排序方式: 共有72条查询结果,搜索用时 31 毫秒
61.
Potential age of aquatic Oligochaeta 总被引:4,自引:4,他引:0
The maximum lifetime of species with exclusively sexual reproduction covers 5–15 years or even more in aquaria, although most specimens die consecutively earlier. The zooids of paratomic species live some weeks or months, their clones usually less than a year, rarely for some years. In the species with facultative architomy (fragmentation) the clonal age also exceeds that of the individual, both lasting for several years. The actual lifetime of worms in nature may be shorter than in cultures. 相似文献
62.
DNA fingerprinting reveals relation between tail ornaments and cuckoldry in barn swallows, Hirundo rustica 总被引:1,自引:0,他引:1
Smith Henrik G.; Montgomerie Robert; Poldman Tarmo; White Bradley N.; Boag Peter T. 《Behavioral ecology》1991,2(1):90-98
In an experimental study in Denmark, it was previously foundthat male barn swallows (Hirundo rustica) with elongated tailstreamers obtained an apparent fitness advantage through earlierpairing, an increased frequency of second clutches, and highertotal reproductive success per season. In a parallel study offive barn swallow colonies in Ontario, Canada, we also foundthat elongated males paired earlier and thus were apparentlypreferred by females. Now, using DNA fingerprinting on familiesfrom two of those Ontario colonies, we show that five elongatedmales fathered only 59% of the offspring in their nests, whereassix shortened males fathered 96% of their nestlings. Thus, althoughelongated males were clearly preferred by females at the timeof pair formation, tail elongation may have hampered the abilityof a male to guard his mate, resulting in an increase in extrapairfertilizations (EPFs). A significant negative correlation betweenthe number of EPFs and natural tail length in this experimentalstudy also suggests that tail streamer length may reflect malequality. (Behav Ecol 1990; 2: 9098) 相似文献
63.
Genetic quality and energy metabolism are expected to have an effect on the level of energetically costly sexual signaling.
To explore this we manipulated genetic quality of male decorated crickets (Gryllodes sigillatus) by inbreeding and measured the resting metabolic rate and total energy budget of males. We also measured several aspects
of the sexual signaling of males: probability to initiate calling, latency, amount of call bouts, first call bout duration,
mean call bout duration and total time spent calling. Inbreeding increased the latency and lowered the first and mean call
bout duration. Moreover, the resting metabolic rate had a positive effect, and body mass a negative effect on first call bout
duration and mean call bout duration. Our results, suggest that sexual signals are indicative of genetic quality but are also
dependent on the physical properties of individuals. 相似文献
64.
Ketola T Laakso J Kaitala V Airaksinen S 《Evolution; international journal of organic evolution》2004,58(4):741-748
Evolutionary consequences of thermally varying environments were studied in the ciliated protozoan Tetrahymena thermophila. Replicated lines were propagated for 60 days, a maximum of 500 generations, in stable, slowly fluctuating (red spectrum), and rapidly fluctuating (blue spectrum) temperatures. The red and blue fluctuations had a dominant period length of 15 days and two hours, respectively. The mean temperature of all time series was 25 degrees C and the fluctuating temperatures had the same minimum (10 degrees C), maximum (40 degrees C), and variance. During the experiment, population sizes and biomasses were monitored at three-day intervals. After the experiment, carrying capacity and maximum growth rate were measured at low (15 degrees C), intermediate (25 degrees C), and high (35 degrees C) temperatures for each experimental line. Physiological changes in the lines were assessed by measuring the expression of stress-induced heat shock protein Hsp90 at 25 degrees C, 35 degrees C, and 39 degrees C. Population sizes and biomasses showed no differences between stable, blue, or red temperature treatments during the experiment. Also, after the experiment, mean carrying capacities and maximum growth rates were comparable in the stable, blue, and red temperature treatments. The expression of Hsp90 was higher in lines from the blue environment than in lines from the stable environment. Lines from the red environment had an intermediate level of Hsp90 expression. This supports the hypothesis that inducible thermotolerance and expression of canalizing genes can evolve in response to rapidly varying environments. Furthermore, we found correlative evidence of benefits and disadvantages of high Hsp90 expression. Lines with high expression of Hsp90 had an increased growth rate at the highest temperature when food resources were not limiting growth. At low and intermediate temperatures the same lines had the lowest carrying capacities. 相似文献
65.
