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991.
Martin U. Grüebler Fränzi Korner‐Nievergelt Beat Naef‐Daenzer 《Ecology and evolution》2014,4(6):756-765
In migrant birds, survival estimates for the different life‐history stages between fledging and first breeding are scarce. First‐year survival is shown to be strongly reduced compared with annual survival of adult birds. However, it remains unclear whether the main bottleneck in juvenile long‐distant migrants occurs in the postfledging period within the breeding ranges or en route. Quantifying survival rates during different life‐history stages and during different periods of the migration cycle is crucial to understand forces driving the evolution of optimal life histories in migrant birds. Here, we estimate survival rates of adult and juvenile barn swallows (Hirundo rustica L.) in the breeding and nonbreeding areas using a population model integrating survival estimates in the breeding ranges based on a large radio‐telemetry data set and published estimates of demographic parameters from large‐scale population‐monitoring projects across Switzerland. Input parameters included the country‐wide population trend, annual productivity estimates of the double‐brooded species, and year‐to‐year survival corrected for breeding dispersal. Juvenile survival in the 3‐week postfledging period was low (S = 0.32; SE = 0.05), whereas in the rest of the annual cycle survival estimates of adults and juveniles were similarly high (S > 0.957). Thus, the postfledging period was the main survival bottleneck, revealing the striking result that nonbreeding period mortality (including migration) is not higher for juveniles than for adult birds. Therefore, focusing future research on sources of variation in postfledging mortality can provide new insights into determinants of population dynamics and life‐history evolution of migrant birds. 相似文献
992.
Interacting effects of age,density, and weather on survival and current reproduction for a large mammal 下载免费PDF全文
Emmanuelle Richard Steven E. Simpson Sarah A. Medill Philip D. McLoughlin 《Ecology and evolution》2014,4(19):3851-3860
Individual‐based study of natural populations allows for accurate and precise estimation of fitness components and the extent to which they might vary with ecological conditions. By tracking the fates of all 701 horses known to have lived on Sable Island, Canada, from 2009 to 2013 (where there is no predation, human interference, or interspecific competition for food), we present a detailed analysis of structured population dynamics with focus on interacting effects of intraspecific competition and weather on reproduction and survival. Annual survival of adult females (0.866 ± 0.107 [ ± SE]) was lower than that of 3‐year‐olds (0.955 ± 0.051), although annual fecundity (producing a foal in a year that was observed during our census) was higher in adults (0.616 ± 0.023) compared to 3‐year‐olds (0.402 ± 0.054). Milder winters and lower densities during gestation increased fecundity. Density negatively impacted survival for all age and sex categories; however, highest adult female survival was observed during high‐density years coupled with a harsh winter, the result expected if pregnancy loss during winter or loss of foals in spring improved survival. Three‐year‐old females, which reproduced at lower rates, experienced higher survival than adults. Our results contrast with a previous study of feral horses that suggested recently feral ungulates might be artificially selected to reproduce even when costs to survival are high. In part, this may be because of the comparably long history of feralization (250 years; at least 25 generations) for Sable Island horses. 相似文献
993.
Inês Miranda Iwona Giska Liliana Farelo Joo Pimenta Marketa Zimova Jarosaw Bryk Love Daln L Scott Mills Karol Zub Jos Melo-Ferreira 《Molecular biology and evolution》2021,38(10):4388
Dissecting the link between genetic variation and adaptive phenotypes provides outstanding opportunities to understand fundamental evolutionary processes. Here, we use a museomics approach to investigate the genetic basis and evolution of winter coat coloration morphs in least weasels (Mustela nivalis), a repeated adaptation for camouflage in mammals with seasonal pelage color moults across regions with varying winter snow. Whole-genome sequence data were obtained from biological collections and mapped onto a newly assembled reference genome for the species. Sampling represented two replicate transition zones between nivalis and vulgaris coloration morphs in Europe, which typically develop white or brown winter coats, respectively. Population analyses showed that the morph distribution across transition zones is not a by-product of historical structure. Association scans linked a 200-kb genomic region to coloration morph, which was validated by genotyping museum specimens from intermorph experimental crosses. Genotyping the wild populations narrowed down the association to pigmentation gene MC1R and pinpointed a candidate amino acid change cosegregating with coloration morph. This polymorphism replaces an ancestral leucine residue by lysine at the start of the first extracellular loop of the protein in the vulgaris morph. A selective sweep signature overlapped the association region in vulgaris, suggesting that past adaptation favored winter-brown morphs and can anchor future adaptive responses to decreasing winter snow. Using biological collections as valuable resources to study natural adaptations, our study showed a new evolutionary route generating winter color variation in mammals and that seasonal camouflage can be modulated by changes at single key genes. 相似文献
994.
