pigments in these organisms were seen depending on the waveband of UV radiation
and species examined. UV-B and UV-B plus UV-A radiation led to a reduction in the overall pigment content of all three diatoms.
The uptake of 15N-ammonium was less affected by 5-h UV-A (WG 320) but significantly reduced after UV-B and UV-B plus UV-A exposure. The pattern
of free amino acid pools varied depending on the applied UV wavebands and the tested diatom. The main protein-bound amino
acids of T. rotula decreased after 5-h UV irradiance except leucine. Contents of adenosine 5′-mono-, di-, and triphosphate (AMP, ADP and ATP)
were affected differently by UV radiation; ATP values increased at the end of UV-B and UV-B plus UV-A exposure. These results
have been discussed with reference to the impact of the different UV sources and the influence on the nitrogen metabolism
in connection to pigments and supply with energy.
Received: 13 May 1997 / Accepted: 11 October 1997 相似文献
113.
Donald G. Miller III. 《Behavioral ecology and sociobiology》1998,43(2):95-103
This study investigated the consequences of communal gall induction on individual and group fitness in the aphid Tamaliacoweni. The possibilities that kin discrimination and foundress density are factors favoring communal gall occupation were examined.
Clonally produced aphid foundresses were collected to create two treatments: clonal groups and groups of less closely related
individuals. These were confined on suitable host plant tissue to compare their respective propensities towards communal behavior.
There were no significant differences in the frequencies of communal gall occupation; therefore, active kin discrimination
by T.coweni foundresses apparently does not play a role in their communal behavior, within the context of this experiment. In a second
experiment, aphid foundress density on the host plant was manipulated in three treatments and was correlated with the frequency
of communal gall occupation. Individual fitness was inversely related to the mean number of foundresses per gall. These results
suggest that communal gall occupation does not necessarily represent mutual cooperation but may instead be the outcome of
competition for limited gall sites on the host plant. However, natural selection at the clonal level may favor communal gall
occupation under the conditions of resource limitation and high within-group relatedness.
Received: 26 September 1997 / Accepted after revision: 28 March 1998 相似文献
114.
An Ecology-Based Method for Defining Priorities for Large Mammal Conservation: The Tiger as Case Study 总被引:2,自引:0,他引:2
115.
116.
PROBLEM: There is limited information about how parents view teen driving risks and intend to handle these risks during the licensing process, and how they will respond to graduated licensing provisions. METHODS: Parents in Connecticut were interviewed when their teens got their learner's permit. The survey was undertaken when the state did not have a midnight restriction or a passenger restriction. RESULTS: Generally, parents were well aware of teen driving risks, thought parents should be thoroughly involved in the licensing process, and plan to be active participants themselves. DISCUSSION: Parents were concerned about the risk of driving after midnight and already restrict that behavior. However, parents do not seem to see or understand the risks of having even one teen passenger in the vehicle. IMPACT ON INDUSTRY: The views and existing practices of parents need to be taken into account in deciding on the provisions of graduated licensing legislation and how to best ensure acceptance and compliance. 相似文献
117.
Gerhard Blickle James A. Meurs Andreas Wihler Christian Ewen Andrea Plies Susann Günther 《组织行为杂志》2013,34(8):1145-1164
Caveats concerning the ability of personality to predict job performance have been raised because of seemingly modest criterion‐related validity. The goal of the present research was to test whether narrowing the context via the type of job (i.e., jobs with complex task demands) and adding a social skill‐related moderator (i.e., political skill) would improve performance prediction. Further, along with political skill, the broad factor of personality demonstrated in prior research to have the strongest criterion validity (i.e., conscientiousness) was joined with a narrow construct closely related to openness to experience (i.e., learning approach) in a three‐way interactive prediction of supervisor‐rated task performance. With the employee–supervisor dyads among professionals, but not with the control group of non‐professional employees, task performance was predicted by the three‐way interaction, such that those high on all three received the highest performance ratings. Implications, strengths and limitations, and directions for future research are discussed. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
118.
