不同能量激光照射后中华大蟾蜍早期胚胎发育及其蛋白质谱变化的研究

应用YAG倍频激光器选择不同能量密度激光微束对中华大蟾蜍4细胞期胚胎进行照射,观察胚胎的生长、发育状况,统计出膜率、畸胎率和死亡率。实验结果表明：低能量激光照射明显地提高了胚胎的孵化速度,且使畸变率降低;而高能量激光对胚胎发育有明显抑制作用,而且使畸变率增高。不同能量密度激光微束照射中华大蟾蜍早囊胚,0．5h后制备样品进行双向电泳,凝胶成像后用PDQuest软件进行分析。结果显示激光照射对蛋白质点数及其分布有影响,影响程度与照射激光密度有关。结论：激光照射可以影响胚胎发育和蛋白质的合成。     

Replaying the tape: recurring biogeographical patterns in Cape Verde Conus after 12 million years

Isolated oceanic islands are excellent natural laboratories to test the relative role of historical contingency and determinism in evolutionary diversification. Endemics of the marine venomous snail Conus in the Cape Verde archipelago were originated from at least two independent colonizations of 'small' and 'large' shelled species separated by 12 million years. In this study, we have reconstructed phylogenetic relationships within large-shelled Conus ( C . ateralbus , C . pseudonivifer , C. trochulus , and C. venulatus ) based on mitochondrial cox1 and nad4 haplotype sequences. The reconstructed molecular phylogeny revealed three well-supported and relatively divergent clades (A, B, and C) that do not correspond to current species classification based on shell colour and banding patterns. Clade A grouped specimens assigned either to C. pseudonivifer or C. trochulus , clade B is composed of specimens assigned to C. venulatus , and clade C comprises specimens assigned either to C. venulatus or C. ateralbus . Geometric morphometric analyses found significant differences between the radular teeth shape of C. pseudonivifer / C. trochulus and C. venulatus / C. ateralbus . In clades A and B, northwestern Boavista and Maio specimens cluster together to the exclusion of eastern Boavista samples. In Sal, populations form a monophyletic island assemblage (clade C). The large-shelled Conus have remarkably replicated biogeographical patterns of diversification of small-shelled Conus . Similar selective forces (i.e. nonplanktonic lecithotrophy with limited larval dispersal and allopatric diversification) together with repeated instances of low sea level stands during glacial maxima that allowed connection between islands, have overcome the effect of historical contingency, and explain the observed recurring biogeographical patterns.     

Monitoring crayfish using a mark-recapture method: potentials,recommendations, and limitations

Crayfish are regarded as useful indicators of environmental quality and freshwater biodiversity. However, reliable methods for monitoring their populations are needed so that this potential can be fully utilised. We report and discuss methodological aspects of the white-clawed crayfish (Austropotamobius pallipes complex) survey conducted in Piedmont, Italy, with the use of mark-recapture. The results suggest that the method can serve as a convenient tool for estimating the size of crayfish populations and inferring their temporal trends. The two populations investigated appeared closed except for wintertime and July. Consequently, the Robust Design, which is regarded as the most reliable mark-recapture approach, can be easily applied. The minimum effective sampling plan for monitoring purposes should comprise one primary period per year, conducted in the summer–autumn season, and consisting of three capture sessions. If gaining insight into the ecology of the investigated species is the prime objective and sufficient resources are available, the optimal plan should include two primary periods (in spring and the summer–autumn season) of five capture sessions each. Capture sessions need to be separated by roughly 2-week intervals in order to avoid the strong, but short-term, negative effect of capturing crayfish on their recapture chances. As the model without heterogeneity in capture probabilities ensures better estimate precision we recommend that data collected for both sexes are analysed separately. Taking into consideration higher male catchabilities and sex ratio being invariably 1:1, it also seems beneficial to estimate only male numbers and double them to achieve total population sizes.     

Trade-offs between melanisation and life-history traits in Helicoverpa armigera

Abstract.  1. Previously we established a homozygous melanic strain (JBM) with 16 black pupae spontaneously occurring within a laboratory population (JBW) of Helicoverpa armigera and demonstrated that the melanisation is controlled by a single recessive autosomal gene.
2. Data obtained indicate that the melanisation is globally expressed in the pupal and adult stages (except for the body hairs of adults) but not in the egg and larval stages. No differences in body colour can be found between the melanic JBM and the wild-type JBW strains before the metamorphic pupation moult. After pupation, the JBM pupae gradually blacken, whereas the wild-type JBW pupae gradually turn brown, indicating that the biosynthetic steps leading to brown pigments are shut off in the JBM strain. In the adult stage, wings are darker and hairs on the abdomen and tergum are lighter in the melanic moths than in the wild-type individuals.
3. Life-table experiments reveal that the melanism is associated with slower development in all life stages, smaller body weight, lower mating rate and fecundity, less mating time, and accordingly, lower net reproduction rate and population trend index.
4. Single pair inbreeding and reciprocal crosses show that the mating rate is much lower in the inter-strain crosses than in the intra-strain crosses, indicating the presence of mating preference for its own colour morph and the presence to some degree of reproductive isolation between the two colour morphs.     