The arrangement of resources in patchy landscapes: effects on distribution, survival, and resource acquisition of chironomids 总被引:3,自引:0,他引:3
The spatial arrangement of resources in patchy habitats influences the distribution of individuals and their ability to acquire
resources. We used Chironomus riparius, a ubiquitous aquatic insect that uses leaf particles as an important resource, to ask how the dispersion of resource patches
influences the distribution and resource acquisition of mobile individuals in patchy landscapes. Two experiments were conducted
in replicated laboratory landscapes (38×38 cm) created by arranging sand and leaf patches in a 5×5 grid so that the leaf patches
were either aggregated or uniformly dispersed in the grid. One-day-old C. riparius larvae were introduced into the landscapes in one of three densities (low, medium, high). In experiment 1, we sampled larvae
and pupae by coring each patch in each landscape 3, 6, 12, or 24 days after adding larvae. In experiment 2, emerging adults
were collected daily for 42 days from each patch in each landscape. In aggregated landscapes, individuals were aggregated
in one patch type or the other during a particular developmental stage, but the ”preferred” type changed depending on developmental
stage and initial density. Adult emergence was lower by about 30% in all aggregated landscapes. In dispersed landscapes, individuals
used both types of patch throughout their life cycles at all initial densities. Thus, patch arrangement influences the distribution
of mobile individuals in landscapes, and it influences resource acquisition even when average resource abundance is identical
among landscapes. Regardless of patch arrangement, high initial density caused accumulation of early instars in edge patches,
75% mortality of early instars, a 25% increase in development time, and a 60% reduction in adult emergence. Because mortality
was extremely high among early-instar larvae in high-density treatments, we do not have direct evidence that the mechanism
by which patch arrangement operates is density dependent. However, the results of our experiments strongly suggest that dispersion
of resource patches across a landscape reduces local densities by making non-resource patches available for use, thereby reducing
intraspecific competition.
Received: 20 July 1999 / Accepted: 28 January 2000 相似文献
995.
Pathogens and parasites can be strong agents of selection, and often exhibit some degree of genetic specificity for individual
host strains. Here we show that this host–pathogen specificity can affect the evolution of host life history traits. All else
equal, evolution should select for genes that increase individuals' reproduction rates or lifespans (and thus total reproduction
per individual). Using a simple host–pathogen model, we show that when the genetic specificity of pathogen infection is low,
host strains with higher reproduction rates or longer lifespans drive slower-reproducing or shorter-lived host strains to
extinction, as one would expect. However, when pathogens exhibit specificity for host strains with different life history
traits, the evolutionary advantages of these traits can be greatly diminished by pathogen-mediated selection. Given sufficient
host–pathogen specificity, pathogen-mediated selection can maintain polymorphism in host traits that are correlated with pathogen
resistance traits, despite large intrinsic fitness differences among host strains. These results have two important implications.
First, selection on host life history traits will be weaker than expected, whenever host fitness is significantly affected
by genotype-specific pathogen attack. Second, where polymorphism in host traits is maintained by pathogen-mediated selection,
preserving the genetic diversity of host species may require preserving their pathogens as well.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
996.
I. L. Boyd 《Functional ecology》2000,14(5):623-630
997.
998.
999.
Ian Simmons 《Journal of Biogeography》2000,27(1):3-5
We can make a history of the world as an ecological history of an empirical nature. But parallelling that is the history of human thought about nature. The two interact at both pragmatic and abstract levels but in essence the outcome is unpredictable and more akin to chaos theory than to environmental or technological determinism. So the pursuit of either environmentalist or cornucopian Utopias seems not only doomed to failure but likely to cause destruction along the way; a step by step improvisatory strategy seems the best we can do. 相似文献
1000.
脓疮草复合体的生物学特性研究 总被引:1,自引:0,他引:1
通过野外和移栽实验观测,对脓疮草复合体(Panzerian lanata complex)居群进行了生物学特性研究。结果表明:浓疮草复合体居群在生活史方面无明显差异,移栽的10个复合体居群生活史十分 相似:脓疮草复合本的花量大,花期可达3个月左右,花为雌雄异熟,以异花授粉为主,自交(同株异花授粉)亲合;叶裂程度、花萼裂片宽窄等性状,在天然居群中是连续变化的,而且移栽后可逆性较大,性状不稳定。 相似文献