R.Z. Liu Alistair G.L. Borthwick D.D. Lan W.H. Zeng 《Process Safety and Environmental Protection》2013,91(5):397-404
Accidental releases of pollution can have severe environmental, societal, economic, and institutional consequences. This paper considers the use of risk mapping of accidental pollution events, and zonal prevention measures for alleviating the impact on large urban areas. An Environmental Pollution Accident Risk Mapping (EPARM) model is constructed according to a mapping index system supported by quantitative sub-models dedicated to evaluating the risk arising from different sources of potential accidental pollution. The EPARM approach consists of identifying suitable indexes, assessment of environmental risk at regional and national scales based on information on previous pollution accidents and the prevailing environmental and social conditions, and use of GIS to map the overall risk. A case study of pollution accidents in Minghang District, Shanghai, China is used to demonstrate the effectiveness of the model. The paper also proposes a systemic framework for accidental environmental pollution risk prevention, and detailed countermeasures for specific risk zones. 相似文献
119.
Doug P. Armstrong Elizabeth H. Parlato Barbara Egli Wendy J. Dimond Renske Kwikkel Åsa Berggren Mhairi McCready Kevin A. Parker John G. Ewen 《Conservation biology》2021,35(3):859-869
Inbreeding depression is an important long-term threat to reintroduced populations. However, the strength of inbreeding depression is difficult to estimate in wild populations because pedigree data are inevitably incomplete and because good data are needed on survival and reproduction. Predicting future population consequences is especially difficult because this also requires projecting future inbreeding levels and their impacts on long-term population dynamics, which are subject to many uncertainties. We illustrate how such projections can be derived through Bayesian state-space modeling methods based on a 26-year data set for North Island Robins (Petroica longipes) reintroduced to Tiritiri Matangi Island in 1992. We used pedigree data to model increases in the average inbreeding level (F ) over time based on kinship of possible breeding pairs and to estimate empirically Ne/N (effective/census population size). We used multiple imputation to model the unknown components of inbreeding coefficients, which allowed us to estimate effects of inbreeding on survival for all 1458 birds in the data set while modeling density dependence and environmental stochasticity. This modeling indicated that inbreeding reduced juvenile survival (1.83 lethal equivalents [SE 0.81]) and may have reduced subsequent adult survival (0.44 lethal equivalents [0.81]) but had no apparent effect on numbers of fledglings produced. Average inbreeding level increased to 0.10 (SE 0.001) as the population grew from 33 (0.3) to 160 (6) individuals over the 25 years, giving a ratio of 0.56 (0.01). Based on a model that also incorporated habitat regeneration, the population was projected to reach a maximum of 331–1144 birds (median 726) in 2130, then to begin a slow decline. Without inbreeding, the population would be expected stabilize at 887–1465 birds (median 1131). Such analysis, therefore, makes it possible to empirically derive the information needed for rational decisions about inbreeding management while accounting for multiple sources of uncertainty. 相似文献
120.
NÁRGILA G. MOURA ALEXANDER C. LEES ALEXANDRE ALEIXO JOS BARLOW SIDNEI M. DANTAS JOICE FERREIRA MARIA DE FÁTIMA C. LIMA TOBY A. GARDNER 《Conservation biology》2014,28(5):1271-1281
Local, regional, and global extinctions caused by habitat loss, degradation, and fragmentation have been widely reported for the tropics. The patterns and drivers of this loss of species are now increasingly well known in Amazonia, but there remains a significant gap in understanding of long‐term trends in species persistence and extinction in anthropogenic landscapes. Such a historical perspective is critical for understanding the status and trends of extant biodiversity as well as for identifying priorities to halt further losses. Using extensive historical data sets of specimen records and results of contemporary surveys, we searched for evidence of local extinctions of a terra firma rainforest avifauna over 200 years in a 2500 km2 eastern Amazonian region around the Brazilian city of Belém. This region has the longest history of ornithological fieldwork in the entire Amazon basin and lies in the highly threatened Belém Centre of Endemism. We also compared our historically inferred extinction events with extensive data on species occurrences in a sample of catchments in a nearby municipality (Paragominas) that encompass a gradient of past forest loss. We found evidence for the possible extinction of 47 species (14% of the regional species pool) that were unreported from 1980 to 2013 (80% last recorded between 1900 and 1980). Seventeen species appear on the International Union for Conservation of Nature Red List, and many of these are large‐bodied. The species lost from the region immediately around Belém are similar to those which are currently restricted to well‐forested catchments in Paragominas. Although we anticipate the future rediscovery or recolonization of some species inferred to be extinct by our calculations, we also expect that there are likely to be additional local extinctions, not reported here, given the ongoing loss and degradation of remaining areas of native vegetation across eastern Amazonia. Doscientos Años de Extinciones Locales de Aves en la Amazonia Oriental 相似文献