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861.
862.
"十二五"期间,沈阳市蒲河的污染控制与水生态修复工程同步实施。通过污水处理设施建设、水资源调控、生态廊道建设和河道水质改善技术示范等工程建设,实现了水质改善和水生态功能修复的目标。文章对重点工程的实施和功效进行了解析,总结了同类河流整治的科学对策和途径。 相似文献
863.
864.
城市生态文明建设评价指标体系构建 总被引:1,自引:1,他引:0
城市作为人类环境问题和危机产生的重要策源地,建立反映城市生态环境问题和生态文明建设状态的评价指标体系,依据评价结论,指导城市生态文明建设十分必要。文章在城市作为社会—经济—自然复合人工生态系统的理论基础上,分析了社会生态亚系统、经济生态亚系统及自然生态亚系统相互作用关系和城市生态系统主要生物成分组成、结构与功能关系,系统的构建了符合中国国情的城市生态文明评价指标体系。该体系以生态经济、生态环境质量、生态社会为评价要素,下设12个一级指标及42个二级指标,为评价中国城市生态文明建设水平提供科学依据。 相似文献
865.
通过以实地调查和京津风沙源治理工程建设任务及投资数据为基础,以县域土地利用及社会经济相关数据作为参考,对内蒙古翁牛特旗京津风沙源治理工程生态效益进行了全面评估。结果表明,内蒙古翁牛特旗森林生态系统服务主要是水源涵养、保护生物多样性和固碳释氧,占总服务价值的86.1%。京津风沙源建设工程在遏制沙化土地蔓延和改善周边区域环境质量等方面效果显著。京津风沙源治理工程在生态、经济、社会方面的贡献巨大,工程建设取得了较好的成效。 相似文献
866.
Contrary to classical sexual selection theories, females of many taxa mate with multiple males during one reproductive cycle. In this study, we conducted an experiment on the “trade-up hypothesis”, which proposes that females remate if a subsequently encountered male is potentially superior to previous mates to maximize the genetic quality of their offspring. We presented bank vole females (Clethrionomys glareolus) sequentially with two males of known dominance rank in different orders, i.e., either first subordinate and second dominant, first dominant and second subordinate, or two males that were equal in dominance (high ranking) and observed their mating behavior. We found that 92% of the females mated multiply and did not base their remating decision on male social status. Therefore, polyandry cannot be explained by the “trade-up hypothesis” based on dominance rank in this species. However, we found that dominant males sired significantly more offspring than subordinate males. This varied according to mating order: dominant males sired more offspring when they were second than when they were first. Moreover, litter sizes were significantly smaller when the dominant male was first (smallest relative success of dominant males) compared to litter sizes when mating order was reversed or both males equal in status. Our results suggest that even though multimale mating includes males that are of poorer quality and thus potentially decreases the fitness of offspring, most of a female’s offspring are sired by dominant males. Whether this is due to cryptic female choice, sperm competition, or a combination of both, remains to be tested. 相似文献
867.
Toby J. Hibbitts Martin J. Whiting Devi M. Stuart-Fox 《Behavioral ecology and sociobiology》2007,61(8):1169-1176
Many species possess multiple sexually dimorphic traits, which incorporate different sensory modalities (e.g., acoustic, olfactory
and visual), although their relative roles in sexual selection and in determining reproductive success are still poorly understood
for most taxa. We assessed the role of multiple male traits, including one acoustic (dominant call frequency) and one visual
(yellow throat patch) trait, in residency advertisement, contest behavior, and breeding success in barking geckos (Ptenopus garrulus garrulus). We show that male barking geckos maintain largely exclusive home ranges, with a trend for larger males to maintain larger
home ranges. We also show that larger males have a lower dominant calling frequency. When aggressive behavior was elicited
in the field using a recorded call of average frequency, resident males with low frequency calls were more likely to respond
aggressively and charge the speaker compared to males with high frequency calls. However, body size and small relative throat
patch size, rather than call frequency, were the best predictors of overall aggressiveness. Body size was also the best predictor
of whether males bred. We suggest that call frequency in this crepuscular species constitutes an effective long-range signal
of body size, used by males for remote rival assessment and to advertise home range boundaries in low-light environments. 相似文献
868.
