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91.
Nikos Nanos Kajsa Larson Matias Millerón Sara Sjöstedt-de Luna 《Ecological modelling》2010,221(20):2415-678
The estimation of the dispersal kernel for the seedling and sapling stages of the recruitment process was made possible through the application of inverse modeling to dispersal data. This method uses the spatial coordinates of adult trees and the counts of seedlings (or saplings) in small quadrats to estimate the dispersal kernel. The unknown number of recruits produced by an adult tree (the fecundity) is estimated - simultaneously with the dispersal kernel - via an allometric linear model relating the unknown quantity with a (easily) measured characteristic of the adult tree (usually the basal area). However, the allometric relation between tree size and reproductive success in the sapling (or seedling) stage may not be strong enough when numerous, well-documented, post-dispersal processes (such as safe-site limitation for recruitment) cause large post-dispersal seedling mortality, which is usually unrelated to the size of the tree that dispersed them. In this paper we hypothesize that when tree size and reproductive success in the seedling/sapling stage are not well correlated then the use of allometry in inverse modeling is counter-productive and may lead to poor model fits. For these special cases we suggest using a new model for effective dispersal that we term the unrestricted fecundity (UF) model that, contrary to allometric models, makes no assumptions on the fecundities; instead they are allowed to vary freely from one tree to another and even to be zero for trees that are reproductively inactive. Based on this model, we examine the hypothesis that when tree size and reproductive success are weakly correlated and the fecundities are estimated independently of tree size the goodness-of-fit and the ecological meaning of dispersal models (in the seedling or sapling stage) may be enhanced. Parameters of the UF model are estimated through the EM algorithm and their standard errors are approximated via the observed information matrix. We fit the UF model to a dataset from an expanding European beech population of central Spain as well as to a set of simulated dispersal data were the correlation between reproductive success and tree size was moderate. In comparisons with a simple allometric model, the UF model fitted the data better and the parameter estimates were less biased. We suggest using this new approach for modeling dispersal in the seedling and sapling stages when tree size (or other adult-specific covariates) is not deemed to be in strong relation to the reproductive success of adults. Models that use covariates for modeling the fecundity of adults should be preferred when reproductive success and tree size guard a strong relationship. 相似文献
92.
Matthew A. Etterson Susan N. Ellis-FelegeDavid Evers Gilles GauthierJoseph A. Grzybowski Brady J. MattssonLaura R. Nagy Brian J. OlsenCraig M. Pease Max Post van der BurgAaron Potvien 《Ecological modelling》2011,222(14):2178-2190
Fecundity is fundamental to the fitness, population dynamics, conservation, and management of birds. For all the efforts made to measure fecundity or its surrogates over the past century of avian research, it is still mismeasured, misrepresented, and misunderstood. Fundamentally, these problems arise because of partial observability of underlying processes such as renesting, multiple brooding, and temporary emigration. Over the last several decades, various analytical approaches have been developed to estimate fecundity from incomplete and biased data. These, include scalar arithmetic formulae, partial differential equations, individual-based simulations, and Markov chain methodology. In this paper, we: (1) identify component processes of avian reproduction; (2) review existing methods for modeling fecundity; (3) place these diverse models under a common conceptual framework; (4) describe the parameterization, validation, and limitations of such models; and (5) point out future considerations and challenges in the application of fecundity models. We hope this synthesis of existing literature will help direct researchers toward the most appropriate methods to assess avian reproductive success for answering questions in evolutionary ecology, natural history, population dynamics, reproductive toxicology, and management. 相似文献
93.
S. Balshine-Earn 《Behavioral ecology and sociobiology》1996,39(2):107-116
Operational sex ratio (OSR) theory predicts that sexual differences in potential reproductive rates (PRRs) create biases
in the OSR and thus determine the relative strength of sexual selection (competition and choice) operating on each sex. Although
this theory is well accepted, empirical studies that quantify it are still lacking. This paper presents such a study. I measured
the natural OSR of Galilee St. Peter’s fish (Sarotherodon galilaeus) in the field (Lake Kinneret) and examined the direction of mate choice in the laboratory. The OSR in Lake Kinneret was male
biased. Both a male-biased sex ratio and higher male reproductive rates (twice as fast as females) contributed to the skew
in the OSR, but the sexual differences in PRR were shown to be the main factor causing variation in the OSR. Females, the
sex with the lower PRR, were more selective for mates. The faster male reproductive rate may explain why females are more
selective for mates despite varying less in quality.
