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61.
S. D. Goldsworthy D. J. Boness R. C. Fleischer 《Behavioral ecology and sociobiology》1999,45(3-4):253-267
When closely related species breed in sympatry, and where hybrids have lower fitness, reinforcement theory predicts that
selection should favour mechanisms that reduce the probability of interspecific matings. If this situation arises among species
that exhibit resource defence polygyny where males and females of different species reside in the same territories, there
may be some conflict between mate choice based on territory-holding ability (sexual selection) and mate choice for correct
species. We investigated this in a population of fur seals where three species are sympatric and where some females breed
in the territories of heterospecific males, and where interspecific matings and hybrid pups are observed. The territorial
status of males and the birthing sites of females were determined during daily observations, as were the movements of males
and females, the location of matings and mating partners. DNA extracted from skin samples was used to determine paternities
using DNA fingerprinting and the mtDNA genotype of individuals. Individuals were also classed on the basis of species-typical
phenotype. We found that extra-territory inseminations (ETIs) were significantly more prevalent (67%) when territorial males
and resident females were of different phenotype than when of similar phenotype (27%), but mtDNA genotype had no effect on
the rate of ETIs. ETIs were probably by males with the same phenotype, as pups born to these females in the following season
had the same phenotype as their mothers, suggesting they were not hybrids. These results suggest that within the resource
defence polygynous mating system of these sympatric fur seals, female mate choice is more influenced by male phenotype than
genotype. Contrary to our predictions, our study indicates that potential conflict between mate choice based on sexual selection
and species recognition is unlikely, because females have some capacity to discriminate between males both within and between
species on phenotypic traits additional to those under sexual selection. Although at least 25% of the pups born in this study
were hybrid, this study can only support reinforcement theory if hybrids have reduced fitness. The fitness of hybrids among
the species studied is currently unknown.
Received: 19 January 1998 / Accepted after revision: 12 September 1998 相似文献
62.
Ariane Verdy 《Ecological modelling》2010,221(8):1098-1107
An Allee effect arising from density-dependent mating success can have significant impacts at the ecosystem level when considered in the context of predator-prey interactions. These are captured by a mathematical model for the exchange of biomass between a structured predator population (continuous weight distribution) and a resource. Because the predator’s mating success affects the amount of resources required for the production of offsprings and their future growth into mature organisms, it influences the flux of biomass between trophic levels. Under simple assumptions, the equations can be reduced to an equivalent unstructured predator-prey model in which the Allee effect modulates the predation rate: the mating probability multiplies the rate of predator growth as well as the rate of resource depletion. Implications of the Allee effect for the bifurcation structure and equilibrium densities are examined. The model is compared to a modified version in which the Allee effect instead modulates the assimilation efficiency, hence the mating probability does not appear in the dynamical equation for the resource density. Both models exhibit qualitatively similar dynamics. However, compared to the model in which the Allee effect modulates predation, the model in which the Allee effect modulates assimilation efficiency predicts (i) unrealistically inefficient resource assimilation when predator density is low, (ii) a higher risk of catastrophic extinction resulting from a change in the parameter controlling the strength of the Allee effect, and (iii) no possibility of an increase in population size when the density dependence is enhanced. 相似文献
63.
Survival is one of the most central population measures when the effects of the pollution are studied in natural bird populations. However, only few studies have actually measured rigorous survival estimates on adult birds. In recent years there has been a methodological advance in survival analyses by mark-recapture models. We modelled local survival (including mortality and emigration) with the program MARK in a population of a small insectivorous passerine bird, the pied flycatcher (Ficedula hypoleuca), around a point source of heavy metals. The local survival of females in the polluted area was about 50% lower than in the other areas. Males, however, survived relatively well in the heavily polluted area, but showed somewhat lower survival in the moderately polluted area. Different pollution effects between two sexes might be due to pollution-related differences in reproductive effort in females and males, and/or more intensive uptake of heavy metals by laying females. 相似文献
64.
The US Clean Water Act and habitat replacement: evaluation of mitigation sites in Orange County,California, USA 总被引:2,自引:2,他引:0
Both permit requirements and ecological assessments have been used to evaluate mitigation success. This analysis combines
these two approaches to evaluate mitigation required under Section 404 of the United States Clean Water Act (CWA) and Section
10 of the Rivers and Harbors Act, which allow developers to provide compensatory mitigation for unavoidable impacts to wetlands.