C. Tate Holbrook Christoph-Peter Strehl Robert A. Johnson Jürgen Gadau 《Behavioral ecology and sociobiology》2007,62(2):229-236
The evolution of polyandry is a central problem in the study of insect mating systems, and both material and genetic benefits
have been proposed to offset the presumed costs of multiple mating. Although most eusocial Hymenoptera queens mate with just
one or occasionally two males, high levels of polyandry are exhibited by several taxa, including seed-harvester ants of the
genus Pogonomyrmex. Previous studies of queen mating frequency in Pogonomyrmex have focused on monogynous (one queen per colony) species in the subgenus Pogonomyrmex. We performed a genetic mother–offspring analysis of mating frequency in Pogonomyrmex (Ephebomyrmex) pima, a queen-dimorphic species with dealate and intermorph queens that differ in colony structure (intermorph colonies contain
multiple queens). Our results demonstrate that both dealate and intermorph queens of P. (E.) pima are typically single maters, unlike their congeners analyzed thus far. Polyandry appears to be a derived trait in Pogonomyrmex, but comparative tests between P. (E.) pima queen morphs and across the genus provide no evidence that it evolved as an adaptation to increase genetic diversity within
colonies or to obtain more sperm, respectively. 相似文献
869.
S. Åkesson Lennart Karlsson Göran Walinder Thomas Alerstam 《Behavioral ecology and sociobiology》1996,38(5):293-302
Extensive ringing data from a coastal site (Falsterbo Bird Observatory) in southwesternmost Sweden were used to investigate
the occurrence of reverse autumn migration among 20 passerine bird species of widely different migration categories. The data
demonstrate that reverse migration is a widespread and regular phenomenon among nocturnal as well as diurnal migrants and
among irruptive migrants, temperate zone migrants, and long-distance migrants destined for tropical winter quarters. The reoriented
movements were directed approximately opposite to the normal migration direction, i.e. between NNW and ENE from the coast
and towards inland. Median distances of reverse movements varied between 9 and 65 km. Some individuals of irruptive and partial
migrants settled to winter in the reverse direction. Bird species with relatively small fat reserves at capture were more
likely to perform reverse migratory movements than species with larger fat deposits. In two species birds performing forward
migration were significantly heavier within 10 days after capture than individuals performing reverse movements. The reoriented
movements probably are of adaptive significance for birds confronted with the sea and pre-disposed to refuelling during migration.
A bimodal orientation mechanism will bring the birds from an area with high competition for food and high predation risk to
more suitable resting and feeding grounds before resuming migration in the forward direction and crossing the barrier.
Received: 11 July 1995/Accepted after revision: 19 November 1995 相似文献
870.
Secondary sexual characters often provide indicators of a male’s resistance to infectious diseases to rivals and potential
mates, but it is unclear why. It is often suggested that males honestly signal their health due to energetic and other physiological
trade-offs between investing into secondary sexual traits vs resistance to infectious diseases. Our aim was to determine whether
such a trade-off exists using wild-derived male house mice (Mus domesticus). We exposed male mice to female scent, a manipulation that induces elevations in testosterone concentration and the expression
of a variety of testosterone-mediated secondary sexual traits, and tested whether this sexual stimulation impaired the males’
ability to resolve or cope with an experimental infection (Salmonella enterica). We kept the males on a controlled diet to prevent them from compensating by eating more food. We found that sexually stimulated
males were able to control bacterial growth as effectively as sham-stimulated controls; however, to do so, they lost more
body mass during infection compared to the controls. In contrast, we found no evidence that sexual stimulation reduced the
body mass of uninfected male mice. These results indicate that males’ responses to female odor are not immunosuppressive per
se, yet they increase the energetic costs of controlling infection. Our findings support the idea that there is a physiological
trade-off between secondary sexual signaling vs resistance to infectious diseases and suggest that studies using only immunocompetence
assays might fail to detect such energetic trade-offs.
We dedicate this paper to the late Professor Chris Barnard who conducted pioneering research on this topic. 相似文献