Received: 29 May 1995/Accepted after revision: 13 April 1996 相似文献
94.
Yanmin M Xin He Keyan Qi Tong Wang Yongchao Qi Lele Cui Fengbang Wang Maoyong Song 《环境科学学报(英文版)》2019,31(3):210-217
Recent research indicates that the human infertility rate is increasing. Although various reasons have been hypothesized for the growing infertility rate, environmental contaminants are potentially important causal agents associated with this change. Chemical contaminants are widespread throughout our environment and human exposure is virtually unavoidable. The overall contribution of environmental exposure to infertility is unknown, but studies involving occupational exposure, together with results from animal experiments, suggest that environmental contaminants may adversely affect fertility. We reviewed the adverse effects of environmental exposure on fertility and related reproductive outcomes. Environmental contaminants covered in this review include heavy metals, organic solvents, pesticides and endocrine disrupting chemicals. It is hoped that this review will highlight the need for further research in this area. 相似文献
95.
Jason?S.?GilchristEmail author Emily?Otali Francis?Mwanguhya 《Behavioral ecology and sociobiology》2004,57(2):119-131
Fecundity is an important component of fitness. In cooperatively breeding species, studies aimed at understanding the factors that affect fecundity have largely been restricted to species that exhibit high reproductive skew, where reproduction is monopolised by a few individuals. In such species, dominant suppression and inbreeding avoidance are the principal explanations for low fecundity in subordinate females. In this paper, we evaluate the relative effects of individual, social, and environmental factors on female fecundity in a low skew cooperative breeding mammal: the banded mongoose (Mungos mungo). Most females (80%) conceived in each breeding event, and most pregnant females (93%) carried their litter to term. The principal determinants of a females fecundity were intrinsic qualities, particularly age and body size. However, there was no evidence of dominant suppression of subordinate reproduction or inbreeding avoidance. Similarly, there was little indication that social or environmental factors influence fecundity. We suggest that in the banded mongoose, the apparent lack of costs to inbreeding, and the absence of dominant female suppression of reproduction in other females result in low reproductive skew. Indeed, in banded mongooses, like lions (Felis leo), multiple breeding may be a consequence of benefits to rearing young communally.Communicated by F. Trillmich 相似文献
96.
ABSTRACT: The Pearson type 3 (P3) and log Pearson type 3 (LP3) distributions are very frequently used in flood frequency analysis. Existing methods for constructing confidence intervals for quantiles (Xp) of these two distributions are very crude. Most of these methods are based on the idea of adjusting confidence intervals for quantiles Yp of the normal distribution to obtain approximate confidence inervals for quantiles Xp of the P3/LP3 distribution. Since there is no theoretical reason why this “base” distribution, Y, should be taken to be normal, we search in the present study for the best possible base distribution for producing confidence intervals for P3/LP3 quantiles. We consider a group of base distributions such as the normal, log normal, Weibull, Gumbel, and exponential. We first assume that the skew coefficient, γ of X, to be known, and develop a method for adjusting confidence intervals for Yp to produce approximate confidence intervals for Xp. We then compare this method (Method A) with another method (Method B) introduced by Stedinger. Simulation shows that the performance of each of these two methods depends on the base distribution Y that is being used, but as a whole, the normal distribution appears to be the best-fit distribution for producing confidence intervals for P3/LP3 quantiles when γ is assumed to be known. We then extend our method (Method A) to the more important case of unknown coefficient of skewness. It is shown that by taking Y to be Weibull, fairly accurate confidence intervals for P3/LP3 quantiles can be obtained for quite a wide range of sample sizes and coefficients of skewness commonly found in hydrology. The case of the P3 distribution with negative skewness needs further research. 相似文献
97.