This study reviewed permit files and conducted field assessments of mitigation sites to evaluate the effectiveness of mitigation
required by the US Army Corps of Engineers for all permits issued in Orange County, California from 1979 through 1993. The
535 permit actions approved during this period allowed 157 ha of impacts. Mitigation was required on 70 of these actions,
with 152 ha of enhanced, restored, and created habitat required for 136 ha of impacts. In 15 permit actions, no mitigation
project was constructed, but in only two cases was the originally permitted project built; the two cases resulted in an unmitigated
loss of 1.6 ha. Of the remaining 55 sites, 55% were successful at meeting the permit conditions while 11% failed to do so.
Based on a qualitative assessment of habitat quality, only 16% of the sites could be considered successful and 26% were considered
failures. Thus, of the 126 ha of habitat lost due to the 55 projects, only 26 ha of mitigation was considered successful.
The low success rate was not due to poor enforcement, although nearly half of the projects did not comply with all permit
conditions. Mitigation success could best be improved by requiring mitigation plans to have performance standards based on
habitat functions. 相似文献
65.
A new, higher dam was installed at Kerkini Reservoir in 1982, causing habitat and landscape disruption. A decrease in the
area of grassland and shallow water areas, the rapid disappearance of reedbeds, the appearance of beds ofNymphaea, and the disappearance of half the forest area were all observed between 1982 and 1991. With the new hydrological regime,
a lacustrine system was created, with an extensive, rather deep (4–8 m), pelagic zone favorable for the development of coarse
fish species throughout the year. After 1982, an increase in fishing effort and a change in the relative abundance of fish
species in the catch, including the disappearance of eels and wels, were observed. The impact of the rise in the water level
of breeding aquatic birds led to a general decline in species typical of marshy habitats in favor of species preferring deeper
open water habitats. A decrease was recorded in bird species that feed largely on invertebrates and to a lesser extent fish
(e.g., glossy ibis) and that require extensive shallow feeding areas. There was a decline in geese, whose nests were regularly
flooded, and a major increase in piscivorous birds, particularly diving birds (e.g., cormorants), which prefer deeper open
water and benefitted directly from the large increase in coarse fish biomass. The disappearance of birds breeding in flooded
meadows (e.g., black-winged stilts) and of those restricted to reedbeds (e.g., marsh harrier) occurred from 1983. Over the
same period, the changes in populations of wintering birds at Kerkini were different from those occurring in other wetlands
in northern Greece. The changes recorded in the populations of wintering birds at Kerkini did not therefore result from overall
regional trends but from the major habitat modifications that occurred to this wetland. As for breeding birds, strictly piscivorous
species increased greatly as a result of the increased availability of fish, but also due to the appearance of many suitable
night roosting sites (flooded trees) and to the great increase in the area of open water greater than 2 m deep. Today, Kerkini
has become the most important breeding site in Greece for a majority of colonial waterbirds. In contrast, wintering shorebirds
practically disappeared. The many changes recorded in the status of breeding and wintering birds at Kerkini can mostly be
explained by the changes that occurred in the functioning of the ecosystem and in the habitat structure following the inauguration
of the new hydrological regime. These changes did not all occur at the same time: some were immediate and others required
a delay before they could be detected. 相似文献
66.
MARKKU T. KUITUNEN JOHANNA VILJANEN ESKO ROSSI ARTO STENROOS 《Environmental management》2003,31(1):0079-0085
The impact of dense traffic on the breeding success in pied flycatchers (Ficedula hypoleuca) was studied using roadside nest-boxes. Nest site selection and breeding success of flycatchers were observed in relation
to the distance from the road. The number of occupied territories was no higher closer to the road than it was deeper inside
the forest. The distance to the road had no effect on the laying date, clutch size, or brood size. However, nests closer to
the road were more likely to fail at the chick stage. The number of broods that were closer to roads and were lost completely
was significantly higher than those further away. As a consequence, the number of fledglings per breeding attempt decreased
closer to roads. The nestlings typically died as older chicks when the parent birds were providing them with maximum quantities
of food. A possible reason for the declining reproductive success was the traffic-related mortality of parent birds, as weather
conditions were not especially adverse for raising healthy offspring. 相似文献
67.
