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排序方式: 共有178条查询结果,搜索用时 15 毫秒
51.
52.
ANTONIO HERNÁNDEZ‐MATÍAS JOAN REAL ROGER PRADEL ALAIN RAVAYROL NICOLAS VINCENT‐MARTIN 《Ibis》2011,153(4):846-857
Survival typically contributes most to population trends in long‐lived birds and its accurate estimation is therefore vital for population management and conservation. We evaluated the effects of age, territoriality and reproduction on survival in Bonelli’s Eagle Aquila fasciata through multistate capture‐mark‐recapture analyses on a long‐term dataset. Monitoring was carried out in southeast France (1990–2008) and involved the surveying of territorial Eagles, the marking of fledged chicks, and the recording of resightings and recoveries of marked non‐territorial and territorial birds. Survival improved with age, but territoriality was not retained in the best model; yearly survival was estimated at 0.479 for fledglings (to 1 year of age), 0.570 for 1‐ and 2‐year‐olds, and 0.870 for 3‐year‐old and older individuals. The second best model supported a further increase in survival from 3‐year‐olds (0.821) to older individuals (0.880). In the third best supported model, territoriality enhanced survival, but only in 2‐year‐olds (0.632 vs. 0.562 for non‐territorial). We found no correlation between the previous breeding stage and future survival, consistent with the long lifespan of the study species. Nevertheless, 4‐year‐old and older successful breeders were more likely to breed the following year than failed adult breeders (0.869 vs. 0.582), suggesting that the cost of reproduction is small in comparison with the variation in quality among individuals or their territories. 相似文献
53.
Zintzaras E 《Journal of genetics》2011,90(1):51-58
Knowledge of genetic correlations is essential to understand the joint evolution of traits through correlated responses to
selection, a difficult and seldom, very precise task even with easy-to-breed species. Here, a simulation-based method to estimate
genetic correlations and genetic covariances that relies only on phenotypic measurements is proposed. The method does not
require any degree of relatedness in the sampled individuals. Extensive numerical results suggest that the propose method
may provide relatively efficient estimates regardless of sample sizes and contributions from common environmental effects. 相似文献
54.
JORDI LÓPEZ-PUJOL MARIA RENÉE ORELLANA MARIA BOSCH JOAN SIMON CÈSAR BLANCHÉ 《Botanical journal of the Linnean Society. Linnean Society of London》2007,155(2):211-222
Allozyme electrophoresis was conducted to survey the levels and distribution of genetic diversity in the tetraploid perennial larkspur Delphinium montanum (Ranunculaceae), which is endemic to the eastern Pyrenees of Spain and France and considered to be endangered. Seven populations were sampled, resolving 14 putative enzymatic loci belonging to eight enzymes. Banding patterns stained in gels revealed several enzymatic duplications attributable to autotetraploidy, such as the presence of both balanced and unbalanced heterozygotes and the lack of fixed heterozygosity. However, variability in D. montanum ( P = 23.8%, A = 1.48, and H e = 0.082) was lower than that expected for an autotetraploid species. This, in addition to the scarcity of loci showing three or four different alleles, could indicate that this species has suffered genetic erosion through population bottlenecks, or, alternatively, that it is undergoing diploidization. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 211–222. 相似文献
55.
SOIZIC MORIN ANNE‐SOPHIE LAMBERT JOAN ARTIGAS MARINA COQUERY STÉPHANE PESCE 《Freshwater Biology》2012,57(8):1658-1666
1. The impact of immigration on the recovery of diatom assemblages after chronic exposure to copper was investigated in laboratory microcosms. 2. We examined the recovery trajectories of copper‐contaminated biofilms after reducing copper stress and with or without the possibility of immigration from unimpaired communities. 3. The biofilms mixed with unimpaired communities returned to a ‘control’ assemblage structure within 6 weeks, with recovery patterns depending on the endpoint considered (i.e. 2 weeks for relative abundances of diatom species but 6 weeks for total diatom biomass). In contrast, no recovery was observed in assemblages placed under control conditions without external immigrants. 4. Immigration has important effects on the recovery of quantitative and qualitative characteristics of biofilms. 相似文献
56.