阿特拉津可对雄性脊椎动物生殖系统造成不良影响,但其中分子机制尚不明了。本文作者将非洲爪蟾(Xenopus laevis)暴露于100 ppb的阿特拉津120 d,利用同位素标记相对和绝对定量(iTRAQ)技术检测了非洲爪蟾睾丸和卵巢中蛋白图谱的变化,结果显示100 ppb阿特拉津可影响爪蟾发育,延迟和阻碍雄性细精管的形成。组学分析显示,睾丸中143种以及卵巢中121种蛋白均表达异常,这些蛋白与细胞凋亡、细胞间紧密连接以及代谢途径相关。
精选自Xiuping Chen, Jiamei Wang, Haojun Zhu, Jiatong Ding and Yufa Peng. Proteomics analysis of Xenopus laevis gonad tissue following chronic exposure to atrazine. Environmental Toxicology and Chemistry: Volume 34, Issue 8, pages 1744–1750, August 2015. DOI: 10.1002/etc.2980
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.2980/full 相似文献
98.
Carl D. Soulsbury Philip J. Baker Graziella Iossa Stephen Harris 《Behavioral ecology and sociobiology》2008,62(8):1289-1298
The costs of dispersal are an important factor promoting natal philopatry, thereby encouraging the formation of social groups.
The red fox, Vulpes vulpes, exhibits a highly flexible social system and one that is thought to represent a possible stage in the evolution of more
complex patterns of group-living. Although the potential benefits accruing to philopatric offspring have previously been studied
in this species, the potential costs of dispersal have received less attention. We contrasted survival rates, nutritional
status, injuries and reproductive output of dispersing and non-dispersing male and female foxes in an urban population to
assess the relative costs of dispersal versus natal philopatry. Mortality rates were not significantly higher for dispersing
foxes, either in the short- or long-term. There was no evidence of increased nutritional stress in dispersing individuals.
Dispersing individuals did, however, exhibit greater levels of wounding, although this did not appear to affect survival.
Dispersing females were more likely to miss a breeding opportunity early in their reproductive lifespan. In contrast, both
dispersing and non-dispersing males were unlikely to breed in their first year. We conclude that the major fitness component
in females affected by dispersing is age at first reproduction. 相似文献
99.
BriAnne Addison Alexander S. Kitaysky J. Mark Hipfner 《Behavioral ecology and sociobiology》2008,63(1):135-141
Sex allocation theory posits that mothers should preferentially invest in sons when environmental conditions are favorable
for breeding, their mates are of high quality, or they are in good body condition. We tested these three hypotheses in rhinoceros
auklets (Cerorhinca monocerata), monomorphic seabirds that lay a single-egg clutch, in 2 years that differed in environmental conditions for breeding. Results
supported the environment and mate quality hypotheses, but these effects were interactive: offspring sex was independent of
paternal traits in the poor year for breeding, while females mated to larger and more ornamented males reared more sons in
the better year. Conversely, offspring sex was unrelated to female condition, as indexed by hatching date. We propose that
good rearing conditions enable females to rear sons possessing the desirable phenotypic attributes of their mates. Results
also supported two critical assumptions of sex allocation theory: (1) dimorphism in offspring condition at independence: daughters
fledged with higher baseline levels of corticosterone than sons and (2) differential costs of rearing sons versus daughters:
mothers rearing sons when environmental conditions were poor completed parental care in poorer condition than mothers rearing
daughters in the same year and mothers rearing either sex when conditions were better. These novel results may help to explain
the disparate results of previous studies of avian sex allocation. 相似文献
100.
Tug-of-war over reproduction in a cooperatively breeding cichlid 总被引:1,自引:0,他引:1
In group-living animals, dominants may suppress subordinate reproduction directly and indirectly, thereby skewing reproduction
in their favour. In this study, we show experimentally that this ability (‘power’) is influenced by resource distribution
and the body size difference between unrelated dominants and subordinates in the cichlid Neolamprologus pulcher. Reproduction was strongly skewed towards the dominant female, due to these females producing more and larger clutches and
those clutches surviving egg eating better than those of subordinate females, but was not so when subordinates defended a
patch. If breeding shelters were provided in two patches, subordinate females were more likely to exclusively defend a patch
against the dominant female and breed, compared to when the same breeding resource was provided in one patch. Relatively large
subordinate females were more likely to defend a patch and reproduce. Females also directly interfered with each other’s reproduction
by eating the competitors’ eggs, at which dominants were more successful. Although dominant females benefited from subordinate
females due to alloparental care and an increase in egg mass, they also showed costs due to reduced growth in the presence
of subordinates. The results support the view that the dominant’s power to control subordinate reproduction determines reproductive
partitioning, in agreement with the predictions from tug-of-war models of reproductive skew. 相似文献