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991.
992.
H. C. Gerhardt J. Schul 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1999,185(1):33-40
The selectivity of female phonotactic responses to synthetic advertisement calls was tested in choice situations. Preferences
based on differences in the linear rise-time of synthetic pulses depended on intensity and carrier frequency. When the carrier
frequency was 1.1 kHz, simulating the low-frequency peak in the advertisement call, females preferred alternatives with slower
rise-time pulses that differed by 5 ms at playback levels of 75 dB SPL and higher. A rise-time difference of 10 ms was discriminated
at 65 dB SPL. When the carrier frequency was 2.2 kHz, simulating the high-frequency peak in the call, females discriminated
a 5-ms difference in rise-time only at 85 dB SPL. Females showed no preference when the difference was 10 ms at lower playback
levels. The difference in the thresholds (about 15–20 dB) for discriminating differences in rise-time at the two carrier frequencies
was greater than the difference in behavioral thresholds for these two frequencies (about 10 dB). This result suggests that
rise-time discrimination can be mediated solely by the neural channel mainly tuned to the low-frequency peak in the call.
Females probably assess differences in rise-time by comparing the first few pulses of each call rather than by averaging over
the entire call.
Accepted: 30 March 1999 相似文献
993.
994.
995.
永瓣藤的地理分布及其种群空间格局 总被引:3,自引:0,他引:3
应用Greig-Smith邻接格子取样法,研究了我国珍稀植物永瓣藤(MonimopetalunchinenseRehd),的地理分布和种群空间格局及其形成机制,分析了其克隆生长格局和生态适应对策,研究结果表明,永瓣藤的分布区域狭窄,其种群空间格局为集群型,克隆生长格避为游击式稀疏形式样式,这与其生物学特性和种群生态适应的对策密切相关。 相似文献
996.
我国水青冈属植物的地理分布格局及其与地形的关系 总被引:6,自引:0,他引:6
利用我国水青冈属(FagusL.)植物的地理分布资料和1∶100万地形图资料,利用Krige空间统计方法对我国分布较广的4种水青冈,即长柄水青冈(F.longipetiolataSeem.etDiels)、亮叶水青冈(F.lucidaRehd.etWils.)、米心水青冈(F.englerianaSeem.)和巴山水青冈(F.bashanicaYang)的空间分布格局及其与地形的关系进行了研究。结果表明,我国水青冈属植物显示出南北变化较小、东西变化显著,一些区域出现较周围地区较高或较低分布的“岛屿化”现象的空间分布格局。这与我国的地形特征以及水青冈的生态特性等有关。沿不同经向剖面,分析水青冈的分布高度与地形平均高度之间的关系显示,随地形高度的增加,水青冈分布上限的高度也逐渐增加,其趋势可用对数或直线拟合,但不同种对地形高度变化的反应存在差异。这些结果不仅从较大尺度上定量说明了我国水青冈分布高度的山体效应现象,也揭示了物种间山体效应的差异。这种差异可能与物种的生态适应性和生态幅度有关。 相似文献
997.
Growth rate of individually tagged juvenile halibut was influenced significantly by the interaction of temperature and fish size. The results suggest an optimum temperature for growth of juvenile halibut in the size range 5–70 g between 12 and 15° C. Overall growth rate was highest at 13° C (1·62% day −1 ). At c. 5 g at the beginning of the experiment, fish at 16° C had the highest growth rate (3·2% day −1 ), but reduced this rate as they grew bigger. At 9 and 11°p C, growth rates were equal or only slightly lower during the later stages of the experiment, while the fish at 6° C showed significantly lower overall growth rate (0·87% day−1 ). Optimal temperature for growth decreased rapidly with increasing size, indicating an ontogenetic reduction in optimum temperature for growth. Moreover, a more flattened parabolic regression curve between growth and temperature as size increased indicated reduced temperature dependence with size. Although individual growth rates varied significantly at all times within the experimental temperatures, significant size rank correlations were maintained during the experiment. This indicated an early establishment of a stable size hierarchy within the fish groups. Haematocrit was highest at the highest temperature while Na+ /K+ -ATPase activity was inversely related to temperature. There was no difference in plasma Na+ , Cl− and K+ concentrations among the temperature groups. 相似文献
998.
999.
Peijian Shi Yabing Jiao Peter J Diggle Rolf Turner Rong Wang Ülo Niinemets 《Annals of botany》2021,128(7):875
Background and AimsIn hierarchically reticulate venation patterns, smaller orders of veins form areoles in which stomata are located. This study aimed to quantify the spatial relationship among stomata at the areole level.MethodsFor each of 12 leaves of M. cavaleriei var. platypetala, we assumed that stomatal characteristics were symmetrical on either side of the midrib, and divided the leaf surface on one side of the midrib into six layers equidistantly spaced along the apical–basal axis. We then further divided each layer into three positions equidistantly spaced from midrib to leaf margin, resulting in a total of 18 sampling locations. In addition, for 60 leaves, we sampled three positions from midrib to margin within only the widest layer of the leaf. Stomatal density and mean nearest neighbour distance (MNND) were calculated for each section. A replicated spatial point pattern approach quantified stomatal spatial relationships at different distances (0–300 μm).Key ResultsA tendency towards regular arrangement (inhibition as opposed to attraction or clustering) was observed between stomatal centres at distances <100 μm. Leaf layer (leaf length dimension) had no significant effect on local stomatal density, MNND or the spatial distribution characteristics of stomatal centres. In addition, we did not find greater inhibition at the centre of areoles, and in positions farther from the midrib.ConclusionsSpatial inhibition might be caused by the one-cell-spacing rule, resulting in more regular arrangement of stomata, and it was found to exist at distances up to ~100 μm. This work implies that leaf hydraulic architecture, consisting of both vascular and mesophyll properties, is sufficient to prevent important spatial variability in water supply at the areole level. 相似文献
1000.
Michael Mutz 《International Review of Hydrobiology》2000,85(1):107-121
In lowland areas, such as the glacial landscapes of eastern Germany, sand‐bed streams are the most common stream type. They have low gradients and their hydrological regime is often subdued due to the frequent interruption by lakes. Very few is known about the influence of woody debris in these streams, since nearly all previous studies are from high‐gradient conditions, where streams have coarse bed sediments and harsh hydrological regimes. The research objectives of this study were first to assess the quasi‐natural quantity and quality of wood in a lowland sand‐bed stream and second to understand the influence of wood on the channel morphology and the flow patterns at base‐flow. The three‐dimensional stream bed relief was surveyed by electronic distance measurement. The position and the size of large woody debris was assessed by close‐up photography. An acoustic Doppler velocimeter was used to record the patterns of flow velocity and turbulence. Overlay and analysis of the spatial data was done using a Geographic Information System. The standing stock of wood was 1.9 m3 and 39 woody elements per 100 m2 of stream bed. The flow pattern was clearly controlled by the wood. Woody elements elevated above the stream bed deflected flow and locally caused strong secondary current, high turbulence, and scour of the stream bed at baseflow. Wood resting directly on the stream bed, which contributed the majority of the wood inside the bank‐full channel, determined the roughness of the stream bed. Near‐bed flow patterns observed were isolated roughness flow and wake interference flow, which was registered inside the accumulations of wood. 68% of the stream bed had shear stress above critical. Hence, the secondary morphological structures of the sand‐bed were controlled at base‐flow by the flow which was determined by the woody debris distribution. 相似文献