TERESA GARNATJE ROSER VILATERSANA ALFONSO SUSANNA JOAN VALLÈS SONJA SILJAK-YAKOVLEV 《Botanical journal of the Linnean Society. Linnean Society of London》2004,145(3):337-344
Twenty-six chromosome counts were made of several genera of the tribe Cardueae from various European and Asian provenances: Acantholepis (one species studied), Amphoricarpus (1), Chardinia (1), Echinops (14 species, 15 populations), Siebera (1), Staehelina (3) and Xeranthemum (4). Eleven of the reports are made for the first time, ten confirm previous counts, while the remainder report disparities with earlier records. The existence of different basic chromosome numbers and ploidy levels suggests dysploidy and polyploidy as the main mechanisms of chromosomal evolution in the taxa considered. © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 145 , 337−344. 相似文献
57.
58.
FORTHMAN DEBRA L.; MILLER NICOLETTE S.; MEAD JOAN I.; PERKINS LORRAINE A. 《Integrative and comparative biology》1993,33(2):144-150
SYNOPSIS. The bongo is one of the least-studied of the Tragelaphini.In a study of five captive bongo calves, two males and threefemales, we measured several behaviors important to parentalinvestment theory (Clutton-Brock et al., 1982), in order todescribe their pattern in a rare species, and add to the databasepertaining to sex allocation theory. Variations in individualpatterns of maternal investment, such as suckling rate and boutlength, were measured and graphed over time, with sex of calf,and age and dominance of dam indicated. Instances of "thiefsuckling" by calves and juveniles were also described in termsof kinship among the animals involved. Only one measure of maternalinvestment was biased in favor of males, which had a somewhathigher birth weight than females. Other measures showed littlesex difference. Among these calves, maternal care appeared tovary more with dominance and age of the dam than with sex ofcalf. Data from these animals generally conform more closelyto those of Byers and Moodie (1990). They found little evidenceof sex-biased investment among pronghorn (Antilocapra americana)fawns, and postulated that many ungulates have such a high rateof development that further differential investment is impossible.Robust biological theories are supported by data obtained froma wide variety of species, many of which are impossible to studyclosely in the wild. Additional studies on captive populationsof sexually dimorphic species would contribute usefully to theaccumulation of data pertinent to parental investment theory. 相似文献
59.
ELIAS RB 《California medicine》1959,90(2):128-129
Among 500 cases of suicide analyzed in Stockholm, fewer than a third were associated with depression. Most forms of psychiatric disease were represented. Nevertheless, most persons give some warning before attempting suicide, and these warnings should be the signal for preventive action. Centers with trained personnel could prevent many suicides, if the potential victims were recognized and referred early enough. Laymen too should be educated to recognize potential suicide and help avert it. 相似文献
60.
Specific Ribonucleoprotein Fragment from the 30S Subunit of <Emphasis Type="Italic">E. coli</Emphasis> Ribosomes 总被引:2,自引:0,他引:2
WE describe here a new approach to the determination of the three dimensional arrangement of the proteins within the ribosome, based on controlled degradation with nuclease. We suggest that by isolating ribonucleoprotein (RNP) fragments and determining which particular proteins each fragment contains, it should eventually be possible to construct a detailed “map” of the protein arrangement. The “mapping” problem has already received attention in various laboratories. Mizushima and Norrtura1 have shown that the proteins of the E. coli 30S ribosomal subunit assemble with 16S RNA in a highly specific order. Further, the reactivity of the 30S particle towards proteolytic enzymes2 and protein-modifying reagents3 shows a striking correlation with Mizushima and Nomura's “assembly map”1, in that the first group of proteins in the assembly process seems to be protected in the completed particle. 相似文献