Variation in needle-trace diameter in respect of needle morphology in five conifer species 总被引:1,自引:0,他引:1
Margus?PensaEmail author Tarmo?Aalto Risto?Jalkanen 《Trees - Structure and Function》2004,18(3):307-311
Needle traces have been used for revealing historical changes in needle longevity of Pinus sylvestris L. and Picea abies (L.) H. Karst. In this paper we compared the needle-trace diameter of five conifer species [Abies sibirica Ledeb., Picea abies, Pinus sylvestris, Pseudotsuga menziesii (Mirb.) Franco and Taxus baccata L.] in respect of needle size. In case of P. sylvestris, we studied how needle-trace diameter varied among different growing sites and among different shoots within a site, and related that variation to needle morphology and structure. Pinus sylvestris had the greatest diameter of needle traces (mean±SD =233±30 m) followed by T. baccata (141±19 m) and P. menziesii (121±30 m). The smallest needle-trace diameter was in A. sibirica (85±21 m) and P. abies (80±18 m). Among species, the needle-trace diameter was strongly correlated with needle length (r =0.93, P <0.05). Within P. sylvestris, the needle-trace diameter was significantly affected by location (P <0.001) and varied significantly among shoots within a location (P <0.001). The shoots of P. sylvestris which had greater average diameter of needle traces, tended to have longer (r =0.36, P <0.05), wider (r =0.55, P <0.05) and heavier (r =0.64, P <0.05) needles with greater stomatal density (r =0.55, P <0.05). Although our results do not allow the use of needle-trace diameter to predict properties of needle structure at the present stage, they nevertheless indicate general trends and point to a need for further studies. 相似文献
66.
Variation is the raw material for evolution. Evolutionary potential is determined by the amount of genetic variation, but evolution can also alter the visibility of genetic variation to natural selection. Fluctuating environments are suggested to maintain genetic variation but they can also affect environmental variance, and thus, the visibility of genetic variation to natural selection. However, experimental studies testing these ideas are relatively scarce. In order to determine differences in evolutionary potential we quantified variance attributable to population, genotype and environment for populations of the bacterium Serratia marcescens. These populations had been experimentally evolved in constant and two fluctuating environments. We found that strains that evolved in fluctuating environments exhibited larger environmental variation suggesting that adaptation to fluctuations has decreased the visibility of genetic variation to selection. 相似文献
67.
68.
A literature review of Polychaeta (Annelida) including Aphanoneura (the oligochaete-like Aeolosomatidae and Potamodrilidae),
living in freshwater yielded 168 species, 70 genera and 24 families representing all of the major polychaete clades, but less
than 2% of all species. The best-represented families were, in order, Nereididae, Aeolosomatidae, Sabellidae, Spionidae and
Histriobdellidae. Fourteen families were represented by a single species and genus. Regions supporting the highest diversity
of freshwater polychaetes were in order, Palaearctic, Neotropical, Oriental, Nearctic, Australasian, and Afrotropical. More
than half of all species and genera inhabitat lakes and rivers, followed by lagoons/estuaries, which have a high proportion
of euryhaline species, and inland seas. Less common, atypical polychaete habitats include subterranean waters, the hyporheic
zone of rivers and plant container habitats (phytotelmata). At least three distinct ecological/historical processes appear
to account for the colonisation of continental waters: invasion of a clade prior to the break-up of Gondwana, as in Aphanoneura,
Namanereis, Stratiodrilus, and Caobangia; relatively recent stranding of individual species (relicts); and the temporary visitation of euryhaline species.
Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens
Freshwater Animal Diversity Assessment 相似文献
69.
70.