Katrin Brauch Keith Hodges Antje Engelhardt Kerstin Fuhrmann Eric Shaw Michael Heistermann 《Behavioral ecology and sociobiology》2008,62(9):1453-1466
In a wide variety of species, male reproductive success is determined by contest for access to females. Among multi-male primate
groups, however, factors in addition to male competitive ability may also influence paternity outcome, although their exact
nature and force is still largely unclear. Here, we have investigated in a group of free-ranging Barbary macaques whether
paternity is determined on the pre- or postcopulatory level and how male competitive ability and female direct mate choice
during the female fertile phase are related to male reproductive success. Behavioural observations were combined with faecal
hormone analysis for timing of the fertile phase (13 cycles, 8 females) and genetic paternity analysis (n = 12). During the fertile phase, complete monopolisation of females did not occur. Females were consorted for only 49% of
observation time, and all females had ejaculatory copulations with several males. Thus, in all cases, paternity was determined
on the postcopulatory level. More than 80% of infants were sired by high-ranking males, and this reproductive skew was related
to both, male competitive ability and female direct mate choice as high-ranking males spent more time in consort with females
than low-ranking males, and females solicited copulations mainly from dominant males. As most ejaculatory copulations were
female-initiated, female direct mate choice appeared to have the highest impact on male reproductive success. However, female
preference was not directly translated into paternity, as fathers were not preferred over non-fathers in terms of solicitation,
consortship and mating behaviour. Collectively, our data show that in the Barbary macaque, both sexes significantly influence
male mating success, but that sperm of several males generally compete within the female reproductive tract and that therefore
paternity is determined by mechanisms operating at the postcopulatory level. 相似文献
68.
Although assortative mating is widespread among long-lived monogamous birds, the underlying mechanisms still remain unclear
in many species. In this study, we analysed assortative mating by age and body mass in the common tern Sterna hirundo with special regard to mate choice decisions of newly paired birds. To assess whether assortative mating by age is an active
decision involving either homotypic or directional preferences or rather a passive process due to restricted availability
of potential mates, we analysed the influence of age-dependent arrival date and cohort size. Furthermore, we looked for direct
benefits in terms of reproductive success. Common terns mated assortatively by age and arrival date but not by body mass at
arrival. Assortative mating by age was age dependent and was detected mainly in younger birds, whereas birds older than 8 years
rather re-paired with younger ones. The availability of same-aged mates was restricted by cohort size and arrival date. We
found no general evidence for better reproductive performance of same-aged pairs. Instead, relative reproductive success was
related to own age and the relative age of mate: It should be advantageous for any bird to acquire an old mate; hence, assortative
mating by age seems to be beneficial only for old terns but not for young ones. Age-assortative mating in common terns occurred
by both passive and active processes, which are not mutually exclusive. Our results do not indicate a homotypic but a directional
preference and support the theory that high-quality (older/experienced) individuals tend to mate assortatively if same-aged
mates are available, which leaves low-quality (young/inexperienced) individuals to mate among themselves. 相似文献
69.
为了解辽阳市蔬菜种植和畜禽养殖基地土壤中重金属状况,依据《环境监测分析方法》、《土壤元素的近代分析方法》的要求土壤采样分析。并根据土壤环境质量标准(GB15618-1995),采用Harkanson"潜在生态危害指数法"对土壤中重金属进行生态风险评价。结果表明,在蔬菜种植和畜禽养殖基地所选典型采样点中,重金属含量无超标现象,均属安全范围,对人体及生物无危害。 相似文献
70.
Ramona Maggini Anthony LehmannMarc Kéry Hans SchmidMartin Beniston Lukas JenniNiklaus Zbinden 《Ecological modelling》2011,222(1):21-32
Climate change is affecting biodiversity worldwide inducing species to either “move, adapt or die”. In this paper we propose a conceptual framework for analysing range shifts, namely a catalogue of the possible patterns of change in the distribution of a species along elevational or other environmental gradients and an improved quantitative methodology to identify and objectively describe these patterns. Patterns are defined in terms of changes occurring at the leading, trailing or both edges of the distribution: (a) leading edge expansion, (b) trailing edge retraction, (c) range expansion, (d) optimum shift, (e) expansion, (f) retraction, and (g) shift. The methodology is based on the modelling of species distributions along a gradient using generalized additive models (GAMs). Separate models are calibrated for two distinct periods of assessment and response curves are compared over five reference points. Changes occurred at these points are formalized into a code that ultimately designates the corresponding change pattern. We tested the proposed methodology using data from the Swiss national common breeding bird survey. The elevational distributions of 95 bird species were modelled for the periods 1999-2002 and 2004-2007 and significant upward shifts (all patterns confounded) were identified for 35% of the species. Over the same period, an increase in mean temperature was registered for Switzerland. In consideration of the short period covered by the case study, assessed change patterns are considered to correspond to intermediate patterns in an ongoing shifting process. However, similar patterns can be determined by habitat barriers, land use/land cover changes, competition with concurrent or invasive species or different warming rates at different elevations. 相似文献