Tree spatial patterns and environmental relationships in the forest–alpine tundra ecotone at Niwot Ridge,Colorado, USA

Forest–alpine tundra ecotones (FTEs) are dynamic transition zones between forest and alpine tundra ecosystems that play an important role in regulating ecological processes, which are in turn directly influenced by the spatial patterns of trees and environmental constraints such as topography and climate. Our objectives were to characterize the spatial patterns of tree species and size classes, determine whether spatial patterns of trees differed among three FTE types, and examine FTE- and tree-environmental relationships in our study area on Niwot Ridge, CO, USA. Overall, spatial aggregation was more extensive for seedlings than saplings or trees. Distributions were largely random in limber pine but were highly aggregated in Engelmann spruce and especially subalpine fir, reflecting these species’ relative shade tolerance and expected sequence of establishment following disturbance. Fragmented and patchy tree distributions were observed in the FTE with the most heterogeneous topography, characterized by high relief and associated physical disturbances. The least patchy distributions were associated with the FTE containing a relative absence of disturbance. Intermediate levels of tree aggregation were associated with low topographic relief and presence of meadows and wetlands. Our results emphasize the importance of spatial structure as an initial controlling factor of vegetation pattern in FTEs occurring in the same landscape.     

Spontaneous coordinated activity in cultured networks: Analysis of multiple ignition sites,primary circuits,and burst phase delay distributions

All higher order central nervous systems exhibit spontaneous neural activity, though the purpose and mechanistic origin of such activity remains poorly understood. We quantitatively analyzed the ignition and spread of collective spontaneous electrophysiological activity in networks of cultured cortical neurons growing on microelectrode arrays. Leader neurons, which form a mono-synaptically connected primary circuit, and initiate a majority of network bursts were found to be a small subset of recorded neurons. Leader/follower firing delay times formed temporally stable positively skewed distributions. Blocking inhibitory synapses usually resulted in shorter delay times with reduced variance. These distributions are characterizations of general aspects of internal network dynamics and provide estimates of pair-wise synaptic distances. The resulting analysis produced specific quantitative constraints and insights into the activation patterns of collective neuronal activity in self-organized cortical networks, which may prove useful for models emulating spontaneously active systems.     

Signaling in plant disease resistance and symbiosis

Interactions between plants and microbes result in plant disease and symbiosis. The former causes considerable economic damage in modern agriculture, while the latter has produced great beneficial effects to our agriculture system. Comparison of the two interactions has revealed that a common panel of signaling pathways might participate in the establishment of the equilibrium between plant and microbes or its break-up. Plants appear to detect both pathogenic and symbiotic microbes by a similar set of genes. All symbiotic microbes seem to produce effectors to overcome plant basal defenses and it is speculated that symbiotic effectors have functions similar to pathogenic ones. Signaling molecules, salicylic acid (SA),jasmonic acid (JA) and ethylene (ET), are involved in both plant defense and symbiosis. Switching off signals contributing to deterioration of disease symptom would establish a new equilibrium between plant and pathogenic microbes. This would facilitate the development of strategies for durable disease resistance.     

Spacing patterns of an Acacia tree in the Kalahari over a 61-year period: How clumped becomes regular and vice versa

Nearest tree neighbour distances and the tree spatial formation on a large scale over time and space replicates were examined. The study was conducted in a natural savanna ecosystem in the Southern Kalahari, South Africa. Nearest tree neighbour and point pattern analysis methods were used to investigate changes in the spatial pattern of trees in two plots. Trees larger than 2 m canopy diameter were mapped. We used aerial photographs of the study area from 1940, 1964, 1984, 1993, and a satellite image from 2001 to follow two plots over time. Field work was carried out too for classification accuracy. We were able to identify and individually follow over 2400 individual trees from 1940 until 2001. Nearest neighbour analysis results indicate that dead trees were on average closer to their nearest neighbouring trees than living trees were to their neighbours. Most dead trees were on average 6 m from their nearest neighbours, while most living trees were about 20 m apart. Point pattern analysis results show a cyclical transition from clumped to random and sequentially to regular tree spacing. These transitions were not correlated across two plots. Generally, decreases in small-scale clumping coincided with periods of high mortality. Our findings show that regular, clumped, and random tree pattern can occur, pending on time, location, and scale within the location.     

Variability in Energy Influences Avian Distribution Patterns Across the USA

Habitat transformations and climate change are among the most important drivers of biodiversity loss. Understanding the factors responsible for the unequal distribution of species richness is a major challenge in ecology. Using data from the North American Breeding Bird Survey to measure species richness and a change metric extracted from the MODerate resolution Imaging Spectroradiometer (MODIS), we examined the influence of energy variability on the geographic distribution of avian richness across the conterminous U.S. and in the different ecoregions, while controlling for energy availability. The analysis compared three groups of birds: all species, Neotropical migrants, and permanent residents. We found that interannual variability in available energy explained more than half of the observed variation in bird richness in some ecoregions. In particular, energy variability is an important factor in explaining the patterns of overall bird richness and of permanent residents, in addition to energy availability. Our results showed a decrease in species richness with increasing energy variability and decreasing energy availability, suggesting that more species are found in more stable and more productive environments. However, not all ecoregions followed this pattern. The exceptions might reflect other biological factors and environmental conditions. With more ecoclimatic variability predicted for the future, this study provides insight into how energy variability influences the geographical patterns of species richness. PR designed study, performed research, analyzed data and wrote paper. CAL, MAL, AMP, VCR, PDC, and EFL designed study and wrote paper.