广州市公园耐湿草本植物及其造景应用

选择广州市具有较长的自然式缓坡驳岸,且植物养护管理良好的6个公园为研究对象,调查其耐湿草本植物种类及其景观应用情况,分析广州公园耐湿草本植物造景的特点与存在的问题。研究表明,在调查区域内共记录有耐湿草本植物77种（含变种、变型和品种）,隶属26科52属,其中一年生草本26种,多年生草本50种,蕨类1种;常用的耐湿草本植物以低矮型和中型草本为主。广州公园的耐湿草本植物应用于水边造景有以下四个特点：①色彩调和,展现水乡风光;②线条变化,增添湿地趣味;③适地适草,体现热带特色;④自然种植,创造观景效果。广州公园建设宜考虑适当增加地带性的多年生耐湿草本植物种类。     

Critical threshold effects of benthiscape structure on stream herbivore movement

In landscape ecology, substantial theoretical progress has been made in understanding how critical threshold levels of habitat loss may result in sudden changes in landscape connectivity to animal movement. Empirical evidence for such thresholds in real systems, however, remains scarce. Streambed landscapes provide a strong testing ground for studying critical thresholds because organisms are faced with substantial environmental heterogeneity while attempting to overcome the physical force of water. In this study, I report on the results from a series of experiments investigating the influence of habitat abundance and current velocity on the movement dynamics of two stream herbivores (caddisfly larva Agapetus boulderensis and snail Physa sp.) that differ substantially in how they perceive landscape structure. Specifically, I ask whether critical thresholds to herbivore movement exist in streambed landscapes. By exploiting the pattern recognition capabilities of artificial neural networks, I found that the rate, sinuosity and directionality of movement by Agapetus and Physa varied nonlinearly according to the abundance of habitat patches, current velocity and habitat-current interaction. Both the study organisms exhibited threshold responses to habitat abundance, yet the location and slope of these thresholds differed between species and with respect to different current velocities. These results suggest that a critical threshold in functional connectivity (i.e. the connection of habitat patches by dispersal) is not an inherent property of the landscape, but in fact emerges from the interplay of species' interactions with landscape structure. Moreover, current velocity interacted with habitat abundance to elicit strong upstream-oriented movement for both the species. This suggests that dispersing individuals may be polarized in the upstream direction and therefore functional connectivity is not equal in all directions. Such results highlight the need for future research addressing the sources of variability of critical threshold effects in ecological phenomena.     

滇西北退化高寒草甸植物群落结构对刈割的响应

为探究滇西北不同退化级别高寒草甸植物群落结构对外界干扰的响应敏感性,以香格里拉市的典型高寒草甸为研究对象,于2018-2020年在三个退化梯度上（严重退化,S1;中度退化,S2;轻度退化,S3）开展控制刈割实验,进而分析草甸植物物种丰富度、群落组成相似性、群落复杂度和关键种的变化规律。结果表明：（1）刈割后,S1的物种丰富度显著增加（P<0.05）,S2和S3的物种丰富度未发生显著变化（P>0.05）;（2）相较于S2和S3,S1梯度的植物群落组成变化最大;（3） S1、S2和S3的植物群落复杂度在刈割后均呈先下降后增加的趋势,但S1的植物群落复杂度变化幅度高于S2和S3;（4）刈割导致各退化草甸植物群落的关键种发生了变化,2018、2019和2020年S1梯度的关键种在豆科（Leguminsae）和蔷薇科（Rosaceae）之间变化,S2梯度的关键种在禾本科（Gramineae）和菊科（Compositae）之间变化,S3梯度的关键种在蔷薇科（Rosaceae）、菊科（Compositae）和禾本科（Gramineae）之间转变。研究表明,滇西北高寒草甸植物物种丰富度、群落组成和群落复杂度对外界干扰响应的敏感性可能随退化加剧而上升,但群落关键种的响应过程较复杂。     

Alternative splicing mechanisms for the modulation of protein function: conservation between human and other species

Alternative splicing (AS) is an important process in eukaryotic organisms by which a given gene may express a set of different protein isoforms depending on the tissue, or the developmental stage of the individual. In the present work, we have compared AS among species, focusing on the conservation of AS mechanisms for the modulation of protein function. For this purpose, we first analysed the frequency with which different species, human, mouse, rat and fruitfly, utilise them. Second, we focused more directly on the conservation among species of the mechanisms themselves. To this end, we compared biologically equivalent AS events between human and mouse, or rat. Our results indicate only minor differences in the frequency of use of these mechanisms, as well as a high degree of conservation among the species studied.     

Horizontal gene transfer in microbial genome evolution

Horizontal gene transfer is the collective name for processes that permit the exchange of DNA among organisms of different species. Only recently has it been recognized as a significant contribution to inter-organismal gene exchange. Traditionally, it was thought that microorganisms evolved clonally, passing genes from mother to daughter cells with little or no exchange of DNA among diverse species. Studies of microbial genomes, however, have shown that genomes contain genes that are closely related to a number of different prokaryotes, sometimes to phylogenetically very distantly related ones. (Doolittle et al., 1990, J. Mol. Evol. 31, 383-388; Karlin et al., 1997, J. Bacteriol. 179, 3899-3913; Karlin et al., 1998, Annu. Rev. Genet. 32, 185-225; Lawrence and Ochman, 1998, Proc. Natl. Acad. Sci. USA 95, 9413-9417; Rivera et al., 1998, Proc. Natl. Acad. Sci. USA 95, 6239-6244; Campbell, 2000, Theor. Popul. Biol. 57 71-77; Doolittle, 2000, Sci. Am. 282, 90-95; Ochman and Jones, 2000, Embo. J. 19, 6637-6643; Boucher et al. 2001, Curr. Opin., Microbiol. 4, 285-289; Wang et al., 2001, Mol. Biol. Evol. 18, 792-800). Whereas prokaryotic and eukaryotic evolution was once reconstructed from a single 16S ribosomal RNA (rRNA) gene, the analysis of complete genomes is beginning to yield a different picture of microbial evolution, one that is wrought with the lateral movement of genes across vast phylogenetic distances. (Lane et al., 1988, Methods Enzymol. 167, 138-144; Lake and Rivera, 1996, Proc. Natl. Acad. Sci. USA 91, 2880-2881; Lake et al., 1999, Science 283, 2027-2028).     

Coccinellid response to landscape composition and configuration

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